Ampex electronics for the best possible sound

RogerD · Mar 20, 2011

Thanks Tony,

The 3741 power supply has been rebuilt. New caps,multi stage,selenium rectifier has been replaced with a diode in both units.

RogerD · Jun 17, 2011

Just a update on the Ampex MR70 project. After restoring the relays,variable speed switches and power supply, the transport is running just as it should. The Ashland Electic reel and capstan motors have been sent to me and will arrive next week. I have contacted Ashland and they can rebuild them for me to orginal specs,which is fantastic news. Next is having John at JRF Magnetics build a set of heads for the 1/4 headstack and aligning and do the required setup. This project has been rewarding for me because I have sourced all the parts for the restoration. Once the motors and headstack are done then the transport ships to me and I can place it in the original console and attach the cables,electronics and do the calibration.

This particular MR70 has the 1/2" motors that can also be switched to 1/4 inch use,so some day I have the option to acquire a 1/2 inch headstack if I want. I also have an original 1/4 inch transport that could be restored at some point. My tech is sending me a DVD of the working transport,so I will post that soon. There were only 75 of these machines manufactured and through my own research I have found that almost all of the major parts are still available.

I was lucky enough to find a true gentleman that has a wealth of knowledge and experience with these machines and without his help this project could not have been possible.

MylesBAstor · Jun 17, 2011

RogerD said:
Just a update on the Ampex MR70 project. After restoring the relays,variable speed switches and power supply, the transport is running just as it should. The Ashland Electic reel and capstan motors have been sent to me and will arrive next week. I have contacted Ashland and they can rebuild them for me to orginal specs,which is fantastic news. Next is having John at JRF Magnetics build a set of heads for the 1/4 headstack and aligning and do the required setup. This project has been rewarding for me because I have sourced all the parts for the restoration. Once the motors and headstack are done then the transport ships to me and I can place it in the original console and attach the cables,electronics and do the calibration.

This particular MR70 has the 1/2" motors that can also be switched to 1/4 inch use,so some day I have the option to acquire a 1/2 inch headstack if I want. I also have an original 1/4 inch transport that could be restored at some point. My tech is sending me a DVD of the working transport,so I will post that soon. There were only 75 of these machines manufactured and through my own research I have found that almost all of the major parts are still available.

I was lucky enough to find a true gentleman that has a wealth of knowledge and experience with these machines and without his help this project could not have been possible.

Do you have 1/2 inch tapes or just want for recording purposes?

RogerD · Jun 17, 2011

Hi Myles,

I am a much smaller version of Ki

, just a severe fetish for reels that go round and big lighted meters. Seriously, I have some 1/2 tapes that I have recorderd with my Studer A820.

RogerD · Jun 17, 2011

Ampex MR70 is Working

Hi,

I received the DVD that Charles made of the MR70 and posted it on you tube. As you can see it's a very large machine,about the size of a Studer A820. I need to source a better or NOS turntable platter dustcover, but on the whole the deck is in pretty good cosmetic shape.

Charles Richardson

has done a tremendous job getting this transport in good order. I need to thank Steve Puntolillo

,Dave Dintenfass

and Jay Mcknight

also for there help in the restoration.

U47 · Jun 17, 2011

Beautiful rebuild on the 350s- that is the way to do it!

R Brown

RogerD · Jun 17, 2011

Thanks Rich, hopefully they get done and picked up next week.

RogerD · Jun 17, 2011

U47 said:
Regarding MR-70s- I brokered 3 for my old tape mentor about 15 years ago. I spent dozens of hours listening to his MR-70 over a 10 year period. Brings back good memories. He had a technician come in about every 3 weeks from NYC to keep one up and running. It was a fantastic sounding deck, but a bit like keeping on old English 50s sports car in top shape. Not for the beginner

R Brown
Portland Oregon

From what Charlie has told me about the MR70 was that Ampex over engineered the transport and the relays created heat as they would arc and the reliability suffered. Charles has used,modded,and rebuilt the MR70 spanning when the deck was made to the present time. The original rocker type switches used in the MR70 were unreliable, they then went to the switch design that my transport has. They also used a high current internal switch that effected the reliability of the 8 or so telephone type relays. Charles describes the benifits of bypassing the switch:

"With the change, they either do not arc or greatly reduce the arcing of the relay contacts, making the contacts last longer, run cooler and result in less current draw from the power supply. Also the change reduces pops, clicks, and ticks in the circuitry which helps make Play and Record functions quieter. The radiated magnetic field from the coil is less and this reduces hum pick up. This new change improves on the original machine design."

I am hoping he is right when he assures me that the few changes made will extend the life and decrease maintenance issues.

I have had trouble free hours on my Ampex 440 since it was purchased 2 years ago. I cannot say that about my Studer A820, but maintenance issues do come up with most reel decks sooner or later.

RogerD · Jun 21, 2011

Yippeee! Fred Thompson just called me and my 350 electronics are ready to be picked up tomorrow. Fred said the sine wave passed is perfect,really sharp,so I am extremely excited. Will post photos later.

naturephoto1 · Jun 21, 2011

RogerD said:
Yippeee! Fred Thompson just called me and my 350 electronics are ready to be picked up tomorrow. Fred said the sine wave passed is perfect,really sharp,so I am extremely excited. Will post photos later.

Roger,

Congrats on Fred completing the 350 electronics. I look forward to the photos.

Then it is on to our 2 project Ampex R2Rs by Fred.

Rich

RogerD · Jun 21, 2011

naturephoto1 said:
Roger,

Congrats on Fred completing the 350 electronics. I look forward to the photos.

Then it is on to our 2 project Ampex R2Rs by Fred.

Rich

Hi Rich,

My main goal is to get your project done on time and for the sound to be better then the RTZ

RogerD · Jun 23, 2011

Just picked them up!

naturephoto1 · Jun 23, 2011

Hi Roger,

The amps look great and remarkably clean especially for being about 50 years old. How do they sound after all the work?

Rich

RogerD · Jun 23, 2011

naturephoto1 said:
Hi Roger,

The amps look great and remarkably clean especially for being about 50 years old. How do they sound after all the work?

Rich

Hi Rich,

Wayne just shipped the transport today. I am going to run them through the tape section and use them as a tube preamp, before I had Fred do the recap,they sounded very good,but the other tech couldn't find a bad cap(s) and resistors. When I get the transport then I will be able to play tapes as well.

I will post a listening report a little later.

mep · Jun 23, 2011

Roger-They look great. I will be interested to hear your opinion after you listen to them. My 350s are all original and they sound so damn good I really don't want to touch them for fear they may not sound as good after the mods. The only thing that I have replaced is the mult-section filter caps on the outboard power supplies. The cool thing was that Ampex socketed the filter caps so all you have to do is pull them straight out and plug the new ones in.

Mark

RogerD · Jun 28, 2011

I received the 440C transport with the 2T4T headstack from Wayne yesterday,very nice. So I am waiting to get the 350's back from Fred. The bias circuit wasn't correct as the previous owner had it modified. So I am having Fred return it to original specs. I hope to have this project finally finished later this week.

RogerD · Jun 28, 2011

" Originally Posted by RogerD
I hear ya, after I finish my Ampex project the A820 is next."

c1ferrari said:
What are you contemplating

I have purchased a set of extra Ampex 440B electronics as I needed a set of original cards anyway and also to have a set for my "RTZ" cards.

I will probably use these as an experiment with my Studer A820 1/2 inch deck, just to see how the RTZ cards compare. Also I could duplicate the AL/BG cards if I wanted to.

I'm starting to feel like a mad hot rodder version of Ki......big trouble!

Update:

After hearing the AL/BG cards, I am really impressed with the AG440 platform. It is compact,very clean, and extremely versatile. I will over the coming months have duplicated another set of the AL/BG cards and have a very nice solid state tape preamp.

RogerD · Jul 6, 2011

I have been doing some research on my StuderPex A820. I can source the correct transformer so I can use the Ampex electronics as a play only preamp for the Studer. Also I can upgrade the stock reproduce and record cards for the A820. This project will be the last for me,but I expect it to be the best. Being able to switch between the Studer and Ampex electronics to do a ABX should be lot's of fun.

RogerD · Jul 14, 2011

I came across this AES paper on Master recorders, good stuff.

http://www.ilk.org/~ppk/Manuals/Ampex_Misc/Ampex-AES_papers.pdf

RogerD · Aug 1, 2011

Ampex MR70 and beyond

I will have my Ampex MR70 capstan and reel motors done this week. There has been some discussion about the tolerance of bearings used in motor rebuilds for studio decks. Some say it doesn't matter because these machines as they wear and age the original specs or tolerances don't need to meet the design and specs of these original motors.

The Ampex MR70 motors were made by Ashland electric. These motors have "aircraft" bearings in them,Hi speed and ABEC7 tolerances. If I want my machine to have low wow and flutter these quality bearings must be used. Btw these bearing are extremely rare and no longer made.

I will also have the capstan flywheel back soon after having new rubber bonded. The flywheel rubber will have the correct durometer and meet original specs also.

Also I have purchased all the components for my "Studerpex" electronics. These electronics will be SOTA to go along with a SOTA transport. I have purchased my first 1/2 inch master recording so I am eagerly awaiting it's arrival.

A side note I requested a quote from Ashland for new motors. The price was quite a bit more than the original cost of the entire transport. Amazing!

Ampex electronics for the best possible sound

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