Schade Common Gate (SCG) Preamp

ra7

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2009-02-07 6:47 am
Davis, CA
I have a batch of the STQ1NK80ZR’s, did you try these?
Yes that one is good too.
@ra7, i am wondering if the board can take the lbb110 SOP package by soldering them on the surface of the pads.
Looks like the pitch between pins is the same but the row spacing is <1mm different. Most likely it will work.
 
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ra7

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2009-02-07 6:47 am
Davis, CA
Tested the signal circuit yesterday and it is a success. Used the STQ1NK80ZR-AP. Did not have the PS caps or the DIP socket on hand and so the PS and muting circuit is yet to be tested. Need to place a Mouser order. Should be wrapped up by next weekend.
4E209B0B-60E1-40CD-84C2-90796D71209F.jpeg
 
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ra7

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2009-02-07 6:47 am
Davis, CA
I'm listening to STQ1NK80ZR-AP and it is absolutely fantastic.

BTW, I did buy a small quantity, so if someone is desperate, I can send them the 80ZR-AP.

This is sort of the point of this circuit--we want to get off our reliance on unobtanium parts, whether it is DHTs from the 1920s or really great modern transistors. There's so many options--some better than others--but hopefully, there will always be sufficient number of options.
 
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ra7

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2009-02-07 6:47 am
Davis, CA
120V to the top FET in the CCS. 100V is also okay but good to have a bit of leeway. I would shoot for 100-120V secondaries.

We need about 20V on the bottom FET, 40V on the gain (middle) FET, and the same amount across the CCS (40V), so end up with about 100V. But with 120V, you get a bit of flexibility if you plan to play with different FETs. The above distribution works for the two STQ parts.
 
5 days later….. almost 4K sold out:confused:
They list 1,719 in stock ATM.

I’ll have at least 8 pairs extra. Similar to Raul’s offer, if anyone’s desperate for a pair of STQ1NK60ZR-AP to build his preamp, I can send a few out too.
 

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ra7

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2009-02-07 6:47 am
Davis, CA
Perfect, I have a trafo just right for the job ;)
What's the diameter and lead spacing on the pcb for the electrolytic caps in the psu section?
25mm Dia/10mm LS?
That is exactly right.

Once the PS section is in, I’ll post some measurements of noise, distortion, etc. Gain is about 20 db (or 10x) and is set by the amount of Schade feedback.
 
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