Valve Pre Amp & Class D Power Amp

Puffin · 12th June 2006, 02:14 PM

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 ?

kevinkr · 12th June 2006, 04:49 PM

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.

awedio · 12th June 2006, 05:55 PM

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.

senderj · 14th June 2006, 02:55 AM

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.

Puffin · 14th June 2006, 07:30 AM

Senderj. Are you saying that after 6 seconds everything is o.k ? and the Valve pre and Class D work in harmony.

byrfan · 14th June 2006, 08:10 AM

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

senderj · 16th June 2006, 02:52 AM

Puffin,

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

byrfan,

THanks for the info. Looks good. Checking it out.

Puffin · 16th June 2006, 04:41 PM

senderj. I have tried it and it works! Thanks, the valve pre and Class D are a great combination.

12th June 2006, 02:14 PM	#1
Puffin diyAudio Member Join Date: Feb 2006 Location: U.K	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 ?

12th June 2006, 04:49 PM	#2
kevinkr diyAudio Moderator Join Date: Sep 2004 Location: Boston, Massachusetts Blog Entries: 6	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. __________________ www.kta-hifi.net

12th June 2006, 05:55 PM	#3
awedio diyAudio Member Join Date: Jul 2005 Location: PA	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. __________________ "Where is my mind? Where is my mind? Wheeere is myyy mind? Waaay out, in the water, see it swimmin'..." Black Francis

Thread Tools	Search this Thread
Show Printable Version Email this Page	Search this Thread: Advanced Search

Similar Threads
Thread	Thread Starter	Forum	Replies	Last Post
Valve Power Supplies?	soundbadger	Tubes / Valves	2	8th October 2007 02:29 PM
wanted class a valve amp	brobarrie	Swap Meet	1	24th July 2007 06:49 PM
High-end Class A valve amplifiers will be illegal in USA?	Jaime	Tubes / Valves	141	8th July 2006 10:50 PM
MOT valve power supply?	Kilowatt	Tubes / Valves	6	10th December 2001 05:13 AM

14th June 2006, 02:55 AM	#4
senderj diyAudio Member Join Date: Feb 2006 Location: Hong Kong	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.

14th June 2006, 07:30 AM	#5
Puffin diyAudio Member Join Date: Feb 2006 Location: U.K	Senderj. Are you saying that after 6 seconds everything is o.k ? and the Valve pre and Class D work in harmony.

14th June 2006, 08:10 AM	#6
byrfan diyAudio Member Join Date: May 2006	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

16th June 2006, 02:52 AM	#7
senderj diyAudio Member Join Date: Feb 2006 Location: Hong Kong	Puffin, Yes, after 6 seconds everything works fine. The DC was measured without load. byrfan, THanks for the info. Looks good. Checking it out.

16th June 2006, 04:41 PM	#8
Puffin diyAudio Member Join Date: Feb 2006 Location: U.K	senderj. I have tried it and it works! Thanks, the valve pre and Class D are a great combination.

Currently Active Users Viewing This Thread: 1 (0 members and 1 guests)

New To Site?	Need Help?
Register to Participate Search Privacy Statement Contact Us	Frequently Asked Questions Did you forget your password? Mark Forums Read