Help / Advice / Suggestions Sought Valves

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Woodnut

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Hello,


I did post a thread a while ago on this topic and still haven't really found any answers since then so here goes:


I have Sheng Ya (Vincent) T100 Mono block power amplifiers. I am interested in tube rolling. They have the following valves:

1 x 6Z4, 1 x 6N6, 1 x 6N1.

The amps are Chinese and I am lead to believe that the valves used are also Chinese. I have sent quite a few emails to various sellers of tubes and have had different responses. Some say that the 6N6 and the 6N1 should only be replaced with exactly the same Chinese replacement as they are different to the Russian tubes of the same name. Others have said it is the 6Z4 that cannot be changed for any other than an exact Chinese replacement. Some suggest that any other than a direct Chinese replacement could damage the amp.

Here is some info I was sent in one of the emails:


Some known problematic tubes to replace:

6N6 (chinese), 6N6P (russian). This tube has NO known direct replacement: the best replacement is another 6N6 - 6N6P. However if you are experienced, and with the proper tools, it could be replaced (given socket rewiring and maybe some circuit tweaks) with 5687, 12BH7, ECC99 or E182CC. This last tube seems to be the closest equivalent.

* 6N1: not much info. Best replacement is still another 6N1. ECC88 and its various cousins might work, but be careful of the much higher filament current for the 6N1, and much lower allowed plate voltage for the ECC88. If the amp runs the 6N1 at less than 130V you can safely replace 6N1 with ECC88 (don't know how it will sound...), but if the quiescent plate voltage is more, ECC88 might fail and ruin your amp.


Another email suggested the following...
"Unfortunately I do not think there is much you can do. The 6z4 is a weird Chinese tube with no sub so leave it be. The 6N6 and 6N1 are chinese tubes that have Russian equivalents. Many folks like the Russian tubes better so they are good to try but they are your only options."



I guess it may be that non of the tubes can be changed for any other than a Chinese replacement.



Many thanks for any suggestions.
 
I certainly wouldn't change any tube unless I was 100% positive that it was a direct equivalent.

In tube rolling, unless you want to be tweaky, the idea (IMHO) is to replace the freebie chinese valve with something of some quality.

Some Chinese valves are excellent, often they bundle the lowest of the low. I would simply get the highest quality you can budget for and keep the type exactly the same (no change at all).

It's a commonly held error IME that 'all chinese valves are bad' - nonsense ! - just that there is wheat and chaff.

If you haven't already try:

Chelmer Valve Company
Langrex Supplies
Watford Valve

Good luck
 
Many thanks very helpful!


I have emailed those three you suggested.


It would make sense to stick to the same type but better quality.


I will of course post any findings.
 
I have received an email back fro the tubestore suggesting that the Chinese 6N6 and the 6N1 can be replaced safely with Russian tubes of the same name. I'm sure I saw a post on a forum from somebody with a Ming Da amplifier who was commenting that the Chinese 6N6 was very poor and there was no alternative to try in its place.

I must say It is still a little confusing as to which can be changed. Would you stick to what you said about sticking to Chinese tubes?
 
I think what Bottleneck was suggesting was that you should only make like for like replacements, so stick to the valve types i.e. don't put an ecc88 in where there is currently a 6N1, better to replace it with a new 6N1. I don't think he was suggesting you should stick to the same manufacturer or country of origin.
 
Thanks. Just a little confusing that some tubes with the same name are a different spec in two different countries as seems to be the case with 6Z4.

The Chinese 6Z4 isdifferent to the American 6Z4. I have been told that changing this wouldn't influence the sound much anyway.

I am going to order some NOS Russian 6N6 and 6N1 matched pairs. I have been told these will function the same as the Chinese ones.
 
I spoke to Watford Valves today and was told that I need to check the exact specs of the 6N6 and 6N1 in my amps as the Russian 6N6 and 6N1 are not necessarily the same spec as the Chinese ones.

Don't really know where to go from here as I am back where I started now...
 
In the manual of your amplifier does it provide details of the tubes?


I have not heard of (for example) an ECC83 from Russia being different (in the sense of incompatible) with an ECC83 from Britain - as an example.

I am not saying this is impossible - I dont want you to damage your amp on my say-so. It's just not been my experience. There is an 'old boy' at Langrex (doesnt answer the phone as much these days) who is a bit of a legend on compatibility. I've spoken to him a few times over the years. He would be my personal choice when it gets weird and whacky.

I wonder if perhaps the chap at Watford V. is covering himself for liability purposes. I probably would in his shoes!
 
Yes I can understand that folk may want to cover themselves in case of damage. I have emailed Langrex but haven't received a reply yet. I may try calling them.

I bought the amps second hand from the forum here and they didn't have manuals. I don't know if ShengYa exist anymore I can't find any reliable email addresses or web site info. The same for Vincent also.

Tubestore in the USA have said that I won't damage my amp with Russian tubes and that they should work fine.

There is an ebay auction I have seen for some 6N6 Russian NOS that are suitable for Ming Da amps and the seller has informed me that if the 6N6 valve in my amp has one part inside it its Western and the Russian tubes he selling won't work. However that doesn't really answer the matter of the potential difference bewteen Russian and Chinese 6N6 and 6N1's.
 
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I opened one of the amps up last night to have a look what was printed on the valves.

Where the 6N6 is the valve has "6h6n" printed on it which means its a Russian 6N6 I think? On the PCB where this valve is it says 6N6 (a little confusing)

Where th 6N1 valve is supposed to be the valve has "Miniwatt PCC88" on it. On the circuit board where this valve is it says 6dj8. Even more confusing because a PCC88 is a 7dj8 from what I can tell!

I think this amp is third hand, surely this amp didn't have these valves in it when it was made, especially the PCC88 which is strictly speaking the wrong valve as far as I can see. This must mean that a previous owner has swapped out the Chinese valves.

I spoke to Watford valves about this and they told me that the circuit could have been modified to allow these valves and that they didn't really want to sell me the original valves (in case it has ben modified making these incompatible) or replacements the same as the ones in there as they are incorrect (even though they are working and have been for nearly a year now).

Not sure what to do? Surely I can get the same as what is already in there without fear of damage?
 
I might be tempted to drop it into a friendly technician to give it a quick once over and to check the valves are appropriate so that you know where you stand. If it's all ok then maybe there's no need to buy any new valves (unless you just want to experiment), but if the wrong valves are in there then I'm sure the advice would be to get the right ones in?

Quick search on the web suggests a 6DJ8 alternative is the ECC88 (not PCC88)
 
Hello,


An update for anybody is interested and perhaps this thread might one day help somebody else who wants to try some different tubes with the Shengya or Vincent T100 hybrid mono blocks.


I bit the bullet and (probably foolishly due to impatience) took a chance on the Russian tubes after not getting any straight answers and the fact that the original Chinese stock tubes had been changed for a Russian 6H6 and a Phillips Miniwatt PCC88 seemingly without any problems.

I ordered a pair of Chinese 6N6 tubes and swapped the Russian 6H6n's out and this seemed to be a backwards step I didn't like the sound as much. I guess the Russian tubes that were in there already were better. Maybe new tubes need a long time to burn in but after a few nights I put the old ones back and the sound was more lively and dynamic. So the Chinese 6N6 and the Russian 6H6 work fine in the amps.


I next ordered some Russian NOS 6H6 and 6H1 tubes and replaced the old Russian 6H6 and the Miniwatt PCC88. The improvement wasn't massive but there definitely was an improvement in dynamics and clarity. I have also now replaced the Chinese 6Z4's with some NOS Chinese 6Z4's but have not really heard any difference with those yet. All these tubes have not been in long so if there are further improvements as they burn in then thats great.

So the amps seem to take the PCC88 (miniwatt) in the 6DJ8 socket as well as 6DJ8 (6N1 & 6H1).
 

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