Leave d6, c8 and r14 open. This is the negative leg of the power circuit and it should mirror the positive leg..Since I'm a novice I just wanted to check I am understanding the above post correctly before proceeding with my build .
Don't populate D5 C10 R10 ?
Does this also mean that you populate D6 C8 and R14 ?
Thanks for a clarification
Did it!
Hey,
First of all, big thanks to Mr. Colburn for the project. It's great!
I've build it and it is driving my Audezes with ease. I have few thoughts about the built and would love to share them. Lets go.
1. Input caps - they are very important, so don't be cheap. Do yourself a favor and buy Mundorf Evo, or in my case, Clarity Cap ESA.
2. Opamps - we all love to roll them, don't we? For me best for now are OPA2132 and OPA2604. Still waiting on Muses.
3. Resistors - somebody posted a BOM with Dale RN60. They are great and I can't recommend them enough.
4. Caps - there are some other caps in the circuit, that in my taste need special attention.
C26/27 - those are caps in feedback path. They don't allow DC to be amplified. Being directly in signal flow, they need to be bipolar! On one video from Burning Amp Bob Cordell talked about them.
C13/23 those are for AC signals in the bias circuit. Those should also be good quality, not to compromise the sound. Go for at least Wima, or Vishay MKP1837.
C12/17/22/25 - they also work with AC, so I recommend them to be bipolar. Nichicon has a neat ES series, that will do great.
I'm working at 58mA bias with 2x15V power supply. For now 78/79, but LT317/337 is conig to me this week. I think you can go with bigger power supply caps at output transistors, like 470uF. I used oversized toroidal transformer from toroidy.pl - great value and awesome performance. I like shiny things and I do a lot of switching, so I decided to invest in over the top connectors. I have a Neutrik locking jack socket, Cardas RCA sockets and Furutech IEC socket with fuse holder. Of course you will be good with standard quality parts here. If you have any questions feel free to ask.
Oh, if you are really on a budget, try Mundorf bipolar caps for input. They will do very decent, being dirt cheap.
Hey,
First of all, big thanks to Mr. Colburn for the project. It's great!
I've build it and it is driving my Audezes with ease. I have few thoughts about the built and would love to share them. Lets go.
1. Input caps - they are very important, so don't be cheap. Do yourself a favor and buy Mundorf Evo, or in my case, Clarity Cap ESA.
2. Opamps - we all love to roll them, don't we? For me best for now are OPA2132 and OPA2604. Still waiting on Muses.
3. Resistors - somebody posted a BOM with Dale RN60. They are great and I can't recommend them enough.
4. Caps - there are some other caps in the circuit, that in my taste need special attention.
C26/27 - those are caps in feedback path. They don't allow DC to be amplified. Being directly in signal flow, they need to be bipolar! On one video from Burning Amp Bob Cordell talked about them.
C13/23 those are for AC signals in the bias circuit. Those should also be good quality, not to compromise the sound. Go for at least Wima, or Vishay MKP1837.
C12/17/22/25 - they also work with AC, so I recommend them to be bipolar. Nichicon has a neat ES series, that will do great.
I'm working at 58mA bias with 2x15V power supply. For now 78/79, but LT317/337 is conig to me this week. I think you can go with bigger power supply caps at output transistors, like 470uF. I used oversized toroidal transformer from toroidy.pl - great value and awesome performance. I like shiny things and I do a lot of switching, so I decided to invest in over the top connectors. I have a Neutrik locking jack socket, Cardas RCA sockets and Furutech IEC socket with fuse holder. Of course you will be good with standard quality parts here. If you have any questions feel free to ask.
Oh, if you are really on a budget, try Mundorf bipolar caps for input. They will do very decent, being dirt cheap.
Few more things camed to my mind. I used heatsinks Mouser #532-513102B25. They are biggest ones you can get into that Hammond case. At 15V max bias is 60mA I wouldn't go higher. Perhaps, if you lower the voltage, you might be good with higher bias.
To get 1W @ 70Ohms I need around 8,5V RMS, so 12p-p. That said I should be good lowering power voltage to dual 10-12V, that might give me some room for more current. If you use high Z cans, then I'd rather do with higher voltage like 18V. If you want to go crazy, then take LME49860 (wonderfull part, really), that can go up to 22V dual. Watch your dissipation though both on transistors and opamp.
Oh I used MUR140 diodes. I have an idea about cool diodes for it, but you will laugh. SiC (literally, lol)
To get 1W @ 70Ohms I need around 8,5V RMS, so 12p-p. That said I should be good lowering power voltage to dual 10-12V, that might give me some room for more current. If you use high Z cans, then I'd rather do with higher voltage like 18V. If you want to go crazy, then take LME49860 (wonderfull part, really), that can go up to 22V dual. Watch your dissipation though both on transistors and opamp.
Oh I used MUR140 diodes. I have an idea about cool diodes for it, but you will laugh. SiC (literally, lol)
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I still have some boards left for this. I hope all who wanted one got them. If you haven't my email is better then the PM system here. Wayne@passlabs.com
Just send me PayPal info and I can invoice you. $30 US and $55 everywhere else. The shipping is priority.
Just send me PayPal info and I can invoice you. $30 US and $55 everywhere else. The shipping is priority.
Gosh, the shipping is killing the deal.
I'll have to try to find someone in the US to bring me the parts.
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