hum in aleph 30

[jos]

I have built 2 monoblocks based on the aleph 30 schematic. The voltage is +/-23v.
I have used for each monoblock + and - 30000 uF. Offset is 30mV. I get a ripple of 180mV on the plus and 180mV on the minusside. I have tried everything changing the central earth point, moving the transformer. Does anybody has any idea or is 180mV simply too much
Jos

 

[Koy]

I use the same values.I did not made any measurements,them is audible only very close to me speakers.Accoding to simulations I have made, the 180mV is normal with 30mF caps. Try to increase this value- not very cheap or add choke.I did it.The toroid cores I got in computer service shop ( from power supply) for free (not at all, this guy got a bottle of home made spirit).

 

[jos]

Thanks for the help Koy.
I do not have space for an inductor, so what is the minimum value of caps that I need to get rid of the hum. Remember, I use 30.000uF per rail per transformer.

 

[WayneS]

Jos,

How do you know that the hum is caused by power supply ripple ? Did you try to run the amp with no input connected to see if the same hum results ? If not, try it out. If the hum goes away, you almost certaily have a ground loop which is causing the hum rather than the PS ripple. The amp should be fairly quiet on its own but still has a amall amount of hum - you have to hold your ear to the speaker to hear it though so it is not a problem at all for listening.

The problem is, to "get rid" of PS ripple, you need an infinite capacitance. Multiplying your caps by 10 will give you 1/10 the ripple (+or-) and that would give you 20dB less ripple.

I'd also put forth the problems I had in my amps as possibilities, but that is just too perverse .

 

[jos]

I did try that, so i have to add more capacity, I have space for another 15000 per rail, totaal 45000 per rail. Is that enough?

 

[Koy]

It should be.An idea struck me.What sensitivity have your speakers? The higher the more the hum is audible.

 

[ralf]

Hi Jos

Why do you not use a capacitance multipler?

I use it in my SOZ with a capacitance of 20000uf, and its cleaner than with 600000uf !!

i tried it myself!!

Ralf

 

[Koy]

Re: Hi Jos

I have not good experience with multiplier.

 

[ralf]

Koy

why do you have made no good experiences with capacitance multipler.

Mr. Pass himselve says it`s a good thing,
Herbert Furtwangler who has build a zen (look in pass`s galery)has also build this circuit with good experiences.

The only thing is to find the right Resistors to integrate it in each amp.

Tell us your experiences...


Ralf

 

[Koy]

Re: Koy

Why?
The amp souded dull without live. Easy to hear difficult to say.Of course I used ordinary cap multiplier ( eg. Rod Elliot) maybe this could be the reason. I know other people with the same meaning.
And you need heatsinks etc. It is cheaper and supress the hum much better than caps. But I left it.

 

[ralf]

Koy ...and all others

... in my last multipler i used high quality caps for my multipler and much more than in rod eliots schematic:

40000 uf in the front end and 10000 in back end, four 1000uf-ers in the middle part. - for each monoblock!
All BC cpacitors. the 10000ers in backend are bypassed with mkp`s and styroflex`s. I know, it`s much more than in rod eliot`s schematic, but nevertheless cheaper than hundred thousands of capacitance.

With this psu the speaker is absolutely quiet in absence of any input-signal.

I did not hear any differences in sound between multipler and big capacitances except of the small hum, using big capacitances.

has anyone else made experiences with the capacitance multilpler?

Ralf

 

[mozfet]

CX

Hi, I'm keen to try a Cap Multiplier, in both the Aleph 30 and the 'New Zen' with the Go-Faster stripes, could you provide a circuit diagram of your circuit, also interested in regulator circuits for use with above.

Mozfet

 

[ralf]

here is one

but as i said, i used bigger capacitances:

here is the schematic of herbert who has build the psu of SOZ with the capacitance multipler, too, but with original values

http://www.geocities.com/fuherb/sonofzen.htm


Ralf

 

[jos]

I have just added 39000UF per rail , the ripple dropped to 50mV but the hum is still the same. You can hear it clearly at a distance of 3 meter. Sensitivity of the speakers is under 90. Disconnecting the amp from the rest does not improve anything.
I have used the 3 ohm resistor (R0) to ground, moved the transformer, added caps. Still the same amount of hum. I use 220 W toroid transformers per channel.

 

[Koy]

Hmmm.I have speakers with cca 87dB, the hum is hearable only in very close distance. Filtration 30000uF per rail. And what about the gain of the amp - really 20dB?

 

[macka]

Hum in Aleph 30

Jos,

I think you have a different sort of hum cremlin lurking in your mono blocks.

Are both channels making the same noise?

Recommend you have a close look at your boards, there maybe an assembly fault.

An earth trace touching where it should not causing an earth loop!

I would also test for all the voltages, particularly around the input pair and current source, or even the orientation of components or and check you bias, it may be too high which could account for hi hum levels.

The first time I turned on my Aleph 3, it draw 6 amps bias and humm..ed a lot but did not break

Just thinking of possibilities .

best of luck

macka

 

[nar]

hum in Aleph

I had same problem.As I told Jos he might think about a PI filter on the supply rails,V+ and V- try something like 10000/4.7mH:10000 in extra to the main big capacitors of the PSU.Remember that caps radiate noise,and a wire just across might take hum pulses and carry it to the circuit!!!!
I do use the Pi filter,and over a 97dB sensivity speaker it is almost inaudible...

 

[jos]

Thanks nar,
I did all try that, but it did not get any better. The hum is still the same whatever I do. I use the layout of Mark Finnis, just changed it a little bit because I have 2 sinks on the side per channel. I checked the voltages, the sound is oke except for the hum.