Tube questions....again

I don't think I ever got a good answer to my question as to which set of tubes in my pre-amp have the most effect on the sound output. My VAC uses 2 12AU7s (input I believe) and 2 12AX7s for the output-gain.

When I took ownership of this pre, the previous owner had 4 12AX7s in it, which will play but not correctly. One could also use 4 12AU7s but again without good results.

I had several pairs (triplets) of Sovtek 12ax7lps and wxt+ from my previous Sound Valves 101i so I used a set of those along with purchasing a set of JJ Tesla ECC82s. I think they were under $15 a piece.

I recently had some AX7s go bad and am looking to replace them but still have questions.

Is it always best to have both sets of matching quality-price range and MFG?

Would I be best off leaving the AU7s alone and focusing on the AX7s? The PSVane tubes have a pretty good rep so far but I don't want to spend $200 right now.

So I'm trying to decide do I go with 1 set of PSVane 12AX7s or get a set of each JJ Tesla Gold Pin or similar keeping my budget somewhere near $100?

Choice of tubes is definitely a personal choice. It all boils down to what sounds best to you. For example, my gear uses 6CG7 or 6N1P tubes. People rave about how great the 6CG7 RCA Clear Tops sound. To me they sound just ok and I prefer my Tong Sol's along with Aprex, Mazda-Brimars and RCA Black Plates.

When rolling tubes there is always a trade off in some part of the sound. You can absolutely go nuts trying to find that right combination. But to answer your question, there is no written rule that you have to have matching price tubes. One of the benefits about tube gear is tube rolling to taylor the sound to your liking.

I hope this helps some.

Larry

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Originally Posted by blackraven

Choice of tubes is definitely a personal choice. It all boils down to what sounds best to you. For example, my gear uses 6CG7 or 6N1P tubes. People rave about how great the 6CG7 RCA Clear Tops sound. To me they sound just ok and I prefer my Tong Sol's along with Aprex, Mazda-Brimars and RCA Black Plates.

When rolling tubes there is always a trade off in some part of the sound. You can absolutely go nuts trying to find that right combination. But to answer your question, there is no written rule that you have to have matching price tubes. One of the benefits about tube gear is tube rolling to taylor the sound to your liking.

I hope this helps some.

Larry

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Thanks BR, but I guess my main question is, will I get a better change in sound by changing the AU7s or the AX7s. I don't understand enough as to what the AU7s do. I do understand the AX7s are the output and add gain.

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Originally Posted by Hyfi

I don't think I ever got a good answer to my question as to which set of tubes in my pre-amp have the most effect on the sound output. My VAC uses 2 12AU7s (input I believe) and 2 12AX7s for the output-gain.

When I took ownership of this pre, the previous owner had 4 12AX7s in it, which will play but not correctly. One could also use 4 12AU7s but again without good results.

I had several pairs (triplets) of Sovtek 12ax7lps and wxt+ from my previous Sound Valves 101i so I used a set of those along with purchasing a set of JJ Tesla ECC82s. I think they were under $15 a piece.

I recently had some AX7s go bad and am looking to replace them but still have questions.

Is it always best to have both sets of matching quality-price range and MFG?

Would I be best off leaving the AU7s alone and focusing on the AX7s? The PSVane tubes have a pretty good rep so far but I don't want to spend $200 right now.

So I'm trying to decide do I go with 1 set of PSVane 12AX7s or get a set of each JJ Tesla Gold Pin or similar keeping my budget somewhere near $100?

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Here's a good site that Raven sent me some time ago. If you go towards teh middle of the page you will see a chart with a list of tubes and the characteristis of each tube. It may be of some help to you.

12AX7 Tube Type Review


Also I to thought about the PSVane. Another good choice would be the Golden Lion tubes...

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Originally Posted by Hyfi

Thanks BR, but I guess my main question is, will I get a better change in sound by changing the AU7s or the AX7s. I don't understand enough as to what the AU7s do. I do understand the AX7s are the output and add gain.

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In my preamp I have a pair AX7's which are the left and right gain. I have a pair of Au7 with one not going through the signal becasue it some how is for the power supply. The other Au7 has both AX7's signal going through it. So I assume the Au7 in your has the gain stage going through your Au7's.

I changed out my stock Au7 for a Tulefunken Au7 and it gave me a better presentation. I think the Au7 would change the sound more...but I have yet to change the AX7's.

This is what Poppachubby sent me some time ago

"Frenchy lots of preamps wil have a final stage which the signal will go through. My EICO has a pair for each channel and then a fifth tube which it all filters through. What it means is that you can have more fun manipulating the tone. I often switch out this fifth tube between a Mullard and a Psvane. I am done rolling for now, so enjoy and hopefully you will find the perfect combo."

He it is again just in case you did not see it.

"Frenchy lots of preamps wil have a final stage which the signal will go through. My EICO has a pair for each channel and then a fifth tube which it all filters through. What it means is that you can have more fun manipulating the tone. I often switch out this fifth tube between a Mullard and a Psvane. I am done rolling for now, so enjoy and hopefully you will find the perfect combo. "

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Originally Posted by frenchmon

Here's a good site that Raven sent me some time ago. If you go towards teh middle of the page you will see a chart with a list of tubes and the characteristis of each tube. It may be of some help to you.

12AX7 Tube Type Review


Also I to thought about the PSVane. Another good choice would be the Golden Lion tubes...

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Thanks Frenchy. I have been going over the previous threads and suggestions. Seems like everyone agrees the Sovtek LPS to be good tubes but I think I can get better sound. I can't afford to buy multiple sets of tubes to experiment but would rather just spring for the best option.

I would really like to know what the 12AU7s do before the signal gets to the 12AX7s. And, which ones have the most effect on the sound output.

"I would really like to know what the 12AU7s do before the signal gets to the 12AX7s. And, which ones have the most effect on the sound output. "

I would imagine its only job is to manipulate the sound according to which tube is in the soket, and then output that sound to amp. I dont know that it does anything before the signal gets to it. But thats just my guess. I got my little knowledge for PoppaC, E-Stat, and Poultrygeist.

Did you see my post above of what PoppaChubby said?

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Originally Posted by frenchmon

"I would really like to know what the 12AU7s do before the signal gets to the 12AX7s. And, which ones have the most effect on the sound output. "

I would imagine its only job is to manipulate the sound according to which tube is in the soket, and then output that sound to amp. I dont know that it does anything before the signal gets to it. But thats just my guess. I got my little knowledge for PoppaC, E-Stat, and Poultrygeist.

Did you see my post above of what PoppaChubby said?

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Yeah, thanks for the info and reposts. I'm going to try emailing VAC and see what they tell me.

Yeah..I agree.

I just talked to Kevin at VAC and he gave me one hell of an education I will probably never understand. By the time we were done and he took the time to answer my many questions, I am considering ordering tubes from them. The 12AU7s are NOS American, Phillips I think he said and the 12AX7s are from one of 3 Chinese MFGs.

He said the JJ tubes have what he describes as a Bark, along with the signature Sovtek sound of being up front and sharp. With their recommendation of tubes, I would have a more linear sound with some more air, mellower highs and more detailed bass.

He also said that if I upgraded my unit to a MK3, do not run Sovtek tubes in it at all. Also, for my pre-amp, I do not need to worry about spending extra for Low Noise but he does suggest matched pairs.

Each tube they sell is $22 so I can do all 4 for under my $100 mark and get a real good baseline sound that the VAC engineers are familiar with and if I am unsatisfied, he can point me in specific directions to alter the sound any way I want.

Other info he gave was that the AU7s are the more critical tube and should be the higher quality if going that route. But, he also said that with a given set of AUs with another given set of AXs that it will sound just great, and by swapping the AXs, the preferred sound from the AUs would change also. It's all pretty confusing to the layman for sure but I think going with the tubes that they put in their new gear today will put me on the road I am looking for without having to experiment and spend too much money playing around.

Who better to suggest the correct tubes as a good start but the people who created my pre amp.

I just ordered 2 matched sets from VAC. $88 plus shipping and they should make it to me by Monday or Tuesday so I can update this thread after that before break in time and then after another 50-100 hours.

Looking forward to some better sound from my VAC after using the cheapest Au7s I could buy along with the old run down Sovteks.

I will also update as to exactly what makes and models they send me when I get them.

Very good Hyfi! Thanks a lots....I think you did the right thing. Peabody's Conrad-Johnson came with some great tubes as well and Conrad Johnson does specify the tubes he should use. I think I will give a call to the USA distributor of Vincent to see what they recommend.

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Originally Posted by Hyfi

I don't think I ever got a good answer to my question as to which set of tubes in my pre-amp have the most effect on the sound output. My VAC uses 2 12AU7s (input I believe) and 2 12AX7s for the output-gain.

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If you look on their website, you'll find the manual for the CPA-1 which adds a phono stage to the line stage of the CLA-1. The 12AU7s are used for gain and the 12AX7s are unity gain buffers. For that reason, the 12AU7s will have a more profound effect on the sound quality - unless you choose the passive buffered mode. The Manley DAC I use in the vintage system also uses 12AU7s where I have experimented a bit. I really like the sound of 60s vintage RCA Cleartops.

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Originally Posted by Hyfi

Is it always best to have both sets of matching quality-price range and MFG?

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For the gain stage, yes. For the buffer stage, no.

rw

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Originally Posted by E-Stat

If you look on their website, you'll find the manual for the CPA-1 which adds a phono stage to the line stage of the CLA-1. The 12AU7s are used for gain and the 12AX7s are unity gain buffers. For that reason, the 12AU7s will have a more profound effect on the sound quality - unless you choose the passive buffered mode. The Manley DAC I use in the vintage system also uses 12AU7s where I have experimented a bit. I really like the sound of 60s vintage RCA Cleartops.


For the gain stage, yes. For the buffer stage, no.

rw

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Thanks E.
While I had seen the manual, just didn't quite understand it. I'm googling my butt off but electronics was never my strength.

So in gain mode, it's more about the AU7s and in Passive its all about the AX7s. There lies another rolling expedition. The trick is putting together 2 pairs that compliment each together and in passive. That is why I am hoping that the VAC suggested tubes gets me to that place.

They go on to say
"The Active modes add a Class A amplifying triode tube to each channel, and causes the main
outputs to have inverted absolute polarity with respect to the line inputs. To correct for this you may
invert the polarity between your power amplifier and loudspeakers."

Should I be reversing one end of my speaker cables? And, are they saying only in active mode, which would mean flipping the cables along with switching from gain to passive?

Both the 12au7 and 12ax7s will affect the sound. The JJ's and Sovtek's are entry level tubes at best and can't compete with vintage NOS tubes. You won't go wrong with tubes like RCA clear tops/black plates, Amperex orange globes/bugleboys, Mullards, Tungsols, Telefunkens etc. NOS Mullards took my Paramours to another level. Had the guy who sold me the Bottlehead Paramours heard them with the Mullards he would never have sold them.

Look for relabled organ tubes such as Conn, Lowery, Baldwin etc as they are built to higher standards. Good testing used tubes will save lots of money over NOS. Preamp tubes can last forever.

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Originally Posted by Hyfi

Should I be reversing one end of my speaker cables? And, are they saying only in active mode, which would mean flipping the cables along with switching from gain to passive?

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That would seem to be the case. Conrad-Johnson preamps also invert phase. Not a problem, but definitely a detail.

rw

I recently replaced stock 12ax7 preamp tubes with Genelex golden lions. Definitely pleased with the decision. Warm and very very quiet.

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Originally Posted by TheHills44060

I recently replaced stock 12ax7 preamp tubes with Genelex golden lions. Definitely pleased with the decision. Warm and very very quiet.

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thanks for that information.

Just looking at some new products on the VAC website and within one of the descriptions, there was a mention of the VAC President, Kevin Hayes.

So when I called yesterday to ask questions, thats who I talked to but had no idea I was speaking to the Pres.

Where do you get that kind of service to a nobody calling to ask dumb questions?

Sounds like great customer service.

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Originally Posted by Poultrygeist

Look for relabled organ tubes such as Conn, Lowery, Baldwin etc as they are built to higher standards. Good testing used tubes will save lots of money over NOS. Preamp tubes can last forever.

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Most of my collection is Conn branded. I also have some Sylvanias which are pretty nice, too.

rw

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Originally Posted by Hyfi

Just looking at some new products on the VAC website and within one of the descriptions, there was a mention of the VAC President, Kevin Hayes.

So when I called yesterday to ask questions, thats who I talked to but had no idea I was speaking to the Pres.

Where do you get that kind of service to a nobody calling to ask dumb questions?

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Sounds like my experience with Richard Gray Power Company. Great customer service is so refreshing.

Quote:

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Originally Posted by Hyfi

They go on to say
"The Active modes add a Class A amplifying triode tube to each channel, and causes the main
outputs to have inverted absolute polarity with respect to the line inputs. To correct for this you may
invert the polarity between your power amplifier and loudspeakers."

Should I be reversing one end of my speaker cables? And, are they saying only in active mode, which would mean flipping the cables along with switching from gain to passive?

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Well that was a little more than a subtle change. I only had a chance to spin one comp at low levels and could clearly hear a difference.

Hard to explain but it was as if the system took a decongestant. Clearer separation, more air and detail. Looking forward to spinning a few of my reference tracks at higher volume later today.

With this change and some new tubes, I should hit another level of performance I have yet to experience in my system.

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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.