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Old 12th June 2006, 02:14 PM   #1
Puffin is offline Puffin  United Kingdom
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Default Valve Pre Amp & Class D Power Amp

I seem to have a mis-match. Do valve pre-amps have a higher gain than solid state. My Class D Tripath 2020 amp goes to mute when I connect the valve pre to it. With passive pre it is fine. Any ideas ?
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Old 12th June 2006, 04:49 PM   #2
kevinkr is offline kevinkr  United States
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Probably there is some dc leakage at the output of your tube pre that your tripath amplifier is not happy about. Try waiting a few minutes after you turn on the pre-amplifier before turning on the tripath, this is assuming that the output caps in your tube pre are ok.
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Old 12th June 2006, 05:55 PM   #3
awedio is offline awedio  United States
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Hmmmm. Sound peculiar, alright. You could post this to the ClassD forum, if you haven't already. DC on your valve preamp outputs is a possiblility, but I think that the T-amp should be immune to this, as it is AC coupled on the input. My best guess is that the T-amp is somehow sensitive to the grounding (earthing) arrangement. On my T-amps I make sure to isolate the RCA inputs from the chassis, as well as B-.

Try lifting the ground on your pre temporarily and see if that helps. If you have a multimeter, check for DC on the preamp outs. Maybe your preamp has some issues if that is the case.
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Old 14th June 2006, 02:55 AM   #4
senderj is offline senderj  Hong Kong
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My GG has DC at output when switch on (6th second) and then die down to normal afterward. My UcD has protection at the input. It cut the amp off when overloaded. However, I still force myself to observe the rule of power on sequence and delay. I am building a time delay in the GG output to cover the rare case of main power recovery after failure.
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Old 14th June 2006, 07:30 AM   #5
Puffin is offline Puffin  United Kingdom
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Senderj. Are you saying that after 6 seconds everything is o.k ? and the Valve pre and Class D work in harmony.
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Old 14th June 2006, 08:10 AM   #6
byrfan is offline byrfan  Norway
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Machmat.com has an nice output delay, 30 sec, for sale. They use is for their own preamp kits. In my set up with tube pre and PWM power it works fine
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Old 16th June 2006, 02:52 AM   #7
senderj is offline senderj  Hong Kong
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Puffin,

Yes, after 6 seconds everything works fine. The DC was measured without load.

byrfan,

THanks for the info. Looks good. Checking it out.
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Old 16th June 2006, 04:41 PM   #8
Puffin is offline Puffin  United Kingdom
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senderj. I have tried it and it works! Thanks, the valve pre and Class D are a great combination.
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