Aleph5 Hummmmm

[Juntuin]

I was going to do a new topic, but it seems that this scenario is familiar around internet and many of them about KK-PCB Aleph 5.

I have also a hum problem in my Aleph 5, i have even rebuild it couple of times; true monoblocks, monos with separate psu's, dual mono, have tried every possible grounding scheme found in diyaudio, ground loop breakers, one star ground, separate star grounds and other stuff. Hundreds of hours work. And still; buzz. It actually doesn't even change no matter what I do, usually just gets louder until I go back to beginning with separate star grounding for both channels.

I have build other amps too and all except Aleph have been dead quiet.

Is there some kinda problem with this board or am I just missing something? Finnish forums they were talking that this kk-pcb's Aleph 5 is bad design anyway, I don't know anything about designing so can't comment that argument.

Any modifications to pcb, updates on Aleph design or anything?

PASS LABS ALEPH-5 - Class-A DIY amplifier schematic & PCB

I think I will rip interior parts off soon and take a shot with totally different amp, maybe Pass, maybe not. Would been tempted to build F6 but PCB's+trafo - set has been out of stock from diyaudiostore for a long while. Never coming back? It would be shame though, I like this amp also.

 

[ElectroNick]

Are you sure its a grounding problem ?
Could also be a 100 hz issue. (i had this)

 

[Juntuin]

Are you sure its a grounding problem ?
Could also be a 100 hz issue. (i had this)

I'm not so sure about it anymore. How did you fixed that?

 

[xrk971]

After struggling with hum for over a year and trying many things, I have found that the worst ground loop offender is having two separate PSU's. Whether they be two independent power trafos and two CRC's or one trafo and two CRC boards, nothing helped. Ground loop breaker resistors, star ground with fat 12 ga wires, etc. When I switched to a single PSU like the new F6 design, the ground loops and hum went away. I am getting 100uV noise at my amp outputs on the Aleph J with the F6 PSU. So in the end, I have given up on dual mono PSU's despite the advantages of better stereo separation - but not worth it if one can't get rid of audible hum. The F6 PSU has an additional stage of separate RC filtering to improve stereo separation somewhat.

I can highly recommend this PSU (follow the topology exactly though - I did mine in P2P with solid 12ga copper from household mains wiring as the GND bus):

Here is my amp with the Fluke 101 showin 0.1mV rms (excuse the messy wiring, it's quiet and with the cover on, no-one notices - also, I move things around a lot - many amps pass through this case, hence the spade connectors on my Aleph J PCB):

 

[Project16]

After struggling with hum for over a year and trying many things, I have found that the worst ground loop offender is having two separate PSU's. Whether they be two independent power trafos and two CRC's or one trafo and two CRC boards, nothing helped. Ground loop breaker resistors, star ground with fat 12 ga wires, etc. When I switched to a single PSU like the new F6 design, the ground loops and hum went away. I am getting 100uV noise at my amp outputs on the Aleph J with the F6 PSU. So in the end, I have given up on dual mono PSU's despite the advantages of better stereo separation - but not worth it if one can't get rid of audible hum. The F6 PSU has an additional stage of separate RC filtering to improve stereo separation somewhat.

I have mounted several amplifiers (Class A, Class AB) in true dual mono with different types of power supply and I have never encountered a single problem of buzzing.

 

[Zen Mod]

ditto

 

[xrk971]

I have mounted several amplifiers (Class A, Class AB) in true dual mono with different types of power supply and I have never encountered a single problem of buzzing.

As I recall, your mono PSU's (or was it Fab's or Pinocchio's?) have isolated GND's not connected to each other nor earth safety GND in any shape or form (like two true un-connected mono blocks that happen to be in the same case and not tied to earth ground). That would indeed break up any ground loops but would not technically be safe or comply with code.

Here is the (beautiful) example you were showing me:

No connections to GND between PSU boards or earth visible...

Here is another one that you pointed out, still no GND connections visible...

Discussed in this thread.

Although, another thing that worked well to get rid of hum was to use two 24v 5A SMPS tied in series and put the center tap at GND. That was in fact, much quieter than any linear trafo and CRC combo.

 

[xrk971]

ditto

Do you connect your mono PSU's GND together and to earth GND? Which schematic do you follow, please share.

 

[Zen Mod]

several examples in my blog , dual mono in one case , monoblocks , zillion of repaired and reworked amps -some of them having baaaad rails routing or gnd routing ditto from factory

all of them made with proper safety grounding , with audio GND either connected through NTC or , in some cases,directly to case

none of them having buzz

wrong theories are ......... well - in majority

 

[Juntuin]

Thanks for replies so far If remember right, I also tried without safety earth, without difference, so it can't be ground loop anyways?

 

[Zen Mod]

pictures , please

everything counts,especially how power rails are routed on filter/cap bank pcb

incoming points, outgoing points etc.

it can be ripple , if ground loop isn't

 

[Juntuin]

pictures , please

everything counts,especially how power rails are routed on filter/cap bank pcb

incoming points, outgoing points etc.

it can be ripple , if ground loop isn't

Let's see if I can get clear shots, problem is that some of the wires are inside the frameworks pipes in present frame.. There's prob quite a mess after trying many grounding variations.

Project | Homebuilt Hi-Fi - A user submitted image showcase of high quality home built hi-fi components.

 

[ElectroNick]

I'm not so sure about it anymore. How did you fixed that?

See here :

http://www.diyaudio.com/forums/pass-labs/297892-aleph-5-clone-issue-2.html#post4858092

I thought i had ground hum, until i used a scope and saw a nasty 100hz triangle on the psu output.....

 

[Juntuin]

See here :

http://www.diyaudio.com/forums/pass-labs/297892-aleph-5-clone-issue-2.html#post4858092

I thought i had ground hum, until i used a scope and saw a nasty 100hz triangle on the psu output.....

Thanks, so far this seems to be cheapest thing to try first! Not the easiest, since there's very limited space to work.

Btw, can't hear humm in the listening spot, it just makes me crazy that you know it's there!

Edit: Oh one more question; did you had CRCC before and did it CRCRC? I have CRCC now..

 

[scottjoplin]

Thanks for replies so far If remember right, I also tried without safety earth, without difference, so it can't be ground loop anyways?

Safety earth can be involved in a ground loop but often isn't, it's only an issue when connecting to other equipment which is also connected to earth and then a loop can be formed including the interconnects

 

[Project16]

Personally I do not connect the GND to the earth and all the connectors are isolated from the case, only the case is connected to the earth.

 

[ElectroNick]

Thanks, so far this seems to be cheapest thing to try first! Not the easiest, since there's very limited space to work.

Btw, can't hear humm in the listening spot, it just makes me crazy that you know it's there!

Edit: Oh one more question; did you had CRCC before and did it CRCRC? I have CRCC now..

I had a CCC power supply (where C is 68mFD).
After i changed it to CCRC, the humm was gone.
R = 0.22 ohm/5W

Have Christian boards with a mono transformer (800VA)
And thus mono power supply with 3x68000uF per rail.

 

[pinnocchio]

Hi xrk,

If you're assembling a true dual mono then the only thing in common is the chassis, so only final ground of each channel PSU should be tied together. Modules shouldn't share anything except earth, just like mono-blocs, right?

You can use a circuit like this one for each PSU and tie the chassis side on the schematics together in a star topology directly to the chassis earth. This way you isolate each PSU. If you connect the 0V of each PSU together then to chassis earth (chassis ground) then you don't have dual mono anymore. Please do correct me if I'm wrong



*** Make sure you always observe the electrical code in your area since some circuits could be illegal.

I know that some of my personal amps are using floating ground and it could be risky but the amp is in my listening room and no one touches it. I'm also not worried about 19Vac (120Vac primary) killing me and the risk of the transformer to go bad is as good as me winning the lottery... So I'll take the chance. When I sell my amps, I always make sure I change it and earth the PSUs appropriately though.

Thanks
Do

---------
Question I've been asking myself... If you look at some commercial amps, DVDs, preamps, blueray players, etc..., many of them don't have earth connected to chassis, just neutral and hot... How do they make this go with certification?

 

[xrk971]

Hi Do,
I made a ground loop breaker (GLB) just like you show to connect the 0v (clean GND) of each PSU to central earth ground. I don’t think having a common low impedance power GND between two monoblock PSU’s makes it a non monoblock anymore. The trick is to prevent large currents in one channel from modulating the other. A common low impedance GND is indeed what is needed to prevent ground loops.

 

[pinnocchio]

This is weird indeed... I’ve not had this issue so hard to pinpoint... Could it originate from the preamp or source?

Please to make sure, did you make one GLB for each PSU or one for both?

Do