How To Identify A Classic Preamp VS A Classic SE? Trying To Make Sure I Wasn't Scammed

[Highlander]

About ten months ago I purchased a Conrad-Johnson Classic SE preamp from an Audiogon member with excellent feedback. He stated that it was just back from Conrad-Johnson after a checkup, and had new tubes that they installed. I've been happy with this preamp, and the recommendations from a number of members here helped me to make the decision to buy, recommending it as a great value in the preamp world, as well as the CJ lineup.

As we all know, with tubes, anything can happen, however, a recent situation has me wondering. About two months ago, I started getting a growing level of background noise in one channel. I ended up changing out the tubes with a pair of NOS Mullards and it eliminated the issue, but that seemed awfully soon to have to replace these tubes. In addition, when I removed the old tubes, something didn't seem right, as I'm certain they were not tubes that CJ would have used when they "supposedly" replaced them when the unit was in for it's checkup. Based on the above, I'm wondering if he misrepresented the CJ checkup and tube replacement, and of greater concern, if he may have misrepresented the model of the preamplifier. How can I verify if this is indeed a Classic SE versus a standard Classic?

JC

[Joe Appierto]

If you're comfortable popping the top, you should see CJD Teflon capacitors which is one of the differences (besides Vishay resistors) between the Classic 2 and the Classic 2 SE. I'm not familiar with that model but it's also possible the serial number plaque on the back may contain "SE" as part of the model designation.

[plurn]

Joe - Classic is different to the Classic 2 - though your points are still valid for either model.

site showing pictures of classic:

http://www.homecinema-fr.com/forum/acha ... 27083.html

Note that there are a number of orange capacitors next to the larger white capacitors. Capacitors look like cylinders.
Also on the back panel in the "model" section it says "CLASSIC"

---

site showing pictures of the classic SE:

http://www.highfidelity.pl/@main-88&lang=en

Note that instead of a bunch of orange capacitors there are small white capacitors, next to larger white capacitors. These small white capacitors would be teflon. I don't think they are labelled teflon though. It is not mentioned on the ET5 teflon capacitors anyway.
Also on the back panel in the "model" section it says "CLASSIC SE" (I think - it is a bit hard to read from the picture). I saw a picture of another one that said "CLASSSE" instead.

---

Highlander, you did not indicate how many hours of use you had with the preamp before the tubes started getting noisy. Conrad Johnson says:

"How long do tubes last?
That varies depending on the type of tube, the number of hours of use and the type of use they have had.
Typically tubes should last, on average, about 1500 hours before gradual degradation of performance becomes noticeable. This translates into two to three years if the unit is turned off when not in use. Usually tubes will continue to be functional for a long while after this, but sound quality will be reduced and noise levels will increase. In power amplifiers, the input tubes are most critical for sonic performance. If output tubes are not causing problems, they can be replaced every other time."

http://conradjohnson.com/faq/

Obviously that 1500 hours will be a different amount of years for different usage patterns. It is less than 3 months if the pre is left on 24x7.

There have been many reports of tubes going noisy very quickly in other recent CJ preamps (ET3, ET5, and GAT) with some tubes going noisy at around 250 hours of use. It has happened to my ET5 too many times. For balance, other people report no issues, with reports of long tube life. I have not read of this being a problem with the Classic but I have not really been following that model.

With your situation, the thing is, it could just be a bad set of tubes. It does happen. Hopefully your current tubes will last you a long while.

Anthony

[plurn]

Regarding the tubes used, I don't think there are many choices for this model. As far as I am aware the tubes have not been manufactured for years (maybe decades) so the ones CJ supply are very likely NOS (new old stock). So I would think it is quite possible that CJ supplies tubes that may not be as attractive as you were expecting. Did they at least say M8080 on them? The classic uses M8080 tubes ( in the line stage ) and there are not many to choose from as far as I am aware.

There are substitutes for the M8080. Some website says these CV4058 6100 EC90 6C4 - but I don't know for sure.

You could try asking CJ support what the service history is for your classic (tell them the serial), and ask what brand M8080 tubes they supply. I don't know if they will be able to tell you anything about the history but maybe they can.

Actually according to this viewtopic.php?t=888 it seems that CJ probably uses Mullard M8080.

Anthony

[Joe Appierto]

Anthony, if you look at the pictures for the Classic SE, you'll note that the small white capacitors have "te" after CJD. Specifically images #10 and #11.

That having been said, do you know which model you have?

[plurn]

Thanks Joe. Well spotted.

Anthony

[Big Dog RJ]

yes, good bit of info there.
I also had the Classic SE at one point, superb preamp! Fantastic value.
The "SE" lettering will be clearly marked on the back stamp next to the serial number, it should read as "Classic SE".
Sometimes by looking at the inside it may be hard to tell, since different caps/parts could be used depending on the batch of production being run at the time. If CJ had attended to it personally and it clearly states Classic SE then you're safe.

If it has been tampered with by a third party, then even if it states SE, I would touch anything from 3rd parties... unless CJ has had the final look.
Sound-wise quite a difference from the standard Classic version; the SE version is more dynamic, more open and more fluid in the midrange, espcially the bass is stronger with greater impact & transients. It also takes a much longer time to nicely settle in due to the use of Teflon caps in the audio signal stage. Tubes needing to be changed cannot be guaranteed, brand new tubes can go bad in a few weeks sometimes dead upon arrival due to shipping and handling. With tubes, always a good idea to have spare sets although they may be new.

Hissing noises are quite common in CJ preamps and usually found in one channel not both. My ACT2 was dam noisy with hiss on the left channel, the ET3SE and Classic SE were much quieter in this regard. The ET5 was not too bad but the GAT was a nightmare with tubes, hence the series 2 is more stable in this regard.

Cheers, and hope you sort out the tube issue.
RJ

[jeffreybehr]

Regarding the tubes used...

There are substitutes for the M8080. Some website says these CV4058 6100 EC90 6C4 - but I don't know for sure.

...

Anthony

AFAIK, the initial model of the tube is the American 6C4, of which the 6100 and 6135 are heavy-duty versions. I've found a few 6C4s* and 6135s* that are quiet enough to use in the surround and bass channels of my preamp. The British version of the tube is M8080 and CV4058 (military number), and AFAIK these were manufactured only by Mullard. I believe the EC90 is a European (and/or maybe British) equivalent. I've bought tubes from c-j and thru eBay; the CV4058 seem to be more available now; I suggest you buy 'em if you can find 'em. For instance...
http://www.ebay.com/itm/Lot-of-4-Vintag ... SwDuJW0tJr

IME, the M8080 and CV4058 sound the same, and that's really good.


* Soon after buying my MET1, I bought many dozens of these; the vast majority were VERY microfonic and useless for audio; I threw them away.