[Gvvt]

I'm resurrecting this topic, originally discussed here http://www.head-fi.org/forums/f5/6922-sub-wa2-406379/ in order to offer a bit of new information.

A couple of days ago, I decided to go back and verify my initial impression that most of the 6922/6DJ8 substitutes did not work in my WA2. Much to my surprise, the hum problem has disappeared in one tube, the RCA 6GU7, and is ALMOST completely insignificant in another, the GE 6CG7. The hum in the RCA 6FW8 is unfortunately as loud (VERY) as before.

The 6GU7 seems to have a momentary buzz when the soft start kicks in, but it disappears instantly, and the tube is silent. It's also rather pleasant sounding; a bit soft edged, but rich. It might be a good match with a less tubey tube, like the 7236. The 6CG7 has a bit more bite, but is also very musical. It does seem to have some fuzz - like tape hiss - that I haven't quite nailed down yet. (The disk I'm listening to is an Exton SACD, so it isn't really tape hiss.)

Does anyone know about preferable brands of these tubes?

Both tubes are new/unbroken-in, so things may change; I'm amazed by whatever it was that has already changed to make these tubes usable - and interesting.

With the RCA 7DJ8s and the Russian 6N1P-EV, there do seem to be a number of opportunities to experiment, each with it's own distinct sound. Mixing with output tubes should be fun.

 

[ManAtWork]

Try JJ 6922, which is heard warmer and sweeter than Russian tubes. There are still many options out there.

 

[xenithon]

I am still one to rather try out 1-2 pairs of good, perhaps a little more costly, tube - rather than experiment with 10-12 pairs of cheap tubes which may or may not work, and may or may not inflict some damage to my baby WA2

Currently got some Philips Miniwatt E88CC gold pins; just got a pair of Mullard (Holland) ECC88 A-Frame tubes, currently making their way via airmail. Will report back as soon as they arrive.

 

[ManAtWork]

Quote:

Originally Posted by xenithon /img/forum/go_quote.gif I am still one to rather try out 1-2 pairs of good, perhaps a little more costly, tube - rather than experiment with 10-12 pairs of cheap tubes which may or may not work, and may or may not inflict some damage to my baby WA2

Bear in mind that costly options may not have best synergy with your device, or the sound characteristic is not the one you prefer. For tubes, higher cost is not equal to better sound. And, what means good sound is very subjective; someone said one has good sound but may be you wouldn't like how it sounds. Audiophile doesn't have any simple way to get the 'best sound' usually and this is what the fun is.

 

[audiowize]

Quote:

Originally Posted by Gvvt /img/forum/go_quote.gif A couple of days ago, I decided to go back and verify my initial impression that most of the 6922/6DJ8 substitutes ... RCA 6GU7... GE 6CG7 ... 6FW8

None of these are direct substitutes for a 6922/6DJ8 (the 6FW8 is pretty close). They happen to have the same pinout, but they are very different tubes. This isn't to say that I do or don't like all of them more than the 6DJ8 (I think the 6DJ8 is kind of a stupid tube to put in a headphone amp incidentally). I will try to keep this simple...

We need to look at three factors to compare these tubes in terms of general compatibility: 1. Heater current, 2. plate resistance at similar operating points 3. mu

6922:
1. 300ma
2. 3k
3. 30-ish

6CG7/6FM7 (6GU7 will be similar)
1. 600ma
2. 7k
3. 20

6FW8
1. 400ma
2. 2.5k
3. 33

Since the pinouts are the same, these will give you a guide as to what you're hearing. The heater current on the 6CG7 and 6FW8 is quite a bit more than the 6DJ8, be sure that isn't a problem with the manufacturer. Both substitutes will run at different operating points than the 6922, so it's tough to judge the sound of each tube since your circuit isn't optimized for them, but I can say that your observations of the differences between the 6GU7 (like 12AU7) and the 6CG7 (like 6SN7) are consistent with the linearity of each tube, with the CG7 being quite a bit more linear. It is odd that you have noise with some and not with others. If you have the AC current to run all these different tubes, you might send your amp back and have the manufacturer rectify the 6.3VAC to make a DC supply for your driver tube(s).

If you want an interesting substitute that is very close, try the 6N1P. Buy 3-4 of them, use the two that sound the best. The 6N1P is not prone to microphonics, and tends to be fairly quiet. You can also try the 6BZ7 which may work, depending on how the triodes are loaded.

 

[ManAtWork]

There are many 6922/ECC88 tubes out there, many are '50-'70 Mullard, Philips. Most of them sound very good but little expensive. You won't be wrong for those Mullard or Philips. See this: http://www.audio.idv.tw/shop/index.php?cPath=22_23

 

[xenithon]

ManAtWork - I am not saying that the costlier ones are always the better tubes; but I would rather get some NOS 6DJ8 or 6922 tubes (which the WA2 was intended to be used with) than tubes which fit in the same socket but may be vastly different, and potentially damaging to the tube and/or amp.

 

[olblueyez]

For the most part, if it aint NOS then it sucks.

 

[ManAtWork]

Quote:

Originally Posted by xenithon /img/forum/go_quote.gif ManAtWork - I am not saying that the costlier ones are always the better tubes; but I would rather get some NOS 6DJ8 or 6922 tubes (which the WA2 was intended to be used with) than tubes which fit in the same socket but may be vastly different, and potentially damaging to the tube and/or amp.

Yes, agreed. I discovered some great NOS 6922/6DJ8 tubes from the market, besides of Mullard and Philips, they are '50 Amperex Budge Boy with D getters but very rare and expensive.

 

[xenithon]

Quote:

For the most part, if it aint NOS then it sucks.

I tend to disagree, mainly because I think it depends a lot on the tube type. For example if you are talking about 6922/6DJ8 preamp tubes, then yes - NOS would be the way to go IMO. But when you like at the likes of power tubes - 5881, KT66/KT77/KT88, 300B, etc. - whilst NOS may still be the most sought after, modern day equivalents are phenomenal. This includes such examples are Gold Lion reissues, Sophia tubes, Tung Sol reissues / new production, and so on.

 

[Skylab]

Quote:

Originally Posted by olblueyez /img/forum/go_quote.gif For the most part, if it aint NOS then it sucks.

My experience actually is that this is almost universally true. I have tried a lot of different re-issues, and have disliked almost all of them. The latest was the Tung-Sol 6550 re-issues - a set of GE 6550A's so mercilessly shamed the re-issued tubes that it was kind of sad.

And the Electro-Harmonix 6922 and the JJ E88CC are also not anywhere close to as good as the very cheap JAN Sylvania 6DJ8, IMO.

One major exception: The Sophia Princess 274B rectifier tube is OUTSTANDING.