Sorry Nelson, but I have found an error ...

[toshiba]

... in the Aleph ONO schematics drawn by Wayne.

Correcting this error should solve all problems concerning the Ono mute circuit in cloned PCB's. Perhaps other problems too ...

Q25, labeled as "9610" in the original schematics of Aleph Ono service manual is wrong.

First it has to be a "610" and second, Drain and Source have to be swapped.

Only then, Q25 works as a simple voltage regulator with an output rail of about 24V to drive a 24 Volt-Relay.

Nelson, or do you work with 40V-Relays ???

The rest of the mute circuit is ok. The need of any additional components like shunt resistors (pquadrats PCB's) isn't required.

Best regards
toshiba with small "t"

P.S.
Nelson I'm sad, that you haven't answered to my quote

[Fred Dieckmann]

The circuit looks fine to me........

From page three of the ALEPH ONO SERVICE MANUAL
REV 0, 1, 2, 3 9/30/1997 :

"Q25 and Q26 are used to power the mute relays."

How it appears to work to me:

The Mosfet act as switches they are low impedance when the gate to source voltage is greater than about 4 volts. This circuit is to short the outputs to ground until the supply comes up and the circuit stabilizes. R77 (750K) and C40 (220uF) provide a delay as the cap charges up and Q26 turns on. Q25 is already on when the 40 volt rail comes up. D11 clamps inductive voltage spikes across the relay coil and D10 provides hysteresis so the relay switches cleanly and does chatter during the switching.

The gate to source voltage for Q25 is about 12V after the 40 V rail comes up. You want to output to mute quickly when the power goes off and Q25 will go high impedance quickly while Q25 will still be swicthed on. You want to unmute after a delay when powering on and to mute quickly when powering down. 48 relays are very common for telecom use and should work for this circuit.

See anything wrong with the audio circuit you want to tell us about?

[UrSv]

I can only agree with Fred as it seems fairly straight-forward and the description Fred gave matches my understanding of the circuit for the Aleph P which I am currently building and which is the same and which in that case also would be faulty. Funny nobody has mentioned it since so many built these? Even more funny that I remember threads about it as well as reading the service manual where it is explained.

Personally, if I did not understand a circuit at all and wanted to I would probably ask how it works first and then claim it is incorrect...but that is just me.

[faustian bargin]

Originally posted by UrSv

...but that is just me.

i'm guessing it's not just you...probably most people.

claiming certainty in almost anything is just asking for a big serving of foot...especially when one is in the company others who probably know more.

[Duo]

Man oh man.

Expert: X being the unkown value; Spert being a drip under pressure.

Mr. Pass knows what he's doing. How else would his work be so respected in the audio community?

imho: I personally think his work should be commended. It's an excellent contribution to this forum and its people for sure.

[jh6you]

Originally posted by Fred Dieckmann


Uh Oh another expert.........

I like your technical response very much.
But, the title is totally wrong.

JH

[Duo]

Lol, Sarcasm ownz.

[grataku]

Originally posted by toshiba
... in the Aleph ONO schematics drawn by Wayne.

Correcting this error should solve all problems concerning the Ono mute circuit in cloned PCB's. Perhaps other problems too ...

Q25, labeled as "9610" in the original schematics of Aleph Ono service manual is wrong.

First it has to be a "610" and second, Drain and Source have to be swapped.

Only then, Q25 works as a simple voltage regulator with an output rail of about 24V to drive a 24 Volt-Relay.

Nelson, or do you work with 40V-Relays ???

The rest of the mute circuit is ok. The need of any additional components like shunt resistors (pquadrats PCB's) isn't required.

Best regards
toshiba with small "t"

P.S.
Nelson I'm sad, that you haven't answered to my quote

They should put this post in the dictionary as the meaning for the word _dork_

I am sure looking forward for your next 'critique' of Nelson's work since I am about to build an aleph

[jan.didden]

Originally posted by Fred Dieckmann
The circuit looks fine to me........

From page three of the ALEPH ONO SERVICE MANUAL
REV 0, 1, 2, 3 9/30/1997 :

"Q25 and Q26 are used to power the mute relays."

How it appears to work to me:

The Mosfet act as switches they are low impedance when the gate to source voltage is greater than about 4 volts. This circuit is to short the outputs to ground until the supply comes up and the circuit stabilizes. R77 (750K) and C40 (220uF) provide a delay as the cap charges up and Q26 turns on. Q25 is already on when the 40 volt rail comes up. D11 clamps inductive voltage spikes across the relay coil and D10 provides hysteresis so the relay switches cleanly and does chatter during the switching.

The gate to source voltage for Q25 is about 12V after the 40 V rail comes up. You want to output to mute quickly when the power goes off and Q25 will go high impedance quickly while Q25 will still be swicthed on. You want to unmute after a delay when powering on and to mute quickly when powering down. 48 relays are very common for telecom use and should work for this circuit.

See anything wrong with the audio circuit you want to tell us about?

Fred,

Sorry, but your explanation still doesn't help me. Most of us know that we need to mute quickly and unmute fast. Why the need for two mosfets, complementary at that, when one could do the trick? toshiba might have been wrong, but nobody yet has proven that or even argued against him. I think it isa a bit cheap to say "...Mr Pass knows what he does...". Hell, we ALL know what we do, don't we? Let's try to keep this discussion intelligent.

Jan Didden

[paulb]

Originally posted by janneman

Why the need for two mosfets, complementary at that, when one could do the trick?

I suspect it has to do with PassLabs having a lot of leftover FETs that failed the hand-selection for matching.

When someone like toshiba comes out with an arrogant-sounding thread title and even refers back to his own earlier post pointing out another supposed error ("I'm sad you haven't answered..."), they can count on a few flames.