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WS Trader 15th July 2012 06:50 PM

NOS NEGLECTED HIGH-END AUDIO TUBE
 
I would like to introduce and recommend a neglected 6SN7 substitute, the Raytheon
5694. It's a made for the military dual AF power triode. The 5694 = premium 6N7 GT
with separate cathode leads, like a 6SN7. It is similar electrically to a Mullard ECC32 /
CV-181, BUT with a different pin-out. The Raytheon tube actually is closer electronically to a 6SN7 than the ECC32s are. The Vfil = 6.3V @ 800ma, versus 950ma for the ECC32s and 600ma for a 6SN7 GTB. These tubes although rare can still be found for between $15 to $50 each delivered. My yield of platinum (5%) matched and balanced pairs and a single quad brought my price per tube to about $100, still a great bargain considering the fact that they are far superior to the $500 to $600 plus a pair of Mullard ECC32 / CV-181, when and if you can find them.
Raytheon has accidentally and unknowingly given the audio world a great gift.

These tubes are far less noisy than the ECC32s and deliver details like a Jazz piano with no close rival. The silent passages are as mute as you have never heard. They are also much easier on the ears, allowing for longer, more pleasant listening periods. I found the Mullard ECC32 lacking in bottom end response. My previous
6SN7 favorite flavor was the "holy grail" of the 6SN7 world, the Tung-Sol 1940s
6SN7 GT, black glass, black plates, round getters, fetching $400 to $500 a pair, when and if you can find them. Not being sentimental or indecisive, my barely used quintet quickly fetched $1,000 on the slightly used NOS market.

They require adapters or re-wiring of the octal sockets they are going into, but it's more than worth it. The required pin-out follows: Pin # 1 Cathode, 2 & 7 Filament,
3 Plate, 4 Grid, 5 Grid 6 Plate 8 Cathode. IF your making adapters, use the following pin-out. Tube base number / Tube socket number: 1 / 4, 2 /3, 3 /1, 4 / 5,
5 / 6, 6 / 8, 7 / 7, 8 / 2.
Good luck treasure hunting, I humbly await your opinions.

Vinylsavor 15th July 2012 09:53 PM

Hi!

Thanks for pointing out this tube! I use the 6N7 a lot and this is an alternative worthwhile to check.

However I would not advice to use it as a substitute for a 6SN7. It has three times the plate resistance as the 6SN7 and a much higher mu. While it might work in some circuits designed for 6SN7, it certainly will not work well in all of them

Best regards

Thomas

WS Trader 15th July 2012 10:32 PM

Raytheon 5694 compatibility
 
You are correct the 5694 does offer a higher plate resistance, but the 5694 does have a LOWER MU than a 6SN7. I have 6SU7 GTYs, driving 5694s, driving 845s!

Vinylsavor 15th July 2012 11:03 PM

Hi!

5694 mu = 35 according to this site:

NJ7P SQL Tube Database Query

6SN7 mu = 20

Very different tubes.

I would not use it to drive large triodes like the 845. Works well as driver for 45 or 801A for which I use 6N7 a lot.

Best regards

Thomas

Palustris 16th July 2012 03:15 PM

$100 for a tube is hardly a bargain. There are still many cylindrical plate tubes with a mu near a 6SN7 that you can buy for $10. Read your tube manual every night before bed and you too can find a few "high end" tube bargains.

Vinylsavor 16th July 2012 04:35 PM

Hi!

Were did you get the $100 from?
The 5694 is $12 at vaccumtubes.net. Still more expensive than 6N7, but worth a try. I ordered some. Thanks to the OP for the hint. Although it is not suitable to replace a 6SN7. I will use it in circuits designed for the 6N7

Best regards

Thomas

Palustris 16th July 2012 05:12 PM

Quote:

Originally Posted by WS Trader (Post 3093250)
My yield of platinum (5%) matched and balanced pairs and a single quad brought my price per tube to about $100, still a great bargain considering the fact that they are far superior to the $500 to $600 plus a pair of Mullard ECC32 / CV-181, when and if you can find them.


Vinylsavor 16th July 2012 05:32 PM

Hi!

I didn't catch that, I agree $100 is hardly a bargain, especially since they can be had NOS for $12. No matching justifies $100 no matter if it is 'platinum' or whatever.

Another alternative to 6N7 would be the 6A6 which goes for $5 for NOS, it has a UX7 base instead of octal but is electrically equivalent.

Thomas

Palustris 16th July 2012 06:26 PM

For $120 I would buy ten and match them up myself although I would guess a 5% match is unnecessary and two or three would yield a good pair.

But it does look like an interesting tube with a mu=35; it could be a useful driver for a small triode. I like the separate cathodes compared to a 6N7; that really makes it more useful.

Roymercer 7th October 2012 02:55 AM

I understand that tubes are not linear and will sound different in different circuits. However I would like to confirm WS Traders opinion of the 5694 as a 6SN7 sub. It is the most dynamic tube I have ever used in my Oppo BDP-95 Modwright player. They have spoiled me to the point that I won’t listen to anything else. My 3 hole bad boys, round plate tung-sols, etc., all sound restricted to me now that I have played my system with these Raytheon’s. If I have the funds, I will pay the current NOS prices of the “Holy Grail” round plates for a low-microphonic NOS pair of these tubes. They do everything my VT-99’s do except better. They are more extended without adding any harshness. I have nothing to gain from this and thought I would jump in and give another opinion. I wonder how many other tubes is out there that sound better/ same as current expensive NOS tubes that we have yet to discover?? Diana Krall’s Temptation sounds like she is playing in front of me. I can feel the snare drum hit as if I were in front of it live. The best way I can describe them is extremely dynamic. They do have quite a bit more gain than the 6SN7. It allows me to attenuate the input of my amp lowering my noise floor. I absolutely love these tubes. I have a feeling that a lot of them are microphonic. I have several NOS pairs that have at least one triode that is overly microphonic. Currently, I have two matched pairs that are perfect. Unless something catastrophic happens I will never let go of these tubes.

Cheers!

Steve


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