Preamp Deal of the Century

My Cab has an intermittent problem :(

After about 10 mins warm up the right channel starts to drop out radnomly and only for a split second. Some times l get some static and noise too, even the occcasional subsonic thump. Even when its not dropping out something doesnt sound right from the right channel, like some freq's are compressed, kinda hard to put my finger on what's missing.

Amps off to Mick today, hopefully its a quick fix because l am ecstatic with my system which for the time being is collecting dust!

Cheers Simon

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Simon,
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Have you tried dropping in another pair of 6sn7's ? You might want to try that before sending it over to Mick.
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Rgds,
Larry
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Mondie - I had a similar problem with my Cabernet. One channel would shutdown after 10 minutes of playing. It turned out to be a bad regulator tube. I replaced the tube and all has been good since. 10 minutes would be about the amount of time it would take a tube to warm up.

Thanks for the suggestions guys.

l did swap the tubes around but didnt have any spares to try. Made no difference, problem is always with the same channel.

Packed it up yesterday and shipped it off. Mick should have it by the end of the week.

For Chenin owners, I have some input regarding tube rolling for this specific model. For three months, I accumulated a lot of tubes and tried different combinations. Here are my observations.

The Bendix 6106 does not work for me. For CD source, it’s okay but not on phono. The 6106 produces a “chugging sound” on my phono section. No other rectifiers I tried (6L6GC, 6F6G, 7581, KT-66, and 5881) gives me this chugging sound on the phono section. I settled for the Mullard 5AR4 metal base on my applications. I had great results with the 5V4(RCA) tubes as well. For the 6F6G’s, it gives a lot of detail. But I noticed that it is “lean” on the phono application especially horn sounds. Vocals seem not as full as the 6L6G’s. This is probably why Mick said that it is only good for linestage. On CD’s, the 6F6G’s are open, airy, and detailed.

The biggest surprised I had was the Sovtek Kt-66 that Mick suggested. Right out of the bat in phono application, the tubes as regulators has the weight of the 6L6G’s (RCA) and very close to airy-ness to the 6F6G’s with good detail. It is not lean sounding at all and the horns (especially saxes) have a big bold sound. These are the tubes I am using at present (at about 30 hours now) and have the RCA 6L6GC black plates as reserve. Very good on CD as source as well.

For the linestage, my vote goes to the Tungsol Vt-231, RCA Gray Glass VT-231, and Sylvania tall bottle VT-231. The Sylvania 6SNW (short bottle) is great with a lot of slam which I find artificial (my preference only) at times just like the Kenrad VT-231’s. Other noteworthy linestage tubes I like are the JAN Raytheon Black Plates VT-231. It seems that most if not all bottom getter VT-231/6SN7 gives great results in this position and micro-phonics was not a problem.

In the phono section, I settled for the Telefunken CCa in the 6922 position. Followed closely by Amperex “A” frame, Siemens 6922 from 1972 and below vintage, and the Amperex Bugle boy’s.. Forget the 1980’s Mullard CV types. They are flat on vocals and ear piercing on the highs. Another great tube for this position is the Mullard ECC88 BVA from the 60’s or earlier. The only problem was that out of 5 pairs I accumulated, three of them are micro-phonic (you can determine this easily by switching to phono and turning the volume knob all the way to the max to listen for tube rush on the speakers with your ears pressed to it). Another good one is the Philips Miniwatt or the regular Philips 6922.

In the 6C4 position, nothing beats the Mullard M8080. I tried RCA, Motorola, Tungsol, Rogers, Sylvania, Raytheon, and GE’s. JAN or otherwise, the M8080 beats them easily with a very big soundstage and great tone. It just sounds right to me! I would say that the M8080 is on the the top of the heap followed closely by Sylvania GB 6135 and Raytheon 6C4’s.

There you have it. All of my observations are based on my system (Jolida CD player using Sylvania GB 5751 and Teres 255 with OL Silver and Shelter 901). Of course, your preference can be way different than mine.

regards