The 6A version is too big. I am burning 10W of heat through a resistor to keep my voltage down. I don't have series resistor low enough in value to drop it otherwise. I think the 4A would be fine. That is what it is rated for.
Thanks Scott. 4A it is.
Does anyone have any recommendation for specific bias trim pots? I can't even tell how much dissipation they need. That little resistor network confuses the hell out of me. 🙄 Are we talking about little sealed trimmers, or 'real' chassis-mount pots? I suppose regular pots would be much easier to wire up P2P.
..Todd
Does anyone have any recommendation for specific bias trim pots? I can't even tell how much dissipation they need. That little resistor network confuses the hell out of me. 🙄 Are we talking about little sealed trimmers, or 'real' chassis-mount pots? I suppose regular pots would be much easier to wire up P2P.
..Todd
I used the Bourns chassis mount. In most cases, you want to be able to reach the pot from the top of the chassis to make bias adjustments. I would use linear taper since we are dealing with voltage not power. Single turn should give enough sensitivity.
And yes it does make P2P easier.
for the current source adjustment, I used a small pc trimpot, but it was a PITA to mount it without a board and have it supported enough to make an adjustment.
And yes it does make P2P easier.
for the current source adjustment, I used a small pc trimpot, but it was a PITA to mount it without a board and have it supported enough to make an adjustment.
I can do that when I get home tonight. I will also post a pictue of how I have the pcbmount trimpot on the current source.
Tubemak, I posted the BOM so far for my amp on the OPUS thread to minimize confusion for the build on this thread.
A couple more BoM-related questions...
The CCS adjust trimmer pot... I calculate 2-3 watts dissipation, which sounds a bit er... unreasonable to me. Is this acceptable, or fixable?
BoyWonder: What bias test-point sockets did you use on your earlier project -- the purple ones? Got a part number for those?
Does anyone else (TubeMack??) have any other questions about the latest BoM and/or schematic? [both attached]
..Todd
The CCS adjust trimmer pot... I calculate 2-3 watts dissipation, which sounds a bit er... unreasonable to me. Is this acceptable, or fixable?
BoyWonder: What bias test-point sockets did you use on your earlier project -- the purple ones? Got a part number for those?
Does anyone else (TubeMack??) have any other questions about the latest BoM and/or schematic? [both attached]
..Todd
Not sure how you get 2-3 Watts. 14mA @ 200 Ohm P = (0.014)^2 * 200 = 0.039W
I am assuming you are talking about p2
p3 & p4 will dissapate 0.043 Watts
I am assuming you are talking about p2
p3 & p4 will dissapate 0.043 Watts
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You see? This is why I need to stick to drawing pretty pictures and avoid complicated topics like grade 3 arithmetic.
I used: 14mA @ 200 Ohm P = 0.014 * 200 = 2.8W
Thanks Scott.
..Todd
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Your doing fine Taj. A while back I spent a day and a half trouble shooting an amp. Wanted 65 mA bias measured over 10 Ohm resistor. Couldn't figure out why it didn't sound right when the voltmeter said 0.065V.
Forgot that I needed to multiply by 10 and needed to see 0.65V across the resistor.
Forgot that I needed to multiply by 10 and needed to see 0.65V across the resistor.
I picked them up locally, but after extensive research 😉 I discovered that they are Pomona 1581 or 2142 series panel mount banana jacks, depending on if you want gold plate or not. They are available in a rainbow of color choices.
Mouser stocks them & sells them individually; Digi-Key has some, but they are non-stocked and they sell them in packs of ten.
pomona 1581
Banana and Tip - Jacks, Plugs | Digi-Key
pomona 2142
Digi-Key - 2142-0-ND (Manufacturer - 2142-0)
An equally good (maybe even better) solution are panel mount tip jacks. These accept the tips from your voltmeter instead of bananas. These are Pomona 3542 Series.
Banana and Tip - Jacks, Plugs | Digi-Key
I cannot find these at Mouser, but Digi-Key has them.
Holy guacamole Batman! $30 ea. Even the plain black ones are $16 ea.
I think I'll check out the local electronics store. Better to see those choices in real life before adding them to a BoM sight unseen.
..Todd
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Somebody's been smokin rocks, use these:
Emerson Electric part numbers, all in stock. 77 cents each at Digikey and Newark, 66 cents each at Mouser
105-0803-001 Black
105-0802-001 Red
105-0801-001 White
105-0804-001 Green
105-0807-001 Yellow
105-0810-001 Blue
No, all seems great.
Still waiting for my edcors to arrive. The massive Electra prints are incredible, though I want to repaint the less than perfect bells. I'll match the edcors, and paint them all. Maybe satin black, or nickel plating...😎
Still kinda stuck on the final chassis plan............ I'll do some cardboard mock ups when I get the Edcors.
I haven't been able to think much about it, as I quit smoking 3 days ago, and i'm presently in a gloomy haze.🙁
Have you thought about a final home for all this info? This forum need a section for completed project designs!
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Don't give up man! I quit cold turkey about 20 years ago and never looked back. It gets easier and easier every day -- even though it doesn't seem like it at first. I smoked for about 12 years.
After the design is tested and the kinks straightened out, it's a good idea to start a 'builder's thread' here. Post the version 1.0 documents in the first message and let nature take its course.
I've thought about creating a DIY project web application, sort of like a version control / document management system designed specifically for projects like this. But I'm pretty sure I won't get around to it. 🙄 It's more exciting as an idea than it is as a project.
..Todd
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Did this project suddenly stop or was it terminated/moved for any reason?
I seem to find posts only up to #819; was wondering what kind of practical gremlins were found ...
I seem to find posts only up to #819; was wondering what kind of practical gremlins were found ...