Preamp Deal of the Century

Hi Gang: Yes indeed, quiet 6sn7's are hard to find and all of that family of tubes tend to be somewhat prone to microphonics. Herbies tube dampeners are a blessing here as well as isolation. The Metal base GZ-34/5ar4 is without doubt the finest sounding of that family of rectifiers. When using substitute rectifiers like the 5v4,gz33,5z4,gz37,6106 etc,it is imperative that they test above 95% and both sides measure the same. The chugging sound some are experiencing here when playing vinyl is due to the excessive voltage drop of the rectifier type used. Insert a weak rectifier of any type and you may experience this artifact regardless of type, however the gz34/5ar4 will not exhibit this trait until it's much weaker than the others.Furthermore, ones choice of regulation tubes will not have any impact on this artifact. While a weaker rectifier may work in many other applications... they will be of marginal success in any of the supratek's that employ a phono stage. I have a nos Valvo gz-34 [test's just below 90%]that I use in a pair of vintage siemens klangfilm amps and they ehibit this trait in both the cortese and the syrah when using the phono stage. I also experience the same thing with a nos 5v4 and a Bendex 6106 and they both test above 90%. " Important Note"... all of the rectifiers that are employed in the supratek's are of the "indirectly heated" full wave variety, the 5y3gt mentioned else where is a "directly heated" rectifier type and not recommended. The use of directly heated rectifier types in the suprateks will eventually strip the cathodes of your other tubes. Not a good thing for those employing rare and expensive nos tubes. A directly heated rectifier will cause premature tube life with the other tubes as the getter of the tubes is used up quickly releasing gas in the tube.When cold,the gas molecules are struck by high energy electrons from the cathode, being positive they are attracted to the negative grid. The gas molecules will shoot right past the grid and onto the cathode,and therefore eventually eroding the cathode surface and compromises the life of the tubes. The other tubes employed in the preamp should not have instantanious voltage applied until they are warm, this allows the tubes getter to absorb the gas molecules that have accumulated from that last use of the preamp.

The last several posts have been most valuable to me. Thanks to all of you!

Hi Guys,
great posts.
Loving my Syrah.
Just bought another pair of Sylvania 6GK5s & a pair of Western Electric 5842s for the phono section.
The 6GK5s are duplicates of whats in place. The Western Electrics seem to hang an image centrally a bit better than
the Raytheons it came with. Tried some Creatura tube dampers on the 5842s - they have worked well for me in the past but I worry the valves are so small, the dampers may be
making them run too hot?
Not tried the NOS MullardGZ34 yet as the guy I bought it from said the 5AR4 was better - maybe the Mullard is below par?
As a matter of habit I have sat both pre & psu on Final Labs Dharumas so that both units 'float'. I can feel no vibration getting to the units even in my small listening room.
The new pairs of valves were bought as one or more of the valves in the phono section was a bit noisy - nothing too troublesome - the new ones have the same problem - ah well I knew I would have to buy at least 3 different pairs to get a quiet set !
Love the amp & can't wait to try some different power cords - using a PS Statement at the moment but will probably end up using a Shunyata of some description to keep
synergy with the rest of the system.
Tried the gain setting at 3 which gives solidity to the sound but bloats the bass a bit over setting 2 (Pass Labs X-250). Will just keep experimanting but any pointers welcome

Tung sol 5881 red/brown base mil spec
Sylvania black base 6SN7s
and the aforementioned in the phono/rectifier sections.

Happy listening,
Si

Ecclectique,

Thanks for the very "educational" explanation on why the chugging sound on the 6106 and not on the 5AR4. As a habit, I researched all the things you said and they are spot on frrom what you said as far as the difference between the two tubes are concern. For me, I will keep the 5AR4!

Anybody looking for a NOS (not even a minute used!) 6106 and a used pair as well? :)

While we're back on tube rolling in the Supratek pre's, I thought I'd offer a suggestion that I haven't seen yet. I believe it was the "Supretek Tubes for Everyone" post where someone talked about how much they liked the sound using a 5y3. Later, in that post and here, it was correctly mentioned that this tube should not be used since it is directly heated. There is an alternative. The Mazda 5Y3GB. Characteristics wise, this is a 5Y3. Where it differs is that it is indirectly heated. This rectifier has an ST shaped bulb and has a pretty cool filament glow to it. I've been using one in my Syrah for several weeks now with no ill effects. It's currently replacing a NOS metal based Philips GZ34 and drops the voltage to the regulators by approximately 20vdc over the GZ34. The tube is not yet fully broken in. As such, I would characterize the main difference in sound to be that the circuit does not roll off the HF as much with the 5Y3GB as with the GZ34. This is in both the line and phono stages. If you have bright system, this tube may not be for you. I had to back off the mid frequency L-pads on my Altec Model 19's due to them being overly bright after this swap. The 5Y3GB is relatively inexpensive and can be had at several different online sites. A search will quickly show these vendors.

Do this at your own risk, YMMV, and all the other usual disclaimers.

Steve