kevin gilmore

but but... its upside down. anyway http://gilmore.chem.northwestern.edu/atten2stereobal.jpg 2.05 x 3 inches but only 2 layers and still have to add or change the drivers

yep 2 colums and both sides. you might as well put it all on one board because of the size of the drivers determines the minimum width if you solder all the resistors first, then possibly the inside row of pins on the relays could be hard to get at.

I actually think I can get a balanced step attenuator with those relays in the same size as the original, all 16 relays. But a human is unlikely to ever be able to assemble it.

transistors need to have a Vceo of 50v or more bias is 150 ma and the current mirror as the VAS means that the peak to peak voltage swing is 40V on +/-24v supplies absolutely flat to more than 5mhz

there were some pictures posted over there on the inside of the amp 7 tubes and a whole pile of output transistors

no matter what i order, or when, mouser is always backordered on something

absolutely. angle bracket version

http://gilmore.chem.northwestern.edu/cfa2.jpg

diodes are there to protect the inputs from voltages > +/-12 on those amplifiers with high power output

the amb method. trouble is they dont switch as fast that way. should be ok though.

been working on this one a while, with all the popular transistors disappearing, I hope that this one won't go obsolete before the boards are out. I don't think so because Fairchild has said that the bc parts should be available for at least 5 years but onsemi said the same thing. This one is a diamond transistor input set, used as a voltage to current converter. A pair of Wilson current mirrors with input and output cascade as the VAS and a triple darlington output stage. http://gilmore.chem.northwestern.edu/cfa2.pdf if someone knows of better surface mount parts to replace the bc series, I might as well do that from the start. ft >150mhz, hfe >100 Vceo >50 etc

how do you drive bipolar single coil relay with single switch to ground?

Birgir will be building the T2's. I am just going to watch. smaller version of my attenuator board, definitely want to see this. if you make it surface mount only, then you can shrink it a fair amount. The one knob control is definitely one of the better ideas.

new board uses 1 x 2n7000 http://gilmore.chem.northwestern.edu/protector3.pdf

no bjt's on that circuit board anywhere

servo has a limited range and is slow

high powered DC amplifier. More than capable of frying headphones if you put dc in the input. Protection circuits always a good idea

not sure where the schematic is, will look later 1n914 or similar 47uf non-polarized ceramic

sure, but that costs almost as much as the rest of the amp especially if you go for the 47 position model

input pot? dual alps 10k (mouser does not sell this) or anything else you can get that is 10k.

those can be replaced with a couple of different parts all of which are fully isolated

definitely like how the diy stuff seems to be outpacing a lot of the commercial stuff.

6db unbalanced 12db balanced

looking very good

not sure those are real, the price is way to cheap. I paid about $1 each for the real ones from mouser.