Akai M8 Restoration

Akai M8 Pre and Main Amplifier - restoration of Akai

Akai M8 Restoration – Part One

Many of the older or vintage tape decks or open reel recorders finding its way onto the market use thermionic tubes or valves in the circuitry.  This has made them a very attractive collector’s piece albeit sometimes at a cost.

Akai M8 Pre and Main Amplifier - Akai M8 Restoration
Akai M8 Pre and Main Amplifier

The Akai M8

Now here’s an open reel tape recorder which gets a lot of publicity. One needs to understand that most of the positive publicity comes from the EF86, ECC83 preamplifier and EL84 output stage.  If one can pick up a unit in working condition for about R1 000.00 (these were about R300-R350 new in the 60s) then it works out as a very cheap alternative to building your own low powered tube amp. But before we all start our engines and run to OLX, Gumtree or eBay remember the following:

a) Look up the Roberts equivalent units on the net e.g. the 770X series was the M8. The M9 does not use tubes, neither the 1800 etc. Buying a reel tape recorder for the sake of it can prove to be an expensive and costly mistake – in many cases the machines up for sale are shot in one way or the other. An M8 in exceptional working order is going to set you back about 200 U$ and then shipping is an extra U$ 200 through eBay. And there are plenty of them around.

b) If you have never heard the so called “tube” sound maybe this is what you need to do first.  Sometimes it’s not always cut out to what people say it is.

c) If you then decide to go ahead, what do you want to do with it?  Will it become only a mic pre-amp, a modular stereo amplifier, will you trash the deck or restore? We see just one module, modified for two mics input only going for about $1 000. And they sell!

First and foremost note that Akai mechanical parts are notoriously hard to find.  Secondly if you do have a working deck in excellent condition then why trash it – these have become collector items. They are 50 years old now.

M8 rubber parts - Akai M8 Restoration
Akai M8 Rubber parts kit

The kit above covered idlers, capstan and tape counter belt and wonder of wonders, a brand new pinch roller. The parts cost R400.00 (this is super cheap) and the shipping about R500.00 through eBay’s global shipping program. (this should mean it will get here). Pinch rollers are hard to come by but bear in mind that many Akai models share the same roller.  (Top secret).

So I went and purchased an Akai M8 off Gumtree for R1 000.00. The lower head cover was missing, the box was in bad shape and the pinch roller had a crease or indent in it where the capstan had been running against it – the process is always to switch the motor off, there is a slide switch for this purpose. In any event…

Slowly applied 60V DC from a variable PSU to the high tension section of the amplifiers to form the still original electrolytic capacitors and then with a 100W bulb in series with the live input applied power. No shards of electrolytic anywhere, things looking good. Then  apply full power by removing the current limiter and still no explosion. Lights on, action, camera.  High tension at 230V. Very little residual hum. Microphone input worked, much distortion.

Next I purchased another M8 off Gumtree and managed to drop the seller from R2  000.00 to R1650.00. My intent was to get one good condition M8 out of the two. This one looked the worse for wear but strangely enough besides using one round knob to control the record and play function and a volume control knob missing this one was amazingly enough still in very good nick except for the pinch roller which was hard as a rock.

Before moving on I do need to show you something which is after all the very reason why we discard the mechanical parts and use the electronics as raw amplifiers.

 

Head block - M8 A Akai M8 Restoration
Head block – M8 A (bottom two heads erase and playback with the head opposing the playback head being the crossfield bias head)
Head Block M8 B - Akain M8 Restoration
Head Block M8 B

Although both these head blocks are filthy they are actually in a remarkably good condition.  (once we have cleaned them of course). The giveaway which makes the bottom image head block look in such a disgusting state is not rust but the tape oxide from lots of use and no cleaning.  I have cleaned tape heads and path for the last 45 years with meths (denatured alcohol) and have never had a problem. Purists will say you need to use isopropyl. By all means use what ever floats your boat.

Akai M8 Restoration – What is recapping?

Although I do believe that some of the older equipment on the market used a better quality of electrolytic capacitor compared to the common and garden variety purchased at your local electronics convenience store it is sometimes advisable to replace all the electrolytic capacitors in the circuit.

Electrolytic capacitors do have a tendency to dry out and become ineffective.  In this case we removed and replaced all the electrolytics in the high voltage section as well as the cathode bypass capacitors for all the tubes.  We kept the split reservoir capacitor in place to act as a mount for the two individual capacitors in the smoothing section using a 22u 350V pre- choke and all the rest 33u 350V after.  Bypass capacitors 25u 25V were all replaced with 22u 25V.

Akai M8 Amplifiers - Akai M8 Restoration
Akai M8 Amplifiers – about to begine the restoration.

Part Two – the process

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.

The weird art of Interfacing

Denon DN-500AV

The weird art of Interfacing

Years back we had the DIN plug and socket, often for interconnection between tape deck REC/PB or turntable.

DIN Socket
DIN

These were dreaded in that users would pull the plugs out by the leads (and had cheap-arsed plastic back ends) and were tricky to re-solder usually ending up like mosquito shit at the joints.  Although these were very popular professional audio had long time been using TRS and XLR plugs and sockets. But DIN still is used for MIDI.

XLR Socket
XLR
TRS Jack
TRS Jack

The TRS (Tip Ring Sleeve) could be used for inserts as well as stereo.   By inserts we mean that once the jack had been inserted completely it would break the circuit inside a mixer, take the output side (hot) into an effects unit and then be returned via the ring – or one could partially insert the jack to only act as an insert without breaking the circuit.

The XLR was usually used in balanced line topology for microphone (or line) to reduce noise.

The weird art of Interfacing – loudspeakers

Speakon for loudspeakers
Speakon

Modern amplifiers can be extremely powerful, such that the voltage across the speaker cable easily surpasses 100V peak-to-peak.  This can be dangerous for installation technicians when troubleshooting live.  The speakon isolates any uninsulated wiring.

Now just assume that you aren’t an avid follower of diamond crusted or gold braided speaker wire and all amplifiers and loudspeakers had a speakon as a terminal connector.  Wouldn’t this just be easier than connecting wires to terminal posts, soldering banana plugs onto wires which plugged into the rear of speakers or having to use 6.3mm jacks into the rear of speakers. The live element is not exposed and cannot short against anything. In most cases of premature amplifier failure it’s due to this very reason and of course transistors self destructing into a 2 Ohm load.

RCA Socket
RCA Socket

The dreaded RCA socket – how many times have you fiddled around with a stereo or home theater system to get one of the channels working only to find that the damned RCA patch cord is open circuit. They serve a purpose but in all honesty its time we moved on.

But the reality is…

Limited space, trying to make things smaller and of course reduce shipping charges. All this results in a cheaper commodity for the end user.

Have you noticed that there are home theater systems with only preamplifier outputs designed to drive a balanced line to audio power amplifiers of your choice. These cost more than a fully blown 7.2 channel pre- and power amplified system.

Denon DN-500AV
Denon DN-500AV

This one is a beaut – for the home theater specialist who can now select his own power amplifiers which will never go out of fashion and will have speakon connectors. Yes, strangely enough many modern professional audio amplifiers, even rated upwards of 400W RMS per channel will set you back less than a moderately priced home theater system with power amplifiers.

And that concludes this part of the article and also a good reason to determine just exactly you really want. I go with XLR, TRS and speakons every time. If it works for the recording industry and live bands it should work for you too.

Beginning your analog dream – the Otari MX5050

Otari MX5050

The Otari MX5050

I am fortunate enough to own both a Zoom H6 and an Otari reel to reel.  When one looks at the technical advances in the recording industry be it for home studio or a multi-million Rand setup there is just no comparison between the analog of the 1960s to early 1990s and the modern digital installation. The H6 is virtually a home studio in the palm of your hand.  And lets not talk about price.

Otari MX5050
                             Otari MX5050 B2

Whilst the Otari comes in various models, some even being 8 track it is still one of the favourites amongst the home collector, along with Pioneer, Teac, Technics, Akai, Revox and Studer.  And no, this list is or should be infinite because each for his or her own.

A well maintained machine, which includes new or lapped heads is a crowd puller.  The question that arises is it because most of the crowd were born post 1990 or is it the quality.  I know of umpteen people that have never heard or even seen a reel2reel. Is it truly vintage and what determines whether something is vintage or not?  In a race against time, setting up the H6 is a breeze and the quality of reproduction will always surpass the Otari, even the highly ranked Studer.  That’s my opinion.  Try to over-modulate the H6 and we end up with one hellava mess. The reel deck is going to beat it hands down.

This is called record slam – pushing into saturation. We have all heard of the wonderful advantages of tube over solid state when it comes to distortion right?  Well it just so happens that some musicians like to slam their recording. You just don’t get the same result with digital.

So is record slamming the only advantage of R2R?

Zoom H6
Zoom H6 – 6 Channel simultaneous recorder

No, it’s not all doom and gloom – reel recorders have their place. We’ll move on later to the real Otari and why people buy open reel recorders.

Index

Analogian definition

Isidore of Seville
Etymologiae
Book II: Of Rhetoric and Dialectics

The tenth kind of definition is that which is called in Greek kaka analogian and in Latin per analogiam or iuxta rationem (according to reasoning), as when one asks: ‘what is an animal’ and the answer is ‘like a man’. The example given identifies the thing looked for. It is proper for definitions to clarify the thing that has been queried.

Make sense? Not to me. We do however know that logic prevails and that an analog signal can be derived from a digital signal at the expense of ‘stuff’.

Recent Posts


Stepping on the toes of DAT, CD and DVD

Time Warp CDP101 First CD Player

Speculation about Vinyl – is it really better quality than your cheap CD

The precursor

There is lots of speculation as to whether vinyl is really better than CD quality when it comes to audio reproduction.  To put more simply, are analog presses or recordings psycho-acoustic? Modern television standards have become so advanced that 4K already shows it’s limitations.  Where do we draw the line between marketing and reality? Is our eyesight really all that good? How about those that can hear 384kHz.

If the shortest distance between two points is a straight line and the best electronic circuits are the simplest, which does imply a straight line then CD can never sound better than a straight analog sound system.  But…

The problem is that the digital media/medium used is cheaper, from raw material to transfer of data to resale and now we have the marketing department.

My first CD player was a Sony CDP1, purchased I think in 1984 at a cost of about R800.00.  (off the shelf in Yokohama but going stale by then). By modern standards it was pretty modest but the sound quality was amazing. Sadly it went bust when some geek forgot to use the 220:110V step-down.

Time Warp CDP101 First CD Player
By Atreyu – Own work, CC BY 3.0

Cue’ing a CD

DJs in the 80s must have seen the beauty of these devices from the outset. Quick setup, no feedback, fast access and no scratches. We had endless blasts, the Sony was reliable but the disks weren’t. The backing started to flake off two disks, both Island Records – Grace Jones and if I recollect, Jimmy Cliff. So they weren’t indestructible after all.

So, when is a CD a mastercopy?

The big issue with CDs and DVDs from an audio standpoint is the processing which takes place.  Sampling, bitrates, DACs – all to get an analog signal.  Logic tells us that a digital copy is a perfect copy. Right? Not really but it certainly should be better than a copy of a vinyl to tape recording.

Modern CD players have become throwaway cheap – not the turntable though. Turntables, even modest units are starting to become expensive. Reel to reel tape recorders which were virtually thrown away ten years back are now are now sold as rare high fidelity devices.  And now our problems start.

Good quality analog recording and vinyl reproduction is exorbitantly expensive.  Digital may have its drawbacks but it will always outperform an entry level or even mildly expensive cassette or reel to reel deck in quality and bang for buck.  What analog sound does have is depth creating that warm fuzzy feeling, that feeling of time travel and His Master’s Voice. Maybe noise, pops, crackles and a few other bits and pieces not tied into the original but we just love it. Or so we should.

Our motto:  “the more things change, the more they stay the same”

From bits to bytes to sampling, over-sampling and converters. The outcome will always be analog. Portable media in digital format will always be the winner.

 

Hello Analogians

Fellow Analogians!

Welcome to the Analog Ian website. Tired of minuscule energy grabbing circuits, gigahertz switching architecture, DACs, ADCs, bits, bytes and nano-particle amplifiers? This is then the site for you – valves, tubes, bottles, psycho-acoustics. Reel to reels, cassette players and turntables.

Officially up and running only on the 1st of January 2017.