i bought few days ago pieces of aluminum to make a case for the pre.
So that before i tried to arrange the sides and the bottom of the casing around the circuit and the hum was really lowered ...not completely gone...but much lower.
I tried different value of capacitors across BC junction.
Instead of having an improvement there were making it worse.
i will re-check all the soldering joint to ground.
I don't think this could be the case, but i' ll check anyways.
All static voltage values are ok and since i tried to match the parts of the two sides as much as possible the voltage value are really symmetric...good!
Casing make it much better and i' m looking forward to get the parts and arrange a case for the preamplifier.
I don't know if it you can do me this favor: could you try to pull the board off the case and see , when connected to the stereo system or to the scope...whatever...if you have this hiss and little hum?
Last thing i tried:
I had a center star right after the first filter cap and so i tried to connect that point to the casing and got a big noise on the speaker.
At a certain point i was also thinking that i was wrongly grounding the circuit.
I don't actually know how to ground the circuit since it is a topic that i never went through.
is there any advice?
Can you describe me how your grounds are arranged?
So that before i tried to arrange the sides and the bottom of the casing around the circuit and the hum was really lowered ...not completely gone...but much lower.
I tried different value of capacitors across BC junction.
Instead of having an improvement there were making it worse.
i will re-check all the soldering joint to ground.
I don't think this could be the case, but i' ll check anyways.
All static voltage values are ok and since i tried to match the parts of the two sides as much as possible the voltage value are really symmetric...good!
Casing make it much better and i' m looking forward to get the parts and arrange a case for the preamplifier.
I don't know if it you can do me this favor: could you try to pull the board off the case and see , when connected to the stereo system or to the scope...whatever...if you have this hiss and little hum?
Last thing i tried:
I had a center star right after the first filter cap and so i tried to connect that point to the casing and got a big noise on the speaker.
At a certain point i was also thinking that i was wrongly grounding the circuit.
I don't actually know how to ground the circuit since it is a topic that i never went through.
is there any advice?
Can you describe me how your grounds are arranged?
sorry, forgot to answer about gain:
the gain resistor is actually set up to 270ohm and that gives me almost a gain 1.
i tried to set up a lower gain putting a 550ohm resistor but the hiss was still there.
I have measured the preamp stage of my commercial integrated amplifier and the gain is 0.5.
the gain resistor is actually set up to 270ohm and that gives me almost a gain 1.
i tried to set up a lower gain putting a 550ohm resistor but the hiss was still there.
I have measured the preamp stage of my commercial integrated amplifier and the gain is 0.5.
Stefano, that was .001 caps across the collector to base junction, not collector to emmiter.
The signal/ supply ground should be connected from the supply negative side through a thermister to case/earth ground and nowhere else, however sometimes it helps to also put a .1 cap from the input ground lug to the case. You'll have to experiment with that if you still have hum, but you're not going to get rid of the hiss, that's coming from the circuitry.
You should go back to PASSDIY.com and read up on the BOSOZ, theres much info there.
Bill
The signal/ supply ground should be connected from the supply negative side through a thermister to case/earth ground and nowhere else, however sometimes it helps to also put a .1 cap from the input ground lug to the case. You'll have to experiment with that if you still have hum, but you're not going to get rid of the hiss, that's coming from the circuitry.
You should go back to PASSDIY.com and read up on the BOSOZ, theres much info there.
Bill
Pretty late getting back to this thread, but I got a pair of veteran's boards and stuffed them with the same parts off of the KK boards. The Aleph P is now performing as designed by it's brilliant creator.
All I can do at this point is speculate as to what the problem actually was. Possibly a manufacturing defect or a marginal layout in the ground scheme. I'm definately not a PCB layout expert by any stretch, but something was going on.
My hat's off to Mr. Pass for allowing the Diyers around the world access to some of the finest sounding audio equipment in existance.
Bill
All I can do at this point is speculate as to what the problem actually was. Possibly a manufacturing defect or a marginal layout in the ground scheme. I'm definately not a PCB layout expert by any stretch, but something was going on.
My hat's off to Mr. Pass for allowing the Diyers around the world access to some of the finest sounding audio equipment in existance.
Bill
Hi C,
I should have emailed you, been pretty busy with other stuff.
I got the Thors straightened out too, thinking about starting a thread on converting the cabs to vented/ported as I did.
Thanks again, Bill
I should have emailed you, been pretty busy with other stuff.
I got the Thors straightened out too, thinking about starting a thread on converting the cabs to vented/ported as I did.
Thanks again, Bill
Bill Fuss said:
sorry can you help me to understand what's wrong with my Aleph P?
I still have a little buzz on the woofer/tweeter.
Can you tell me if you hear anything with your hear close to the speaker at the maximum volume?
So you hear any fuzz on the tweeter?
Just one stupid question: have you used matched mosfets?
This is the only thing that i haven't done...and i don;t know if it matters with regard to the noise at the output.
I will send you a private message as well.
Hi Stefano,
Why not try to get your hands on a couple of veteran pcbs too and see if they work for you, with match fets. I've build two p1.7s with more or less no problems at all. try to rule out all potential problem by using proven solutions (pcbs, matched fets, caps and so on)
And about fuzz on the tweeter, i don't hear any fuzz, only a little hum but my guess it's because off my chassis-less f4. Time will tell!
Cheers,
c.
Why not try to get your hands on a couple of veteran pcbs too and see if they work for you, with match fets. I've build two p1.7s with more or less no problems at all. try to rule out all potential problem by using proven solutions (pcbs, matched fets, caps and so on)
And about fuzz on the tweeter, i don't hear any fuzz, only a little hum but my guess it's because off my chassis-less f4. Time will tell!
Cheers,
c.
you are using a logical line of reasoning.
Next step will be to match mosfets within 10mV and see.
Would it be possible....but i haven't found any clear picture....so would you or anybody there that is using a Veteran Board.....kindly post a picture of the bottom of the main and PSU board so that i can compare with mine and see if i am missing anything?
I would really appreciate it if this would be possible.
Thanks in advance.
Next step will be to match mosfets within 10mV and see.
Would it be possible....but i haven't found any clear picture....so would you or anybody there that is using a Veteran Board.....kindly post a picture of the bottom of the main and PSU board so that i can compare with mine and see if i am missing anything?
I would really appreciate it if this would be possible.
Thanks in advance.
bottom side of the pcb:
http://www.backdoor.unisonus.com/projects/aleph_p.htm
ill post a picture of the bottom side of the psu pcb tonight.
cheers,
c
http://www.backdoor.unisonus.com/projects/aleph_p.htm
ill post a picture of the bottom side of the psu pcb tonight.
cheers,
c
thank you very much.
Just another stupid question.....
if my layout is correct, then the reasons couldbe only two:
unmatched fets or wrong ground wiring.
Could you please, tell me what ground scheme did you follow? (have you separate the psu ground from the signal ground through the thermistor?)
thank you soo much for your help.
Just another stupid question.....
if my layout is correct, then the reasons couldbe only two:
unmatched fets or wrong ground wiring.
Could you please, tell me what ground scheme did you follow? (have you separate the psu ground from the signal ground through the thermistor?)
thank you soo much for your help.
Stefanoo said:
or a wrong/faulty/bad part
No, I didn't use a thermistor, just hooked up the lot 😉
My ground scheme is not optimal.. i should have a ground loop but don't hear anything. i have to do a bit more of experimenting...
I'll post pcb pictures later tonight
btw, on veterans board there is a (ground) wire bridge underneath C6
cheers,
c
culture said:
yes i knoow there is ground bridge under the board.
I have conncted it.
No, i would exclude a faulty part...since i have changed them more than one time...getting same result.
Layout look the same to me...i will check very carefully with a magnifier 🙂
just one thing...on a website....penguinlover i saw that on the aleph chapter...it talks about + and - (dual) power supply.
I guess there must be a mistke since the service manual only shows a single +60V supply.
am i wrong?
Stefano, if you have a + then you must have a -
What everyone is referring to as ground is actually not a ground, it is a reference point, a common connection, much as the neutral in the power grid used in the USA and Canada. It is the return path, but is not in itself a ground.
Please check your email.
Bill
What everyone is referring to as ground is actually not a ground, it is a reference point, a common connection, much as the neutral in the power grid used in the USA and Canada. It is the return path, but is not in itself a ground.
Please check your email.
Bill
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