I've got two other original monoblocks and plenty of spare valves. But the chances of two monoblocks behaving exactly the same way must be minimal.....
What did Quad say on valve matching +/-10% and their voltages again +/- 10% some of which would be due to Voltmeter ohms per volt.
Your DVM will have a very much higher impedance and sometimes this needs to be factored in when fault finding.
Your DVM will have a very much higher impedance and sometimes this needs to be factored in when fault finding.
Hi juancho,
Honestly, these should go together without any trouble. As much as you would hate to do this, return one amp to factory trim and try it.
Honestly, these should go together without any trouble. As much as you would hate to do this, return one amp to factory trim and try it.
It is in factory trim except for the earth lift. This is a well documented tweak and easily bypassed
One possible idea us to separate electriclly the driver stage from power stage just only disconnect the 0.1 uF and put a resistor , 100k, between pin5 of each 66 to ground
And check the bias
Walter
And check the bias
Walter
There already is 680k to ground.
The extra 33pF capacitors people like to add are not necessary.
The extra 33pF capacitors people like to add are not necessary.
I had had a quick look at your photo. On the bottom KT66 there appears to be a blue resistor which connects pin 3 plate to ground. I think it would be useful to publish your mods say in schematic markups or where you sourced the information from - I can also see a bridge rectifier there too. You resistor tag board looks correct.
https://keith-snook.info/quad-ii-mods-grey-pair.html
https://keith-snook.info/quad-ii-mods-grey-pair.html
'I had had a quick look at your photo. On the bottom KT66 there appears to be a blue resistor which connects pin 3 plate to ground. I think it would be useful to publish your mods say in schematic markups or where you sourced the information from - I can also see a bridge rectifier there too. You resistor tag board looks correct.'
I've answered this previously in the thread
I've answered this previously in the thread
I would lose all the mods. The amplifier is already designed. None of this is necessary and some of it may be harmful.
Specifically I already addressed the extra pF caps, and there is already a 100R ground lift. No need to try adding another, and you look to have added it in the wrong place anyway.
Specifically I already addressed the extra pF caps, and there is already a 100R ground lift. No need to try adding another, and you look to have added it in the wrong place anyway.
Please read the thread. The amp is totally standard apart from the earth lift mod. This can be taken out of circuit by shorting.
The amp is totally standard apart from 2x22pF redundant capacitors and the redundant and possibly incorrect ground lift. Remove it all.
If you read the thread the 22pf were added as they are one possible tweak to improve stability. Clearly you don't care for modern safety standards if you say 'remove the (correctly implemented) ground lift' Which can easily be shorted out of circuit as a test and which cannot cause oscillation of this type
I read the thread. I repeat. The 22pF capacitors are not required. and it has nothing whatsoever to with safety, and that also applies to the ground lift. I can give you 5 or more separate reasons why the capacitors aren't required, but the only one I need is that the amplifier is stable without them.
You seem to believe that all your work is perfect. If that's the case why are you posting here?
I'm afraid I have neither the time nor inclination to argue with you and your misinterpretation of posts and picture. Anyone with any knowledge of these amps and their literature would know the function of the 22pf caps along with the fact that an earth lift is a common safety improvement. There's already an 100r earth lift as standard? Sure.......see attached schematic.Please stop threadcrapping. I stated at the beginning of the thread what I hoped for by posting.
Both amps do work in exactly the same way. I've parked this for the moment to focus on another amp. Once again there are no mods beyond earth lift and trying the 22pf caps. The amps behaved exactly the same without the 22pf. I've previously installed the same earth lift system in a Quad 2 with no issues. It's easy enough just short it so there is just an earthed chassis which I'll try when I get back to it