Substitute for 6SL7GT?

[Ty_Bower]

I can't be the first to try this...

[Geek]

Nope, but why the downgrade to a 12AX7?

Cheers!

[Ty_Bower]

Couldn't find a 5751 in time for the photo shoot?

[Quad]

Ty, I saw the pic of this mod which you posted on audiokarma.
Could you please post the details of the 12AX7 adapter
socket? Is it a drop in replacement, or do you
need any other changes to the circuit?

[TerrySmith]

I've been wanting to try a 6SU7, anyone tried one yet?

[lth1]

Quad, they are 6SN7 to 12AX7 adapter, easily found on ebay, and yes they are drop in replacements.

Terry, the 6SU7 is IMHO one of the best sounding 6SL7's. I have reciently gone to 12SN7/12SL7 tubes, which are alot cheaper. There is a 12SX7 which is a premium 12SN7, but I have not found a 12V equivalent of the 6SU7.

[Ty_Bower]

Quad, they are 6SN7 to 12AX7 adapter, easily found on ebay, and yes they are drop in replacements.

Yes, that's exactly where I got mine. I recall the seller was Zhang Sheng. He didn't have any of the 12AX7/6SL7 variety up for auction, but I was able to contact him and request exactly what I wanted. I figure for what he charges, I couldn't build it myself for much less. The whole assembly is nicely potted in epoxy and it works perfectly. I've also bought some 6BQ5/6V6 adapters (don't ask why) and they work great too.

The exact details of the adapter are easy enough to figure out. Just look up the datasheets for the 12AX7 and 6SL7. I like to use TDSL, but you may use anything you like. By the way, it's also a fair approximation for an 12BH7/6SN7 adapter. At least the pinout matches up.

No circuit changes are required. Just plug it in and away you go. Do I think it offers any sonic benefit over a good 6SL7? No, not really. But it's fun to be able to roll any variety of 12AX7 in the amp.

[TomMcNally]

The eBay scammers must have read this post already!
The 6SU7 and 12SX7 are priced like gold. Wow!

[Ty_Bower]

The eBay scammers must have read this post already!
The 6SU7 and 12SX7 are priced like gold. Wow!

I don't think I have any 6SU7... and at those prices ($150/pr!) I doubt I ever will.

According to legend, isn't Tung Sol the only manufacturer to make them? I thought they made some with white printed bases, and some with black printed bases. One flavor was supposed to be better than the other. Then again, my recollection is pretty foggy...

I do have an RCA "red base" 5691 around here somewhere, which is allegedly the RCA version of a "premium" 6SL7. To be perfectly honest, I wasn't very impressed with it.

[Quad]

The exact details of the adapter are easy enough to figure out. Just look up the datasheets for the 12AX7 and 6SL7.

No circuit changes are required. Just plug it in and away you go. Do I think it offers any sonic benefit over a good 6SL7? No, not really. But it's fun to be able to roll any variety of 12AX7 in the amp.

Thanks! I have a few 12AX7s lying around, so it may worth
making one of those adapters and trying them out. As you say,
more the tubes to roll, more fun...

[lth1]

Ty, the 5691 and 5692 are designed for long and rugged use, but I have found that their sound in audio equipment is rather disappointing, they are mid pack sounding in the 6SL7 and 6SN7 family IMHO.

[badassbob]

I have an RCA 5691 and a Tung Sol 6SU7GTY, both are very nice tubes IMO. I prefer the Tung Sol over the RCA, as it seems to have a darker background in my experience. If you can find a decent deal on em, snatch them up ASAP. I picked up a pair of the Tung Sols locally for $30, much better than the $100+ per pair common on eBay.

[Hollow Fate]

The eBay scammers must have read this post already!
The 6SU7 and 12SX7 are priced like gold. Wow!

I feel I can comment authoritatively on the 12SX7 (6SN7-type) tube. My line pre takes 6SN7 /12SN7 /12SX7 tubes. Of all the 6SN7 types I have rolled into this pre-amp in the past, the JAN 12SX7 RCA is the King. Equal is the JAN Rogers (Canada). Forget the GE (Canada) 12SX7. It sounds like a typical 6SN7. All other 6SN7 tubes I have tried in this pre are ordinary in comparison including ones like the JAN Sylvania 6SN7WGTA tri-plate tube that is starting to command bigger bucks now. The three aforementioned are the only 12SX7's I have heard. I bought sixteen NOS of the JAN RCA's and JAN Rogers five years ago for cheap from a fellow in Holland who priced them as 12SN7's. Big hooray on that one. (Thanks, Jan!)

Years ago, after hearing them, I continued to collect them. I consider these tubes to be the gold standard of 6SN7 tubes. Nothing else is as full, wide, deep, accurate, and emotionally all-enveloping as the JAN RCA and JAN Rogers 12SX7 tubes. By the way these two 12SX7’s have entirely different plate structures. Weird. They still sound the same.

Recently I have watched prices of ST-shaped 6F8G Tung-Sol “round-plates” (6SN7 equivalent/different pin-out) go crazy on eBay. Audio-folks are bidding these tubes up to about $250 a pair because the Tung-Sol 6SN7W’s (round-plate again) have hit up to $450 a pair.

So let’s have a listen......

I wired up a couple of adapters to fit one of my pairs of Tung-Sol 6F8G round-plates (JAN tan 1942) to fit into the 6SN7 sockets of my Pre (Mapletree Ultra 4A SE) to have a listen. What could all this high-dollar fuss be about? Holy Moly. These tubes are the first 6SN7-type tubes I have heard in five years to come close (match?) to the RCA JAN 12SX7’s. I was surprised. In an eBay world of used Western Electric 205D tubes stated by the seller to be “Untested, don’t know, could be dud.” going for $500 you don’t expect true quality to manifest itself from amongst all of the hysteria.

So in conclusion, don’t pay $450 for a pair of Tung-Sol 6SN7W’s. Don’t buy my pair of NOS/NIB Tung-Sol 6F8G’s for $250 when I list them on eBay. Buy yourself a pair of NOS/NIB RCA JAN 12SX7 tubes and fit a small 12 volt transformer into your pre-amp to feed them. These tubes are the ones to beat.

Also, ignore eBay asking prices. Silliness. New Old Stock 12SX7 tubes can be had from the tube sellers for about $20 to $28 each. You must however inquire of the seller that you are looking for JAN RCA 12SX7 tubes in their original MILITARY boxes. (Mine are in JAN Tan boxes vintage 1955). RCA 12SN7 and RCA 12SX7 both look identical, as in, flat-box black ladder plates. My RCA 12SN7‘s sound flat. Be careful, but if you know you’ve got the real deal then my recommendation is to buy them.

Visually mine are imprinted around the base “JAN CRC-12SX7-GT MADE IN USA 4-48 (RCA logo) followed by (Army logo ~ Eagle clutching arrows with three stars above) these are the ones to get. Some RCA JAN’s also add the Navy Anchor. By the way, the “4-48” on the tube base mentioned here does not mean “April 1948” but rather “the 48th week of 1954” Go figure?? The military box they came in says “delivered 1955”; so it fits.

Keep in mind these are pre-amp tubes. If you bundle them up with other tubes in a design I can’t vouch for them.

My System is: “CD Source” to “RCA JAN 12SX7 (only)” to “Power Amp” to “Speakers”.
Playing vinyl my stereo goes: “Vinyl” to “Russian Voskhod 6N2P-EV (great tube after LONG break-in)” to “RCA JAN 12SX7” to “Power Amp” to “Speakers”.

If you don’t buy them now, then maybe in 3-4 years time they will match the high prices we are now seeing for the Fave Rave Rarities that are in fashion today.

Dunnit say I hadun’t warned yee.

Donald.

[kku]

While searching google for a good 6SL7, I came across a discussion board. Most of the people there claimed that the new production TungSol 6SL7 sounds very good and close to NOS US. I wonder if anyone here on diytube has tried this new prod. 6SL7.