Search found 78 matches

by ilya
Mon Jan 04, 2021 11:56 am
Forum: Pro Audio Design
Topic: Cohen/Transamp output stage
Replies: 30
Views: 60355

Re: Cohen/Transamp output stage

The first QuantAsylum was unbalanced so pretty useless for pro audio. The ne one is balanced but uses a pair of BNC’s for the connection. It doesn’t inspire confidence. What a stupid choice. I'd argue that's not that stupid. First, you can easily make an XLR to double BNCs break-out. Second, there'...
by ilya
Mon Jan 04, 2021 11:12 am
Forum: Pro Audio Design
Topic: Cohen/Transamp output stage
Replies: 30
Views: 60355

Re: Cohen/Transamp output stage

AD2, while useful, is not that low noise (but ok for general purpose work).
You may check QuantAsylum QA401. This is the most affordable and versatile analyzer that I found (and use regularly).
by ilya
Sat Jan 02, 2021 8:40 am
Forum: Pro Audio Design
Topic: Cohen/Transamp output stage
Replies: 30
Views: 60355

Re: Cohen/Transamp output stage

Very interesting discussion!
While we're wandering around the subject, I've got one more question. In TA documents, Valley recommend to use tantalums as phantom blocking caps. What's the reason behind this? Why tantalums?
by ilya
Wed Dec 30, 2020 4:49 pm
Forum: Pro Audio Design
Topic: Cohen/Transamp output stage
Replies: 30
Views: 60355

Re: Cohen/Transamp output stage

mediatechnology wrote:
Wed Dec 30, 2020 4:44 pm
That's it though the polarities on the 1606 are reversed.
The top one is 1606 positive.
Well, of course! For some reason I thought those were inverting stages. Doh!
Thanks for spotting this!
by ilya
Wed Dec 30, 2020 4:36 pm
Forum: Pro Audio Design
Topic: Cohen/Transamp output stage
Replies: 30
Views: 60355

Re: Cohen/Transamp output stage

So to make sure I did that correctly, here's the crude scheme attached. Is it how 1606 should be connected to the Cohen circuit?
by ilya
Tue Dec 29, 2020 2:21 pm
Forum: Pro Audio Design
Topic: Cohen/Transamp output stage
Replies: 30
Views: 60355

Re: Cohen/Transamp output stage

What was the load on the 1510 ICs during the tests? Was it buffered? It was pretty much the circuit from the datasheet. I think the output was buffered and sent to 1646 driver. This was quite some time ago, so I can't remember the exact details. John, I know that you're not a fan of uncontrolled li...
by ilya
Tue Dec 29, 2020 2:03 pm
Forum: Pro Audio Design
Topic: Cohen/Transamp output stage
Replies: 30
Views: 60355

Re: Cohen/Transamp output stage

Thanks, JR. Yes, I know about their mic preamp chips. Although, we did a comparison between different preamps in our studio, and the 1510 type preamp was the total looser sonic-wise. I have no idea why that happened. It surely measured just fine on the bench. Maybe because of the lack of "color" (ot...
by ilya
Tue Dec 29, 2020 12:45 pm
Forum: Pro Audio Design
Topic: Cohen/Transamp output stage
Replies: 30
Views: 60355

Cohen/Transamp output stage

I'm researching the pure discrete mic preamp circuits and I think I'll settle on either Transamp (by Paul Buff) or Cohen type topology. Looking at the output stage, I often see the floating source output that resembles D. Pontis work (from an old HP journal). I'm thinking to replace this stage with ...
by ilya
Tue Jun 23, 2020 5:37 am
Forum: Pro Audio Design
Topic: Method for testing thermal coupling
Replies: 9
Views: 24951

Re: Method for testing thermal coupling

Can you tell more about what you want to thermal couple and why ? JR nailed it. Yes, that's for coupling transistors in LTP, current mirrors etc. Maybe I'll get to the discrete VCA (JR will probably laugh at that). It's still not clear to me how to measure the amount of tracking between the coupled...
by ilya
Sun Jun 21, 2020 5:54 am
Forum: Pro Audio Design
Topic: Method for testing thermal coupling
Replies: 9
Views: 24951

Re: Method for testing thermal coupling

Thanks!
Sometimes the correct search phrase is important. I tried searching for "thermal coupling" and got no useful information. That's why I posted here.
I'll check out the Netional stuff and see what the "thermal resistance" brings.