Topic: New toys!!! AQ-1001DT

[Genghis Cougar Mellen Khan]

Just got a visit from the UPS man yesterday...   Can't wait to give it a listen.  I'd have it running already except I need to move a ton of stuff around.

Thanks Trey!

[pfife]

+T for new toys!  She's a beauty - makes me miss my old one... 

[Genghis Cougar Mellen Khan]

+T for new toys!  She's a beauty - makes me miss my old one... 

It's only a couple hours away... If you're ever in town I'll let you spend a few minutes alone in the room with her, no sick shit man.

+backatcha

[pfife]

+T for new toys!  She's a beauty - makes me miss my old one... 

It's only a couple hours away... If you're ever in town I'll let you spend a few minutes alone in the room with her, no sick shit man.

I can't promise no sick shit man!

[Genghis Cougar Mellen Khan]

On a side not, I wouldn't mind having a backup set of tubes since it's used.  It has the JJ / Tesla KT88's (2 of the stock AQ branded KT-88's) and JJ / Tesla ECC82 (extra set of (RCA 12AU7a's) as well.

I was thinking of getting these: Electro-Harmonix KT88EH from tubestore.com, either as a backup set or to play around once I really get a feel how this thing sounds.

Any suggestions on where to get tubes, I only found a few online retailers?

[pfife]

sorry... can't help much... the only relevant experience I had was with my guitar amp... just tossed some Sovteks in there...  its not as critical as a playback system.

[Nick Culbreth]

I've had very positive experiences with Triode Electronics and Upscale Audio.  In my experience Triode is a little cheaper but Upscale does more exhaustive testing and matching, either way you can't go wrong.

http://store.triodestore.com/tubes.html

http://www.upscaleaudio.com/view_category.asp?cat=38

If I were you I'd try swapping out the signal tubes first, in my experience they have a bigger impact on sound quality.  I did a shootout awhile back and posted my results, to my ears the RCA cleartops were second best but they offered the best value.  They seem to sell on Audiogon fairly regularly for a decent price (I paid $25 for a quad) but otherwise I think SND has some in stock for a $25 a piece.  Even at $25 I think think they're a great value.

http://www.vacuumtubes.com/12au7.html

Enough of my rambling, good luck with the new amp. 

[Genghis Cougar Mellen Khan]

I've had very positive experiences with Triode Electronics and Upscale Audio.  In my experience Triode is a little cheaper but Upscale does more exhaustive testing and matching, either way you can't go wrong.

http://store.triodestore.com/tubes.html

http://www.upscaleaudio.com/view_category.asp?cat=38

If I were you I'd try swapping out the signal tubes first, in my experience they have a bigger impact on sound quality.  I did a shootout awhile back and posted my results, to my ears the RCA cleartops were second best but they offered the best value.  They seem to sell on Audiogon fairly regularly for a decent price (I paid $25 for a quad) but otherwise I think SND has some in stock for a $25 a piece.  Even at $25 I think think they're a great value.

http://www.vacuumtubes.com/12au7.html

Enough of my rambling, good luck with the new amp. 

Thanks!

I already have 2 sets of signal tubes, the RCA's an JJ's.  I only have 1 full set of Output tubes, so if one of those goes I'd be down for a bit, hence me wanting a backup set.

Is it bad to use unmatched tubes?  For example, if one of my JJ KT-88's went, could I throw in a EH KT-88 to get me by until I get more, basically is it a big no-no or does it just affect optimum performance?

Also I see tubes being sold in matched pairs/sets.  How important is this?  If I use 4 output tubes, I'm assuming it's 2 per channel.  For the best results would I want 4 matched tubes or is 2 pairs of matched tubes fine?

 

[keepongoin]

+T for new toys!  She's a beauty - makes me miss my old one... 

your old one is holding up fine with daily use.

[Nick Culbreth]

Thanks!

I already have 2 sets of signal tubes, the RCA's an JJ's.  I only have 1 full set of Output tubes, so if one of those goes I'd be down for a bit, hence me wanting a backup set.

Is it bad to use unmatched tubes?  For example, if one of my JJ KT-88's went, could I throw in a EH KT-88 to get me by until I get more, basically is it a big no-no or does it just affect optimum performance?

Also I see tubes being sold in matched pairs/sets.  How important is this?  If I use 4 output tubes, I'm assuming it's 2 per channel.  For the best results would I want 4 matched tubes or is 2 pairs of matched tubes fine?

 

As long as you're buying current production new tubes I don't think matching is a big deal, though the added cost of matching is pretty minimal so I've always spent the extra buck or two for peace of mind.  Generally keeping the output tubes the same is a good idea to keep a balanced sound but you could use a different brand if you're in a pinch.  If you're replacing the power tubes it's a good idea to replace them all at once unless you break one really early on, as tubes age they lose strength and if you put two brand new tube in with two old tubes you're going to notice.

I'm assuming that each channel has one 12AU7 for the input and the other is the driver, if this is correct I'd experiment with the tubes you have to find out which is best suited to be the input and which sounds best as the driver.  Have fun with your tube rolling.

[pfife]

+T for new toys!  She's a beauty - makes me miss my old one... 

your old one is holding up fine with daily use.

THis might be a bit presumptious, but I'm very glad you dig it.

[BobW]

+T for Tubes!

[cheshirecat]

Is it bad to use unmatched tubes?  For example, if one of my JJ KT-88's went, could I throw in a EH KT-88 to get me by until I get more, basically is it a big no-no or does it just affect optimum performance?

You should use pairs of tubes that are about the same strength.  Depending on how the amp is biased (individually or in pairs) putting a new tube with a weaker one can put extra stress on the weaker tube, so replacing pairs is the way to go.

Also I see tubes being sold in matched pairs/sets.  How important is this?  If I use 4 output tubes, I'm assuming it's 2 per channel.  For the best results would I want 4 matched tubes or is 2 pairs of matched tubes fine?
2 pairs should be fine (yes, 2 per channel).  If the tubes were all produced at the same time, they should be pretty closely matched as is, but for a few extra bucks, it's no big deal to get matched ones.

[Genghis Cougar Mellen Khan]

Is it bad to use unmatched tubes?  For example, if one of my JJ KT-88's went, could I throw in a EH KT-88 to get me by until I get more, basically is it a big no-no or does it just affect optimum performance?

You should use pairs of tubes that are about the same strength.  Depending on how the amp is biased (individually or in pairs) putting a new tube with a weaker one can put extra stress on the weaker tube, so replacing pairs is the way to go.

Also I see tubes being sold in matched pairs/sets.  How important is this?  If I use 4 output tubes, I'm assuming it's 2 per channel.  For the best results would I want 4 matched tubes or is 2 pairs of matched tubes fine?
2 pairs should be fine (yes, 2 per channel).  If the tubes were all produced at the same time, they should be pretty closely matched as is, but for a few extra bucks, it's no big deal to get matched ones.

+ thanks for the info

Since I have it up and running I have a few more questions.

Next post...

[twoodruff]

yes looks right, no idea on the t - p issue

[pfife]

is it ok to turn it on with no speakers connected?

[cheshirecat]

T is for Triode mode, P is for Pentode mode.... According to ASL you'll get about 29 watts in Triode mode and 50 in Pentode. There is a lot of debate on what is the 'best' way to run your tubes, but you choose.  There is a ton of info out there, do a bit of google searching.

is it ok to turn it on with no speakers connected?

Depending on how the output transformers (OPTs) are configured you can end up f'ing up your amp with no speaker load connected.  Basically the OPTs are looking for a certain amount of resistance (determined by the type of speaker and tap you use 4,8,16 ohm).  With nothing attached it acts too efficiently and can end up crapping out the OPTs, but again depends on whether they configured the amp to deal with this or not, but the safe bet is to use either a dummy load (big ass 25-50W 8ohm resistor) or connect your speakers, and use a 100k shorting plug on the RCA inputs when biasing.

[Genghis Cougar Mellen Khan]

T is for Triode mode, P is for Pentode mode.... According to ASL you'll get about 29 watts in Triode mode and 50 in Pentode. There is a lot of debate on what is the 'best' way to run your tubes, but you choose.  There is a ton of info out there, do a bit of google searching.

is it ok to turn it on with no speakers connected?

Depending on how the output transformers (OPTs) are configured you can end up f'ing up your amp with no speaker load connected.  Basically the OPTs are looking for a certain amount of resistance (determined by the type of speaker and tap you use 4,8,16 ohm).  With nothing attached it acts too efficiently and can end up crapping out the OPTs, but again depends on whether they configured the amp to deal with this or not, but the safe bet is to use either a dummy load (big ass 25-50W 8ohm resistor) or connect your speakers, and use a 100k shorting plug on the RCA inputs when biasing.

I DID have had the speakers hooked up, I know for a fact I DID NOT have the RCA's hooked up, could this be a potential problem?  All sounds well.  I wasn't sure and then I looked at the "Tube glow" pictures I took, I did connect the speakers, and the interconnects.  I might have interpreted it wrong, but from what I've read I thought you were suppose to bias the amp without a signal present, so I removed the interconnects before biasing, perhaps I took it too far by removing the RCA's?

[pfife]

Did you say before that the speakers were not hooked up? I swear I read that... am I losing my mind?

[Genghis Cougar Mellen Khan]

Did you say before that the speakers were not hooked up? I swear I read that... am I losing my mind?

You're not losing your mind, I said w/out speakers/interconnects, I did have the speakers hooked up, my bad.

[Genghis Cougar Mellen Khan]

All seemed well, guess it wasn't.  I had the amp playing at softly and VB1 whatever (1st output tube?) decided to start glowing red.  I turned off the amp and gave it time to cool off.  Turned it back on and watched the bias for the tubes, VB2-4 went right back to the middle, VB1 stayed low then pegged into the red after about a minute, even turning the bias adjustment screw didn't budge the meter, flip over to VB2 and it's fine.  Turn the pot all the way to the left and the needle will drop all the way to the left, but then seconds later peg to the right.  Powered down again.  Cool.  Threw in the extra pair of KT-88's, same thing, If I push down on the bias pot slightly it drops the needle, magically the needle finds it's way to the middle and then it pegs again.  When I first hooked it up it seemed like the right channel was quiter than the left, nothing gave me an indication that something was wrong with the biasing, the needle was in the middle for each tube. 

If i push down with minimal force on the adjustment screw it drops to zero, let off and it pegs to the right into the red.  If I lift up on it with a pair of neddle nose gently it biases adjusts (whatever) fine.  Put any pressure on it and it's pegs again.  Is the pot somehow shorting out?  If I lift up on it gently again it'll adjust, take the up pressure off and just the weight of the screwdriver on the pot and the thing peg to the right.

It came well packaged and everything played fine all day, I had it hooked up last night but couldn't turn it up much.  It worked fine as far as I could tell and then out of nowhere this problem...

Can one of these adjustment pots go bad?

Did I fuck something up or is the adjustment pot possibly shorting or something? 

Sounded good while it lasted... 

[Genghis Cougar Mellen Khan]

Whatever that was, it's toast now, hopefully nothing else. 

I have a friend that restores older tube amps, hopefully he'll be able to fix it.   

Anyone want to loan me some gear? 

[pfife]

+T for troubles... that sux.   I have no advice for fixing, I wish I did.   

[cheshirecat]

I DID have had the speakers hooked up, I know for a fact I DID NOT have the RCA's hooked up, could this be a potential problem?  All sounds well.  I wasn't sure and then I looked at the "Tube glow" pictures I took, I did connect the speakers, and the interconnects.  I might have interpreted it wrong, but from what I've read I thought you were suppose to bias the amp without a signal present, so I removed the interconnects before biasing, perhaps I took it too far by removing the RCA's?

That is fine.  No signal is no problem and basically what the plugs do.  No speakers would be bad, but since thats not the case, no problem there either.

It came well packaged and everything played fine all day, I had it hooked up last night but couldn't turn it up much.  It worked fine as far as I could tell and then out of nowhere this problem...

Can one of these adjustment pots go bad?

Did I fuck something up or is the adjustment pot possibly shorting or something? 

YOU probably didn't f' something up, but the fact that the particular valve that you are having trouble with needed more adjustment in the first place may lead you in the right direction.

Do a little troublshooting, you can determine whether it is a bad tube or something in the circuit by swapping the tubes from the L channel to the R channel (so VB1 becomes VB4 and vice-versa).  Rebias the amp and see what happens.  If the problem follows the tube, you have a bum tube.  If the problem follows the socket, you have another issue (bad coupling cap?  bad solder joint somehwere?).

[Genghis Cougar Mellen Khan]

Do a little troublshooting, you can determine whether it is a bad tube or something in the circuit by swapping the tubes from the L channel to the R channel (so VB1 becomes VB4 and vice-versa).  Rebias the amp and see what happens.  If the problem follows the tube, you have a bum tube.  If the problem follows the socket, you have another issue (bad coupling cap?  bad solder joint somehwere?).

I did do a little trouble shooting, swapped tubes and the problem was consistent. 

To make things clear, the amp was in good working order when I got it from Trey, came safely packaged, not even a concern AT ALL there.  I'm completely happy with the deal I got.  Something went awry after the fact, I always open things up to take a peek, the resistor shown above was not like that, it happened after the fact.   

Trey offered to split repair costs, I feel I got a good deal and I know the problem wasn't there when it arrived. +T there...

Might be a common problem.  Found this post on Audiogon, and a couple along the same lines.  I'm thinking the bias pot might have flaked out, I bet that I gave it more work than it's seen in quite a while.  I talked to my friend that does restoration on tube gear, he echoed the same thing for the most part.  He also said it might be a good idea to replace the stock pots with a better parts, and possibly do a few tweaks if he sees any room for improvement while he's under the hood.  I've given him some gear in the past and he's always said "if you need anything", guess I'll take him up on the offer.   

Anyway, I'm having a problem with one of the tube sockets. I've tried switching tubes within the quad of Electro Harmonix I'm using now and I've also tried going back to the stock Chinese tubes. Every time I get the same effect, to some degree or other, which is that the tube in this particular socket won't hold bias. The needle creeps towards the "red zone" over and over. A little fiddling with the adjustment screw and it will drop suddenly (accompanied by a soft "pop" from the left speaker), then start climbing again after 10 seconds or so. I've been able to tease it into the right position every now and then, but it doesn't seem wise to rely on this technique indefinitely.

The first time this happened, I powered up the amp and noticed a buzz getting louder in the left speaker, accompanied by a scary orange glow from the metal cage in the middle of the tube in that slot! Freaky...I quickly shut off the amp, and with careful attention to the adjustment screw, that hasn't happened again, but it seems like a bad sign.
http://forum.audiogon.com/cgi-bin/fr.pl?aamps&1085015350&openusid&zzBobgates&4&5#Bobgates

[keepongoin]

+T for new toys!  She's a beauty - makes me miss my old one... 

your old one is holding up fine with daily use.

THis might be a bit presumptious, but I'm very glad you dig it.

i do dig it quite a bit.  it sounds so much better than my oldsystem, it is almost scary.

[cheshirecat]

I'm thinking the bias pot might have flaked out, I bet that I gave it more work than it's seen in quite a while.  I talked to my friend that does restoration on tube gear, he echoed the same thing for the most part.  He also said it might be a good idea to replace the stock pots with a better parts, and possibly do a few tweaks if he sees any room for improvement while he's under the hood.  I've given him some gear in the past and he's always said "if you need anything", guess I'll take him up on the offer.

Could be, pots are carbon based and can get dirty and cause this type of behavior, also you can have a loose pin in a tube socket.  If you don't feel like waiting for your friend, you can pick up some contact cleaner (De-Oxit) and spray it on the pot to see if it clears up the issue, just work the pot back and forth a bit to get it in there.  If it is a socket issue you can tighten the grip on the tube pins with a pair of needle nose pliers.  Could also be a cold/loose solder joint that was irritated in shipping plus the heat up of the amp.  At any rate these are all generally quick fixes.  Tube amps are really pretty easy to work on if you're comfortable around electricity.  Just remember to let the amp sit for a good while (say 20 min or so) to allow the power supply caps to discharge before opening it up.  Otherwise you can be in for a helluva shock (in the ball park of it may kill you).