Dennis Had Inspire Amps

[Bombadil]

National Union manufactured tubes and even rebranded them for others. You can find Zenith branded 6SN7 tubes which were made by National Union. A NU manufactured tube will have a tube code of 247 somewhere on the base of the tube.

Here are two National Union tubes, branded Zenith and Sentinel. Both show a 247 code and both were made in 1951.
http://tubesound.com/wp-content/uploads/2007/12/247.jpg

[CoGT3]

☝️☝️☝️☝️☝️☝️

Those are the tubes I'm looking for. Thanks for the manufacturer code. Will certainly help with the hunt.

[Bombadil]

6SN7 trivia follows

The VT-231 designation means nothing. People pay more for them, thinking these tubes are ruggedized or low-noise military variants of 6SN7s. However this is not true. The VT-231 (and the VT-229 6SL7s) numbers are simply military inventory numbers. The tubes are not changed in any way from the manufacturers' standard 6SN7 tubes.

Likewise people pay more for 5692 tubes, which were originally advertised as having much longer life than a standard tube. The longer life was due to running them at lower specifications, if you take a standard 6SN7 and run it at 5692 specs, then it too will have a much longer life.

There are 10 different Sylvania manufactured 6SN7 type tubes. Not counting rebranded Sylvanias. 6 of these are commonly sold as "Chrome Domes." However 5 of these are not really chrome domes, they just have an appearance similar to them. The only true Chrome Domes are Sylvania 6SN7GT tubes made in the early 1950s. In these the chrome flashing covers nearly the entire tube, not just the top.

The 6SN7GTA and GTB versions were introduced in 1950 and 1954 respectively. They have ‘upgraded’ ratings, which are as follows.

GTA: maximum anode dissipation upgraded to 5W (the GT is rated for 2.5W)
GTB: identical to the GTA, but with a controlled heater warm up time for use in equipment with 600mA heater strings

This is significant because it means that a circuit designed around the 6SN7GTA/GTB cannot have 6SN7GTs substituted into it. Substituting a GT in place of a GTA/GTB in your equipment will precipitate its rapid destruction and possibly damage your equipment.

[FloridaBoy]

Originally Posted by CoGT3

☝️☝️☝️☝️☝️☝️

Those are the tubes I'm looking for. Thanks for the manufacturer code. Will certainly help with the hunt.

322 on a tube is the code for Tung Sol. Philco, Zenith and others sourced tubes from different manufacturers.

[Bombadil]

Okay, I finally gave in and inserted a 6SL7/VT-229 tube into my Inspire HO 17wpc amp. Right now running it with Tung-sol KT120 power tubes and a new Genalex GZ34 rectifier.

With the 6SL7, a vintage Ken-Rad, there is significantly more detail. Cymbals shimmer, upper piano notes stand out, vocals tilt to a higher register. More energy everywhere.

I could see someone liking the 6SL7 better, depending on their output tubes, speakers, and room. To my ears the extra detail is intriguing but is fatiguing over time. Which is what 6V6 output tubes in my system do to me. Perhaps I should pair the two of them up. Or maybe I will try the 6SL7 with EL-34 tubes, as I find them a bit too relaxed through the upper midrange.

Edit: Must admit that I didn't make through a full CD before I had to pull the 6SL7, started getting a headache. So much for that experiment.

[FloridaBoy]

Originally Posted by Bombadil

Okay, I finally gave in and inserted a 6SL7/VT-229 tube into my Inspire HO 17wpc amp. Right now running it with Tung-sol
With the 6SL7, a vintage Ken-Rad, there is significantly more detail. Cymbals shimmer, upper piano notes stand out, vocals tilt to a higher register. More energy everywhere.

I could see someone liking the 6SL7 better, depending on their output tubes, speakers, and room. To my ears the extra detail is intriguing but is fatiguing over time. Which is what 6V6 output tubes in my system do to me. Perhaps I should pair the two of them up. Or maybe I will try the 6SL7 with EL-34 tubes, as I find them a bit too relaxed through the upper midrange.

Edit: Must admit that I didn't make through a full CD before I had to pull the 6SL7, started getting a headache. So much for that experiment.

KT120 power tubes and a new Genalex GZ34 rectifier.

That tube complement is high energy. The 6SL7's extra gain may be too much or the Ken Rad may not be a good match.

[Comzee]

I recently started getting into rectifiers.
After I bought the iha-1, somebody at head-fi suggested 5R4.

To my surprise, it was leaps and bounds better in terms of detail and sparkle, versus the 5U4 types I was using. I does the same for my Fire-Bottle.

To talk quickly on that, I've found the rectifiers behave in the same way for both my iha-1 and Fire-Bottle. I had the Fire-Bottle upgraded with IIPS too.
I know some said the rectifier doesn't matter as much after IIPS, I'm finding it does, but that's YMMV.

This is my scale as it directly relates to detail retrieval,
0 to 10 scale: (edited in a few I forgot)

JJ GZ34 - 0
JJ 5U4G - 3
RCA NOS 5v4g - 3
JAN-Sylvania 5Y3WGTA - 5
Mullard f31 fat base gz34 - 5
Preferred Series 274b - 5.5
Bendix 6106 (5Y3 Variant) - 6
Sophia Electric 274b mesh - 6
Psvane 274b treasure mkii - 6.5
Sylvania 5931 (5U4WG sub) - 7
GE NOS 5R4GYA - 7.5
Philco Sylvania 5U4G Hanging Filament - 8
RCA 5R4GY hanging filaments single bottom getter - 8
PHILIPS 5R4GYS (made in holland) - 9
NOS 596 (sub for 274A 5U4G 5R4)- 9.5
1940s RCA Jan Crc 5R4GY hanging filaments double bottom getter - 10

Apart from detail, each tube as it's own properties. Warm, nuetral, bright, soundstage, decay etc... I don't really want to go into specifics, because it's all opinion anyway. If someone sees a rectifier I've tried and has specific questions on it, I'll try and articulate more.

Also, I picked up some 6C8G and 6F8G, both round plates. You need an adapter for these, but initial impressions are very promising.

[Musica Amantem]

Originally Posted by Bombadil

Okay, I finally gave in and inserted a 6SL7/VT-229 tube into my Inspire HO 17wpc amp. Right now running it with Tung-sol KT120 power tubes and a new Genalex GZ34 rectifier.

With the 6SL7, a vintage Ken-Rad, there is significantly more detail. Cymbals shimmer, upper piano notes stand out, vocals tilt to a higher register. More energy everywhere.

I could see someone liking the 6SL7 better, depending on their output tubes, speakers, and room. To my ears the extra detail is intriguing but is fatiguing over time. Which is what 6V6 output tubes in my system do to me. Perhaps I should pair the two of them up. Or maybe I will try the 6SL7 with EL-34 tubes, as I find them a bit too relaxed through the upper midrange.

Edit: Must admit that I didn't make through a full CD before I had to pull the 6SL7, started getting a headache. So much for that experiment.

Mmmhh ... shame! I was hoping to find some nice surprises there. I have not yet started rolling-in 6SL7's, as my work with the 6SN7's is not finished just yet with some output tube types. But, I will eventually try those too. Maybe I'll get lucky Currently trying VA 6550's with Westinghouse 5AR4 and the CV-181 T.

[Analog Addict]

Here are some references for common EIA codes, used for tubes, passive components, iron, etc....

http://www.triodeel.com/eiacode.htm

http://www.thevintagesound.com/ffg/eia-codes.html

And a large 18 page list....

http://www.audiophool.com/Misc/1994%20EIA%20Codes.pdf

[Musica Amantem]

Partial quote from Comzee

This is my scale as it directly relates to detail retrieval,
0 to 10 scale: (edited in a few I forgot)

JJ GZ34 - 0
JJ 5U4G - 3
RCA NOS 5v4g - 3
JAN-Sylvania 5Y3WGTA - 5
Mullard f31 fat base gz34 - 5
Preferred Series 274b - 5.5
Bendix 6106 (5Y3 Variant) - 6
Sophia Electric 274b mesh - 6
Psvane 274b treasure mkii - 6.5
Sylvania 5931 (5U4WG sub) - 7
GE NOS 5R4GYA - 7.5
Philco Sylvania 5U4G Hanging Filament - 8
RCA 5R4GY hanging filaments single bottom getter - 8
PHILIPS 5R4GYS (made in holland) - 9
NOS 596 (sub for 274A 5U4G 5R4)- 9.5
1940s RCA Jan Crc 5R4GY hanging filaments double bottom getter - 10

Apart from detail, each tube as it's own properties. Warm, nuetral, bright, soundstage, decay etc... I don't really want to go into specifics, because it's all opinion anyway. If someone sees a rectifier I've tried and has specific questions on it, I'll try and articulate more.

Also, I picked up some 6C8G and 6F8G, both round plates. You need an adapter for these, but initial impressions are very promising.

Interesting results from an outstanding tube-rolling effort! I may be missing these maybe due to different denominations, but did you try the 5AR4 or 5Z4? Those two are low-voltage drops and in my case work very nicely with the larger tubes like the 6550/KT-88, etc.

Curious about some of your favorites, which I've never heard yet, as these are rated substantially higher than my current "goto" rectifier, the SE 274B mesh plate.