You might check out this site and type in 6922 in the "find" box on the upper right portion of the page.

You'll get a load of information to sort through. Some will be junk and some will be worthwhile.

You want to keep the Carver and just buy new tubes? Without trying to be rude, I would tell you it's time to move from the Carver.

I always enjoy talking to Kevin Deal of Upscale Audio about tubes. He knows his stuff and enjoys advising and assisting. You may want to try giving him a call.

I understand having "X" amount of money to spend. I do think the Carver can easily be bettered by something not too expensive from Audiogon. My suggestion would be a used Audible Illusions, but that's because I own an AI which also uses 6DJ8's. I think you can pick up a Modulus 2C for under $500 with some decent NOS tubes.

Understand that a tube is only as good as the circuit it goes in. Upgrading the tubes in the Carver will gain an improvement but probably not what the same tube would achieve in a better circuit. As an example, I have a good friend who had his Carver power amp upgraded when it was refurbished last year. Most everyone told him he had a good sounding system but he would have better if he replaced the Carver. He hesitated and hesitated, thinking he had a very good amplifier in the Carver,until I loaned him an older McIntosh amplifier I wasn't using. That was three weeks ago and he now has a McIntosh power amp coming from a purchase on Audiogon. Now I'm not suggesting you need to buy Mac to improve your system but I am suggesting that buying new tubes is a stop gap. If that's what you can afford, then that's what we'll work with.

The best of the 6922's are the NOS Seimens and Amperex. The very good portion of those lines are from the pre 1970's production and the prices begin around $125-150 per tube. There are lots of stops between what you own and the best NOS Amperex for over $300 per tube.

I would ask why you think the tubes presently in your pre amp are "tired". Most pre amp tubes are not run very hard and are not subject to heavy loads. A well built pre amp tube in a good circuit can last ten years or more. I just changed out the phono tubes in my AI after about fifteen years use on those NOS Seimens tubes. Remember 6DJ8's/6922's were designed for use in oscilloscopes and are meant to be in use for extended time periods year after year. Are your tubes sounding distorted on big dynamic passages? Do they wimp out when the bass goes down deep or loud? Do cymbals crash more than they should? Are the tubes just plain noisy? If none of the above, then the tubes are very likely still in good shape and you are hearing the circuit rather than the tubes. Granted, better tubes will sound better. And maybe that's all you want to do right now.

I've got to run off to an appointment. Please answer the questions about the condition of your present tubes and what you think of spending for NOS tubes and I'll give you some more feedback later.

http://cls.audiogon.com/cgi-bin/cls.pl?preatube&1190941862

http://cls.audiogon.com/cgi-bin/cls.pl?preatube&1190933883

http://cls.audiogon.com/cgi-bin/cls.pl?preatube&1190498721
http://www.tejastubes.com/catalog.htm#e188cc

http://cls.audiogon.com/cgi-bin/cls.pl?preatube&1189436701

http://cls.audiogon.com/cgi-bin/cls.pl?preatube&1189219586

http://cls.audiogon.com/cgi-bin/cls.pl?preatube&1188608773

http://cls.audiogon.com/cgi-bin/cls.pl?preatube&1188423933

(If you aren't familiar with David Berning's designs, do a Google on him. I would buy anything he ever designed.)

http://cls.audiogon.com/cgi-bin/cls.pl?preatube&1188351920

**********************************************************

http://www.tejastubes.com/catalog.htm#e188cc

http://www.vacuumtubes.com/6dj8.html

http://www.zeitmann-tubes.com/tubes/NosTeslaMilitaryAudioTubes/Nose88ccTeslaGold.htm

http://www.thetubestore.com/6dj86922types.html

http://www.thetubestore.com/6dj8links.html

http://www.audioasylum.com/audio/faq/joes-tubes.html#6DJ8

http://www.altavistaaudio.com/tubes.html

http://www.vacuumtube.com/FAQ.htm

http://users.rcn.com/brentjes/bjtubes.htm

If you don't want to spend the money for the NOS tubes, you can try a cryogenically treated tube.

http://www.tubeman.com/

I hope something in there gives you some ideas.

Microphonics can be due to external vibration, but are usually just a bad tube. As far as replacing your phono tubes, those are the most important in selecting good quality tubes.

If your tubes are 10 years old and you have put a considerable amount of listening time through your system then you are more likely to notice an improvement in replacing them.

I would encourage you to go ahead and spend a little extra on having the tubes matched and tested for noise. That usually involves a few dollars per tube over and above the normal cost.

Jan thank you for the Tube sites. Found a few I hadn't seen before, I too am looking for a 6922 replacement and 3 ECC83's types.

Any vacuum tube is microphonic. Pre amp tubes, or more correctly small signal tubes, are going to reflect this problem more so than power output tubes due to the finer structure of construction, higher gain and location in the system. Phono circuit tubes will be the most microphonic if you consider how much gain is required of a tube in this situation compared to the same tube used in a line level stage or as a phase splitter in a power amplifier. The power amp tube has the benefit of lower gain in most of its input and driver stages as well as typically higher mass to minimze microphonics. But any tube will be microphonic.

Audiophiles have a tendency to think of themself as the only group interested in high quality this or that. Remember that, as a group, low microphonics in a vacuum tube are only really desired by audiophiles and we constitute a small portion of the tube buying public. The majority of vacuum tubes are still being purchased by musicians who often value the very qualities that we, as audiophiles, distain. In a guitar amp microphonics and a quick transition into overdrive or clipping is a very desirable trait and the tubes we would discard as worn out are just getting broken in to the blues player. So, when considering which tube to buy, make certain you understand the purpose of the tube's design.

Microphonics will come from both internal and external forces. A large diference between the AI Modulus 2 and the same pre amp in Modulus 3 form is an external power supply and transformer. If the chassis of the pre amp is vibrating due to the location of the power transformer, you can have a tube that becomes microphonic with no other signal running through the circuit. Obviously, playing music through such a circuit will only make the matter worse due to the external forces in the room.

When looking at tubes many buyers wrongly assume a military spec tube (JAN or Joint Army Navy) will be better quality. This would be a mistake. Military spec tubes, whether JAN or the numbers assigned for other country's military, may have been purpose built. Consider a 12AX7 as a ubiquitous audio tube used in numerous applications. In its military guise (5751, most military spec tubes will have only numerical designations) it may have been commissioned as a tube used in the field; driven, shipped, walked or flown into its location of service. As such ruggedness, reliability and low microphonics will be essential to its operation. The same tube used in a stationary location, say, at the base of a mountain in a circuit embedded in several tons of cement, the tube's microphonic nature and even reliability can be considered secondary to its small signal carrying capabilities. So, all miliatry spec tubes wil not be equivalent.

I've often found the better sounding the tube is in consumer audio use, the more microphonic the tube will be. Mostly this is a function of its construction and the finer elements used to gain very small signal carrying capability. The rougher the handlinhg the tube is expected to take - a musician packing gear into the back of a truck - the heavier the contruction and the lower the quality of tube for consumer use.

Consider microphonics as a very important aspect of the tube you buy. Consider where you will be using the tube in your system when you decide how much in the way of microphonics you should avoid.

As a rule tube matching is not required for most pre amp tubes unless they will be placed in a phono section. However, the anxieties of audiophiles and the low cost of matching most tubes makes it a worthwhile expense.

Great posts, Jan!

Another stop gap option is to replace the tubes with some decent quality modern production - much less expensive, although certainly not at all sexy. If the tubes are old and well-used you will hear an improvement. Then take the money saved by not buying NOS and use this toward buying a new preamp.

I am with Jan in believing that a good replacement preamp is a better place to put your money. I think you would be very pleased (and perhaps surprised) by the improvement.

Quote:
I am anxious to see just how revealing my system is

Have you considered running a passive pre amp with a dedicated phono stage? Would your current set up support such a system?

I'm not familiar with the particular company you've linked to. In one very broad sense, a passive pre amp is a passive pre amp. The aim is to get the cleanest signal through the unit by using the best parts, shortest signal path and usually the least amount of parts.

I like the idea of the dual trim pots as most vc's of any type do not track equally across their range and this is certainly true of most ladder type controls. Stepped ladder type controls are generally the best quality but can leave a bit to be desired if they are not constructed with the best parts and attention to detail. Dual pots can be a bit of a nusance until you get used to them but they can turn an OK sound into a much more three dimensional soundstage by gentle tweaks of one pot or the other. After living with the dual pots of the AI for a many years, I am always surprised when I go to a friend's home to listen to music. They will just turn up the volume and assume both channels will track equally and never think to check balance to improve the sound. If you buy this unit, I think you'll learn to appreciate the dual vc's advantages.

Passive pre's have their own set of compromises and you should make certain you understand what these are before you take the plunge. OTH, this unit is fairly inexpensive and you can learn about passive units at a not very steep price. Stereophile ran a DIY construction article on passive pre amps many years ago. If it's still available in the on line archives, you might check it out for tips on passive units. There have been several passive pre amps reviewed in Stereophile also.

I'm a bit surprised the blurb you linked to doesn't mention the brand of resistors used in their ladder type control. Since they emphasize the fact the vc is the most important quality item in a passive, I would have thought they would want you to know they are using the best quality parts in their construction. Just so you know, you can buy ladder type controls and build your own passive with a moderate amount of soldering skills.

The trend today is heading toward slightly more elaborate passives with autoformer type controls and buffering to mitigate some of the impedance issues which are the main compromise of passive control units. Put "passive pre amp" in a search engine to get a better idea of what's available for what prices and what to expect from a passive unit. The folks at DIY audio also have some good information on passives. Many of the links you'll find in your search engine will probably lead you to these pages.

As to the Audio Research hybrids, they have received mixed reviews. If, after doing some research, you think one might suit your needs, I would say you can buy and try a pre owned product without fearing too much loss if you decide to resell. Sometimes, when you are interested enough in a particular item, the small cost of buying and reselling is worth the experience you gain. Overall, I would consider the AR units to be an improvement over the Carver.

The PrimaLuna products are all very good values. They respond well to some mild tube rolling and give very good sound for the money spent, another improvement here over your current pre amp. The Prima Luna line typically uses tube regulated power supplies in preference to a solid state regulation. There are quite a few listeners who feel you cannot fully appreciate a tubed unit unless the power supply is tube regulated. So, chalk one up for PL. Whether their sound suits your tastes would be the issue to decide before spending money.

Again, Jan, a wonderful job. A vote for another star - but I have already done what I can for your rating.

Another thing to kep in mind as you shop for preamps is to be honest with yourself as to whether you care if it has remote volume control. This isn't an issue for me, but many can't stand not having a remote.

LOL!

I should have noticed your sig!

Has anyone done any testing using Blu-tack on tubes?

Quote:
Has anyone done any testing using Blu-tack on tubes?

I assume you mean as a damping material. It gets messy. Then it hardens when the tube cools and cannot be removed from the tube's envelope. If you wish to pay for the specialty market's tube dampers, there are plenty to choose from in either simple rings of various design and materials or devices which incorporate weight and mass which sit on top of or clamp around the tube's envelope. After my set of AudioQuest Sorbothane tube dampers finally stretched out of shape I went to a local gasket company and bought a set of neoprene high temp gaskets. I can hear no difference between these $2.50 rings and the AudioQuest, though mulitples of either set did not totally stop the microphonics in the pair of NOS Seimens I use in my phono section.

Quote:

Quote:
Has anyone done any testing using Blu-tack on tubes?

I assume you mean as a damping material. It gets messy. Then it hardens when the tube cools and cannot be removed from the tube's envelope.

I was not being serious, but from your response it sounds like you tried it. If so, good for you. Willing to try stuff and evaluate it. I would dismiss this idea based on personal bias.

I have no personal biases. I had some at one time but I went to Catholic high school. That cured that!

The phono section is required to provide distinctly more gain than the line stage. Probably somewhere in the range of +40-50dB of gain through the phono section to likely no more than +6-10dB for the line stage. But how hard the tube is "worked" is a function of the voltage and current designed into the circuit to get the tube up and running at all. If the pre amp sat for years in a "standby" mode, the tubes would still wear. Using the tube wears it out faster but it would be unpredictable without knowing how the tubes are used in your pre amp.

You didn't say whether you listened to both input sources or just the line stage after doing your swap. If just the line stage, I would say you heard some benefits from cleaning of the tube pins and sockets. But, if you listened only through the line stage with "phono" tubes in place, the phono stage tubes are generally lower noise and quite often, if these are factory installed tubes, they have been more closely matched to each other. Try listening to the phono section with the line tubes in place.

As to the chocolate doughnuts, refer to my post regarding BluTak'ing tubes. It gets messy.

Everybody knows sprinkles sound best.
For the ultimate tweak, remove the red sprinkles.
They store to much infered energy.

Quote:
Everybody knows sprinkles sound best.
For the ultimate tweak, remove the red sprinkles.
They store to much infered energy.

And you're hoping to get a third star with that answer?

Quote:

And you're hoping to get a third star with that answer?

I didn't even know I had two stars untill you brought it to my attention.
I'm not here for the fame and fortune but just want to give something back to those less fortunate than me.

And you're hoping for a third star with that answer?!

Quote:
And you're hoping for a third star with that answer?!

I get it. I don't know everything (where do the stars come from?). You have more stars than I do.

Hehehehehe

Quote:
OOOH......OOOH....
I just got a great idea...........

Hey Cyclebrain!!!!!!
Wanna buy a Star?!?!?!?

Hell no. They just attract the media. Besides stars produce way to much wideband interference.

Kevin is great that way. He knows what works in each application. I have always found his advice to be dead-on.

Yes!

Fun, isn't it?

Quote:
This tube rolling thing could get addictive.

Yes, which turns into a problem in its own right. People do get addicted to tube rolling and, similar to cable rolling, they begin to search for a difference rather than an improvement.