Tube questions....again

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Originally Posted by frenchmon

Sounds like great customer service.

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I guess when you sell an Amp that goes for $39,900 you better have the right people answer questions. That is what thier heavy hitting stereo amp goes for.

Knowing how good the VAC gear really is, and how lucky I was to get this Pre Amp for a steal, I sure wish I actually had the money to purchase some of the newer pieces. Absolutely gorgeous gear for sure.

http://www.vac-amps.com/Stmt450.jpg

Sounds like you got your new tubes in....and wow, that is a nice looking set up...$39.900??? Oh come on Hyfi...you know you got the coin. Just write one of those checks and have it for Christmas

Very nice gear there Hyfi! I have never heard VAC gear but it looks great and I have always admired VAC gear from a far. I'm sure it sounds awesome.

Speaking of tubes, I just ordered some 6CG7 Raytheon and Tung Sol Black Plate tubes from the 1950's. They are used but test about 95% new. The Black plates are supposed to have a warmer sound then the grey plates. I don't know if that is true but it has been my experience so far with the RCA's.

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Originally Posted by frenchmon

Sounds like you got your new tubes in....and wow, that is a nice looking set up...$39.900??? Oh come on Hyfi...you know you got the coin. Just write one of those checks and have it for Christmas

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No new tubes yet, that change was from reversing the wires at the speaker as per the manual. Tubes should be here Monday or Tuesday.

WRONG WRONG WRONG WRONG WRONG!-!-!-!-

I see several postings here which are absolutely incorrect regarding these tubes.
I have been an electronics hobbyist since 1960, and have designed amplifiers using these tubes; I am intimately familiar with them.

THE RIDICULOUS MISINFORMATION BEING POSTED ABOUT THESE TUBES HERE WOULD BE FUNNY IF IT WASN'T SO TRAGIC AND STUPID.

1) THESE TUBES ARE VERY DIFFERENT AND SHOULD NOT BE INTERCHANGED-YOU CAN DAMAGE CIRCUITS IF YOU DO.!!!
ONE IS HIGH-GAIN, THE OTHER IS LOW-GAIN, AND A CIRCUIT DESIGNED FOR ONE IS GOING TO DISTORT IF YOU SUBSTITUTE THE OTHER (AND THE TUBE CAN BE DAMAGED ALSO) !!!!!!

2) The 12AX7 has a gain (u) of about 100; the circuit gain may be slightly lower depending on the associated components in the circuit, but it is typically used in high-voltage-gain circuits, such as a phono stage (circuit STAGE GAIN 40-80 typically). Its typical plate current is approximately 1 milliampere.

3) The 12AU7 has a gain (u) of about 18; it is used mostly as a buffer or as a driver stage coupled to power tubes (typical circuit stage gain 8-14). Its typical plate current is approximately 10 mA.

Substituting one of these tubes for the other will usually result in substantial distortion and always results in improper circuit operation! It can also cause the tube to be damaged. Putting a 12AX7 in a 12AU7 circuit is especially bad, since it will probably be subjected to a plate current far in excess of its design limits.
Once a 12AX7 has been placed in a socket where a 12AU7 belongs, it almost certainly has been overstressed and damaged.

NEVER SUBSTITUTE ONE OF THESE TUBES FOR THE OTHER !!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!

THEY ARE NOT NOT NOT INTERCHANGEABLE !!!!!!!!!!!!

You have these tubes backwards, basically; typical voltage gain for a 12AX7 stage is 40-80; typical voltage gain for a 12AU7 circuit is 8-14.

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Originally Posted by blackraven

Very nice gear there Hyfi! I have never heard VAC gear but it looks great and I have always admired VAC gear from a far. I'm sure it sounds awesome.
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This is the pre I have. It's from the 90s. CLA-1 MKII
Dual Mono with Outboard Power Supply(20lbs)
VAC cla 1 mk ii: Image
http://pic4.audiogon.com/cgi-bin/ima...AC-cla-1-mk-ii

[QUOTE=Hyfi;372024]This is the pre I have. It's from the 90s. CLA-1 MKII
Dual Mono with Outboard Power Supply(20lbs)
VAC cla 1 mk ii: Image
http://pic4.audiogon.com/cgi-bin/ima...AC-cla-1-mk-ii[/QUOTE

Very nice. I like the gold look, very unique! I wish my AVA gear looked that nice. Frank VA is finally getting with the times and trying to spruce up the look of his more expensive gear.

The new Tubes are in.

What I received were a set of NOS JAN-Phillips identical to this but with a date of 9/87.
http://www.shine7.com/audio/tubepre_philips5814a.jpg

The 12ax7s came wrapped in bubble bags and do not have clear markings. in a yellowy-green writing, one side of the tube has the 12AX7 and on opposite side it just says China and there is a small number running vertical at 90 degrees to the other writing. They look to be a long plate construction.

After only a half hour warmup, I could tell I was on the right track. Things opened up a bit on both the bottom end and specially at the top end. After about 4 hours they were really sounding good. My Danes have never put out the current sound before. So much more detail and sparkle in the mids and highs. Maybe a tad bright at first listen but also a more live sound. Bass was deeper, tighter, and just plain more of it.

I listened to a couple well recorded disks, one HDCD, and a few older or not so great recordings and all sounded better by a long shot. I was hearing percussion, cymbal sounds, chimes and bells in tracks I previously never noticed.

I also flipped the Pre to it's Passive setting which cuts out the AU7s and just goes thru the AX7s. These new China tubes blow away the Sovtek AX7LPS and WXT+ tubes I have always used. It was like a whole new pre amp in Passive and not lacking a thing but some gain from the AU7s.

More to come as they break in and I get used to them.

I'm glad the new tubes worked out for you. It's always fun when a new pair of tubes gets it just right and a big disappointment when they don't work out. I just bought a pair of Raytheon Black Plate and Tung Sol Black Plate 6CG7's from the 1950's that I have been searching for over the past 2 years. Both tubes have a nice warm if not slightly darker sound with really smooth treble that I have been looking for, the best sounding 6CG7's I have found. And at a great price of $40 and $50 pr.

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Originally Posted by Hyfi

The new Tubes are in.

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Ooooo I like :-) Sounds like you made a good choice.

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Originally Posted by blackraven

It's always fun when a new pair of tubes gets it just right and a big disappointment when they don't work out.

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So true. I try not get too pissed off when I choose a stinker of a tube (i do though) but you don't know until you've tried em first hand, it's all a part of the process.

Thanks for the review of the tubes Hyfi! I await your final thoughts.

Keep in mind as well the insides of one man's preamp may be different from another's. For instance, mine uses four 6922's. Some good info shared though. Like I was under the impression all Chinese tubes were inferior.

Hyfi, now that you have the recommended manufacturer tubes, do you think you will ever roll? Me personally, I won't say never but it's not likely.

With Chinese tubes it's still a crap shoot. I've encountered some terrible sounding no name 12AX7, 12AU7, 6N1 and 6N3 Chinese tubes which came as standard equipment in amps while the 2a3c Shuguangs that came in my Dared proved outstanding. A second pair of Shuguangs replaced the highly regarded RCA 2a3 in my Bottlehead Paramours. Interesting that the Shuguangs came in boxes labeled Shuguang while the tube itself only reads "Electron Tube 2a3c Made in China".

Beware of bogus tubes on ebay which are sold as NOS but are new tubes made to look vintage.