Hi all, I have a few questions about parts for the PSU:
1. If I'm using a 400VA 20V transformer and the universal PSU, will 18KuF / 35V capacitors work? I see those values in use in some of the builds on the thread, but with 18V transformers. Do I need to increase the uF to account for the extra voltage?
2. Are the Nichicons what people usually use for the PSU capacitors?
3. What are the pros/cons of using the diode section of the PSU board vs. the diode bridges that 6L6 uses in the build guide? The monolithic blocks 6L6 uses seem to simplify things, which is appealing to me...
4. I see on the BOM a range of possible values for the bleeder resistors. Any preferred value for this particular application?
1. If I'm using a 400VA 20V transformer and the universal PSU, will 18KuF / 35V capacitors work? I see those values in use in some of the builds on the thread, but with 18V transformers. Do I need to increase the uF to account for the extra voltage?
2. Are the Nichicons what people usually use for the PSU capacitors?
3. What are the pros/cons of using the diode section of the PSU board vs. the diode bridges that 6L6 uses in the build guide? The monolithic blocks 6L6 uses seem to simplify things, which is appealing to me...
4. I see on the BOM a range of possible values for the bleeder resistors. Any preferred value for this particular application?
1.with this load , you'll get around 1.25x more DC Volts than inputting AC Volts , so you're good with 35Vdc caps
in any case , don't go lower than 60mF as sum of all caps , per channel
2. these are good quality ones
3. personal preference ; I'm using metal diode bridges almost always
4. I=U/R ; 20mA to 30mA is enough ; calc dissipation as P=I^2 x R , go for 3-times declared power of resistor
in any case , don't go lower than 60mF as sum of all caps , per channel
2. these are good quality ones
3. personal preference ; I'm using metal diode bridges almost always
4. I=U/R ; 20mA to 30mA is enough ; calc dissipation as P=I^2 x R , go for 3-times declared power of resistor
I agree with everything Zen Mod says.
1) You are fine with the caps you have.
2) Nichicon are great.
3) Simple is good. It's also less expensive. There may be an advantage to the fancy diodes and such, but I've built plenty both ways and can't tell much difference. I've been using discrete lately.
4) 2.2k 3W.
. But anything 2K-20K 3W will work great, It just drains the capacitor bank when powered off.
1) You are fine with the caps you have.
2) Nichicon are great.
3) Simple is good. It's also less expensive. There may be an advantage to the fancy diodes and such, but I've built plenty both ways and can't tell much difference. I've been using discrete lately.
4) 2.2k 3W.
. But anything 2K-20K 3W will work great, It just drains the capacitor bank when powered off.
The ones on the BOM...
https://cdn.shopify.com/s/files/1/1006/5046/files/P-PSU-1V30-bom.xls?15967766640867126881
https://cdn.shopify.com/s/files/1/1006/5046/files/P-PSU-1V30-bom.xls?15967766640867126881
I completely agree, because part numbers get old faster than that should, but it's one of those things that can be useful.
The biggest thing I like to see is a BOM that has PCB spacing and such for the capacitors and hints for if anything is special, to try to order the right kind of part in the future, once the specific part number is gone.
The biggest thing I like to see is a BOM that has PCB spacing and such for the capacitors and hints for if anything is special, to try to order the right kind of part in the future, once the specific part number is gone.
BOMs are learning preventers
in Yore days , magz , you suffered to get to pcb
then you cherish it in your hands , checking what parts you need with ruler , simply because most parts named in mag were unavailable for you on advertised locations and their designation didn't make sense
Holco an all those fancy names .... I was happy first time obtaining metal films instead of carbons , even if paying them dearly in DM
this is mp3 time , vinyl cherish is forgotten
no , I refuse that ........ everything I will ever make must be in range of MYB (Move Your Butt) gadgets
in Yore days , magz , you suffered to get to pcb
then you cherish it in your hands , checking what parts you need with ruler , simply because most parts named in mag were unavailable for you on advertised locations and their designation didn't make sense
Holco an all those fancy names .... I was happy first time obtaining metal films instead of carbons , even if paying them dearly in DM
this is mp3 time , vinyl cherish is forgotten
no , I refuse that ........ everything I will ever make must be in range of MYB (Move Your Butt) gadgets
BOMs are learning preventers
in Yore days , magz , you suffered to get to pcb
then you cherish it in your hands , checking what parts you need with ruler , simply because most parts named in mag were unavailable for you on advertised locations and their designation didn't make sense
Holco an all those fancy names .... I was happy first time obtaining metal films instead of carbons , even if paying them dearly in DM
this is mp3 time , vinyl cherish is forgotten
no , I refuse that ........ everything I will ever make must be in range of MYB (Move Your Butt) gadgets
I used 35 AMP FAST RECOVERY BRIDGE RECTIFIERS (FDB3506P) in a 40W / channel pure class A amplifier, that I still have and love very much (modified to sound really nice, has IR-controlled relay input switching right next to the RCA's / XLR's, IR-controlled motorised TKD pot because I'm sooo lazy, bare annealed silver ribbons....).
This is what I found:
The original bridge rectifier was a bog-standard one, something like KBPC2510 - a $2 per pop thingy.
Once I replaced them with the fast recovery bridge rectifiers, the sound became soft, with no definition - suffocating.
Had to go back to the original $2 rectifiers.
I think that in class A amps, going fast switching and/or soft recovery might be too much of a good thing. I see that Aleph J already has WIMA polypropylene and ELNA Silmic II, so... complementing this combo with fast switching soft recovery diodes might be toooooo "soft"?
I'd love to hear what other members think (those who tried both types of rectification)
it's really hit ...... and miss 
it depends - which xformer , which diodes , which caps, snubber or not on secondaries etc
look for Quasimodo around , clever trickery to decrease (negative) influence of type of xformer and type of rectifier
once when you implement it , it becomes pretty much irrelevant which type is in , as long there is enough Cojones
it depends - which xformer , which diodes , which caps, snubber or not on secondaries etc
look for Quasimodo around , clever trickery to decrease (negative) influence of type of xformer and type of rectifier
once when you implement it , it becomes pretty much irrelevant which type is in , as long there is enough Cojones
+1
Quite a number of inquiries, "I just want to confirms," and "quick questions" about BOMs can be summarized:
Tell me what to dooooo, I don't want to thiiiiiink
My Aleph J is still sounding very good but I'm concerned it's a bit warm. My heatsinks are slightly smaller than the store 4U kit. They are 300x152x48mm from Conrad heatsinks. I've borrowed an IR temp gun from a fellow enthusiast and measure the following with 400mV bias. Mosfets range between 58C and 63C. JFETS all ~49C. Ambient 21C. Lid off.. I'm planning on making a new very perforated lid.
The ambient here will be up around 35C soon.. Do you think I'm going to need to look into the fans proposed earlier or is the 65C mosfet maximum suggested on the first page a bit conservative?
Also interested if winding the bias voltage down a bit (to reduce the fet temps) is much of a compromise on sound quality.
The ambient here will be up around 35C soon.. Do you think I'm going to need to look into the fans proposed earlier or is the 65C mosfet maximum suggested on the first page a bit conservative?
Also interested if winding the bias voltage down a bit (to reduce the fet temps) is much of a compromise on sound quality.
Hi Roo2,
I would definitely use a perforated lid. Are there holes in the base of the chassis?
Have you considered building ZM's babysitter for your AJ to help with cooling?
Babysitter for Papa's Koan
You can turn off the baby sitter when the weather cools down.
6L6 has some distortion measurements at different bias (on the first post of this
thread). Perhaps it's something to experiment as well.
Cheers,
Dennis
I would definitely use a perforated lid. Are there holes in the base of the chassis?
Have you considered building ZM's babysitter for your AJ to help with cooling?
Babysitter for Papa's Koan
You can turn off the baby sitter when the weather cools down.
6L6 has some distortion measurements at different bias (on the first post of this
thread). Perhaps it's something to experiment as well.
Cheers,
Dennis
