NOS-style JTM50 Black Flag build

[shakti]

Beautiful!
SInce you have a 220k dropper in line with the AC feed to the bias diode, you may need to go to 56k to have enough range, or else you may not get enough negative bias voltage to keep the Winged Cs happy.

Are you sure you don't want to go with a carbon comp for the 8.2k? Marshall never used Pihers for the dropping resistors until the 70s.

[emmjaydubya]

Well I'm a little concerned with a CC on the dropper, if there was a failure I would hate to roast something important! As I'm sure you know 8.2k Iskras are non-existant so I thought a Piher would be safer than a CC...

[shakti]

Safer probably, but OTOH...how many burnt CCs in original Marshalls have you seen? Someone else will have to do the math, but that dropper is only subjected to the current draw of the three 12ax7s. Would a 1W resistor be in trouble?

[emmjaydubya]

An ABCC sure would look better, that's for sure. So the draw is from the pre-amp tubes? Doesn't seem like a danger... to be honest I've never measured voltage across this resistor.

[neikeel]

Looks beautiful!

Presume you are going to reform caps (or have you already?) if you do suggest use a cheap GZ34 to reform then use the nice one

[emmjaydubya]

Thanks! Yes I reformed them in the 45/100, so easy! I think that amp will be my new cap forming rig since it's such a snap.

[awangotango]

let me know when you're ready to sell that beauty !