Thanks Dennis. I used snap in caps for all builds, this is my first with pc grade caps so wanted to rule that out. I do kinda have long wires, 6" or so from cap to .1ohm,
any issues with that? the power resistor are mounted to the bottom of the chassis
hence the long wires.
I disconnected both aleph boards, power supply is floating, well it has 2k bleeder resistors out the output caps. With my toy scope, I'm seeing around .1Vpp AC with ref to ground
on both plus minus and ground terminals. this is pointing there is no hum from toroid and cap filter?
so hum is caused because of some incorrect wiring some where when it's hooked up to the aleph boards?
any issues with that? the power resistor are mounted to the bottom of the chassis
hence the long wires.
I disconnected both aleph boards, power supply is floating, well it has 2k bleeder resistors out the output caps. With my toy scope, I'm seeing around .1Vpp AC with ref to ground
on both plus minus and ground terminals. this is pointing there is no hum from toroid and cap filter?
so hum is caused because of some incorrect wiring some where when it's hooked up to the aleph boards?
there is a 500ohm trimmer in place of R8 221 to adjust the DC offset.
I was planning to change R27,R28 from .33 back to .47 but I don't think it will
reduce the hum that much. That was my last ditch effort on this.
I am also removing the twisted wires on the power lines and twisting the plus and minus wires together this time till it reaches the aleph boards.
I know Mr. Pass builds puts the transformer in the front. My thought was longer AC
wirs from rear to front would cause more noise. other member used copper pipe to
shield the AC mains. I can do it thay way but lot of work to redrill all mounting holes
and might not have enough room.
Toroid cover removed did not add or take away from hum noise which I was surprised.
would think the steel shield would be effective.
Thx
I was planning to change R27,R28 from .33 back to .47 but I don't think it will
reduce the hum that much. That was my last ditch effort on this.
I am also removing the twisted wires on the power lines and twisting the plus and minus wires together this time till it reaches the aleph boards.
I know Mr. Pass builds puts the transformer in the front. My thought was longer AC
wirs from rear to front would cause more noise. other member used copper pipe to
shield the AC mains. I can do it thay way but lot of work to redrill all mounting holes
and might not have enough room.
Toroid cover removed did not add or take away from hum noise which I was surprised.
would think the steel shield would be effective.
Thx
I had hum problems with my Aleph H headphone amp when it was biased at 0.5 Amp per FET from a simple CRC psu with 2 x 10000uF for C and a small R per rail. If I remember corrrectly EUVL mentioned that this amp is sensitive to high ripple from the PSU. Note that due to headphones sensitivity you notice every bit of hum.
After suggestions from members I changed the wiring but eventually found PSU ripple was the culprit. The hum was gone when I smoothed the ripple by adding a lot more capacitance (I replaced the 10000uF by 68000uF caps
) and decreased the bias.
If you have any more of those 33000uF caps, just add some to the second bank (outside the case, hooked up with long wires is fine for a test) and see what happens. That's how I tried it on mine (same 33000uF caps, easy to test with the screw connections).
You could put an extra small R between the transformer and the first C in the CRC (i.e. making it RCRC).
It was some time ago that I last used my Alpeh H and I actually have some LM317 psu's lying around to test and if and how it changes the sound.
Hope this helps.
After suggestions from members I changed the wiring but eventually found PSU ripple was the culprit. The hum was gone when I smoothed the ripple by adding a lot more capacitance (I replaced the 10000uF by 68000uF caps
) and decreased the bias.If you have any more of those 33000uF caps, just add some to the second bank (outside the case, hooked up with long wires is fine for a test) and see what happens. That's how I tried it on mine (same 33000uF caps, easy to test with the screw connections).
You could put an extra small R between the transformer and the first C in the CRC (i.e. making it RCRC).
It was some time ago that I last used my Alpeh H and I actually have some LM317 psu's lying around to test and if and how it changes the sound.
Hope this helps.
The SMPS output is probably dirty. What happens when you feed the SMPS 12V into the CRC psu?
Im stumped. Changed R27,R28 back to .47ohms
R8 is still trimmer and measures 190ohms, should be ok.
I removed the small piece of metal sheet that had all 3 irfp9610 mounted to them.
Reflowed all solder points.
only other thing I added was vishay mkp bypass caps on the bottom of each 220uf cap.
that should help reduce noise not add to it.
if I built another set of alephs boards would I get the same hum is what I'm wondering now.
some builders are saying they get a little hum or hiss. so this is common
for this circuit? again, you have to put your ear to the speaker to hear it.
originally with the toroid and 66,000uf cap bank per rail, the hum is louder
though its voltage output is also higher vs. the 12V switching supplies.
R8 is still trimmer and measures 190ohms, should be ok.
I removed the small piece of metal sheet that had all 3 irfp9610 mounted to them.
Reflowed all solder points.
only other thing I added was vishay mkp bypass caps on the bottom of each 220uf cap.
that should help reduce noise not add to it.
if I built another set of alephs boards would I get the same hum is what I'm wondering now.
some builders are saying they get a little hum or hiss. so this is common
for this circuit? again, you have to put your ear to the speaker to hear it.
originally with the toroid and 66,000uf cap bank per rail, the hum is louder
though its voltage output is also higher vs. the 12V switching supplies.
I have not tried this but I will tomorrow. Thanks for other post on
increasing the cap values. If aleph retail build uses 60,000uf per rail
and Im using 66,000uf per rail at way less power and bias, there
should be no hum! lol
One thing I'm unclear if someone could educate me, is hum a form of ripple
or it's created by how things are wired correctly or incorrectly started from the AC mains.
or hum and AC ripple are 2 different beasts?
theoretically if you increased capacitance to extrememly high amount,
that would eventually reduce the hum or it is always going to be there?
I just tried this, hum is slightly reduced but still present.
I don't have any extra caps lying around. I would not mind adding another RC as you mentioned if I knew for sure it would help in removing the hum.
I guess what I am trying to say is already with 66,000uf per rail for a mini aleph, is that not a lot already? adding another 33,000-66,000uf per rail to it
may reduce hum by small sum or a lot.
Thx
I have 33000uF, 4 x parallel 0R47, 33000uF CRC PSU in my DIY Aleph J (P Daniels boards) and it is quiet, but I do not have very sensitive speakers.
I used big blue 33000uF 50V United Chemicon caps that I got from Apex Jr. (could be the same caps you are using).
I noticed in my Aleph H that with sensitive speakers (well, very sensitive headphones) I needed more capacitance to get rid of the hum than in my Aleph J.
I used big blue 33000uF 50V United Chemicon caps that I got from Apex Jr. (could be the same caps you are using).
I noticed in my Aleph H that with sensitive speakers (well, very sensitive headphones) I needed more capacitance to get rid of the hum than in my Aleph J.
If you're measuring about 0.1V of AC on the output of the caps, I would think that's
pretty good.
With the input grounded, can you measure any ac on the amp's output?
When you say there's still a hum, how far do you need to be from the speakers to
hear it? Do you have to be very close to the drivers?
Cheers,
Dennis
pretty good.
With the input grounded, can you measure any ac on the amp's output?
When you say there's still a hum, how far do you need to be from the speakers to
hear it? Do you have to be very close to the drivers?
Cheers,
Dennis
An externally hosted image should be here but it was not working when we last tested it.
don't put the transformer under the case...
Just noticed 0V1 ripple with NO LOAD.
How much ripple with 1 channel attached? And 2?
Perhaps faulty caps?!
Sorry...I missed that part where you disconnected both boards. You have
bleeders but that's still less than a 10mA draw. Do you have the ripple values
with load?
I found this post by Mr. Pass:
http://www.diyaudio.com/forums/pass-labs/22450-aleph-ripple-voltage.html#post261195
This should give an idea of the expected ripple at the output compared to
that at the power supply.
bleeders but that's still less than a 10mA draw. Do you have the ripple values
with load?
I found this post by Mr. Pass:
http://www.diyaudio.com/forums/pass-labs/22450-aleph-ripple-voltage.html#post261195
This should give an idea of the expected ripple at the output compared to
that at the power supply.
sorry, not clear on the drawing. I have remove the toroid shield and it did not make any difference.
I really appreciate everyone's help here.
I need to wire it back to the toroid and CRC since it's wired with the dual 12V switching supplies right now. I will connect only one channel, ground the input and measure.
The post also mentions hum and ripple are two different things some I'm still confused.
I will post a wiring diagram of the grounding, you can let me know if it's ground loop related.
btw, I am using an Antek 12V 400VA, I know it's overkill. Can the extra power, meaning much more windings create more hum then say a 200VA trafo?
Thank you!
I need to wire it back to the toroid and CRC since it's wired with the dual 12V switching supplies right now. I will connect only one channel, ground the input and measure.
The post also mentions hum and ripple are two different things some I'm still confused.
I will post a wiring diagram of the grounding, you can let me know if it's ground loop related.
btw, I am using an Antek 12V 400VA, I know it's overkill. Can the extra power, meaning much more windings create more hum then say a 200VA trafo?
Thank you!
Hi,
wiring diagram attached. I can hear the hum about 1 feet away from
tiny test speakers with the toroid/CRC psu. So on 94dB speakers it
must be quite audible.
The last thing I will consider doing is adding another cap bank.
I have the brian gt aleph psu board, CCRC. I was thinking just
adding this on the output of the current one, so CRC-> R(0.1ohm?) ->CCRC.
Already at 66,000uF per rail with CRC, that is a lot of capacitance! lol
That's my only concern spending more money for caps but still have hum.
mores caps reduce ripple but not hum, yes???
wiring diagram attached. I can hear the hum about 1 feet away from
tiny test speakers with the toroid/CRC psu. So on 94dB speakers it
must be quite audible.
The last thing I will consider doing is adding another cap bank.
I have the brian gt aleph psu board, CCRC. I was thinking just
adding this on the output of the current one, so CRC-> R(0.1ohm?) ->CCRC.
Already at 66,000uF per rail with CRC, that is a lot of capacitance! lol
That's my only concern spending more money for caps but still have hum.
mores caps reduce ripple but not hum, yes???
Attachments
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Hum from power source (50-60hz) --> it mean problem from power supply .
Aleph class A is so simple and get so much unstable about current & temp.
1, How much current bias now? Did you try reduce bias ~ 100mA? and see.
2,Look photo ..why they twist 02 wire ( 01 line) it is wrong. Just twist (+,-).
3,...
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