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JIMV
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A tubed amp question??

I bought a Primaluna Dialogue II in feb. It sounded great. today, with about 500 hours on the tubes, I am getting a loud noise out of the right channel (intermittent). If I thump the amp with a paperback, the noise appears. If I tap any tube on the top, I get the noise. If I tap the second from the right KT88 tube on the side, I get the noise. None of the other tubes make a noise by being tapped in the side.

Do I have a tube problem or an AMP problem???

Can anyone recommend any other tests I can do to determine what the problem is? I have no spare tubes.

Elk
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Re: A tubed amp question??

It is probably a tube going prematurely bad.

Tapping on hot tubes is hard on them, so stop it!

Give Kevin Deal at Upscale Audio a call to get help to troubleshoot it. Generally one replaces each tube in line until the problem is localized.

It appears you have already figured out the tube in question. Turn down the lights and look carefully to see if it is glowing differently than the others.

Jan Vigne
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Re: A tubed amp question??

Power down the amplifier and swap the right channel tubes for the left channel tubes and vice versa. Does the problem move with the tubes or stay in the same channel?

JIMV
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Re: A tubed amp question??

Thanks for the advice...I'll try tomorrow and let folk know.

JIMV
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Re: A tubed amp question??

Shifted the tubes, the noise shifted sides so I take it the problem is a tube.

Thanks

Elk
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Re: A tubed amp question??

Yes, indeed and it appears that you already located the culprit.

This is early even for a power tube, but no big deal. Give Kevin a call and he will take care of you. (I assume there is no warranty on the tubes at this point.)

JIMV
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Re: A tubed amp question??

correct...I ordered a replacement. The tubes have less than 500 hours. I have had tubed amps for almost a decade and never had one fail. I expected it to...fail, not simply make noise....

Jim Tavegia
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Re: A tubed amp question??

www.thetubestore.com is one of my favorites. There are many others you can find using your searchengine. You might also try www.partsconnexion.com as Chris often has some NOS goodies. Let the "rolling" begin.

Elk
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Re: A tubed amp question??

I have yet to have one of the spectacular failures others describe.

I have had input tubes go crackly on me as you describe for your power tube.

Otherwise my tube equipment has been wonderfully dull maintenance-wise. A short warm-up and it is always ready to go.

JIMV
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Re: A tubed amp question??

I ordered a replacement KT88 and 4 substitute KT77's from Upscale Audio...Now the long wait for the tubes, then burn in.

JIMV
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Re: A tubed amp question??

I also have a 10 year old Jolida 202 with EL34's and those original tubes still work, though I suspect not as well as they should. That is after maybe 800 hours a month for 10 years!

I will never own a non tubed amp again. Tubes simply sound too good to do solid state (except in my TV system, which is LOFI at best)

EDIT...blast, I cannot type...that should have been 80 hours a month...

Elk
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Re: A tubed amp question??

Great taste - EL34s for the midrange and KT88s for the extra pop, sparkle and extension on both ends. Nummy.

JIMV
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Re: A tubed amp question??

Do you know anything about KT77's? I have nver heard of them but have orered a set to try in the PrimaLuna amp.

Elk
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Re: A tubed amp question??

All I know is that the NOS are very expensive, but I have been tempted to buy a set of the new JJ Electronic's KT77s. They are said to have the midrange of EL34s, but with more extension and greater dynamic openness.

My Carey V12 would need 12 of them however, making this a semi-expensive experiment.

Let us know what you think when you try them. I am very curious.

JIMV
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Re: A tubed amp question??

They cost me $50 each so I am also hot to try them, though they will take 50 or so hours before they sound right so it may be a while.

JIMV
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Re: A tubed amp question??


Quote:
All I know is that the NOS are very expensive, but I have been tempted to buy a set of the new JJ Electronic's KT77s. They are said to have the midrange of EL34s, but with more extension and greater dynamic openness.

My Carey V12 would need 12 of them however, making this a semi-expensive experiment.

Let us know what you think when you try them. I am very curious.

I got the KT77's today. They are smaller than the original KT88's, more like EL34's. Out of the box they have a bigger soundstage and, though I suspect they put out less power, they sound 'bigger' than the KT88's. The low end seems stronger but the individual instruments are less well defined in place. The triode mode seems to favor the KT77's BUT the KT88's are better in push pull. Also, the KT88s are much better in high end resolution.

This perception may well change when the new tubes have some time on them. So far they sound very like a more expansive and slightly less discerning EL34.

Elk
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Re: A tubed amp question??

Fun!

It will be interesting to learn if your impressions change after you get a chance to listen to them more.

SAS Audio
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Re: A tubed amp question??

Hi Elk,

Do you know if JJ fixed the problem of the pins being too small on the KT77s?

Thanks.
Steve

Elk
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Re: A tubed amp question??

No clue. I read that and it surprised me that they didn't get it right from the start. Pins are not that complicated.

SAS Audio
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Re: A tubed amp question??


Quote:
No clue. I read that and it surprised me that they didn't get it right from the start. Pins are not that complicated.

I agree. Why not use the same pins that are used for the 6550 or some other octal tube?

Thanks Elk.
Steve

JIMV
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Re: A tubed amp question??

I have about 20 hours on the tubes now and find my quibbles about instrument placement have about dissappeared. The sound stage is without a doubt wider and deeper. There is also no question that the instruments at the higher end of the scale, stuff that shimmers and decays, is not as defined as with the KT88's. I am also less thrilled with the KT77's in triode mode than I was originally.

Bottom line, KT77s have a bigger sound and sound stage, the KT88s are more defined and detailed. Not sure which I like more.

Elk
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Re: A tubed amp question??

So the reports that the KT77s are sort of like big sounding EL34s are true?

JIMV
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Re: A tubed amp question??

Yes..I have 10 years experience with EL34's and these are like EL34's on steroids. The simply sound like they are putting out more power in the midrange.

linden518
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Re: A tubed amp question??

I can attest to this, although I'm running Gold Lion Genalex Reissue KT-77s (I was warned off JJs b/c of quality control issues, although I heard they were addressed.) I love the midrange of the KT-77s even more... the EL34 midrange always felt too 'fat'. KT-77s bring much more balance, and better frequency extension. The bass w/ the EL34s was too bloated/boomy in my system; now that problem is gone. I kind of see the KT-77s as bringing the best of 6L6 family and the EL34 family together. Love them.

JIMV
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Re: A tubed amp question??

My only issue is with the top end, the most shimmery of sounds, is lacking with the KT77's. The KT88's really shine in that area on my system.

linden518
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Re: A tubed amp question??

I'd like to try the KT-88s, but that would mean I'd have to keep the cover off my amp to accommodate the taller bottles, which I'm hesitant to do... might do it anyways.

Elk
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Re: A tubed amp question??

I agree, the KT88's are very nice in this regard. They also have a nice low end, much better than the EL34.

I still really like the EL34s run as triodes however. Nummy!

JIMV
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Re: A tubed amp question??

Another observation....symphonic music seems to be much more involving with the KT77's despite its lack of high end sparkle. The larger sound stage really seems to work with big orchestra classical. I wish I had some big band swing to play with

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