Well, I’m kinder than ZM 
… but much less knowledgeable
That would work. But we need more info on the part, which at least I don’t have. You’d have to pick a different operating point than yhe TDV depending on the transformer ratio. I don’t know what the max drain voltage is that the device can sustain. You would also need more gain from the preamp depending on the step down. Lots of unknowns.
… but much less knowledgeableThat would work. But we need more info on the part, which at least I don’t have. You’d have to pick a different operating point than yhe TDV depending on the transformer ratio. I don’t know what the max drain voltage is that the device can sustain. You would also need more gain from the preamp depending on the step down. Lots of unknowns.
OK, B+ power supply connected to PT-159ZC choke, connected to VFet drain, output from drain to output transformer primary winding start, in parafeed config. with cap connected from primary finish to ground to block DC current. I have several transformers to try but the UTC measures 98 ohms on the 25W winding, 4 or 8 ohms secondary winding.
I'm going to start building as TDV stock design and listen, then try the parafeed idea.
I'm going to start building as TDV stock design and listen, then try the parafeed idea.
Wondering if the reason the fixed bias version sounds a little funny is due to the series regulators?
Romy, with his MELQUAIDES amplifiers used an LCRC filter for his bias supply.
His amps are powered by the PUREPOWER regenerators, or whatever they are classified as. I assume that these give a more consistent AC voltage which I suspect makes the series regulation unnecessary.
I have recently installed a 5000 watts "pure sine wave" inverter and the AC this delivers is very stable - 98 percent of the time it is at 122 volts though on occasion it can toggle one volt above and below.
I have found the inverter to be a worthwhile improvement to the sound. I wonder if that stable AC is part of the key notwithstanding the removal of line noise, etc. Not many of us have amplifiers with regulated supplies for the output stage, I know I never have, but could this be the functional equivalent with the benefit of not being current limited?
The fixed bias versus cathode bias is an old argument. Could one gain the extra efficiency of fixed bias without the well documented sound degradation due to series regulation? After all that bias supply is in the signal path.
Take all of this as the ravings of an audio dilettante.
How much current does the bias supply require? ZM's LAZY SINGING BUSH specifies 11 mA.
I am going to try one of these - I have a bunch of chokes laying about might as well put them to use.
Certainly the regulator would be easier to implement.
Romy, with his MELQUAIDES amplifiers used an LCRC filter for his bias supply.
His amps are powered by the PUREPOWER regenerators, or whatever they are classified as. I assume that these give a more consistent AC voltage which I suspect makes the series regulation unnecessary.
I have recently installed a 5000 watts "pure sine wave" inverter and the AC this delivers is very stable - 98 percent of the time it is at 122 volts though on occasion it can toggle one volt above and below.
I have found the inverter to be a worthwhile improvement to the sound. I wonder if that stable AC is part of the key notwithstanding the removal of line noise, etc. Not many of us have amplifiers with regulated supplies for the output stage, I know I never have, but could this be the functional equivalent with the benefit of not being current limited?
The fixed bias versus cathode bias is an old argument. Could one gain the extra efficiency of fixed bias without the well documented sound degradation due to series regulation? After all that bias supply is in the signal path.
Take all of this as the ravings of an audio dilettante.
How much current does the bias supply require? ZM's LAZY SINGING BUSH specifies 11 mA.
I am going to try one of these - I have a bunch of chokes laying about might as well put them to use.
Certainly the regulator would be easier to implement.
This sounds pretty neat. Yes, the variation in the bias is due to mains variation.
The bias supply doesn't need a lot of current. It depends on how you do it, but 10 mA for both channels would be sufficient.
CYOF TDV boards
I made a smol run of the CYOF rev 0 boards at JLCPCB from CodyT's gerbers and ra7's circuit, I have three pair available. I'm into these for $3.58/pair (let's call it $4, ok?), and will ship to US addresses for $10, or hold for pickup at Burning Amp. If you're ex-US you should probably just have them made & shipped to you directly. First come first served.
I made a smol run of the CYOF rev 0 boards at JLCPCB from CodyT's gerbers and ra7's circuit, I have three pair available. I'm into these for $3.58/pair (let's call it $4, ok?), and will ship to US addresses for $10, or hold for pickup at Burning Amp. If you're ex-US you should probably just have them made & shipped to you directly. First come first served.
@codyt , did you use Keratherm in your test build? Did you cut your own rectangles? I’ve surmised that the pre-cut sections from the diyAudio store will fit around the metal die of the 2SK2087C, but I want to make sure I won’t jeopardize anything with those before ordering. Crop from your picture attached.
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