Gotham Audio Studer C37 60HZ 1960’s

RogerD

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May 23, 2010
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BiggestLittleCity
#21
Some photos of the playback preamps 1026181345.jpg
 

RogerD

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May 23, 2010
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BiggestLittleCity
#22
Hi Roger,

Thanks for the C37 rack info. I had been using a Rubbermade rolling cart that fits almost perfect for C37 on the top section and a shelf underneath to place a PS Audio Power Re-generator P1000 with the Multiwave II option for going from 60Hz input AC power to 50Hz output power with me adding a 110V to 220V step up transformer inside the P1000 to feed my European C37 at 220VAC 50Hz. I can change the output frequencies in 1 Hz increment and it's been an excellent remedy for varispeed needs with some of the old tapes that were recorded with slight variance in speeds.

Congratulations on getting your US C37 finished.
Thanks Ki and yours sounds like a nice setup....Congrats a well.
 

RogerD

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May 23, 2010
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BiggestLittleCity
#23
The C37 was originally owned by RCA in NYC and they tinkered with a few things. The machine uses 4 relays for NAB and CCIR and specialized EQ. All the caps are German Roderstein / Vishay, resistors are all Low Noise metal film 2%.. I am trying to keep it as stock as possible. 1026181345ab.jpg
 
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RogerD

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May 23, 2010
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BiggestLittleCity
#24
I was talking to my tech and found out some real interesting improvements that can be made to the record and playback preamps. So I told him to do his magic....exciting. There are several impediments in the signal path on all the preamp designs which are now 60 years old. So the result will be a much cleaner and more powerful signal which will enhance the sound of tube compliment, which is excellent and with the improved EQ, bias levels.
 
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RogerD

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May 23, 2010
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BiggestLittleCity
#25
Here's the record preamps with swapped out transformers replacing the inadequate Beyers. Just one of the upgrades Dan is doing for me. These transformers will make a overall big difference and these had excellent specs. 1101181625.jpg
 

RogerD

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May 23, 2010
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BiggestLittleCity
#26
With New capacitors.
 

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May 2, 2012
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Munich - Germany
#27
The sound is really amazing
If you listen modern music the bass is no good like A80 and other less old and high is little roll off vs A80 and A816 and 820
but for jazz and classic music from mid bass to mid high the sound is magic,very natural,dynamic and impressive

The price for rack i don't remember but tomorrow i ask to Fabio Liberatore,owner of therecorderman,or you can send mail to him
Which audio heads of Studer are you using, Butterfly ones or the standard heads?

Best
airbearing


https://audiocirc.com/2018/04/30/tape-is-my-love/
https://audiocirc.com/2014/05/05/the-holy-grail/
https://audiocirc.com/2015/07/05/c3...ly-head-set-as-well-as-with-the-standard-set/
 

RogerD

Active Member
May 23, 2010
3,224
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38
BiggestLittleCity
#28
Did away with the paper and oil Bosch 4uf caps.. FDA99498-9205-4A9E-9E0F-51D8869FC027.png
 

RogerD

Active Member
May 23, 2010
3,224
14
38
BiggestLittleCity
#29
About done.....minor issues

 

RogerD

Active Member
May 23, 2010
3,224
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38
BiggestLittleCity
#30
Cleaned up very nice .
 

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Likes: Skylab

RogerD

Active Member
May 23, 2010
3,224
14
38
BiggestLittleCity
#31
Cleaned up very nice .
Here is video I made stitching the small piece together.I over dubbed the music “Stairway to Heaven”. I currently feel that way, as I waited so long, it’s a gift from heaven.Coming home soon.
 
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Likes: Skylab

RogerD

Active Member
May 23, 2010
3,224
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38
BiggestLittleCity
#32
I heard from Dan Zellman today regarding the playback on the C37 . His reply below .Nice to hear from a tech that knows these recorders.
_____________________________________________
Hi Roger,
I'm amazed at the lack of flutter products in this transport. It sounds pretty good so far.It's closer to real NAB EQ than any other C or J37 I've seen .

Still; a few adjustments to EQ values will get that.
There's a 2+ dbboost at 32 Hz a half db drop at 500, up a half at 2K to 8K, flat at 10KHz down a half at 20KHz.15 IPS.

The Bass boost is easiest to deal with. It will be clearer when I start the record trouble shooting.
Also It's nothappy with dis-similar reel sizes.
There is also Head positioning I have yet to deal with. Next.

Dan

_______________________________________________
 
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RogerD

Active Member
May 23, 2010
3,224
14
38
BiggestLittleCity
#33
I heard from Dan Zellman today regarding the playback on the C37 . His reply below .Nice to hear from a tech that knows these recorders.
_____________________________________________
Hi Roger,
I'm amazed at the lack of flutter products in this transport. It sounds pretty good so far.It's closer to real NAB EQ than any other C or J37 I've seen .

Still; a few adjustments to EQ values will get that.
There's a 2+ dbboost at 32 Hz a half db drop at 500, up a half at 2K to 8K, flat at 10KHz down a half at 20KHz.15 IPS.

The Bass boost is easiest to deal with. It will be clearer when I start the record trouble shooting.
Also It's nothappy with dis-similar reel sizes.
There is also Head positioning I have yet to deal with. Next.

Dan

_______________________________________________
I forgot to mention the extremely low flutter...that’s why I supplied Dan with all aircraft spec ABEC 5 and 7 bearings. It does matter.
 

RogerD

Active Member
May 23, 2010
3,224
14
38
BiggestLittleCity
#34
Latest report on the C37

Hi Roger,
You may have guessed I had some issues with one of the playback amps. Still do but almost done. The EQs were pretty good Left channel is flat 32 Hz to 20KHz, plus/minus .5 db. Right channel is the same up to 10Khz but rises to +3 at 20 KHz. Most of the issues were around the speed relay and the relay socket. This relay is a custom, very non standard relay. It has 4 form A contacts and 2 form B contacts. Never even heard of this before. Normally they come with only form C contacts. I was able to rebuild it using a coil from a standard relay. I had to replace the socket as well. In order to find these issues I had to make a set of extender cables, power/signal and head connections, so I could trouble shoot the amplifier on my bench under power. I will include them in the shipment back. I hope to have the right channel hi end issue solved, over the weekend.
Dan
 

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