Not a red herring, thats important information.
From your test results, I would say that Q8 is faulty.
Amusing bit, shorting G-S of Q6 or Q8 would create a low impedance path for the 5mA of the JFET CCS to the minus rail, ~500 Ohm.
(5mA times 500 Ohm makes 2.5 V, which is less than the ~12V drop across the LED string).
Shorting G-S of Q8 should kill the LED string, kill Q9, and turn all of ampy into dead duck.
Shorting G-S of Q6, but greeny Xmas tree remains burning : apparantly busy traffic at R(oute) 12 & 26 .
(5mA times 500 Ohm makes 2.5 V, which is less than the ~12V drop across the LED string).
Shorting G-S of Q8 should kill the LED string, kill Q9, and turn all of ampy into dead duck.
Shorting G-S of Q6, but greeny Xmas tree remains burning : apparantly busy traffic at R(oute) 12 & 26 .
I still think we are all missing a point here.
BOTH Pumpkins are exactly the SAME. Only one is being subjected to fault finding.
Alexander says that it is probably a component choice somewhere.
The resistors are all 1% Low Noise Metal Film.
C1 and C2 are Silvered Mica
C3 is an Orange Drop
C4 and C5 are Metalised Polypropylene
C6 is a WIMA MKS4
C7,C9 are Orange Drops
C8,C10,C13 and C14 are Rubycon
C11 and C12 are Orange Drops
All semis are matched - actually supplied by Alexander himself.
BOTH Pumpkins are exactly the SAME. Only one is being subjected to fault finding.
Alexander says that it is probably a component choice somewhere.
The resistors are all 1% Low Noise Metal Film.
C1 and C2 are Silvered Mica
C3 is an Orange Drop
C4 and C5 are Metalised Polypropylene
C6 is a WIMA MKS4
C7,C9 are Orange Drops
C8,C10,C13 and C14 are Rubycon
C11 and C12 are Orange Drops
All semis are matched - actually supplied by Alexander himself.
Unlikely unless there is a design issue.
I've been buidling electronic circuits for over 30 years and have NEVER yet fried anything.
Including working in strict ESD environment and soldering CMOS components.
Common, this build has been short circuited from day one years ago till yesterday, one comprimise after another, faulty wire connections (XLR's), etcetera.
Oops !
Papa's DIY designs from Alephs to the latest FW ones are fairly fool proof, basically an idiot can assemble them, which also makes them rather elegant.
Point is that fully balanced designs require a lot of "seasoning", and attention to every single detail.
Example is the Aleph-X, few have managed to get it working properly : sticking two halves together transforms an amp that anyone can build into a completely different animal.
Comments such as : "As we are reducing the frequency, the amplitude is increasing", implies you're way over your head, despite 30 years of building circuits.
Following Itsmee's suggestion of shorting Gate to Source of the current sinks again suggests one definitely does not have the basics covered.
In such cases, one should follow the assembly manual by the letter.
Example : a youngster overhere was hell bent on having a big flat screen, despite my advice not to, he got the biggest Samsung TV his pig saving account could handle.
When it shut down after a water accident, the screen had to be opened.
Inspection turned up a fried resistor and a couple terminated MOSFETs in the high voltage section.
Second glance also showed a couple of cheap azz electrolytic caps, which were half way en route to heaven, and would have terminated the screen anyway within a year or so.
That's 30 years electronics experience, and attention to detail.
Little reminder : you entered the BS, not Brag, and keep the savvy to yourself bar.
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I am sorry KatieandDad that you did not find the problem....
on the other side I am happy that the "drama" is over.....
good luck with the search of a new pre....
The B1 is working perfectly. It is SILENT in operation and does its job impecably.
The Pumpkin is horrible. It is difficult to use and is only suitable for the experts.
So far I have seen quite a few Pumpkins that work, and none that didn't.
So to claim that they probably don't work, is gonna be on your own account.
Magura