50s RCA 2A3 vs new JJ 2A3: electrical differences?

[grantray]

I have an Asano 2A3 amp (I bought it new from EIFL a few months ago) that's currently running grey plate RCA 2A3 tubes from 1954. It sounds amazing hooked up to my 846A Valencias, with very little hum, but I wanted to roll the JJs as a backup to the RCAs because we regularly run the system for hours at a time to listen to radio. However, I plopped in the JJs and immediately got a rather loud, unavoidably distracting hum, to the point that I sent the JJs back. The Asano 2A3 amp uses the 75A to drive the 2A3, with a 5V4G for regulating the power. Here's a link to the manual.

I've read the JJs are more of a 300B in drag than a traditional 2A3, and I'm wondering if anyone can explain the differences between the JJ and a standard 2A3? Because, with the exception of the hum, the JJ was better in the lows and extended highs, as well as having a bit more dynamic punch. It's a really, really great performing tube.

Thanks!
-Grant

 

[maxhifi]

I have an Asano 2A3 amp (I bought it new from EIFL a few months ago) that's currently running grey plate RCA 2A3 tubes from 1954. It sounds amazing hooked up to my 846A Valencias, with very little hum, but I wanted to roll the JJs as a backup to the RCAs because we regularly run the system for hours at a time to listen to radio. However, I plopped in the JJs and immediately got a rather loud, unavoidably distracting hum, to the point that I sent the JJs back. The Asano 2A3 amp uses the 75A to drive the 2A3, with a 5V4G for regulating the power. Here's a link to the manual.

I've read the JJs are more of a 300B in drag than a traditional 2A3, and I'm wondering if anyone can explain the differences between the JJ and a standard 2A3? Because, with the exception of the hum, the JJ was better in the lows and extended highs, as well as having a bit more dynamic punch. It's a really, really great performing tube.

Thanks!
-Grant

Hi Grant

First of all, very interesting and great choice of amplifier.

Second, no, there is not any electrical difference which should have caused this hum. The JJ uses a larger anode than a conventional 2A3 but performance is the same.

Question. Did you attempt to adjust your amplifiers hum balance control after changing the tubes? This has to be done if the output tube is replaced, to null the hum.

By the way, I think that the JJ 2A3-40 sounds better than NOS tubes, I prefer my pair to the Westinghouse NOS I also have. Also, over a year of 5+ hours per day they are still testing almost as new. I think the JJ 2A3-40 is an example of a very good new production tube.

Best regards

Max

 

[grantray]

Hi Grant

First of all, very interesting and great choice of amplifier.

Second, no, there is not any electrical difference which should have caused this hum. The JJ uses a larger anode than a conventional 2A3 but performance is the same.

Question. Did you attempt to adjust your amplifiers hum balance control after changing the tubes? This has to be done if the output tube is replaced, to null the hum.

By the way, I think that the JJ 2A3-40 sounds better than NOS tubes, I prefer my pair to the Westinghouse NOS I also have. Also, over a year of 5+ hours per day they are still testing almost as new. I think the JJ 2A3-40 is an example of a very good new production tube.

Best regards

Max

Hi Max.
Thanks for the input. Adjusting the bias is something I'm new to. I went up to a half turn either way, but I got chicken after that because I didn't want to damage the transformers, and because I just don't know what I'm doing. Koji-san's manual leaves a lot to be desired. For example: what's the optimal bias range setting for a 2A3 tube? How many turns are appropriate for hum adjustment? Etc.

Here's a shot of the meters with bias screw under each meter for reference, and I'll take any tips you've got for proper procedure. View media item 12255-Grant

 

[maxhifi]

Hi Max.
Thanks for the input. Adjusting the bias is something I'm new to. I went up to a half turn either way, but I got chicken after that because I didn't want to damage the transformers, and because I just don't know what I'm doing. Koji-san's manual leaves a lot to be desired. For example: what's the optimal bias range setting for a 2A3 tube? How many turns are appropriate for hum adjustment? Etc.

Here's a shot of the meters with bias screw under each meter for reference, and I'll take any tips you've got for proper procedure. View media item 12255-Grant

HI Grant,

Those screws under the meters are for meter calibration, not bias adjustment. You adjust them so the meter reads exactly zero when the amp is off, and leave it like that. They aren't an adjustment.

This amplifier does not have adjustable bias since it is cathode biased, and the meters are just got assessing tube condition and looking cool.

What you want to adjust are the "hum balancer potentiometers" which are on top of the amp. Look at the manual to find them. Put your ear right up to the speaker and adjust each potentiometer for minimum hum. There's one for left and one for right. That's it, there is no harm to be done by trying them with the RCA tubes, you will find a spot where hum is minimum and it gets louder in either direction, I. E. a null. Adjust it to that and leave it alone until you change tubes.

Best regards

MAX

 

[megasat16]

Agreed with Max! You need to readjust the meter null point with the unit powered down completely. These adjustment below the meter for the zeroing the meter readings. There is no bias adjustment on this amp. You need to look for the hum adjustment pot behind the 5V4 rectifier tube. Depending on the type of the pot and the shaft style, you may need a flat head screw driver to adjust them.

When you use JJ 2A3, you need to adjust these two pots (one at a time) till you hear the lowest hum or no hum from each side of the speakers. It takes a little patience to find the lowest hum sometimes so be patient while doing it.

 

[grantray]

You guys are awesome. I'll play with the bias adjustment when I get back home later tonight. And reset the meters to zero.
After that, it looks like I need to put in another order for the JJ 2A3 tubes

 

[maxhifi]

.

You guys are awesome. I'll play with the bias adjustment when I get back home later tonight. And reset the meters to zero.
After that, it looks like I need to put in another order for the JJ 2A3 tubes

As above, there is no bias adjustment

Hum balance is something different from bias, what it does is shift the point the tube's filament is grounded. so that the hum induced by each half is equal but inverse, and it cancels. Since tubes have tolerances and aren't identical, this needs to be adjusted for each specific tube.

 

[grantray]

.


As above, there is no bias adjustment

Hum balance is something different from bias, what it does is shift the point the tube's filament is grounded. so that the hum induced by each half is equal but inverse, and it cancels. Since tubes have tolerances and aren't identical, this needs to be adjusted for each specific tube.

Right. I was sneaking in a reply between meetings. But also, thanks for giving more detail about how the hum balance works.

 

[grantray]

Okay, so I've reset the meters to zero when the amp was powered down and played with the hum adjustment (can't believe I forgot about that) after powering up. However, I still need to figure out what value defines a given power tube's condition. (The sleep depravation from a 6-week old baby isn't helping.) From my understanding, the meters show the 2A3's fixed plate current of ~70 ma if the tube's perfectly healthy, correct? Any ideas on what level of variance from 70 ma is considered acceptable before it's time to replace the tube?

 

[bimasta]

I have a Cary 2A3, with the same 50's RCA's Grantray mentions. As he says, "they sound amazing" — but it's time for replacement. It's a push-pull amp, not SE, so I need 4 output tubes, and that doubles the cost.

I hope this isn't considered off-topic, but I've seen great reviews for the Shuguang 2A3-C — at half the cost of the JJ. Does anyone have experience with the Shuguang 2A3-C?

(The pic of the Cary below, with Shugangs, is taken from the web; where mine is located, it can't be photographed.)

 

[maxhifi]

I have a Cary 2A3, with the same 50's RCA's Grantray mentions. As he says, "they sound amazing" — but it's time for replacement. It's a push-pull amp, not SE, so I need 4 output tubes, and that doubles the cost.

I hope this isn't considered off-topic, but I've seen great reviews for the Shuguang 2A3-C — at half the cost of the JJ. Does anyone have experience with the Shuguang 2A3-C?

(The pic of the Cary below, with Shugangs, is taken from the web; where mine is located, it can't be photographed.)

View attachment 1032564

No, but I have the cheap Valve Art 2A3, made. By Shuguang, and they sound just fine. Between the NOS, JJ and Valve Art, JJ is definitely best, but the difference is really quite subtle, and if cost is a factor just go for the cheap ones, it will still work just fine.

 

[grantray]

No, but I have the cheap Valve Art 2A3, made. By Shuguang, and they sound just fine. Between the NOS, JJ and Valve Art, JJ is definitely best, but the difference is really quite subtle, and if cost is a factor just go for the cheap ones, it will still work just fine.

Agreed on the different power tubes not being that drastically different in a push-pull amp. At least that's been my experience. When I had an integrated push-pull, rolling the preamp tubes made the biggest difference by a mile.

 

[bimasta]

No, but I have the cheap Valve Art 2A3, made. By Shuguang, and they sound just fine. Between the NOS, JJ and Valve Art, JJ is definitely best, but the difference is really quite subtle, and if cost is a factor just go for the cheap ones, it will still work just fine.

Thanks Max. I couldn't find a dealer/price for the Valve Art 2A3. The Shuguang C is $75, add a bit for matching — how does Valve Art compare (are we all allowed to talk price here)? When I got the Cary 25 years ago, it came with basic Shuguangs, not the newer fancier ones. Sounded great. If the Valve Art 2A3 is a Shuguang, maybe it's those old ones, still in production. I've tried 3 or 4 2A3's over the years — you're right, the difference is subtle. Only the Electro-Harmonix were duds — sound was flat, one-dimensional — and one of them died after 2 weeks. Vaccuum failure, turned white inside and hummed like crazy.

 

[bimasta]

Agreed on the different power tubes not being that drastically different in a push-pull amp.

Interesting that a push-pull would make such a difference, Grantray — but makes sense I guess. In a SE circuit, the tube is basically a soloist — its qualities or deficiencies are on distinct display.

 

[maxhifi]

Thanks Max. I couldn't find a dealer/price for the Valve Art 2A3. The Shuguang C is $75, add a bit for matching — how does Valve Art compare (are we all allowed to talk price here)? When I got the Cary 25 years ago, it came with basic Shuguangs, not the newer fancier ones. Sounded great. If the Valve Art 2A3 is a Shuguang, maybe it's those old ones, still in production. I've tried 3 or 4 2A3's over the years — you're right, the difference is subtle. Only the Electro-Harmonix were duds — sound was flat, one-dimensional — and one of them died after 2 weeks. Vaccuum failure, turned white inside and hummed like crazy.

I got them at antique electronic supply, about 10 years ago.. yep they're the same basic old bi-plate Shuguang tubes. I just checked and they don't have them anymore, sorry about that! I paid $40/ea at the time and thought I was being robbed. I see Sovtek tubes are on sale there now, about $50/ea. Never tried them though, so can't comment on quality, but given the price is half a JJ I would be looking at those if I were you. If I needed four I would hesitate on the JJs too though, I hesitated long and hard before buying two of them, let alone four! I guess I'm still mentally stuck in the 1990s, when even NOS tubes could be had relatively cheap. That said, three years after buying the JJs, I'm no longer thinking about the price, and am happy I bought them.

 

[bimasta]

I see Sovtek tubes are on sale there now, about $50/ea.

Mmm, thanks — but I'd hesitate. I think Sovtek is related to Electro Harmonix, and those were a bad experience. Seems many of the new "Russian" tubes aren't nearly as good as the old "Soviet" tubes. The USSR used tubes long after the West transistorized — even in Military applications. Quality of those tubes had strategic importance.

 

[maxhifi]

Mmm, thanks — but I'd hesitate. I think Sovtek is related to Electro Harmonix, and those were a bad experience. Seems many of the new "Russian" tubes aren't nearly as good as the old "Soviet" tubes. The USSR used tubes long after the West transistorized — even in Military applications. Quality of those tubes had strategic importance.

You know, in the 1990s people called Chinese tubes "Chinese firecrackers", and now they're putting out some decent stuff we're talking about spending actual money on. I remember I got a set of Chinese 807s in about 2001, and they shorted out and failed one after another over about a year. All I'm saying is don't rule them out, out of hand, based on what people were saying in the 1990s, I've been reading good things about new production Russian tubes for ages already.

 

[bimasta]

Thanks Max — but I'm hijacking Grantray's thread. It's about his Asano amp and hum problem — not my generic 2A3 questions.
Sorry Grantray...

 

[Kim G]

Sovtecs came with my Paramounts and it didn't take long for one to go south. I replaced them with the Shuguang 2A3C and I have been happy with them.

 

[bimasta]

Sovtecs came with my Paramounts and it didn't take long for one to go south. I replaced them with the Shuguang 2A3C and I have been happy with them.

Same as my E-H tubes — 25% failure rate. Small sample, but still... How long have you had the Shuguangs?