EXPIRED 5751 valves wanted -used ok

[Cooksferry]

Interested in any 5751 valves that anyone might want to part with. I have a reasonable selection of current EH and Sovtek models and a few NOS types(Sylvania Gold Brand/PIn-RCA BlacK plate Command-GE 5 star etc) but am interested in trying some more variants in that elusive search.

 

As long as the tube still runs ok so I can get an idea of how it sounds in my amp is my main concern at this time.

Also could be interested in any 12AX7/ECC83s.

[Owen Y]

Let me know some more details of what you have tried, what you are looking for, etc & I MAY be able to help.

 

Looking at the cct diag, it looks like you need a 5751/12AX7 with good channel balance, ie L/R sections fairly well matched.

 

The cct also suggests to me that the 1uf coupling caps could be audibly important, also the 33/160v electro cap, cathode bypass cap. What parts do you have here? Do you have the upgraded version and/or was it a kit or fully assembled version?

 

The psu would be another obvious area of potential improvement, if you have solderig skills (if it is kit assembled and warranty is not an issue.)

Cheers, Owen

[Cooksferry]

thanks for your reply Owen.

At the moment I'm running a 1950s RCA 5751Command blackplate that is working pretty well for me.

Since my original post I've picked up a Tung Sol 5751, an RCA 12AX7 blackplate,a GE 3 mica blackplate, a Sylvania 3 mica greyplate, a couple of 1950s Sylvania 12AT7WA plus a couple of others.

Although the amps builder and designer thinks they work fine with a current production Sovtek there's always the thought that there's something better, especially with nos valves.

The premium Sovtek I tried wasn't too bad but not as nice as the RCA or the Sylvania Goldbrand(gold is right for the prices they're starting to fetch)

I've been mainly buying from established dealers in the states and all the valves I've purchased so far are pretty well matched if not perfect.

The amp I have was one of a limited run of 5 built by Dr Peppard to celebrate the 100th headphone amp so it comes with all the best bits he lists. Because of this I'm a bit loath to start changing anything inside. I know from threads posted at Headfi

(http://www.head-fi.org/) that some owners have 'hot rodded' their amps to gain increased performance.

It's been tempting to try one of the better 12AX7s like a Mullard just to see how it sounds but am a bit reluctant to take that chance.

 

What I was/am looking for is any 12AX7/5751 with a bit of life left that i could purchase to try. If I like what I hear then I can try for some nos items with confidence.

[Owen Y]

Hi Cooks

 

I have some NOS stuff, some other loose older ones + a valve tester, so I may be able to find and/or test up some valves for you if req'd.

 

Have you had time to establish a preference yet, amongst all the tubes that you now have purchased?

 

Was the Sovtek a 12AX7LPS?

 

Who have you been buying from?

 

Mullards may not be better, maybe just different!

Owen

[Cooksferry]

Hi Owen.

Its been a learning curve with this, first time with valve gear.

Although the amp normally ships with a Sovtek 5751 Lloyd didn't have any in stock and rather than keep me waiting it arrived with a NOS GE 12AT7 which was quite acceptable.

The only tubes I've had time to have get a few hours on so far have been the RCA Command(v Nice-will try for more), the Sylvania Gold Brand-ditto, not the best for rock but wonderful for acoustic instruments and vocals.

EH 5751 premium gold pin(EH box,Sovtek on tube) matched sections and one I'll stock up on as they're cheap-quite smooth and clean sound.

Yes the 12AX7LPS is a Sovtek, haven't tried it yet.

Also tried an EI 12AX7 elite Gold- sounded not too bad for a start but after a few hours found it to be a little grainy on some of the higher notes although the treble extension was better than some of the 5751.

I dont think I've really had enough time with the amp or any of the tubes to pick a default tube yet. With the number of tubes I now have and the small amount of time I get for listening it'll be well into next year before I work my way through everything.

Purchases so far besides some from e-bay have been from

BOI Audioworks(current production tubes)

Audiotubes.com-nos valves

both have been very good to deal with and efficent.

Just ordered some more nos items from Vacuum Tubes Inc.

 

re the Mullards, the current trend amongst headphone amp users seems to be to bypass the 12AX7, even the top rated nos tubes and go for 5751. Much of this seems to be based on the review at the link below

http://www.audioasylum.com/audio/faq/joes-tubes.html

still there's an itch to try a Bugle Boy or a Telefunken just to see

for yourself.

Don't know if you're very familiar with headphone amps, but there's been a huge upsurge in valve amps being made, some costing several thousand US dollars. A friend took one listen to my Mapletree amp and ordered one for himself. Nice to see there's still life in these obsolete technologies.

 

Do you have anything you're interested in parting with?

 

Robin

[Owen Y]

Hi Robin,

Let me know how you get on, when you have waded through all those fine tubes that you have and have defined some personal preferences.

 

I should be able to locate a sample or two of a British or European tube brands.

 

Looks like you need only one pc 12AX7/5751/7025/ECC83/M8137 for your cct.

Cheers, Owen

[Owen Y]

Hi Robin,

I see that you mentioned a 12AT7...this would be a much lower gain tube. Note that it also draws much more tube current, than a 12AX7 (ie, if that has been sanctioned by the designer).

Owen

[Cooksferry]

Hi Owen.

yes the 12AT7s are ok. see mail below from Mapletree

 

quote'

" sent you two Sovtek 5751 tubes today by small packet airmail. I find them the best sounding to my ears of the currently manufactured types. They have a full, gutsy sound. I have also tried JJ Tesla ECC83s which were detailed but a bit thinner sounding. The best is an NOS (or used) N. American 5751 such as the GE 5 star, RCA, etc. The JAN GE 5751 is probably of later manufacture (1980s) when the U.S. government was stocking up before the factories closed for good. I haven't tried the EH gold 5751 but it is likely to be based on the Sovtek as they are made in the same factory I believe. The 12AX7LPS is felt by some to be the best of the Russian 12AX7s. There are also premium low noise versions of the 12AX7 such as the 7025. Of course, if you have money to burn you can go for the Amperex Bugle Boy or Telefunken NOS 12AX7/ECC83s. The 12AT7 I sent you actually sounded pretty good when I tested it. Wait until the 5751s arrive and you can use them as a basis for further experiments."

 

and in reply to my question re using any of the 12AT7 family

 

"I think any 12AT7 equivalent can be tried in the Ear+. The restriction is the heater current must be the standard 0.15A. Sounds like you are having fun. I think that the Sovtek 5751 is a good choice from among the currently manufactured tubes. "

 

"Looks like you need only one pc 12AX7/5751/7025/ECC83/M8137 for your cct."

you've lost me with that one Owen-not to good with abreviated text.

Robin

[Owen Y]

Sorry, what I meant was;

- All these tube types are 12AX7 types.

- I think I recall from the EAR+ cct that there is only 1 piece 12AX7 tube? ie the (twin triode) tube is shared/split betw L+R ch's.

Let me know how you get on with tube tasting. Regards, Owen

 

Originally posted by Cooksferry

 

"Looks like you need only one pc 12AX7/5751/7025/ECC83/M8137 for your cct."

 

you've lost me with that one Owen-not to good with abreviated text.

 

Robin

 

[Cooksferry]

 

Originally posted by Owen Y

 

Sorry, what I meant was;

 

- All these tube types are 12AX7 types.

 

- I think I recall from the EAR+ cct that there is only 1 piece 12AX7 tube? ie the (twin triode) tube is shared/split betw L+R ch's.

 

Let me know how you get on with tube tasting. Regards, Owen

 

Yes, only the one tube needed. From what I can recall from other users comments it doesn't seem too critical how well the triodes are matched..well I think that's what they mean. Gets a bit confusing at times. Good thing is not having to buy matched sets.

Really liking the RCA 5751 Command I've been using for awhile now, should be nicely run in and sounds good, definitely be after another.

Just put a 12AT7WA in this morning, a mid 50s Sylvania 3 mica black plate, reserve judgement until I get a few more hours up.

 

Do you use many of the 12AX7 variants yourself, if so in what amp?I'd be interested in your opinions on any of that tube family you're familiar with although I'm well aware what works for one person may not jingle my bells.

Cheers

Robin

[Owen Y]

Hi Robin,

For best stereo image balance & accuracy, you should have 2 tube sections matched. This is probably more discernable with (i)headphone listening, (ii)a simple, preamp cct like the EAR+.

 

I don't use 12AX7 much these days. I have used them in American & older British valve equipment in the past, eg Audio Research, Leak, Radford.

 

Sonically, NOS types may not necessarily be the best or most cost effective choice. It will, of course depend on your own ears.

 

I have had success even with some Sovtek(high gain, full sound, WXT type, haven't tried LPS) or Chinese(12AX7 is one of the better tubes made in China).

 

Some NOS types have more "finesse", ie sweeter tone, even tonal balance. If you have a system of adequate dynamics, gain & sensitivity, and bandwidth ...such as a good headphone setup, you could well appreciate the particular "style" of (some) NOS tubes. However, IMO, these expensive, non-renewable tubes acan be wasted on some modern equipment.

Regards, Owen

[Cooksferry]

Its nice that the internet dealers i've used all list the tube section test results on the pack. The modern EH(sovtek) premium 5751 had perfectly matched sections and as I said in an earlier post, sounds pretty good.

There's so much hype about NOS valves that it's hard not to get caught up, and of course the only way to find out is to buy/try which gets back to my original post.

I guess most modern equipment is designed to use current tubes

so as you say older types may be wasted.Certainly Mapletree feel quite strongly that the Sovtek 5751 is an excellent match for my amp.

 

I've pulled the pin on buying any more just now and concentrate on what I have. At a quick calculation based on hours listening per day, average tube life etc it could take me 30 years to wear out the tubes I have.

 

I have some items ex e-bay coming from France, would you be interested in possibly testing them for me at some stage.

 

many thanks for your input

Robin

[Owen Y]

Hi Robin,

Sounds like you are well set up for a while.

Incidentally, if you are paying significant money for tubes, they should be matched (if req'd) if NOS or tested if not new.

Regards, Owen