Hello! Just signed up for the forum. I had looked at diyAudio for sometime, but never got around the registering. I look forward to being a part of the forum.
I've been looking at the two tube circuits that G Forrest Cook has on his Solorb site and I've been trying to read up on how to determine the current needed for them. I'd like to put both circuits in an enclosure to save on space as well as money with only one transformer. I've been having a hard time figuring it out, so I thought I'd post my analysis and see what smarter brains make of it.
Let's start with the liquidator
Liquidator Tube Phaser/Chorus Effect
I've found you can determine max current that can be passed by doing supply voltage/plate resistor. In that case, going from left to right on the schematic, we get 1.9mA + 18mA + 18mA + 18mA + 3.9mA + 2.6mA = ~63mA.
I've read that these numbers are the max the tubes could draw, but it's unlikely that they will ever draw that much. How would I determine what is a likely number? Do I split it in half and hope for the best?
The second schematic has me more baffled as it employs a push pull type poweramp using a 12AX7.
FuzzniKator tube distortion
I would forgo the last triode as I would just switch between clean and distorted instead of blending them, but the first two come in at 2.5mA using the method above.
Cook mentions 10k resistance on the primary OT, so I assumed it would be something like 180V/5k, just guessing on the voltage for B+2, would be 36mA for both.
That puts us at 140mA total, excluding heaters. That seems like a lot. It sounds unreasonable, but I don't know anything. Thank you for any guidance!
I've been looking at the two tube circuits that G Forrest Cook has on his Solorb site and I've been trying to read up on how to determine the current needed for them. I'd like to put both circuits in an enclosure to save on space as well as money with only one transformer. I've been having a hard time figuring it out, so I thought I'd post my analysis and see what smarter brains make of it.
Let's start with the liquidator
Liquidator Tube Phaser/Chorus Effect
I've found you can determine max current that can be passed by doing supply voltage/plate resistor. In that case, going from left to right on the schematic, we get 1.9mA + 18mA + 18mA + 18mA + 3.9mA + 2.6mA = ~63mA.
I've read that these numbers are the max the tubes could draw, but it's unlikely that they will ever draw that much. How would I determine what is a likely number? Do I split it in half and hope for the best?
The second schematic has me more baffled as it employs a push pull type poweramp using a 12AX7.
FuzzniKator tube distortion
I would forgo the last triode as I would just switch between clean and distorted instead of blending them, but the first two come in at 2.5mA using the method above.
Cook mentions 10k resistance on the primary OT, so I assumed it would be something like 180V/5k, just guessing on the voltage for B+2, would be 36mA for both.
That puts us at 140mA total, excluding heaters. That seems like a lot. It sounds unreasonable, but I don't know anything. Thank you for any guidance!
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Thank you all for the posts! Seems like 100mA for the B+ would do. Antek has a toroidal transformer that I think will do the job, using and the 220V tap. With the two 6.3 2A in parallel there should be tons of current on tap for the heaters as well.
Antek 240V Transformer
Antek 240V Transformer
Moving to I & A.I don't know how you came up with all those 18ma, but if you look at the first schematic, in the B+ supply, voltages are given. We don't know the current draw from B+1, but I suspect it is real close to the draw from B+3.
But because there is 75v dropped across a 5k resistor between B+1 and B+2, we can infer by Ohm's Law that 15ma is drawn from B+2, so 15ma total for V2 and V3(four triodes). B+3 is 70v down from B+1 across 56k, or 1.2ma. If we assume B+1 has at most 2ma drawn, the total draw for the whole circuit is under 20ma. So 100ma is way more than plenty.
But because there is 75v dropped across a 5k resistor between B+1 and B+2, we can infer by Ohm's Law that 15ma is drawn from B+2, so 15ma total for V2 and V3(four triodes). B+3 is 70v down from B+1 across 56k, or 1.2ma. If we assume B+1 has at most 2ma drawn, the total draw for the whole circuit is under 20ma. So 100ma is way more than plenty.
The tube amp section is mainly for hifi. Guitar tube amps are a special subset of tube amps, having their own needs as well as their own design goals. For example a hifi tube amp is intended to faithfully and accurately amplify an input signal. Guitar amplifiers are instead designed to intentionally add their own tonal signature to the sound. Guitar amps are not reproducers of sound, they are fundamentally part of the instrument. Guitar amps are not remotely flat in their response.
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