Ampex 351-2 restoration project

[Deleted User]

Hello,
I've recently begun restoring a classic Ampex 351-2 studio tape recorder that I've been collecting parts for over 10 years. Slowly accumulating NOS motors, head blocks frames, etc. This type of deck was used by countless recording studios to record every type of music you could imagine. The sound of Elvis, Frank, Hank Williams, Miles Davis and hundreds of other icons were captured by decks similar to this one. It was only after convincing myself that I had gathered enough experience with other pieces of gear that I would begin this project.
The 351 electronics is vacuum tube based with a 6X4 as rectifier and 12AX7 and 12AU7 used for the gain stages. I have three of these chassis and have rebuilt the power supply of the one I've shown.
In order to work on the bulky transport I made a rough rack frame on wheels so I can turn it around easily. The upper mechanism is the 351, the lower is another project a Scully 280B which is a solid state classic machine. The final version will go in a nice rack with the associated electronics.
Regards, Ken

madmax

That is really cool! I'm sure it will be a quality restoration by the time you are done with it!

ken brydson

https://www.youtube.com/watch?v=M0gzQS4w1sc

littlewoodboats

Awesome project. If you still need any parts shoot me a pm. The person who sold me my Revox had one with a few spares.

mhardy6647

Ken, not encouraging you to compete with the Tape Project or anything, but if you ever get the urge to make some dupes of any "safety copies" of any two-track master tapes you might have... well... be sure to let us know! ;- )

Very cool -- I try really hard to resist those "Pound Puppies" decks when they I come across them. Yeah, I couldn't resist a trio of shabby but functional Otaris, but so far the occasional Ampex or Scully deck that's crossed my path I've managed to resist. I would never do them justice -- but you can, will, and do.

Thanks for sharing these updates with us, sir!

[Deleted User]

Thanks for the offer @littlewoodboats, that's very generous. Mark, I'll be have to make a transfer using the SP7 to 351 for you. Maybe a sampler? I was listening to a 2 track Everest tape the other night and it sounded so convincingly real I was startled. Woody Herman on clarinet playing a Stravinsky's concerto.
The SP7 is spooky good.

mhardy6647

Haven't yet found catalog info on a 351-2, but the 1954 Radio Shack catalog :- ) lists, among many others, the 350-2. Note those prices in 1954 dollars; you could (literally) almost buy a house for that kind of money (in the Northeast) in 1954.


source: www.radioshackcatalogs.com (of course!) 1954

From Phantom Productions vintage catalog archive, in the year of my birth :-P



and from '59...

txcoastal1

I dig that remote

[Deleted User]

This article is an interview with James Boyk who has built the ultimate Ampex, known as the Magnesaurus. I know the appeal on a speaker forum is limited, but good audio gear is good audio gear.

http://www.its.caltech.edu/~boyk/rep-int.htm

Enjoy, Ken

mhardy6647

Loves me some magnetic media!
That was an excellent little vignette; thank you for sharing it.

I always enjoy the intersection of music and recording technology -- Pete Townshend of the Who was a big recording/studio gear head,at least in his younger days. He took recording very seriously. A listen to his early solo work (i.e., his excellent and very un-Who-like album Who Came First) provides some evidence that he was pretty good at it, too.




Gotta love that pair of G36s up on the wall! :- )
(EDIT: oh, and the Nagra behind him, too!)

Ken, do you have a G36 (or two)?

mhardy6647

Just looked at the link to the Magnesaurus' specs:

Frequency Response: ± 1/2 dB, 23 Hz to just under 15 kHz;
-3 dB at 18 Hz and 22 kHz,
-6 dB at 13 Hz and 30 kHz, at 15 ips at 0 VU (230 nW/m ANSI, 250 DIN). Recorded on 351.5TM, played back on mastering deck at The Mastering Lab, Hollywood, as for Lp and CD transfers.

whoo-hoo!
Gotta like that zero VU bandwidth!

To quote Will Smith from ID4":

"I have got to get me one of these!"

[Deleted User]

That's a great photo, you can see a bulk eraser on the left and a 3 channel 3M deck on the right. I'm afraid I don't have any G36 decks and I could have. Many years ago a good friend offered one to me for free. At the time I was enamored with Japanese tape decks, namely Sony. I thought who would want something that used those old tubes so I declined. Dumb move on my part, that's for sure.

mhardy6647

This thread needs a bump to keep it in fressh in folks' minds and near the top of the recent messages list :- )





We might never have had reel to reel tape in the Free World if it weren't for Der Bingle.

mhardy6647

mhardy6647

more photos & tales Mr. Swauger, more, I say! Tell us more! ;- )

P1030132 by Mark Hardy, on Flickr

[Deleted User]

Well, I'm trying to do two things at once (never a good idea). I'm trying to get the transport functioning as well as two amplifiers. For the transport I have to take the control switches off of another deck and clean them up and transfer to the main deck. The transport switches can be difficult to take off because there is a knurled nut on the outside and they can be tough to take off without scratching the faceplate. I made a thin open ended wrench that I can loosen the position nuts on the underside of the main plate. So, once I take away the pressure from the threaded shaft I can loosen the knurled nuts. I did find a guitar repair shop online that sells a clever looking tool to take knurled nuts off more easily.
As to the electronics, two of the 351 amplifier chassis I have someone previously removed the tube socket for the rectifier and substituted two diodes and a resistor. I need to find some 7 pin tube sockets that fit the PCB. Most tend to be too small.
The 351 amps have become something of a sought after device for using as a microphone preamp. This accounts for their very high selling prices, but on the good side it means there's a cottage industry for enterprising aftermarket guys. Here's a link to someone selling (I've received them and they're beautiful) all three of the PCB for those who want to replace the originals.

http://www.recordingwithgas.com/GAS_351_PCBs.html

In the photo you can see the old PCB board that I've stripped and cleaned as well as the inside of the other main transport.
Regards, Ken

mhardy6647

Not trying to rush you on your project, Ken! Just trying to keep this thread near the top of the heap. I (and I think a few others here) really love the vintage decks, and I (at least) get some vicarious satisfaction out of seeing your exploits in living color.

Thank you very much for sharing your updates!

These old workhorses, like WWII-era military and civilian "boatanchors" (radio receivers and transmitters) are just so beautifully made.

[Deleted User]

Not a problem, Mark, believe me I appreciate any interest, it gives me the incentive to keep working. Here is a photo of the three replacement circuit boards, the power supply, playback and recording including bias circuitry. There are also two Beyer "peanut" transformers that I'm hoping will work with lower impedance heads. My goal is to be able to use older high impedance heads directly into the 351 and newer low impedance heads into the two transformers.
Keener eyed readers will see on the left side of the schematic two pathways from the playback heads. One is for high impedance and the other is for low. Evidently Ampex had to use low impedance heads for some of the multi-track applications where long cable runs were used.
Modern tape playback amplifiers such as the well respected de havilland Model 222 use an FET for low impedance heads. This is all very similar to high and low output phono cartridges needing different gain approaches.

txcoastal1

DSkip wrote: »

There is next to nothing I'd listen to on the format,

But you have to admit all though the music was not your flavor, it did sound sweet on Luther's R2R setup

Of course these were 1st run tapes

Thanks Ken

mhardy6647

You might feel differently if you acquired one or two copies of 'safety backups' (or, for that matter, the early-generation copies of masters that got sent out for the production of lacquer masters) of the original master tapes of albums that you do like.

They're around -- they're not cheap, but "chance favors the prepared mind".

[Deleted User]

That's how I got interested in this whole side of audio, buying safety backups and 2 track tapes from people like Rich Brown and the "Reel Lady". In fact that was my wife's wedding gift to me, a two volume copy of Bach's unaccompanied cello by Janos Starker. At that time all I had was my trusty Sony TC-850 which I bought as a Sony employee on Okinawa. I went through every circuit path and replaced all of the electrolytic capacitors with tantalum capacitors (bad move). When I understood better what I was doing I re-replaced everything with Black Gate capacitors. Also replaced every resistor with Roederstein metal film resistors and every inch of internal wiring with Cardas in a complex star grounding pattern. So each connecting wire had a grounding lead that took it to a grounding buss. Took me well over a year to get it done.
Then Rich suggested I buy a high speed A77 and I found one and went through the same process, instead I could use film type capacitors since there was more room. I ended up owning five A77 and learned everything I could about how they work. Then I got the Revox PR-99 and a second. In the meantime friends gave me their old Teac machines, now I have two of those. I added a beautiful condition Crown deck and a couple of Tandbergs. Then I got a Stellavox SP7 from Charles King and that was the best sounding deck I've ever heard, unbelievable. But the problem is that it doesn't rewind or fast forward very well.
I can't afford a Studer, now that the Tape Project and others are releasing these master tape copies the price on Studer decks has skyrocketed. People use these in combination with de haviland amps or Manley or build the Bottlehead Eros as a tape playback amp. I have 12 of the Tape Project tapes and I've only listened to 2 of them, the rest are waiting for my ultimate deck to arrive. Kind of like Sleeping Beauty waiting for the prince.
Champagne taste and a beer budget and I want it to look brand new.

mhardy6647

Charles "Stellavox" King built my high-speed A77 for me from a trio of organ donors (two I had and one he acquired for the job) :- ) -- but I think I told you all that before, probably multiple times!

Ken, that's a great memoir; thanks for sharing it with us!

I smiled broadly when I read about your tantalum re-cap of the Sony! ;- )

Do you have an Otari?

I still have one spare in the basement if you'd like one -- it'll need some TLC*, but it does work and it's got plenty of... potential ;- )

DSC_0056 by Mark Hardy, on Flickr

(Actually this is the other spare deck I had -- which I gave to one of the MA-area vacuum tube hifi gurus, who mostly wanted the cart. The other carted one I have is actually in slightly better cosmetic condition than this poor ol' soldier)

* The two spares were both in "rode hard and put away wet" condition :-P

EDIT: This thread is reminding me -- THIS winter I need to grit my teeth and rebuild my RT-909!

mhardy6647

speaking of Studers :- )

[Deleted User]

Ah, the sin qua non of transports, I messed up not buying one when NPR closed down the DC facility. They had a sealed bid auction, I was too cautious (read poor).
Many people run Otari decks into Model 222 playback amps. I keep seeing them on CL, they used to go for small sums, now people have caught on.
The current "hot tamale" is the Lyrec Frida from Scandinavia, if one shows up at your salvage emporium, please let me know.

http://museumofmagneticsoundrecording.org/ManufacturersLyrec.html

Enjoy, Ken

[Deleted User]

Since we're dreaming, another choice is the Ampex ATR102, the last analogue tape recorder built by Ampex. The transport is so sophisticated and gentle there's no pinch roller. The tension on the two motors keeps the tape in perfect contact with the heads.
In fact the number one company for refurbishing them is right up the road in York, PA.

http://atrservice.com/

Until his untimely death Mike Spitz was the owner of ATR Services, now his wife and son are running the company. Real shame, years ago I called him on the phone and bent his ear about tape recorders and how I would be a real great employee. He was nothing but gracious and gently offered to keep me in mind. Real shame.
Cheers, Ken

littlewoodboats

I always enjoy following your projects Ken. Like Skip said above I just never have anything productive to offer. I get to tinker vicariously through your threads. Cool stuff.

mhardy6647

I think we all do (tinker vicariously through Ken's threads, that is); well put!

pitdogg2

DSkip wrote: »

Ken, I always enjoy these threads. I just have no input to offer. In the case of r2r, I have no horse in the race... Literally. There is next to nothing I'd listen to on the format, so the knowledge you share is about as close as I get to it. Keep it up. We are all voyeurs of your trek.

well said I too am in that boat...

question Ken do you ever find that the wiring insulation on that old wire coming off or about to come off. Reason I ask is every piece of gear I had found back in the day the wiring insulation was gummy, loose or gone or if it looked good it was one breath away from FIRE....

[Deleted User]

Actually I've been fairly lucky. I've worked on some really old McIntosh tube gear and the wiring was still pretty good. I've had a tape deck that was completely covered in an oily gritty coating as if a motor run capacitor had leaked oil. I've found dead spiders and bugs and plenty of grunge but the wires had been fairly good.

mhardy6647

In my experience, and FWIW, I don't routinely run into wire problems until the units date back to the 40s or 30s... although old rubber-insulated power cords definitely don't hold up well!

littlewoodboats

What are the different coatings that have been used to insulate wire? Is there a timeline of insulator by date or are there types that should be replaced regardless?

I am looking for an old radio to restore for out in the shop. Knowing more about the wiring I am looking at would be a good thing. Thanks