AMP 10 unmute problem.

[gec]

For more than 14 months i have been using an AMP10 with a 140VA 0-16v,0-16v .Everything has been working fine.I have ordered a 300VA 0-22v,0-22v toroidal from Antek and when i connected it to the AMP10 i have 2.75v on both outputs and cannot trim the DC offset though the led and relay behave normally when using the switch to mute and unmute the amp.
When i reverted back to the 140VA transformer everything normal and i can listen to my favourite music
Can someone help
Thanks and regards
GEC

[DanielS]

Hi did you get any answer on problem.
I have got the same problem, but i have only got the 2x22v 300va.
With 2.73v on the speaker terminal.(No speaker connected).
So I don`t know if the amp works.

[audiophool]

Your description is consistent with this: When you use the 22V transformer, VPP and/or VNN is too high and this is causing it mute on overvoltage (ie before it even gets a chance to unmute.)

[wadoka]

Sounds like the voltage sense resistors are correct for the 16vac tranny, but too low for the 22vac one?

[DanielS]

vnn sense is R45 pin 18 (220k ohm)
vpp sense is R46 pin 19 (220k ohm)
Would bigger resistor make it tolerate the 22v transformer ?

[DanielS]

I measure 32.5v dc over C80 and 32.2v dc over C83
Is this to high ?
Could it be the peak volt when the 230v is turned on.
Who triggers the over voltage senns .Or would that disappear when the volt stabilizes ?
The diode and reele mutes and unmutes .
1,14v over Ref R42.

Is there some more things to check ?

[pepolman]

The over voltage resistors may need to be increased a little. In the technical info sheet for the TA2022 they (Tripath) calculate 243k for the Rvppsense and 249k for the Rvnnsense resistors to give a trip voltage of about 36V.

From the tech sheet:

The TA2022 is guarded against over-current, over / under-voltage and over-temperature conditions.
If the device goes into an over-current or over / under-voltage condition, the HMUTE goes to a logic HIGH indicating a fault condition. When this occurs, the amplifier is muted, all outputs are TRISTATED, and will float to approximately 2.5VDC

This sounds like what is happening in your amp, especially if it was functional with the lower transformer voltages.

[pepolman]

Daniel:

Test your amp with a load on the speaker terminals. Find an 8 ohm resistor (a few watts preferably) or an old speaker. A functional amp when muted will put a voltage on the terminals that will disappear with a load. Are you using a mute/unmute switch?

[DanielS]

Still No Sound !Help !

I have measured every thing I can find in the manual,tripath pdf
and what I have found in the forum.

1 I have tried with 2 diferrent psu one 2x22v (giving 32,4 v dc over c 81 and c82)
and 2x18,5v (giving 24,1 vdc over c81 and c82)

2 Mute unmute switch,led and speakerreele is working.

3 Hmute = 1,68v(muted) 0,82v (unmuted) ? is this correct ?

4 vnnsense pin 18 = 249 kohm Muted 0,5v UnMuted 1,3v : vppsense pin 19 = 243kohm Muted 5,6v UnMuted 2,6v

5 Vref pin 17 = 1,14v Over R42 : Bias pin 27 = 2,47v no signal

6 J1 speaker out = 2,73v L+R no load 0v with 8 ohm speakers connected.

Anyone got some more ideas ..

[wadoka]

Try to trim the outputs, and overly large offset here can stop these amps from un-muting.