Pimping your amp

behringer ep 4000 - pimping your amp

How to remap your amplifier.

Since our first post we have received three requests with regards to boosting amplifier performance from our younger readers. By boosting amplifier performance we are talking here wholly about power output, not quality of course. Well this can be done of course, usually at some exorbitant price.

The Sound Wars Vs Whisky in the Jar

The idea of increasing output power of any amplifier lends itself to the fact that we usually need this power after a few jugs or to impress.  Many years ago with a tube 15W per channel amplifier and paper coned speakers sound volume was the last thing on our mind.  Amplifiers just did not come more powerful, for a price at least. Solid state engineering and the marketing machine put paid to this.

behringer ep 4000 - pimping your amp
Behringer EP4000 – a convincing best seller

Bridging your amp

For starters, the easiest way to get more power from an amplifier is to bridge-mode the output. This means the speaker is connected between the (+) terminals of each amplifier and the inputs are driven out of phase with each other. The restriction is speaker load. This effectively should double the amplifier power at twice minimum speaker impedance as suggested or warned by manufacturer.  However we have now lost stereo.  And I don’t like bridging- this is something which should only be done by an experienced audio or electronics person that understands SOA and loading.

The connection between high voltage rails and low impedance loads?

So what to do, what to do? In one of our mails our newbie pointed out that he had a Sony STR-DG600 which he wanted to modify to drive a 4 Ohm load by adding extra output devices.   I am familiar with the 500 and 600 series and whilst pretty good home theatre amplifiers they are prone to switching off in high humidity (if you live in Sea Point or Durban you may know the feeling).

They are both rated about 100W per channel (in stereo mode, which I doubt). The output stages of these amplifiers should be able to put out the advertised 100W per channel into 8 Ohm loads but not with the mains transformer used – it’s essentially a home theatre amp after all and according to my own calculations the transformer is only about 200VA max.  Transformers are very expensive.

behringer ep-4000 rear pimping my amp
Behringer EP4000 Rear

Playing into a 4 Ohm load may double the power dissipation but will fuse the input to the transformer or take out the power transistors – this is not a possibility but a definite. (for continuous periods at high volume control settings).

The Sony does not have the real estate to allow for higher powers, both in cooling capacity and a more powerful transformer.

Recommendation

Unfortunately modern integrated amplifiers (pre-amp and power) don’t lend themselves easily to modifications and it’s advised to leave as is. A common modification however would be to increase supply rail filter capacity, replacing the rectifier with fast switching diodes and adding fan cooling (not always a great idea for home use because of the noise).

Attenuation - from power amp to power amp
Attenuation – from power amp to power amp

The STR600 is no exception but I wouldn’t worry at all about any changes to the supply or rectifier.  What one could do is of course reduce loading on the two front channels which would give the power supply room to breathe.  This would mean a resistive potential divider chain, usually a 50K and 10K resistor in series, the 50K leg going to the (+) speaker terminal and the lower 10K to (-) with the mid connection feeding another power amplifier.

This will reduce the loading on the two channels, less hum and noise – and less distortion at higher levels of volume.

Note:  The attentuator schematic above is for conventional amplifier outputs and not a bridged output.

Budget power amplifiers – what the hell does budget mean anyway?

As a budget amplifier the Dixon MA-200 or MA400 are pretty good. Don’t be put off by the sneer brigade,  the resellers have a name to protect and if one had to actually open the chassis and peer inside you’d be surprised at the size of the toroidal. On our South African market that would easily set you back at least R 1 200.00.  I don’t like the cooling though but it suffices and of course this applies to many other amps on the market. Will cover this in another article. In any event, these amplifiers can be purchased for about R 2 000.00 second hand, even through Cash Crusaders.

Behringer EP4000 (or EP2500)

My personal favourite though is the Behringer EP4000 which for home use may be total overkill.  The price is a problem however, they are also very much in demand on the 2nd hand market.  Sticking to a R2 000.00 budget with the MA-200 would be cheaper than what it would cost to modify most 100W amplifiers with a small power supply.

Even the power supplies used in some stereo amplifiers from the “snob lineage” can be pretty meagre which is a great disappointment. NAD as a rule don’t market their products without the recommended USA power approved method and this will cover supply rating as well.  In our sister-website, Parts-Ring I tested a 7200 which is rated at about 50W p.c. and although it uses a now fairly common type voltage shift supply the power output did not have the punch of the MA-200.

I have tested the MA-200 on the STR500 and the results were impressive.  I don’t have the scope tests at hand (analogue scope) but there was no sign of supply droop at 100W per channel, unlike the original load testing. Distortion was near non existent at 28V across the 6 Ohm speaker load.

Attention: No modification required

In my opinion most home theatre amplifiers shouldn’t be modded to get extra power, the entry level units, even some high end stuff,  were just not designed for continuous flat out music reproduction.  The mains transformer definitely not. A professional category amplifier may be better for this purpose with the added precautions*.  A 100W amplifier does not sound ten times as loud as a 10W amplifier and therefore it stands to reason if one really wanted to beef up an H.T.  100W amplifier the time and effort required does not justify the cost.

A practical solution

The best solution here, my recommendation and opinion here of course, an attenuator and MOSFET amplifiers such as at Rod Elliott or Yebo. Guaranteed to fly your kite and at the same time, can be used as a proper “musical” sounding amplifier by switching inputs to a first class pre-amplifier.

*Added precautions

The best amplifier I have ever heard used a MOSFET output stage.  This is an opinion.  Separate power and pre-amplifiers are better than an integrated solution. Another opinion. Professional audio uses more robust connectors.  A fact.

Professional series power amplifiers are designed for long duration high power usage. My opinion.

Professional does not mean one can throw the kit around. My opinion.

There are so many opinions and facts out there that it has become difficult to sift through marketing ploys, opinions, Kudu droppings and what we may see as “real” fact. For the novice, coming into the audio arena this can be challenging.

The article above serves to lay out the rationale, in my opinion, why it is best not to adopt an “upgrade” approach to modern audio circuits, more the home theatre variety.  It’s just not worth the time and effort (and financial outlay) for simply put, a higher output into a pre-determined load.

Better to build from scratch and use your existing gear as a driver.

Consumer goods, e.g. HT DSP preamplifers which have XLR preamplifier outputs are prohibitively expensive. It numbs the mind. I have personally modified a Sony 600, ripped out the output stages and wired to XLR outputs to feed a Behringer NU4-6000 and MA-200. The resulting reproduction, in my opinion, was phenomenal. I put this down to limitations in the headroom of the Sony.  It’s not a kW ear-burster.  But using an old Pioneer stereo amplifier as a driver to the Behringer amplifier was even better. Because it was designed for audio and not HT. I prefer “analogue style” tone controls.

Because many will not feel inclined to blow a substantial amount on an amplifier such as one in the iNuke series, a better bet is the MOSFET amplifiers advertised by Yebo and on Rod Elliott’s pages.  I have nothing against the iNuke, MOSFET amplifiers just have such an incredible dynamic range. 

In all my tests I used Eltax Millenium 500s. Why? Because they handle vast amounts of power.  Power pundits like these speakers for this exact reason. And no, they sound awesome. My opinion. 

I promote Behringer products because for me they are the underdogs of the musical world. Criticism, rubbishing and just plain ignorance are the order of the day. I could go on and on.  Since more Behringer gear gets used than any other manufacturer they must be doing something right.  Also how many permutations of an audio amplifier do we actually get?

[Ed’s note:- although mention is made of the MA-200 and MA-400 we are not affiliate to Cash Crusaders through any means. Likewise Behringer of course].

Next:  Sony amplifier’s MN2488 and MI1620 Power Darlingtons. (2SD2488 and 2SB1620)

Where is the North West Audio Video Guy?

asus xonar u7 headphone preamp

The missing NwAvGuy

Thanks to Bob Moodley, electronics guru and a work colleague for this interesting article on the missing genius, the NwAvGuy.  Also the article on a double blind listening test where some “so called” cheap arsed components, a Behringer A500, Sony DVP-NS355 and mass retail signal cables were compared to a Classe CAP-80, YBA (Yves-Bernard André) 2A, Wadia 6 CDP and MIT Terminator 3 XLR signal cables.

asus xonar u7 headphone preamp
The Asus Xonar U7 7.1 192kHz/24 Bit 114dB A Weighted headphone preamp

The YBA amplifier boasts 70W into 8 Ohms with an even more boastful frequency response: 5Hz-80kHz, -3dB. The Behringer is a pretty ugly looking amplifier with 150+150W into 8 Ohmswith a “modest” 10 Hz – 25 kHz, +0/-1dB frequency response.

The common factor were the near-field monitors, the ATC SCM 12 series.

Readers can go on to the page which covers this DBL test at Matrix Hi-Fi to get more details. I don’t have anything against YBA amplifiers of course, just that sometimes we shouldn’t write off that which is supposedly budget. But then again, that’s what Behringer does best and yes, I am a proud owner of numerous Behringer pieces of equipment which has never let me down (I look after my stuff) and of course, I don’t turn my nose up at budget equipment.

The NwAvGuy and the OBJECTIVE2

Now getting onto the more important details,  the NwAvGuy designed and built a headphone amplifier which refrains from boasting some incredible Eskimo and Mamba oil cures – the frequency response is great for human ears, the output impedance can drive 16 Ohm and up headphones happily, the power supply is two times common and garden PP3 9V battery supplies which then does not have a “verboten” virtual earth, it has circuit and headphone protection and is called simply, the “O2”.  What is even more irregular is that the design engineer released the headphone amplifier under the Creative Commons CC BY-ND.  This requires as most creative commons licences, attribution but the ND aspect means no reverse engineering – or No-Derivs (derivatives).

Write up to this great piece of design is found on the NwAvGuy website.

The NwAvGuy is now missing in action, akin to Sugar Man fame. He designed this great piece of equipment and then disappeared into thin air.  He even dared the competition to take him on, staking his own money.

While we are waiting to find him we decided to do our own non-technical tests on two headphone amplifiers lying around:

Asus Xonar U7 – headphone listening 

I have two pieces of equipment which I love listening digital recordings to, one being the Focusrite Scarlett 18i20 (anyone will do) and the other, the much talked about Asus Xonar U7. Sure, an older guy can listen to almost anything through almost any amplifier and it should sound great but truth be told the Focusrite’s reproduction quality of CD and lossless FLAC files is almost insanely good. Now the Asus of course is not a mic preamp, it’s cheaper but here again the quality is exceptional.

In South Africa I believe the Asus now costs in the region of R 1 500.00 ~ R 2 000.00.  The Cirrus Logic® CS4398 2-channel DAC and the DSP  C-Media 6632A sound processor plays a big role in this quality but truth be told, it does boast a 114dB SNR (A-weighted), front out. THD+N is a minute 0.0006%.

Hyper Grounding technology

Exclusive ASUS Hyper Grounding PCB fabrication ensures strong signal insulation to reduce distortion and interference, also known as component crosstalk.

Bitrate and Sampling  (ugh, this is digital)

The Xonar U7 is a 192kHz/24 Bit sound card which is powered through the USB port of your PC or notebook.  Current draw I believe is in the vicinity of 500mA.  Use USB2.0 or higher.

Being a non-audiophile and just liking to compare quality of sound with same program source and audio transducer, be it loudspeaker or headphones, the Asus is in a class of it’s own.  I dare say I cannot believe that a dedicated 2-channel 1000 Dollar headphone amplifier is going to sound that much better.  But, and this is a big BUT, the Asus is a 7.1 channel monster and for gaming, it’s an absolute killer.

Output/Input Full-Scale Voltage :
Line output (RCA, 3.5) : 1 Vrms (2.828 Vp-p)
Headphone output : 1.3 Vrms (3.677 Vp-p)

I do not have the minimum loading at output.  Some users complain about lack of volume (too high an impedance) – the amplifier is comfortable pushing into a 32 Ohm or 54 Ohm load with wallops of headroom available before one’s ears fall apart.

Oh yes, Dolby HTv4 also means it comes with dialog enhancement as well as dynamic compression.

The Focusrite Mic-preamplifier used as headphone amp

Now this is a  difficult one because a) the pre-amplifier is meant for the professional market as a microphone pre-amplifier and b) it costs more than 5 times that of the Asus. And, yes it also uses USB if you need to record and use the application software.

We don’t often read about microphone pre-amps used for high quality sound reproduction and possibly this could be because the manufacturers are aiming at near perfect microphone amplification. The Focusrite doesn’t only look good (which one doesn’t?) but the output quality is just so damned perfect (to my hearing). I have tested the 18i20 with the HD-800 which I would presume to be in the top 5 of anybody’s wanna haves and I was gob-smacked.  I have two Sennheissers, the 380 and the 650, both of which I rate very good.  The 800 was a loaner.  Leaving the technicalities out of the equation the Asus unit may be good but from a listening viewpoint,  the Scarlett did what it was supposed to, reproduce the signal as if it came straight from the studio.

(all tests done on FLAC lossless and CD).

So what does this tell us?

Pay more, get more? Get a dedicated unit? Simply put, money doesn’t always buy the best. Bob Carver proved that a long time back.  Your headphones may be the stumbling block. Good technical specs should make great listening. The 18i20 is a mic-preamp. The U7 is great value for money.

Having never heard the O2 it does whet our appetite. It’s on the to do list. It has a SNR of supposedly 131dB so this is a serious design, one needs to follow design criteria to the T.  It won’t be built to resell so who cares if I use a nasty cabinet and some components which didn’t come from Mouser.  What I and hopefully most of us do know is price is not everything. I do not know how close the Asus or the Focusrite will compare to the O2 but I am sure, based on it’s design to strictly compete with high end HP amplifiers it will be better than the Focusrite.  It’s not a mic preamp after all. If one cannot wait, the U7 is a marvel – it’s now 3 or 4 years old but is still possibly for it’s price, better than any rival.

The kits for the O2 can be obtained at the O2 Wiki site.

Definitely on the projects list. See you soon.

Another but not so missing guy:  Bob Carver, the genius behind Phase Linear

 

 

 

 

Inside the The ART Digital MPA II

The Tube Digital MPA II from ART Pro Audio

The ART Digital MPA II – Solid state and tube preamplifier

This was my first microphone preamplifier and admittedly it was a grudge purchase. I was looking for the Behringer 2 channel 12AX7 preamplifier to do some mods, higher voltage plate and RIAA preamplifier.  At the price it’s a steal, then just over R1200.00 for Mic200 and about R1900 for the Ultragain Pro.

ART Digital MPA II
ART Digital MPA II

Unfortunately none of the agents in South Africa had stock (what’s with Behringer in South Africa, first first class monitors then the preamplifiers). In any event  Pieter Smuts Music in Parow had the ART Digital which I purchased knowing I would never modify it, let alone open it.  The pricing was very good as is most of this music shop’s pricing.

Then I had the good fortune of having a colleague, Brian, a part-time musician confess to me that he has never played on tube equipment, not even the main stream stuff. So after about a two month loan period he staggered in one day saying that it was absolutely brilliant.  Well there has been a lot of snobbery going on those days, not much changes of course, and one such device which took a fair bit of hammering was the previous ART Pro MPA II, non digital. So I did eventually decide to crack the hood and have a look inside.

12AX7 Preamplifier
12AX7 Preamplifier
ART MPA II Tube Preamplifier 12AX7
Tube Preamplifier 12AX7

First of all the build quality is exceptional, the two large meters make this series extremely attractive but what does it really sound like?  I can say that at least three people I know have tried it and they recommend it, highly.  The tube voltages can be varied from +48V (phantom supply most probably) and the more conventional >+200V.  There is variable input impedance and yes, I did try it with a turntable pre-amplifier expecting some ghastly results. Definitely worth a listen.

There’s quite a few websites which offer modifications to improve performance (Bless them!) and they are listed below:

Audioproz

Revive Audio

Moddefecation

The tubes inside these microphone preamplifiers were not added as a gimmick measure neither for pure market value – I used this in conjunction with a Focusrite Scarlett 18i20 through optical and it was great to draw a comparison between the two although one shouldn’t, they are two completely different types of preamp but with both with great reviews.

Inside the ART Digital MPA II
Inside the ART Digital MPA II

Getting right down to the nuts and bolts we now have the chief rival of many high performance chips and the nemesis of the famous 4558, the 5532.

Showing PCB build quality and one of the op-amps.

NE5532P Preamplifier used in MPA ii
NE5532P Preamplifier used in MPA ii

There will be an outcry amongst the op-amp extremists because the 5532 chip is now also considered a bit dated. We apologise upfront of course, unfortunately we had no part in the design of these lovely preamplifiers. Modifications sheet includes changing these from 5532 to OPA2132, OPA2134, OPA2107, LT1358, or LME49860NA.

The main interest in modifying these preamplifiers is making them “sound better with less noise” and having read as much as possible about these modifications one wonders what we are really looking for here.  Whilst in search for the holy grail I have no doubt in my mind that the final result will be better because we have paid more I always think more positive results can be obtained by adding more features but not at the cost of noise or quality. balancing transformers may be a good start but as the inputs are variable impedance this will take some doing unless it’s for long output feeds. The other thing is having headphones output – this is sadly lacked. This would be a switched stereo/mono type.

Pros:

I think the only con I could find on this preamplifier was a lack of headphones output. The pros are plenty, one being the variable impedance.  So the preamplifier does have a tube stage and although some of us complain about the hybrid setup the advantage of tubes in the preamplifying stages are not missed, especially in over-driving a signal.

What is better than the quality of this professional series preamplifier is no doubt the cosmetic finish. I love the fact that the designers used VU meters (along with LED peak). The front panel is thick alauminium, CND machined.

From the manufacturers:

Two Ch. Mic Pre w/ A/D Conversion

The all new ART Digital MPA-II delivers all of the same great features of the ProMPA with the added versatility of digital output. Like the ProMPA-II, each input circuit has 48v phantom power and features variable input impedance which can radically vary the overall performance of any high quality dynamic or ribbon microphone. The Digital MPA-II can be configured for dual mono or stereo operation with selectable mid/side mic support, summing the adjacent channel, to decode left/right signals.

The input section of the Digital MPA-II operates at either a low or high plate voltage applied to the two integrated hand-selected 12AX7 tubes for wider variation of preamp tone and performance. Large back-lit analog VU output meters display output levels while multi-colored LED arrays, with average or peak hold, show tube gain and digital output levels.

In addition to XLR and 1/4″ analog outputs, the Digital MPA-II features a high quality A to D converter which offers digital connectivity on S/PDIF, ADAT, or AES/EBU outputs. A rotary control on the front panel allows selection of format and sample rates from 44.1 to 192 KHz and 16 bit dithering. There is also a push button for, and two wordclock jacks, allowing loop-through.

The Digital MPA-II comes in a standard 2u space rack-mountable steel chassis, with CNC routed black anodized aluminum face panel.

 

That awful JRC4558 audio IC

That nasty 4558 beater the Texas Instruments INA217

The JRC4558 – tried and trusted workhorse

So there you have it, out of the horses mouth, the op amp we covered in the Dixon PM121USB is awful.  Reading about this chip on nearly all the forums I am surprised that we still use it. It’s cheap, nasty, has piss-poor bandwidth and lacks “quality” sound.

 

That nasty 4558 beater the Texas Instruments INA217
That nasty 4558 beater the Texas Instruments INA217 instrumentation amp.

 

The first time I came across this chip was when the Titanic was still afloat, perhaps in a preamplifier but more like a graphics equaliser.  The equaliser is about late 70s vintage early 80s. It was a repair job and once completed sounded damned good. Ahem, does that mean that the modern equalisers sound better? Does this chip do any circuit justice?

Let’s backtrack a bit and look at some of the older, so called mediocre ICs of our time. The 741 series was a masterpiece. We built all sorts of circuits with these chips and even for “mediocre” use, the disco mixers used them in droves in preamplification. Now in the 70s maybe this was like magic, this little chip which sounded pretty good. I recall the JRC (Japanese Radio Company) getting into the act – bringing out a dual op-amp, the JRC4558.  Now I did a lot of work on JRC equipment in the 70s and 80s, all marine receivers and transmitters and let me tell you, they were anything but junk. In fact when I hear anyone on the forums talking about junk gear, I, like many, would want to get into the persons head and discover for ourselves where they get their information from.

No, the 4558 is not junk, at the time it was a very able little dual op-amp and was well justified to be used in almost all audio (and other) gear. The TDA741 still enjoys use today and no, it is neither junk nor ill suited for any application.  The bigger issue is when it starts being put into high quality audio gear – the 4558 has a bandwidth of about 3MHz under optimum configuration, the 5534 10MHz, slew rate 1V/uS compared to 13V/uS and near immeasurable noise figures on the 5534. (real engineers don’t worry about all this especially when our hearing maybe caps at 16kHz and not 16MHz). So it’s no wonder that people complain about these units been used in a preamplifier. But when mass feeding the peoples we suddenly have a problem – the 5543 costs R15.00 each and the 4558 R1.00 to R5.00.

There is an advantage however, DIY.  Sticking expensive chips into breadboard is never a solution. The 4558 lends itself perfectly to the cause. Once all is good we can hopefully transpose with a better chip, like the 5532 or 5534.

The 4558 is still useful as a comparator, DC work or anything which doesn’t require very fast switching.  Sonically the more expensive chips do sound cleaner but then we need low noise resistors and high tolerance circuits.

For general purpose work I find nothing wrong with this old workhorse. If you really want good quality sound then I do suggest looking at the INA217 or the THAT1510P. Definitely NOT for HOT exchanges but then if you want to rip off the JRC4558 then you need to start afresh.

So no, sorry to retract – the 4558 is not crap. Different strokes for different folks. This article may be slightly tongue in cheek but be wary of why we don’t like something, it could be because we were told so.

 

The Wonderful Art of Mastering

home recording with Focusrite Scarlett 2i2

Everyone wants to become a world famous musician, conductor, cello player in a James Bond movie but what about a recording engineer?

A very good, rather excellent, website to get your talent juices flowing is that of David Mellor’s Audio Master Class,  where valuable time and money is spent in training dunces like me in the world of professional recording, giving free titbits of information and real world case studies.

home recording with Focusrite Scarlett 2i2
Focusrite Scarlett 2i2

I had just purchased a Focusrite Scarlett 18i20 and whilst doing some recording tests realised very quickly how important having a proper studio for this function is. And I mean, really is.  Spending millions on a home studio is obviously not within everyone’s reach but knowing what to do and how to do it on a budget is inevitably the best route to follow. Whilst we sing the old adage, “a bad workman blames his tools”, it’s no surprise to find that many started somewhere, mostly on a tight budget working their way up to being extremely knowledgeable in audio or sound engineering.

My first experiences in home recording is somewhat vague suffice to say it was with a four track tape recorder and ceramic microphone. Moving on a couple of decades and with a Live sound card and a great little mic I did some more tests and was amazed at my progress.  The thing is that when you do go the “professional” route, even with what the glassy eyed, snobbed out wannabes classify as an entry level mic preamp, the Focusrite delivers. It delivers so well that the Shure SM7 microphone and quiet little preamplifiers reproduced the stunning performance of the refrigerator next door. Ditto my Zoom H6 picking up the air-conditioner compressor outside switching on and off.

Yes, sound engineering isn’t for the faint-hearted.  I have heard some absolutely incredible recordings from solo artists and their Scarlett 2i2 rigs and to be honest, times have changed for the better.

This website is not affiliate to master Audio Class in any way. Before going out and spending upwards of R20 000 on a course in sound engineering maybe have a look and do some reading. Lots and lots of reading.  Exciting stuff!

You can get your 2i2 in South Africa at Sound Select the Shop (and no, we’re not affiliates here either).  Shop around if you wish 🙂

The Sneaky world of Pre-amplification

Art pro digital mpa 2 - microphone preamplifier

Changing the Ambience with quality voltage control – the Preamplifier

One of the biggest advantages of having separate preamplifier and power amplifier stages is that the user can swap between the two either for upgrading or listening purposes.  The pro audio world may see this in  powered mixers versus the un-powered variety but it is a step invariably anyone interested in sound systems will eventually take.

Art pro digital mpa 2 - microphone preamplifier
ART Digital MPA II

Of course the so called best preamplifiers are supposedly just attenuators so here I need to tread carefully.

The path without a circuit is best

The shortest distance between two paths is invariably the straight wire so presumably we should ban the pre-amp entirely.  Not so quick though, the power amplifier usually needs about 1V at it’s input which does mean we need some sort of voltage amplifier of sorts. The attentuation is fine if one is feeding off a CD Player for instance which has a high enough voltage output sufficient to drive most consumer audio amplifiers.  Not if one is using a phono cartridge without preamplifier of course.  Attentuation is just that, usually a high quality potentiometer used in a passive setup which means less transistors, capacitors, noisy resistors and a hummin’ power supply.

Phono preamplifiers come in all shapes and sizes but is a necessity to amplify the very low mV values from the humble turntable cartridge, moving coil or moving magnet. The MC output, more popular amongst turntable junkies and audiophiles has an output often measured below 1 mV at full amplitude. This means in the wrong setup we are going to get a lot of noise, poor compensation and a very poor listening experience. Didn’t the supplier warn you that the cartridge was not MM?  Normally the cost alone is the “verboten’ element. Then we have the preamplifier or phono-preamplifier often advertised as MC ready but is not really, in fact it’s a bloody mess. High quality preamplifiers with MC input are simply put, rather expensive. But you can make your own then…

See DIY Audio Projects for MC

Rod Elliott for moving MM

The vintage era phono preamplifiers are making their mark as well and it’s absolutely no surprise.

See DIY Audio Projects “the Groove Watt”

Some consumer preamplifiers, especially high end have Hi-Lo MC and MM preamplifier input stages.  These come at a price, like the tube variety.

Mars 9 Phono Preamplifier Kit

Our article title, “sneaky world of preamplification” is really another way of looking at preamplification because in it’s simplest configuration would be a straight wire. We pay lots of money for high quality equipment and the one which we should be monitoring is this little voltage amplifier, with or without gain, levels and tone controls. Here we need to become aware of some interesting facts:

Build your own

  • Price doesn’t necessarily mean great quality. Read about the $5 preamp from Audio Master Class.
  • Building your own preamplifier will always sound better than any other – pseudo acoustic syndrome.  But hang on, there’s merit to this.  You can chop and change, make modular, run off batteries and even bypass for line use. And of course we have those that roll their tubes, why not the ICs.
  • Often the price you pay is for cosmetic appearance – what it looks like. Nothing better than having fancy looking gear in the sound room. I think the ART Digital MPA 2 is a typical example of very good looking gear – and the build and sonic quality is exceptional as well. ART are known for this.
  • Looking at the Dynaco ST-70 amplifier which was by no means the best looking amplifier (compared to MacIntosh methinks) in the world but having more than 300 000 avid owners bears testament to David Hafler’s technical know how and experience.
  • The low noise instrument preamplifier INA217  [pdf spec sheet](replacement for the SSM2017). This little chip in a ludicrously simple configuration outperformed many costly preamplifiers.

The essential recipe to the success of any circuit is simplicity, ease of design and cost.  Your cost will nearly always come down to what the end result should look like.

A vintage catch:  I had the option to purchase either the NAD 1020 or Hitachi HCA-6500 in the early 1980s.  Although I opted for the NAD which I used solely as a preamp in a DJ mixing console I was put off by how weak the pre-amp input board was – the RCA inputs felt weak and pressed in when exchanging input sources, which was quite often. The Hitachi was a more expensive piece of gear and to my ear was a better piece of equipment sonic wise.  You can pick the NADs up for over R2 000.00 on eBay, not a bad return on a preamp which I paid R200.00 for. Both, as you will know are very much in demand, the HCA-6500 is known as a sleeper (hidden away, not to be sold), the NAD a workhorse. Also, the NAD, if you do own one, has the same board as the 3020.

Article photo, the ART MPA II Digital

This is the digital version of the older PRO and it has a remarkably quiet front end and even with entry level microphones the sonic output quality is remarkably like, umm, well, tube like.  Remember that this is a tube microphone/instrument preamplifier but it reproduces phono (MM) with the proper RIAA compensation and preamplification front end (before the line in) in a remarkably civilised manner.  As this was never intended to be used for this purpose I can vouch that the quality is exceptional. (the RIAA circuit is the one sold by Yebo Electronics – due to be upgraded to the one linked above, the Rod Elliott link).

Changing the argument in modern audio – the digital sound

Asus Xonar U7

The DAC and digital sound – big quality at half the expense

Coming from an analog website it may sound as if we are doing a 180 here but the truth remains, we still have the analog versus digital argument.  Something which will never quite be put to bed, the digital war continues.

My first CD player was the Sony CDP1, a small, heavyweight, state of the art digital ‘icon’ to the audio world. In fact at the time I was not even aware that it was first commercial release, rather just wanting to get my hands on a CD player, a Sony, to impress my friends.

The vinyl years

Two things stood out at the time, one without doubt the easy way to play the media – damn but vinyl was finicky, and then you had the problem of friends playing disks which were so bad that it would damage the stylus (was I the only guy that had a freakin’ sound system) and the big one,  no crackles, pops, buzzing, clicks, jumping, feedback and of course,  the big one – lifting the arm to change tracks.

As time went by CD players dropped in price, had more functions and became quite a part of our lives. Everyone had one by the 1990s. Turntables were packed away or trashed, vinyl was dead. Or was it?

The CD years

I stopped listening to vinyl for about fifteen years, it was always cassette tape or CD and then DVD.  I gave away both my Sony turntables which I DJ’d with in the early 80s. The marketing machine was fine tuning us for the silver disk and they did a remarkable job except for one thing – multimedia computers came on the scene in the mid-90s.  (PCs and Windows, Apple was always the front-runner).  We suddenly could compress our 40MB file to 4MB in the form of MP3s. We became used to this,  piracy was no longer something we found on the high seas, it was in everyone’s home.  iTunes suddenly kicked in and we could buy individual tracks not the whole CD where the artist possibly had only one good track. CD prices started falling and before we knew it the audiophiles started reminded us of a couple of things that we had forgotten about.  CD quality is 20 to 20, vinyl is so much more.  In the last decade suddenly we found vinyl on the shelves again.

The shortest route between two points is the straight wire

The digital versus analogue argument is all about the shortest path, sampling frequency and DAC quality. Vinyl has two paths, de-emphasis at the RIAA amplifier (where disk cutting excursions on the lower registers uses a lot of space the engineers de-emphasise these excursions and boost the treble). On playback the reverse is applied. The second path is the amplifier itself.  Simply put, cut out the unnecessary and only amplify the necessary.  Add tone controls if you wish but make sure the amplification is flat, as close to dammit from 0Hz to 100kHz. Wishful thinking but yes, technology can allow this.  Makes one think how the NAD 3020 became so popular with an output stage using transistors from the Ark.   But let it be said that these amplifiers were very popular and indeed, more because of vinyl than anything else.

Vinyl supposedly reduces fatigue, is non-sterile, not compressed to hell and back and also, importantly, does not have the 20 to 20 limitation.  A guru even went so far as to say that music is something we also sense outside the audio spectrum.  He is a very good musician, who am I to argue. So what has made that incredible CD player now near redundant?  The DAC and the internet of course.  Breaking up an analog signal into parts and then re-assembling  these parts or as in a CD, taking 1s and 0s and then re-assembling to get a ‘resemblance’ of analog is just not on.

Technology has allowed us to push the clocking of a digital circuit into the hundreds of Megahertz, the Digital to audio converter now even runs at 384kHz or higher.  CD players, or rather the media is sampled at 44.1 kHz. Using the Nyquist–Shannon thereom, sampling frequency must be a minimum double the sample rate – 44.1kHz also encompasses anti-aliasing filters which reduce the bandwidth.  Lots more of that on wiki.  Bottom line is that all CD players run at 44.1kHz – man decided that our uppermost frequnecy limit is 20kHz so let it be. But DACs have improved in leaps and bounds over the years, high end DACs costing upwards of R30 000.00.  Ouch. But here’s the thing.

We take an analog signal, slice and dice so it can fit nicely onto your computer and then rebuild this signal through the DAC to reproduce a nice sliced and diced analog signal. Why not just copy your vinyl onto a high end tape recorder, preferably an R2R where the media can sit for 10 to 20 years and hopefully not be subject to degrading.  Oh, yes this happens.  The Audio Technica AT-LP120-USB Turntable sells for about R 7 500.00, throw in a RTR for about R 10 000.00 and Bob’s your uncle, or aunt.

Asus Xonar U7
Asus Xonar U7 – 192kHz A-weighted 114dB front at 24bit/96kHz freq response 10Hz to 46kHz

But no, not to be, not to be.  Just have a look at how long it takes to set up your reel to reel – your computer boots up in 20 seconds and then you have the Xonar U7 as I have. Exceptional quality and in only 60 seconds you have YouTube, access to free downloads, very good quality audio. And that’s the thing – if you want a no frills, high quality audio setup go the digital route. If you are looking at the pseudo-acoustic route go analog. Real analogue. In the real world a high quality setup of either can be expensive. For Sunday afternoon listening pleasure I opt for the analogue.  Day to day listening, digital. It’s all in the head any way.

The Internet of Everything

We have all heard this phrase and it’s not one which will go away quickly – the IoT or Internet of Things is going to change the way we react with the net and the universe.  At home you will have a menu listing trillions of songs and movies. You won’t need to keep a library – you will need to pay royalties but as the companies supplying this service become more popular these royalties will be measured in terms of cents.  It’s happening now already.  We live in a quick fix world – digital streaming media is the way things are happening.

 

The Harman/Kardon AVR161S

Harmon/kardon AVR161 review

Home Theatre AVR161S 5.1 harman/kardon

Being pretty frugal when it comes to buying audio equipment I felt it time to replace my tattered old 2004 JVC with a receiver which would not break the bank. Having four options at hand,  Yamaha RXV379, Harman/Kardon AVR161S and the new Yamaha RXV381 or HTR4068 I was stumped for choice. Knowing someone years back with a harman/kardon repair job who was a first class arsehole left me dodging the 161 like a Bryan Habana. But and this is a very big BUT, many folk have raved about the reliability of this brand and of course the quality. As the retailer was selling this unit for at least R500.00 cheaper than competitors I felt it was money well spent for a known good brand with a switched mode power supply. Not that I have anything against either Yamaha or linear supplies.

Harmon/kardon AVR161 review
Harmon/kardon AVR161

The audio output is nothing to write home about, 85W RMS x 2 channels driven.  I needed the HDMI more than anything which was 5 inputs, more than I needed in any event. Optical and coaxial inputs, 2 x analog RCA inputs and composite video output make this HT receiver as barren as the Sahara but this is what appealed to me.  And the setup is ridiculously easy. Neat and tidy. An omni-directional microphone is part of the package and we were up and running within ten minutes.

AVR161S - rear connectors
AVR161S – rear connectors

Not going into what it can and cannot do, it’s all in the manual, it must be emphasised that this little receiver has excellent reproduction quality, it is quick to set up and the power is more than ample.  The on screen display is simple to understand and all inputs are easily allocated – in fact I would say it’s the easiest installation I have ever done. But then again this is what HK is all about.

This is not a multi zone receiver like the 171 – I really don’t know of many people using this function either properly or on a practical level.

I did not like the volume control illumination but I did like the fact that the dimmer on the remote reduces this to a pleasing level.

For a little home theatre amplifier albeit big brand coming in at just under R 8 000 on the South African market is a rare steal.  Thumbs up to Govan Mani in Durban.

harmon/kardon AVR161S
The AVR161S all set up and in action

I’d like to say this was an elementary review but when one purchases something for their own entertainment and nobody else it may come across as being biased justifying the purchase. In essence – just Iove it.

[Editor’s Note:  Harman International Industries is headed up by Dinesh C. Paliwal as CEO. In November 2016 the company revealed it was to be acquired by Samsung. I wonder what Mr. Trump thinks of this?

Brands include: Harman Kardon, Becker, JBL, Crown Audio, dbx, Martin Professional, AKG Acoustics, Lexicon, Infinity, Mark Levinson, Revel, Soundcraft and Studer]

Starved Anode designs

starved anode designs

And on that controversial note of starved anode designs

The starved anode design has become fairly popular amongst guitarists because first and foremost these are highly affordable tube preamplifiers and secondly, well because they use tubes of course.

Behringer has brought out the Ultragain Mic-100 which is a cost effective instrument and microphone preamplifier. Trying to *purchase one in South Africa recently was useless, suppliers are always out of stock.  OK, I wanted two because I would have been modifying them for line preamplifiers at 250V anode supply.

The starve anode topology has been around since the beginning of time and is therefore not some new gimmick.  Read more about this on our sister website here.  In the good old days we had an accumulator pack for radio receivers and although looking back this was  archaic it did work. And work well. Better than the Note 7 at least.

Now we have armchair critics complaining about these starved anode and guitar effects preamplifiers and to be blunt, “if you don’t know what you are talking about then shut up”.  The internet is full of Behringer harbingers of doom that I wonder how they (the company) manage to make profits. A quick word on this as I am sure we are all tired of the same crusty bullshit:  Behringer did make good gear when it was manufactured in Germany. There were teething problems when they moved their manufacturing to China. They no longer have these problems or at least there is control. They do manufacture certain of their products cheaply to remain competitive.  You will pay more for equipment to be thrashed around but electronic equipment was never designed to be thrown around. Ditto to every other single company which moved their manufacturing to China. I can mention at least ten.

starved anode designs - the MIC-100
Ultragain MIC-100

The preamplifier below is not necessarily a starved anode design. In fact it is not, it can be switched to starved anode as a mode (either high plate or low plate).

Art Pro MPA 2

The reason why we are covering this is because in at least two forums some expert or other warns potential buyers off this design because of the plate voltage.

What is the Art Pro like considering I have never used the Mic-100.  In a comparison between the unit I have which is the digital version and the Focusrite 18i20 there is a distinctive “warmth” to the tone of the tube pre-amp, more so at full plate voltage with the same program material at line level. The preamplifier has variable input impedance for mic which some artists like.  From a studio perspective many home enthusiasts stick to either a full solid state design or tube.  Different strokes for different folks.

*The Mic-100 used to retail for under R800.00 at one stage. Our problem obviously is ROE.  The Mic-100 can be modified fairly simply for turntable use by adding RIAA IC amplification before the 12AX7/ECC83 tube and modding the supply rails.  Sure, there are some wishing to rather use an EF86 voltage amplifier before the dual triode ECC83 but in this case a very low noise IC costs R10.00 as opposed to the R250.00 for a tube which is fairly difficult to purchase locally.

As far as I am concerned the starve anode design does it for us.