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analag

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Apr 23, 2005
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Sharing thing this one before I build it. Lately I have been having fansties about some black plate 12SL7s and 12SN7s I have laying around. Mind you 6SL7 and 6SN7 will work. In fact I plan to get a couple of those new Tung Sol offering I see on the market. I have grown a love for the sound of the CCS triode stage. You see you can use it to hold even a crappy reproduction tube in it's sweet spot. Dynamic plate resistor kicks as, period!  Let the beatings begin
 
Trannys will be 1:10 in and 15:1 out. R 14 will be variable and will bottom out at 10K
 
How often are tubes used in an op-amp type configuration like this, for a preamp or otherwise? I don't think I've ever seen such other than the pre-709 times when all op-amps were made with tubes.
 
There's a Fred Forssell drawing out there which has an article in Glass Audio #3 (1995).

https://www.forsselltech.com/media/attachments/VT_Opamp.PDF

Different for many reasons.

May or may not relate to his Millenia M-2B preamp. 

 
analag said:
Trannys will be 1:10 in and 15:1 out. R 14 will be variable and will bottom out at 10K

If C6 really is 5 picoFarads then the max gain from the tube stage is 20dB. With 20dB from the input transformer that gives 40dB in total but a 15:1 output transformer this drops by 23.5dB to just 16.5dB

Do you really mean 15:1 ratio at the output? Did you really mean 5:1?

I think you need more gain in the tube stage but maintaining stability over a reasonable gain range will not be easy.

Cheers

Ian
 
ruffrecords said:
If C6 really is 5 picoFarads then the max gain from the tube stage is 20dB. With 20dB from the input transformer that gives 40dB in total but a 15:1 output transformer this drops by 23.5dB to just 16.5dB

Do you really mean 15:1 ratio at the output? Did you really mean 5:1?
If the OT was 5:1, that would probably make it the most useful mic pre for recording pop/rock; I've found that most of the times I use between 25 and 35dB of gain.
Now, one would ask why making it so complex?
 

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