Valve amps, great with Jazz, shit with everything else.

[anthonyTD]

The output valves are 5881, which are a military grade 6L6GC, nothing realy wrong with those as far as being a good workhorse, the next one down look like JJ 6SN7, which can easily be upgraded by either NOS versions, Brimar's for instance may suit your pallet in this instance Mike, as for modern equivilents the Tungsol's are ok, as are some from Shuguang [chinese] first valve, if you can make do with a bit less gain, and there is already an ECC83/12AX7 fitted, then you could try a Military spec ECC81 CV4024 in there, or a 5751, hope this helps.
A...

[anthonyTD]

Hi, yes silly mistake as my source was also talking about Chinese made EL34's which confused me.

"The Russians sold NOS EL84 for 200$ per 1000, and from China you could buy good EL34 and ECC83 for incredible low prices, if you knew the way. It was by that time that TESLA decided to sell off their line of Audio tubes to JJ. In the last years, the TESLA ECC83 was sold for only 2 € in OEM quantities, by company in Austria, who claimed to be their exclusive distributor. From this you can see that the factory price must have been very low. After selling off the audio line, TESLA went on making transmitter tubes, and other devices like vacuum capacitors, and military devices, which they considered more profitable.

So the TESLA tubes like ECC83, EL34, and KT88 were out of production now. The machines were moved out of the building and reinstalled at a factory of a man called Jan Jorgo, better known as JJ." from https://jacmusic.com/tesla/tesla-jj.html

[Marco]

The output valves are 5881, which are a military grade 6L6GC, nothing realy wrong with those as far as being a good workhorse, the next one down look like JJ 6SN7, which can easily be upgraded by either NOS versions, Brimar's for instance may suit your pallet in this instance Mike, as for modern equivilents the Tungsol's are ok, as are some from Shuguang [chinese] first valve, if you can make do with a bit less gain, and there is already an ECC83/12AX7 fitted, then you could try a Military spec ECC81 CV4024 in there, or a 5751, hope this helps.
A...

Ok, so essentially leave the output valves alone and upgrade the rest to NOS?

I reckon then that the main source of the 'strident' sound Mike's getting will be the currently fitted 6SN7s and 12AX7, as in my experience JJs can sound a little 'zingy'. And like you say, if he can afford to lose a little gain, then popping in a CV4024 or 5751 instead of the 12AX7 would defo help smooth things out.

If not, a nice NOS Mullard CV4004/ECC83 would do the biz!

Marco.

[anthonyTD]

Yes, i think by changing all the small signal valves for something better, that should make a considerable diffrence, the Sovtek 5881's don't tend to have anything really objectionable about them sonicaly, infact, i would say they can be a bit polite in some fitment, [i use lots of them in Guitar amps ie; Fender's etc] so i would defo start with the small valves first.
A...

Ok, so essentially leave the output valves alone and upgrade the rest to NOS?

I reckon then that the main source of the 'strident' sound Mike's getting will be the currently fitted 6SN7s and 12AX7, as in my experience JJs can sound a little 'zingy'. And like you say, if he can afford to lose a little gain, then popping in a CV4024 or 5751 instead of the 12AX7 would defo help smooth things out.

If not, a nice NOS Mullard CV4004/ECC83 would do the biz!

Marco.

[anthonyTD]

Just one example from a recent customer who was a bit sceptical about the diffrence Valve's make:

Hi Anthony,

Just to give you a bit of feedback on the Mullard M8137 tubes I picked up from you today .

First they sound nothing like the CV4004 I have been using in the Croft for the last few days which is a good thing gone is the slight top end glare that I told you the above valve exhibited.

I’m the cat that’s got the cream I cannot believe the sound these valves produce there is no aspect of the sound that I could possibly say I dislike in fact the complete opposite the bass was the first thing that hit me so solid and pronounced, the top end is also everything I could want nothing glaring just so right on every type of music I have played . I don’t normally take much store in reviews but on this occasion I have to agree it stated the best Ecc83 by a mile and from what I am hearing I cannot dispute this and although the price is high worth every penny .

[Marco]

Cool... I might have a 5751 in my spares box Mike could have for nowt, so will have a look later - at least that would be one less thing for him to buy

And yeah, M8137s are lovely! Not cheap, however. They're a 12XA7/ECC83 equivalent though, aren't they, or am I thinking of something else?

Marco.

[anthonyTD]

Correct!

And yeah, M8137s are lovely! Not cheap, however. They're a 12XA7 equivalent though, aren't they, or am I thinking of something else?

Marco.

[Marco]

Ok, so it depends then if Mike can afford to lose some gain or not then, in terms of fitting a 5751, and also whether he can afford the ticket price of an M8137.. What are you talking about, £100?

Marco.

[anthonyTD]

For those who have stock of genuine new Box anode type, around £150-00, £170-00 now!
https://www.ebay.co.uk/sch/i.html?_f...M8137&_sacat=0

Ok, so it depends then if Mike can afford to lose some gain or not then, in terms of fitting a 5751, and also whether he can afford the ticket price of an M8137.. What are you talking about, £100?

Marco.

[Marco]

Just goes to prove though how much better the best NOS types are compared with the pish (in comparison) that they make today!

Marco.