opinion of using a 6SN7 over a 12AU7 in an amp driver boards

[trainbuftony]

Great. How many db is missing in the mid range? What frequency does it start, and what frequency does it get better?
Once you identify rolloff points you can start looking for time constants that correspond with them.
If you want to roll tubes, roll tubes.
If you want to diagnose a problem we can help with that too.
Rolling tubes isnt likely to solve a problem, which you cant identify.

 

[Dr. Ears]

I own over 300 6SN7's and believe on average that they are a better tube than the 12AU7, which I own over 100.
Even better are the previous generation the 6J5-GT's, the 6J5-G's and the British L 63's, each of which is the exact equivalent of one half a 6SN7 and there are ready made adapters available on Ebay.
Search for 6J5 + 6J5 = 6SN7.

 

[grindfix]

Air-- someone suggested clear-top 12AU7. I have several dozens of those from Allen organ. I believe they are all RCA made.
Pay shipping and I'll send you a pair or two. I can run them through my Hickok 533 to get better "matched" tubes.

 

[zackthedog]

Air-- someone suggested clear-top 12AU7. I have several dozens of those from Allen organ. I believe they are all RCA made.
Pay shipping and I'll send you a pair or two. I can run them through my Hickok 533 to get better "matched" tubes.

Those are next on my list to tweak the W5 clones. They have a good reputation.

 

[zackthedog]

So I should by a $350 power cord. In some forums that WOULD be the answer. Yeah, I'v seen those posts.

I have a dear, dear old friend, a devout music lover, who constantly buys this sort of tweak and then tells me nothing sounds right. I always have to talk him down off the tweak ledge to get his system back to normal. ;-)

 

[grindfix]

Those are next on my list to tweak the W5 clones. They have a good reputation.

I have more then I will ever need. In fact, they've been sitting for 2 years and I didn't have anything they could be used for!

 

[sKiZo]

I like it. Standard VTA board in my somewhat modified Latino ST120 using a handy dandy converter socket in the middle, with matched 5814's in the sides. Plug and play with the appropriate adapter.

As with any tube choice, lot depends on the brand. Currently running a '50's Graylock. That makes for a stronger midband, but also tends to push the bass a bit hard for my tastes. No problem - I run a "lighter" tube in my buffer to compensate. I bounce between the Graylock and a '60's era RCA coin base. Both are inexpensive "classic" tubes.

 

[zackthedog]

I have the most important test gear in the world - my own ears.

And your ears are telling you that the system doesn't please. Perfectly reasonable. I think you've hit a brick wall of taste. Something in the system isn't delivering what you want. A perfectly reasonable conclusion.

 

[grindfix]

For me, most of gear has midrange stepping forward and can be harsh. Flea watt SET completely solved that. That made me think that harsh midrange is the product of smallish, less then perfect acoustically room and large power headroom. Everything has to be in compliance...

 

[FlaCharlie]

You should spend $350 On some basic test gear and stop guessing.
You need an equalizer.
That's the tool which gets the job done until you have the ability to collect some data.

I have the most important test gear in the world - my own ears.

Test gear? . . . Check.

Equalizer? . . . ???

A graphic EQ with a lot of bands or a parametric WILL allow you to boost the midrange frequencies you find lacking. Or, you can spend a fortune on rolling tubes and perhaps you'll get lucky and find some that get you closer. Perhaps.

Use the right tool for the job.

 

[airtime]

Or, you can spend a fortune on rolling tubes and perhaps you'll get lucky and find some that get you closer.

Sometimes you have to just give it up and give in. Just because an amp is well made and enjoyed by others, doesn't always fit your own taste in sound presentation. That IS the beauty of this hobby. Choose your style and enjoy.

Heck, I have friends that have purchased $5k amps and absolutely hated them. I think I'll stick with the EL84 types.

 

[nj pheonix]

try a 6CG7 or 6FQ7. Basically the same thing as a 6SN7 but in the smaller bottle. I'd be surprised if adapters do not exist to make it work, the only change is to the heater connections.

The adapters clearly exist . I have a couple.
FWIW, I had a VTA ST120
The driver board is the same.
I suspect I tried more variants than almost anybody ( 12AU7s and 12BH7s, also IIRC E80CC in the middle) I'd guess upwards of 75 versions in every position on the small pin driver board. ( I'm not sure but I think the board evolved somewhat since I built around '11).
At first I was amused at how the sound was altered by rolling tubes in it. Then I came to believe it was a flawed design because the tubes shouldn't alter a properly designed circuit.
At some point , I was exchanging messages with Kegger. He said the tubes weren't at their proper operating point and suggested the changing ( i think )3 pairs of resistors. I mention this because I think tubes4hifi actually altered the value on these resistors in later revisions ( let me say I believe I was told this , but I'm not sure , so don't take it as fact).
I did find after the resistor changes the tube rolling made much less difference. I have no measured test results, so take everything i say with a grain of salt.
Anyway, at the end , being so far down the rabbit hole i put the 6SN7 driver board. I thought it performed about as well as some of my preferred 12AU7 and 6BH7 variants.
There wasn't an OMG I can't believe I wasted all this time with the small bottle tubes.
I wasn't aware at the time of the 6CG7 option so that was never tried.

 

[airtime]

He said the tubes weren't at their proper operating point and suggested the changing ( i think )3 pairs of resistors. I did find after the resistor changes the tube rolling made much less difference. I have no measured test results, so take everything i say with a grain of salt..

I did try tweaking the plate voltage of the driver and inverter tubes. It did make an significant difference in sound. The only problem is I don't know enough about how to rebias those tubes. I understand the graphs, etc.... but in real life terms I'm not educated enough on how to refigure the entire circuit. I also don't have the equipment to be reinventing the driver board.

But yes, if I had the know how, I would rework the voltages on the driver tubes.

 

[nj pheonix]

It's a very good amp. It has its personality.
I used it for several years while other pieces came and went.
It eventually went as well.
At some point ( sooner or later) it is what it is.
You have to say this is it or perhaps look elsewhere.
There isn't a right or wrong path on it.

 

[airtime]

It's a very good amp. It has its personality..
At some point ( sooner or later) it is what it is.
.

Exactly
I'm deciding on two paths.
1- revert it back to the original driver board using 7643 tubes
2-sell it before I start thinking of re-tinkering and trash it for resale.

I'm comfortable with either option. It's a great amp the way it is right now, but it's just not my taste. I'm good with moving on.

 

[gadget73]

Less than optimal op points would definitely make a thing way more sensitive to individual tubes. For some that might be a plus, for me who hates having to own an arsenal of tubes just to find the magic one in a given amp that would be a nightmare. For me the ideal would be absolutely any tube that is in good electrical condition sounds identical.

 

[airtime]

For some that might be a plus, for me who hates having to own an arsenal of tubes just to find the magic one in a given amp that would be a nightmare. For me the ideal would be absolutely any tube that is in good electrical condition sounds identical.

Exactly. I hate having something that has to use the "golden tube" or nothing. If I can't use a wide number of "what ever's" then how good could that design be.

I have a bit of that problem with my CJ preamp. It can only use either a EH or GL 6922's because of how hard it drives them. And even the Gold Lions start to hum after about 9 months.

I'm getting too old to have picky stuff.

 

[Lavane]

I've tried RCA 12AU7 clear tops, 12BH7's, E80CC's and ECC99's in mine along with several 6SN7's with an adaptor socket. I used one E80CC and two Philips 12BH7's for several years and liked it. I tried a 6SN7 and didn't really notice any difference between it and the 12AU7. In the end I settled on an old stock 12BH7 and two RCA clear top 12AU7's. The new manufacture 12BH7 I tryed I did not like much.

 

[sKiZo]

As mentioned, a 12AU7 variant amp usually is a bit of a compromise as there's so many tube types you can plug in with no mods. The CCS tail used in some of them does a real decent job of minimizing any inconsistencies, and also mostly eliminates any potential matching problems in the channel drivers.

That said, if you're really anal (sonically sensitive?) about it, you can find several mods that are alleged to result in improved sonics. I know of at least one that does the resistor swaps specifically tailored to the 12BH7 series. Never tried it here as I'm quite happy with what I'm hearing more times than not, and a simple swap cures any "problems".

PS - midrange push? Just flip the switches, eh ... ;-}

 

[FlaCharlie]

I'm deciding on two paths.
1- revert it back to the original driver board using 7643 tubes
2-sell it before I start thinking of re-tinkering and trash it for resale.

I'm comfortable with either option. It's a great amp the way it is right now, but it's just not my taste. I'm good with moving on.

Again . . .

Equalizer? . . . ???

A graphic EQ with a lot of bands or a parametric WILL allow you to boost the midrange frequencies you find lacking.