SA-134 frequency Correction

[ecaltd]

... while waiting on parts for the other projects on the bench I decided to revisit this one. A few years back I had a pair of these that I went through and re-capped etc..

One of them I racked up on a 3U shelf with remote gain an Daven attenuators on the output. Time to do the same with this one, additionally I will install a Hammond 369AX power transformer to make it worldwide compatible.

Question to throw out there is : has anyone changed the C9 and C13 values to get a different curve out of the unit ? What do you think about a two or three way switch to change the caps depending on the source material being amplified. If I used shielded cable to a front panel switch would that few inches of wire make a difference or would it be better to mount it on the chassis ?

gb

 

[ecaltd]

... which meter ???

 

[andYz00m]

I just went through mine and lowering Just the NFB resistor without the proper cap (C9) associated caused motor boating the final tube stage.

I too am about the rack up one of these and pan to just use the current gain pot and add a meter. The schematic doesn’t specify the buffer circuit for the meter or which meter model was used in the rack version. That being said I believe the Gates meters used in these were the big 3” Simpson models.

Doug would know.

Im curious how you did the out attenuator?

 

[ecaltd]

I just went through mine and lowering Just the NFB resistor without the proper cap (C9) associated caused motor boating the final tube stage.

I too am about the rack up one of these and pan to just use the current gain pot and add a meter. The schematic doesn’t specify the buffer circuit for the meter or which meter model was used in the rack version. That being said I believe the Gates meters used in these were the big 3” Simpson models.

Doug would know.

Im curious how you did the out attenuator?

I did the attenuator post output and meter post attenuator so you can get that lovely round distortion !