Preamp Deal of the Century

Hi Ecclectique, thank you so much for your comprehensive reply.
My used Syrah came with a pair of matched metal based 7029's ("made in U.S.A.", the reputed dealer here in Germany wipes out the branding and re-brands them with his own name), but Mick wrote me they could be inadequate for the Syrah, because they are not exactly equivalent with the 5881/6L6. That is why I am considering 6F6's.
Otoh a pair of Heathkit W-5M's I used to drive my original Quads with, prior to getting the Radford STA-25, sounds best with 7027's!
Ecclectique, speaking about rectifiers, could you please let me know something else? With the Syrah when I play my LPs using my ZYX Fuji (not with FM or CD; sounds great) there are funny noises coming out of one channel after ten to twenty minutes, sometimes earlier. The noises sound like tearing paper or like the noise between channels in a radio or sometimes like a muffled heartbeat!
My Syrah came with a brown based Mullard GZ-37 rectifier, which Mick says should be OK for the Syrah if in very good shape. I have changed the 5842 and 6GK5 phono tubes and the 7029's but the problem persists.
Once you wrote that phono play could be affected if the rectifier is not 100%, except if it is a GZ-34 which could be less with no problems. Do you think that getting a GZ-34 would solve this problem (apart from sounding better)?
Thank you so much. Best,
frankiealverti

Houstonreef. The Ge 6sn7gtb.... if it is the sidegetter version, it is the proverbial "over achiever" if there ever was one in the 6sn7 family. A great score for paltry sum these can be bought for and they fly way below the radar relative to the cost of the other nos tubes in the family. [for the time being anyway]and they sound very good in the Supratek's. Sonically speaking, they are very smooth with a well balanced tone from top to bottom, decent at resolving subtle detail and posses a very punchy bass line [one of the best of the nos 6sn7's in that regard] a robust and reliable tube that's generally free from microphony and low in noise.Certainly not as texturally layered and transparent sounding as the Kenrad blackglass or Tungsol roundplates but certainly not bad in that dep't either. [ then again, only a few others nos examples are] and they generally sell 5x the price. It has been mentioned in the thread that Mick has voiced his current preamps with the stock EH6sn7 and it is a large improvement over the sovtek 6sn7. I would certainly agree with the general concensus when compared with the sovtek however, I do not concur with the general consecus here when compared to many nos 6sn7/vt-231/5692 varieties. The GE 6sn7 sidegetter easily best it, the reasonably priced RCA grey glass versions literally stomp all over the stock EH 6sn7 in every dept. Move further up the family food chain.... to the Kenrad Black or the tungsol roundplate....well.... a whole nother stratosphere to experience. Comparing the two would be like comparing the Supratek Chenin to an old Conrad Johnson preamp employing tired tubes. The 6GK5's in the pro/comm box are probably a late production tube rebadged with their label. Most of the 6gk5's out there are late production tubes and probably all made at the same facility anyway and then rebadged with a Mullard logo or number of other company's name. The early nos examples all had factory date codes. I have a pair of old stock Amperex's with factory codes and bugle boy labels that are far better sounding than the later production examples without the codes. The US made RCA 6gk5's are the way to go here if you can't find the older tubes as they are generally low in noise and all sound consistent.I suppose it's a moot point here for those with the latest production Supratek preamps that are sporting the Covi designed phono stage however those with older Syrah's and cortese models that employ Micks version of the renowned Loesch design should go out of your way to dig up some old stock 6fq5's in place of the 6gk5....A major impact and a big surprise to be had here folks! Regarding the 6bg6???????? Houstonreef, are you positive they say that somewhere on the tube! I am surprised, no more than surprised they would even work in the Syrah, unless the previous owner had the tube socket rewired to accomodate a 6bg6. The 6bg6 is electrically very close to a 6L6 however,it is traditionally employed as an output tube in an ampifier but requires a top hat on the top of the tube to operate in any given circuit. Just "Mind Boggling" to me as to why anyone would go to the trouble of using that tube for regulation duty in the Syrah anyway.

Frankiealverti. Houston...We have a problem!!!! Are you certain the tubes are 7029's. I have never heard of a 7029 designation. Perhaps you are confusing it with the 7027 or the 7027a. If it is a 7027.... Yup, the 7027 is electrically similiar to a 6L6 and should be fine in the supratek. That said: Am I missing something here? No offence but I would be "highly suspect" and immediately ask myself why anyone one would go through the exercise of relabelling tubes,and for what reason other than financial gain. Flat out Fraudulant if you ask me! The original old stock 7027 is a rare breed indeed and I have only come across this tube once or twice in over 30 years. A local musician brought in an old Ampeg guitar amp that employed the 7027 tube. I could not find replacements for them and had to retrofit his amp to operate with the 6L6's. Rumour has it, that the 7027 is the King of Tone and the cats meow in the this old Ampeg. The gentleman I am referring to is an incrediblly talented blues player and quite a famous recording artist. His comments were....What the f_ck did you do to my amp man! Well sir... " I put some [old stock] 6L6g's in it man as I couldn't find the 7027's anywhere" I could only imagine that the guitar amp crowd would probably trade in their back up guitar for a pair of these! Frank...I don't doubt the original old 7027 sounded better in the Heathkit W5's but I would be willing to wager that they are probably new stock chinese or russian metal base 6L6's with the labels washed off. Why take the chance in your Supratek anyway? Regarding the preamp making noises when your using the phono stage. Have you tested the rectifier? I would hazard to guess that your Mullard GZ-37 is either very weak or has grossly imbalanced halfs.This artifact you describe is really not that uncommon particularly in the supratek with phono stages. Yes, I believe the GZ34/5ar4 would be the safer choice. By the way: WOWZA and well done man!... You have one fabulous rig there sir and a very fine ear. To this very day I am still kicking myself for selling off my Radford ST-25. Over the years....I have had my share of highly regarded amplifiers paired with the Quad 57's and I can honestly say I have never heard a better amplifier than the STA-25/quad combo. Outfitted with the Genelex kt77 is pure magic with a capitol M. Now add the mighty supratek into the mix....sigh. Can only imagine!!!!

Hello ecclectique,
I am so fascinated by your kindness, experience and knowledge that I have waited until this hour (02.14 over here) for your reply. THANKS!
YES, you are right, I meant the 7027A. My RCAs and Westinghouses did a great job in my Heathkits. I also have a pair of new Sovtek 5881s. They do sound much inferior to the metal base 7027A's in the Syrah, but maybe it is just because they still are brand new. Anyway, I will try my burnt-in RCA 7027A's in the Syrah (I hope Mick isn't reading this ;-))
The tube seller is the most reputed and most expensive in Germany, thank god the previous owner paid him for these tubes, not me. If you would like to know who he is, just out of curiosity, you can email me privately and I will gladly give you his site address. This practice of wiping the branding off is very old, he has been doing it for many years. He then writes his name and the tube type in different colours depending on the quality of the tube according to his measuring, testing, matching etc.
A huge thanks for the rectifier tip, a Hytron GZ-34 is on its way here and hope it will reach me before Xmas. I know I need the metal base GZ-34, but before I spend what is big money for me for the metal base Mullard or Philips, I thought I should try the Hytron, see if the problem vanishes. No, I did not and cannot measure the Mullard GZ-37, I really hope that the rectifier tube is the problem.
Thanks for your kind words on my system, your systems are truly extraordinary (I have heard the TW once in a show twelve or more years ago, WOW!). My Quads have PK (absolutely great guy) treble panels, new EHT blocks and protection clamps. New PK bass panels maybe next fall. The Radford STA-25 MkIII is a really good match, indeed. Before the Syrah I used a (Bruce Moore designed) Precision Fidelity C-7a sp (with step-up trannies for MC inside). Not at all bad, not at all, but the Syrah is in a different league. Now if the problem could go before Xmas so that I can enjoy my LPs for more than a few minutes!
Many thanks and regards, ecclectique!
Best,
frankiealverti

It has been my experience that the regulators affect the sound much more than any of the 6SN7's. Yes, the WE 350B's are very expensive, but worth it, IMHO. The Genelex KT66's aren't even close to the WE's in my system. Since I have the 350B's, I haven't tried the 6F6's.

As far as the 6SN7's go, I have tried them all. The EH 6SN7's kicked out the Kenrad blackglass and Tungsol roundplates. Still have the Kenrads and the Tungsols, but they are sitting in a box. The EH's are just as good as the 'Rads and Tungsols and better than everything else.

It is my opinion that in most any other application the Kenrads and Tungsols would probably best the EH's, but I simply believe the 6SN7's contribute very little to the sound in the Supratek as compared to the regulators and the rectifier. Having rolled them all, I wish I had saved a bunch of monney on NOS 6SN7's and bought the EH's in the first place. Taking the money I wasted on NOS 6SN7's, I could have bought 3 pairs of WE350B's which do greatly affect the sound of MY Supratek.

Not trying to argue with Ecclectique, just offering a different experience.