sorenb

@mwl168 is right 40V offset doesn't sound right. The static may origin from leaking resistors or bad solder joints. Check the 175k's (r10+r11) , r14+r29 and r7+r30 , as well as their joints

Check the current source at the front end should source more than ~1.3mA or so look here for more

+ some human = Hopper

most likely you are measuring at BIAS output, having an output impedance of 5Meg ... and the DMM most likely 10Meg, so the +380V is actually 570V Use the test point (TP) rather to get the right voltage

Indeed a remarkable piece, and always good for a listen ... reminds me of Pears/Britten Winterreise ... and the recent announcement from the Britten-Pears and Snape Malting foundations announcement of an "exciting and logical development": to merge and forget all about Peter Pears ... wonder if the next "logical" step will be announcing that Pears lured Britten into living with him against his will, and the foundation begins to twitt #metoo on behalf of Britten ...

BTW there are (at least) two versions of version 1.8 ... One has the CPC wrongly hooked up, but can easily be fixed: pics are of a skinny

Either remove the CPC if you are not gonna use it, or apply +2V across As said, if you have +18V with cpc1117 shorting, the cascoded CSS most likely needs to be reduced, 4k7 usually works bad soldering?

did you populate the CPC1117 ...either remove the CPC1117 or applie +2V across the pins If you have ~18V on the output, with the CPC1117 populated you probably have to reduce the cascoded CCS current....are you using 2k8 or 4k7?

...sure it wasn't ZIF10?

Have some from PCBNet, 1.6mm and 3oz. Anyone who wants to build the Transconductance amp and post a few pics here, can have a set or two. Promise to show a few pics of the build here, and I'll cover the shipping as well ?

I do

No 0,5 C°/W per channel will do if you go with stock values

Finally got around to finalize my Megatron, fitted into one chassis with GRHV.

continuing like that, you soon end up wearing a beret, eating fois gras, smoking two packs of Gauloises each day and driving a Renault 4, while complaining about the englishmen ...

you might check the current sources:

I might have two sets I want to depart with 2mm/4oz

<10V offset isn't a problem. Engaging the servo should quickly get you <1V

lower the tail resistor by some ~50ohms and re-adjust

seeing only a few people have signed up for Carbon boards. I have some version 6g from PCBNet 2mm/3oz, that I don't mind departing from (16.75USD/ea). If interested shoot me a PM.

....same source as for the other 10m90's in your build?

where did you get those 10m90's from?

unless you've got bad 10m90's (I've never come across any) I find it peculiar that both seems to be acting up pull out one 10m90 and test it with a DMM at ohms, test drain-source: short all legs, before measure drain-source => very low ohms if you don't get that the 10m90's are probably bad if you have a breadboard you might find it useful to build a cascoded css including the trimmer, and test as previously described. If you can't adjust the current using the trimmer, the DN2540 is probably bad (I've seen that a few times) Or you can use an 8pin IC-socket with resistors+trimmer soldered to build a bug-style test CCS-fixture. .

Very nice build Jose con grat!

Yes, check your rectified input voltage ...probably too low ...or you might be pulling too much current >3A or so