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Post subject: 12AX7/7025 Tubes
Posted: Sun Apr 06, 2014 8:28 pm
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I need the experts' advice... I want to find the right tubes for V1/V2/V4 for my BF/SF amps. It's so hard for me to find one that gives me what I'm looking for, I've tried new and old tubes, with little success over the past few years.

Here's what I'm looking for: clarity, brightness, higher output, and some gain.

I've had luck with a couple of RCA that were the perfect match, specially for V4. But I've also had some RCAs that were kinda warm and not enough output, probably old and tired. Other older tubes I've tried include Telefunken, Tungsram, Amperex. Almost all of them were kinda warm and low output. Some I bought (NOS or ANOS), some came in the amps and were probably original to the amp.

I've tried a number of new production tubes and the only ones I always go back to are the Mullard RI. Didn't care for the JJ. TS, EH... The Mullard provide the right amount of clarity, brightness and the right gain, although sometimes it's a little too much. However, these tubes tend to be microphonic and don't do well in combos, specially at loud volumes. The Sovtek LPS, which I thought were the same as the Mullard, did not do well, way too noisy and microphonic, and didn't sound as good as the Mullard I like.

In the 66 PR I recently got it came with some older Ruby preamp tubes, RCA 6V6 and the Mullard rectifier. I thought I'd hate the Rubys but I actually love them! They do exactly what I'm looking for. These are Russian made tubes I think. V1 is labelled as 7025 STR (High Grade) and the other says 12AX7 (Made in USSR). Here's some pics.

Image

Image

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Any idea what kind of tubes they are? If they're still available I don't mind giving them a try...

So what should I be looking for? Was my experience with older tubes the result of old worn out tubes? Even though some were bought as NOS? Will the older tubes always have lower output? I have not tried any old Mullard yet, or any Sylvania, it's next on my list though. What new production tubes would do the trick? I can keep trying the Mullard RI but it's a hit or miss! Some are way too microphonic new, reliability is the other issue.

Thanks for any help! And sorry for the long post. My amps actually sound pretty good, but I'm just being anal :mrgreen: it's that last 2-3% of tweaking I like to do...


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Post subject: Re: 12AX7/7025 Tubes
Posted: Sun Apr 06, 2014 8:41 pm
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I believe the tube on the right is Chinese. Sounds like you have tried about all of them, and your preference might lean toward the Chinese. You might try the GT 12AX7 C, which is Chinese, high gain, very sturdy for combos (triple-mica spacers), and probably the same as the Ruby (on the right). I don't know if you can specify a Chinese made Ruby, maybe you can, but look for that extra metal piece beside the Plates for the Chinese versions.

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Post subject: Re: 12AX7/7025 Tubes
Posted: Sun Apr 06, 2014 8:57 pm
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Yeah I thought the STR tube might be Chinese... I'll have to look for some and give 'em a try.


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Post subject: Re: 12AX7/7025 Tubes
Posted: Sun Apr 06, 2014 9:20 pm
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As you probably already know, Ruby, as well as GT, tests, selects and relabels tubes from other manufacturers. Since the tube on the left is Russian made and doesn't look like a JJ, that leaves the other Russian manufacturer, which means it's probably either a Sovtek, EH, Mullard, or Tung Sol (I don't know if they are making any Svetlana branded 12AX7s yet). Checking the tubes that I have, the getter is wrong for both Tung Sol and Mullard, and judging by the faint lettering from the original manufacturer, it looks like maybe a Sovtek, although the newer Sovteks have a different style getter, and I haven't seen any Svetlana 12AX7s.

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Post subject: Re: 12AX7/7025 Tubes
Posted: Sun Apr 06, 2014 9:36 pm
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I believe these tubes were bought 10 years ago, at least that's what the guy who sold me the amp said.

The only thing I was able to find about the 7025 with the silver plates is this, not sure if it's the same tube though

http://www.dougstubes.com/preamp-tubes/12ax7-ecc83-7025/ruby-7025-ss-hg.html


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Post subject: Re: 12AX7/7025 Tubes
Posted: Sun Apr 06, 2014 9:52 pm
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That is also a Chinese tube, triple-mica, has the extra metal piece beside the Plates, so it might be the same tube as yours (the one on the right). Shuguang is a Chinese manufacturer, probably the best Chinese tubes.

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Post subject: Re: 12AX7/7025 Tubes
Posted: Sun Apr 06, 2014 9:58 pm
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" Here's what I'm looking for: clarity, brightness, higher output, and some gain. "


First off, no new 7025 has spiral wound heater filaments. They are labeled "7025" because they are supposedly selected as the quietest of the lot.

Many 7025-STR are Chinese made. There is a 12AX7A-C = Chinese. Chinese 12AX7 types tend to sound more warm than their Russian counterparts. In my experience, the new Russian made Tungsol 12AX7 and the Sovtek 12AX7LPS make the cleanest high notes. You must buy selected 12AX7LPS for low microphony and low hiss.

Some say that the new Tungsol (Russian) 12AX7 is a bit too bright. And may not work well in a modern amp, voiced more for highs and lows.

The best new tube that I've personally tried, for extension, bass response, and good gain is the Gold Lion B759/ECC83. This tube has all the extension and bass that you'll need. They are $$$. So, I'd use one in input section. Or moved one around the different 12AX7 sockets and check the amp's response.

http://www.thetubestore.com/Tubes/12AX7 ... ECC83-B759


For all eras of 12AX7, IMHO there are a few that have unsurpassed clarity, bass, and good gain character.

1.) Telefunken ECC83. I find little difference in tone, between smooth plate TFK and ribbed plate models. These tubes and the German Valvo E83CC are the Kings of clarity and bass.

2.) German made Valvo (Berlin) or Siemens/Halske (Munich) ECC83 or E83CC. Early 1960's are the best. Hard to find good ones.

3.) Sylvania black plate mil spec JAN-JHS 12AX7 (early 1950's), square getter rings. Best of the US made 12AX7 for clarity and clean tones throughout frequency range.

4.) Raytheon black plate mil spec JAN-CRP 12AX7A and 5751 (square tilted or windmill getter rings).

5.) Tungsram ECC83 (already described). 1970-80's era.

6.) CBS-Hytron and Tungsol (USA) 12AX7 are also noted for good extension. BP a bit better than gray plates. Long plates are the best.


Last edited by BMW2002Ti on Sun Apr 06, 2014 10:12 pm, edited 5 times in total.

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Post subject: Re: 12AX7/7025 Tubes
Posted: Sun Apr 06, 2014 10:00 pm
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The only difference I think is the solid square getter, hard to see from the pic on Doug's site, but you can see it in my pics.


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Post subject: Re: 12AX7/7025 Tubes
Posted: Sun Apr 06, 2014 10:07 pm
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Cedarblues, the tube on the right is Chinese. The one on the left is Russian. Chinese tubes have that characteristic small "bowl/flat square" getter.


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Post subject: Re: 12AX7/7025 Tubes
Posted: Sun Apr 06, 2014 10:19 pm
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BMW2002Ti wrote:
" Here's what I'm looking for: clarity, brightness, higher output, and some gain. "


First off, no new 7025 has spiral wound heater filaments. They are labeled "7025" because they are supposedly selected as the quietest of the lot.

Many 7025-STR are Chinese made. There is a 12AX7A-C = Chinese. Chinese 12AX7 types tend to sound more warm than their Russian counterparts. In my experience, the new Russian made Tungsol 12AX7 and the Sovtek 12AX7LPS make the cleanest high notes. You must buy selected 12AX7LPS for low microphony and hiss.

Some say that the new Tungsol (Russian) 12AX7 is a bit too bright. And may not work well in a modern amp, voiced more for highs and lows.

The best new tube that I've personally tried, for extension, bass response, and good gain are Gold Lion B759/ECC83. They have all the extension and bass that you'll need. They are $$$. So, I'd use one in input section. Or moved one around the different 12AX7 sockets and check the amp's response.

http://www.thetubestore.com/Tubes/12AX7 ... ECC83-B759


If this mean all tubes, there are a few that have unsurpassed clarity and good gain character.

1.) Telefunken ECC83. I find little difference in tone, between smooth plate TFK and ribbed plate models.

2.) German made Valvo (Berlin) or Siemens/Halske (Munich) ECC83 or E83CC. Early 1960's are the best. Hard to find good ones.

3.) Sylvania black plate mil spec JAN-JHS 12AX7 (early 1950's), square getter rings. Best of the US made 12AX7 for clarity and clean tones throughout frequency range.

4.) Raytheon black plate mil spec JAN-CRP 12AX7A and 5751 (square tilted or windmill getter rings).

5.) Tungsram ECC83 (already described). 1970-80's era.

6.) CBS-Hytron and Tungsol (USA) 12AX7 are also noted for good extension. BP a bit better than gray plates. Long plates are the best.


I tried a couple of pairs of Sovtek LPS, bought from two different vendors, was disappointed by both! Too noisy and microphonic in my amps.

I thought about trying the Gold Lion, but with that price I might as well keep looking for some good NOS tubes... I'll order one just to try it and see if it's the right tube for me.

Here's my experience with the tubes you listed:

1) Telefunken: found them to be a little too warm, both smooth and ribbed plate. Nice sounding and very smooth.

2) No experience

3) No experience (very expensive based on what I saw on ebay)

4) No experience

5) The Tungsram I tried was also too warm sounding

6) No experience


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Post subject: Re: 12AX7/7025 Tubes
Posted: Sun Apr 06, 2014 10:37 pm
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OK, if the Telefunken and Tungsram are too warm, there maybe something in the setup of the amp, that simple tube rolling won't help.

I'd try either a reissued Tungsol 12AX7 or that GL B759. Both are definitely not considered too warm (but, neither is the TFK or Tungsram). If they are too warm, you prolly need more voice shaping in the gain stage setup. Perhaps, a tone-stack tune-up.


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Post subject: Re: 12AX7/7025 Tubes
Posted: Sun Apr 06, 2014 10:49 pm
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cedarblues wrote:
...I thought I'd hate the Rubys but I actually love them! They do exactly what I'm looking for....


Why modify the amp? :wink:

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Post subject: Re: 12AX7/7025 Tubes
Posted: Mon Apr 07, 2014 7:09 am
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BMW2002Ti wrote:
OK, if the Telefunken and Tungsram are too warm, there maybe something in the setup of the amp, that simple tube rolling won't help.

I'd try either a reissued Tungsol 12AX7 or that GL B759. Both are definitely not considered too warm (but, neither is the TFK or Tungsram). If they are too warm, you prolly need more voice shaping in the gain stage setup. Perhaps, a tone-stack tune-up.


We're talking about 40+ year old amps here :) so I'm sure some caps might need replacing, but I'd hate to change anything in these precious amps, as long as they're working fine.

The differences in tone that I hear are minor, overall all 4 amps sound great! But whenever I find the right combo of preamp tubes in V1 and V4 it takes the amp to another level. When I say warm, I don't mean that the amp sounds too dark, it just sounds too smooth maybe and it's missing some clarity or definition, and that metallic kinda tone, this is when playing a Strat. The output is the other issue I have, it seems the amp volume drops a bit when I plug in most of the older preamp tubes.

For example, in my '73 SR with CTS Alnicos, using an older tube in V2 makes the amp sound smooth, still very sweet tone. Plug a good Mullard RI in V2 and the amp wakes up, a little brighter and louder, tighter bass too. Plug the right tube in V4, in this case it happens to be one of the only RCA 12AX7 that sounds right to me, and the amp turns into this monster! Perfectly balanced in every way possible! For me at least :)

I've had the same results in the other amps too, '67 VLR, '74 DR...


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Post subject: Re: 12AX7/7025 Tubes
Posted: Mon Apr 07, 2014 7:40 am
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cedarblues wrote:
We're talking about 40+ year old amps here :) so I'm sure some caps might need replacing, but I'd hate to change anything in these precious amps, as long as they're working fine.

The differences in tone that I hear are minor, overall all 4 amps sound great! But whenever I find the right combo of preamp tubes in V1 and V4 it takes the amp to another level. When I say warm, I don't mean that the amp sounds too dark, it just sounds too smooth maybe and it's missing some clarity or definition, and that metallic kinda tone, this is when playing a Strat. The output is the other issue I have, it seems the amp volume drops a bit when I plug in most of the older preamp tubes.

For example, in my '73 SR with CTS Alnicos, using an older tube in V2 makes the amp sound smooth, still very sweet tone. Plug a good Mullard RI in V2 and the amp wakes up, a little brighter and louder, tighter bass too. Plug the right tube in V4, in this case it happens to be one of the only RCA 12AX7 that sounds right to me, and the amp turns into this monster! Perfectly balanced in every way possible! For me at least :)

I've had the same results in the other amps too, '67 VLR, '74 DR...


Cedar, try the RI Tungsol 12AX7. Get it from a supplier that tests the tubes for low noise and strength. For the price, this tube has the cleanest high end of any of the similarly priced modern 12AX7. If this tube is still too "smooth" or mellow in your amp, I'd start looking at electrolytic bypass caps and main filter caps feeding these 12AX7 tubes.

The volume drops most likely because those NOS tubes are not truly NOS. Or even close to ANOS. If you take a truly new, high testing TFK or Raytheon (these normally test off the scale, when brand new) and plug it into a critical stage, you are not going to get a too-mellow tone. There are very few truly NOS, "A-one" TFK ECC83 or Raytheon 12AX7A out there anymore.

If you can spring for the Gold Lion B759/ECC83, you may want to try one. The tone is BIG and clear. Very good bass. A good step above the Mullard or TS reissues. No other modern 12AX7 has it's tone. They are black plates, so should give good consistent tone and long life.

One other thing, what kinda strings do you use. Not to get you angry... when was the last time you changed them? Just asking.

Good luck! :D


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Post subject: Re: 12AX7/7025 Tubes
Posted: Mon Apr 07, 2014 10:58 am
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One other tube you may want to look for is the mil spec Sylvania 12AX7WA. Good black plates are getting hard to find ( esp square getter ring variety).

But, the gray plate Sylvania 12AX7WA (halo getter ring) also has a nice neutral, clean tone.

http://i.ebayimg.com/00/s/MTE2MlgxNjAw/ ... 8/$_57.JPG

Just an FWIW...

:mrgreen:


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