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Ideas for Ampex 600 Series
Old 23rd January 2013
  #1
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noah330's Avatar
 
🎧 15 years
Ideas for Ampex 600 Series

I picked up a pair of Ampex 600 series tape machines really cheap a few months ago. One has an input transformer, the other one does not.

I bought a little XLR plug to do the required pin swap and have an external phantom power box that I have experimented with as well.

Usually I do not need it as I am using them with some Mojave tube mics.

The sound is nice, although it's a little noisy. I have adjusted the record and hum pots, so there is not a lot of hum or anything. My thoughts are the tubes should probably be replaced.

I have found that the one with the transformer overdrives easily, so I have ordered a pad for it. The one without the transformer does not have the octal socket, it just has a plate screwed on top of the chassis.

I have searched around for information on these and aside from finding people who will mod them I can't find much.

I would like to remove the tape machine circuitry and find a source to replace the large capacitors on the top of the unit.

If anyone can suggest any simple mods to these I would be very appreciative. I have done simple tube amp maintanance (caps, pots, tube swaps, etc...).

All I would like is to use them as mic pres, which I am doing now, but before I go changing tubes I would like to know which tubes work for the line portion and which are for the tape portion so I don't waste money replacing tubes not in the signal path or if there are any neat tricks for these.

Here are some pics:











Old 24th January 2013
  #2
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noah330's Avatar
 
🎧 15 years
My question (and I will reference the schematic below) would be I am thinking I need to disconnect one, three and four from the red block below to remove the bias control and the erase controls. It looks like I need to leave 1 connected, as it is a ground (is this right?)

Then I can disconnect the tape playback by leaving the switch on input (which is what I am doing). I can unsolder the tape side and then remove that section at C2.

Am I way off or am I at least on the right track? Any help would be amazing.

Thanks!

EDIT - I see now that the whole connector can be removed as power comes not from the harness but from C1. That being said, I suppose I would remove the harness then the connection @ C16 and at the switch?

Old 25th January 2013
  #3
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Radardoug's Avatar
 
🎧 10 years
You keep the playback amp, remove the frequency shapiing components, and use it with jack input as a high gain d.i.
Old 20th February 2013
  #4
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noah330's Avatar
 
🎧 15 years
I finally got around to doing some work on this. A good friend of mine from college is an electrical engineer and I sent him the schematic and some questions.

I sat down one Friday evening and removed all the tape machine electronics. It was not that difficult.

I kept a pair of headphones and a mic next to me and after I disconnected something I would see if everything still worked. At one point I unsoldered some things I shouldn't have and was able to find the problem and get things working again.

It was a lot of fun and since doing it I'm a lot more comfortable reading schematics and about halfway through everything clicked and it became really enjoyable and I felt like I actually am starting to understand everything I have read about tube electronics.

If any novice 600 series users need any info on how to do this feel free to shoot me a PM.
Old 20th May 2014
  #5
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Tardo's Avatar
 
🎧 10 years
Ampex 600

Hi,

was really interested to read of your experience. I've just purchased an Ampex 600 as just the preamp and mine had a transformer fitted, and mine too overloads at the input too easily. I particularly interested in your idea of adding a pad - I have a very basic knowledge of modding gear, but not high voltage stuff. Would this be a simple mod do you think? And what sort of component - a resistor of some sort I assume. Or maybe the transformer is inappropriate?
Old 29th April 2015 | Show parent
  #6
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noah330's Avatar
 
🎧 15 years
Quote:
Originally Posted by Tardo ➑️
Hi,

was really interested to read of your experience. I've just purchased an Ampex 600 as just the preamp and mine had a transformer fitted, and mine too overloads at the input too easily. I particularly interested in your idea of adding a pad - I have a very basic knowledge of modding gear, but not high voltage stuff. Would this be a simple mod do you think? And what sort of component - a resistor of some sort I assume. Or maybe the transformer is inappropriate?
You can buy a pad and just stick it in. You can make one, but I just bought one.

Hosa ATT-448 Input Attenuator, XLR Female to XLR Male, New
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