Need help adding output transformers to an ADC ss-1 EQ

[Vyvyan]

I would like to add 1:1 10k output transformers with a level control. Can I replace the termination resistors on the outputs with a 10k pot driving a transformer w/trs outs?

 

[abbey road d enfer]

I would like to add 1:1 10k output transformers with a level control. Can I replace the termination resistors on the outputs with a 10k pot driving a transformer w/trs outs?

I would not recommand it, because a transformer should be driven with the lowest possible source impedance, otherwise the frequency response and distortion may degrade.
You could put tehepotentiometer after the transformer, though.
But what do you want to connect it to? And why add a transformer?

 

[Vyvyan]

Thanks, i would be connecting it to the line inputs on my antelope audio discrete 8. im always perplexed when these forums seem to praise the color and character of transformers, but always ask why someone wants to use them?

i have a lot of parts, im a bit of a hoarder collecting old broken gear so i have somewhere around 100+ old transformers (tamura, hammond, mci/sony, carnhill, altec, freed, berlant etc,,,) ive used many for ground up builds such as API/neve/hileos and tube builds to great success and i have a lot of old consumer gear id like to experiment with like these EQ's. now im not expecting some mastering grade EQ. ive got plenty of plugins for when i need something transparent. i mess with analog for the dirt and color.

so i think ill try some transformers with pots on the secondary, but am i right in thinking it best to remove the 10k resistor?

 

[abbey road d enfer]

so i think ill try some transformers with pots on the secondary, but am i right in thinking it best to remove the 10k resistor?

R119? Yes.

 

[Vyvyan]

yes r120 and r119. and i 10k pot on the secondary seems proper? ive seen schematics with 10k pots, but have also seen some with 1k pots on the output of a 10k optimal transformer. i will give this a shot tonight thanks!

 

[Newmarket]

Thanks, i would be connecting it to the line inputs on my antelope audio discrete 8. im always perplexed when these forums seem to praise the color and character of transformers, but always ask why someone wants to use them?

Well tbf everyone is an individual. Not everyone is a fan of transformer "colour" as a default baked in feature. And there are configurations eg Zero Field and Feedback configurations thatvseek to make txransformer implementations as transparent as possible.

 

[Vyvyan]

Well tbf everyone is an individual. Not everyone is a fan of transformer "colour" as a default baked in feature. And there are configurations eg Zero Field and Feedback configurations thatvseek to make txransformer implementations as transparent as possible.

that makes sense. im still learning, but love to experiment and have had great luck with xformers so far. i also like "lofi" and distorted/abused gear for effect when a source calls for it

 

[marcuswilson007]

I have used transformers in similar situations but I wouldn't use a 10K/10K line transformer, best to use a proper output transformer. The output stage of your device has a low impedance and can happily drive a standard output transformer like a Jensen 10K61M and you can have a switch on the output to series or parallel the secondaries for 2 output levels. Adding a 10K pot before a cable will produce a low pass filter varying with the control position. Not a good idea. Placing it before the transformer will produce the same problem.

 

[abbey road d enfer]

I have used transformers in similar situations but I wouldn't use a 10K/10K line transformer, best to use a proper output transformer. The output stage of your device has a low impedance and can happily drive a standard output transformer like a Jensen 10K61M and you can have a switch on the output to series or parallel the secondaries for 2 output levels.

That would result in 12 or 18 dB attenuation. I'm not sure it's a welcome feature.

Adding a 10K pot before a cable will produce a low pass filter varying with the control position.

That's why I asked he OP what he wanted to drive with his unit. With a decent quality 10k:10k xfmr, it is possible to drive a 10k input via a 5 meter cable without noticeable HF attenuation.

 

[CJ]

Doctors recommend a diet rich in iron as to prove oxygen uptake.

 

[Vyvyan]

That would result in 12 or 18 dB attenuation. I'm not sure it's a welcome feature.

That's why I asked he OP what he wanted to drive with his unit. With a decent quality 10k:10k xfmr, it is possible to drive a 10k input via a 5 meter cable without noticeable HF attenuation.

Ive got a hammond 835 i was thinking of using. datasheet says its a 1:1 but also states the primary and secondary as 10k/40k:10k/40k and it seems to have enough pins for multiple windings. I also have an altec 15335a 15K:15K and a handful of old 600:600

which one would you recommend?

 

[abbey road d enfer]

The Hammond is not ideal, it's designed to drive very large impedances. Even wired as 10:10k it may lack HF response.
The Altec 15335A is a 600:15k
A 600:600 is probably a better proposition, of course they are not equal, you should experiment for teh one that has the best LF response.

 

[nsalis]

The Altec 15335A is a 15k : 15k transformer.

Nick Salis

 

[abbey road d enfer]

OK. The datasheet is so poorly written it's confusing.
Then it seems it's the most likely to do the job.

 

[Rob Flinn]

Ive got a hammond 835 i was thinking of using. datasheet says its a 1:1 but also states the primary and secondary as 10k/40k:10k/40k and it seems to have enough pins for multiple windings.

That is quite a nice interstage transformer if you decided to build an RCA BA6a.

 

[Vyvyan]

That is quite a nice interstage transformer if you decided to build an RCA BA6a.

well, now im on a mission! was thinking of trying a UA175, but a BA6a will do!

 

[nsalis]

I would like to add 1:1 10k output transformers with a level control. Can I replace the termination resistors on the outputs with a 10k pot driving a transformer w/trs outs?

BTW: Why do you want to be able to adjust the output level of the SS-1?

 

[nsalis]

Thanks, i would be connecting it to the line inputs on my antelope audio discrete 8. im always perplexed when these forums seem to praise the color and character of transformers, but always ask why someone wants to use them?

i have a lot of parts, im a bit of a hoarder collecting old broken gear so i have somewhere around 100+ old transformers (tamura, hammond, mci/sony, carnhill, altec, freed, berlant etc,,,) ive used many for ground up builds such as API/neve/hileos and tube builds to great success and i have a lot of old consumer gear id like to experiment with like these EQ's. now im not expecting some mastering grade EQ. ive got plenty of plugins for when i need something transparent. i mess with analog for the dirt and color.

so i think ill try some transformers with pots on the secondary, but am i right in thinking it best to remove the 10k resistor?

If you're going to go through the hassle of converting an unbalanced RCA output to a balanced input using a transformer, it's better not to use an output transformer after the source, but to use an input transformer just before the load. Read points 2.2 vs. 2.3 in accompanying paper by Bill Whitlock.

 

[Vyvyan]

BTW: Why do you want to be able to adjust the output level of the SS-1?

I just like having options. I have some gear with 600 ohm input impedances, some 10k, and some hiz. Is there a better way of accommodating for that?

I also have some Sony/mic 10k 1:1 transformers and an opamp labs 10k 1:1 as well, would these be a better choice than the altec 15k?

 

[Vyvyan]

If you're going to go through the hassle of converting an unbalanced RCA output to a balanced input using a transformer, it's better not to use an output transformer after the source, but to use an input transformer just before the load. Read points 2.2 vs. 2.3 in accompanying paper by Bill Whitlock.

Thanks! I've been looking for some useful reading material!