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 Post subject: 12ax7 for Stereo Receivers—Which Brands?
PostPosted: Nov Wed 25, 2020 11:35 pm 
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RE: HK TA 3000x Stereo Receiver

I had great success in having my above named receiver rebuilt, i.e. recapped, etc. At this point, I’m thinking about changing out the current set of 12ax7’s (four, paired to each channel).

There are tons of choices out there, but there is a difference between the sound of a guitar amp type of tube for a hi-fi... I don’t want a guitar amp tube. I was curious to see what the opinion was for a specific recommended brand. Of course a NOS, such as RCA, would be nice, but... $$.

While my HK was being worked on, I used my KLH 24 as a substitute (the same speaker set up for for each situations). Actually, I guess since the KLH has germanium transistors (I’m not an expert and I humbly have to say that I know enough to be dangerous :lol: ) the KLH had a crisper, perhaps, a cleaner sound than the HK (of course, it has more wattage). So, I guess I would prefer a cleaner sounding 12ax7 that would be similar to what I heard with the KLH... (Crazy reasoning perhaps.)

Thought?

Thanks!


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 Post subject: Re: 12ax7 for Stereo Receivers—Which Brands?
PostPosted: Nov Thu 26, 2020 12:08 am 
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Please explain how your current set of 12AX7s fall short of expectation. Please share test results too. That would help those that can make some recommendations.


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 Post subject: Re: 12ax7 for Stereo Receivers—Which Brands?
PostPosted: Nov Thu 26, 2020 12:27 am 
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Thanks for your response. The current 12ax7s are EH brand, I think. When I was listening to the KLH system ( a lot of listening while I’m working from home nowadays), I just noticed the KLH was a lot crisper in sound. I’m wondering if I change out the 12ax7s in the HK, the sound would improve even more so. I like my HK and it really has a good warm sound and all, and I plan to hold on to it. Just wanting to see if I can fine tune it ( the overall sound). I hope that makes sense. Thanks


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 Post subject: Re: 12ax7 for Stereo Receivers—Which Brands?
PostPosted: Nov Thu 26, 2020 12:37 am 
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I'm happy with any brand as long as the tube tests good on my TV-7D/U and is operated within 12AX7 design criteria and specifications.

Dave


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 Post subject: Re: 12ax7 for Stereo Receivers—Which Brands?
PostPosted: Nov Thu 26, 2020 12:41 am 
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Be aware that the brand printed on a tube may not correspond to who made it. Tube manufactures frequently bought tubes from other manufacturers when they suddenly ran out of stock or all their production facilities were tied up with other types. They would mark these "foreign" tubes with their own brands. So it is common to find GE tubes branded RCA, Sylvania tubes branded CBS, or any other variation. Toward the end of tube production, almost all tubes were made in other countries and marked with U.S. brands. There is some evidence that this practice is still going on with current production.

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 Post subject: Re: 12ax7 for Stereo Receivers—Which Brands?
PostPosted: Nov Thu 26, 2020 12:47 am 
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Very interesting point—thanks for that heads up.


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 Post subject: Re: 12ax7 for Stereo Receivers—Which Brands?
PostPosted: Nov Thu 26, 2020 1:27 am 
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Mullard were good; unknown where they come from now.

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 Post subject: Re: 12ax7 for Stereo Receivers—Which Brands?
PostPosted: Nov Thu 26, 2020 2:24 am 
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Realistic 12AX7's - to me even the name implies warmth.

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 Post subject: Re: 12ax7 for Stereo Receivers—Which Brands?
PostPosted: Nov Thu 26, 2020 5:06 am 
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"but there is a difference between the sound of a guitar amp type of tube for a hi-fi... I don’t want a guitar amp tube."

not trying to be mean or rude, but there is no such thing as a "guitar amp" 12ax7.

We seem to living in a 2nd era of tubes (at least audio tubes)/

Just look at all these choices for New tubes.

https://www.thetubestore.com/preamp-tub ... tube-types

Personally i doubt you will notice any difference unless there is something wrong with your current EH tubes. However many folks seem to like the Gold Lion brand that EH makes. Interestingly enough I have EH Kt88s and Gold Line KT88s for my citation II. The construction looks identical and were most likely produced on the same tooling in the same factory at different times. I've never bother rolling them to try and hear a difference cause I have better things to do.

In other words you probably already have a quality set of 12ax7s unless they are weak or unbalanced.

Steve


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 Post subject: Re: 12ax7 for Stereo Receivers—Which Brands?
PostPosted: Nov Thu 26, 2020 5:51 am 
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MississippiKid wrote:
While my HK was being worked on, I used my KLH 24 as a substitute (the same speaker set up for for each situations). Actually, I guess since the KLH has germanium transistors (I’m not an expert and I humbly have to say that I know enough to be dangerous :lol: ) the KLH had a crisper, perhaps, a cleaner sound than the HK (of course, it has more wattage). So, I guess I would prefer a cleaner sounding 12ax7 that would be similar to what I heard with the KLH...


I kind of doubt that changing the brand of preamp tubes will significantly change the tone balance of a receiver that is otherwise working properly. Transistor equipment (germanium or otherwise) is generally more accurate than tube equipment and almost always has more bandwidth, although the details of the design, good or bad, makes more difference than the type of active device.

Don't overlook the effects of more power or current drive, either, depending on your speaker and how the impedance changes over frequency, that could make a very big difference. Solid-state equipment generally has vastly more damping factor.

I pretty much always use JJ ECC-83s in these applications, but the EH is generally very neutral, too. Both are much less microphonic than the sainted Telefunkens and to me the modern tubes are much preferable for that reason. The Telefunkens last a lot longer, that's about all I can say about them.

The most obvious answer is to use the KLH all the time! But you can do much better than either of these pretty easily depending on what you would like to or be willing to spend.

Brett


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 Post subject: Re: 12ax7 for Stereo Receivers—Which Brands?
PostPosted: Nov Thu 26, 2020 11:51 am 
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I'd think in a radio, with any 12AX7 that tests good or better, with no leakage or shorts, the only difference you might hear is if a tube is microphonic. I tend to think the same of "guitar" tubes as well, but you'll never convince the owner of a Fender amp that's the case lol.

Yes, the tube could have some other defect your tester may not catch. But assuming all "good" 12AX7 tubes, hearing the difference is in the mind of the beholder. And of course, the wallet. Some like to spend $85 for a $7 tube. If it makes them feel better, fine. I may be selling some soon ........

The different brands of any given tube .... some are Mullard loyalists, some like RCA. I suppose there are track records out there that relate to how long a tube might last, or whether it can survive if dropped from a 50 foot tower.... but beyond that........

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 Post subject: Re: 12ax7 for Stereo Receivers—Which Brands?
PostPosted: Nov Thu 26, 2020 4:18 pm 
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Everyone — I’m appreciative of the good advice that was given. Thanks everyone and Happy Thanksgiving!


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 Post subject: Re: 12ax7 for Stereo Receivers—Which Brands?
PostPosted: Nov Thu 26, 2020 9:29 pm 
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Back in the mid 1950's my job was selling and installing group hearing aids. Translated that meant push pull parallel 6l6's driving a 12 ohm headset on a deaf kids head. While over several years it did vary but over all Telefunken was usually the best choice. Less hum, less hiss.

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 Post subject: Re: 12ax7 for Stereo Receivers—Which Brands?
PostPosted: Nov Thu 26, 2020 9:54 pm 
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manualman wrote:
Realistic 12AX7's - to me even the name implies warmth.

On that note, I have a Realistic tube, I don't remember the type, where they didn't completely remove the GE logo. They just printed the Realistic brand over it!

Besides legitimate cross branding by manufacturers, there was, and probably still are, those who buy second, reject, or used tubes and relabel them. Not to mention real crooks who do that with known defective tubes.

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 Post subject: Re: 12ax7 for Stereo Receivers—Which Brands?
PostPosted: Nov Fri 27, 2020 1:48 am 
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Dave Doughty wrote:
I'm happy with any brand as long as the tube tests good on my TV-7D/U and is operated within 12AX7 design criteria and specifications.


As a collector of early Fisher stereo tuners, tuner-preamps and receivers, most of which "live and breathe" 12AX7s in their audio sections, I wholeheartedly agree with this statement.

That having been said though, it is my understanding that most folks consider vintage/NOS Telefunken to be the "gold standard", followed by vintage (not new Russian-made) Mullard.

For me, as Dave said, if it tests good and is operated within specs, I'm happy with it - regardless if it is JJ, E-H, or vintage GE or RCA.

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 Post subject: Re: 12ax7 for Stereo Receivers—Which Brands?
PostPosted: Nov Fri 27, 2020 1:55 am 
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Hi-fi amplifiers are operated with their voltage amplifier stages (12AX7, etc) always in their linear regions. As tubes are designed to operate in this region all will sound the same.

Guitar amplifiers, on the other hand, are often deliberately over-driven to create harmonics, with their voltage amplifier stages operating far out of their linear regions. As tube operation outside of the linear region is not specified, different manufacturers or vintages of the same tube type may well sound different.

-David


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 Post subject: Re: 12ax7 for Stereo Receivers—Which Brands?
PostPosted: Nov Fri 27, 2020 5:17 am 
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Thanks!


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 Post subject: Re: 12ax7 for Stereo Receivers—Which Brands?
PostPosted: Nov Fri 27, 2020 5:24 am 
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dberman51 wrote:
Hi-fi amplifiers are operated with their voltage amplifier stages (12AX7, etc) always in their linear regions. As tubes are designed to operate in this region all will sound the same.


Actually, they won't, because their other characteristics affect the circuit around them, particularly the intrinsic capacitance, and the aforementioned microphonics issues. It's particularly true for triodes (which is what 12A.7s are). It can be both audible and measurable.

I agree that guitar amps are doing something inherently different than audio amps, but that's a different type of problem - and artistic problem much more than an engineering problem.

Brett


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 Post subject: Re: 12ax7 for Stereo Receivers—Which Brands?
PostPosted: Nov Fri 27, 2020 11:51 pm 
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Vintage Mullard may be best, Telefunken second, then other Europeans may be close. Then you got vintage USA brands. As far as modern made AX tubes I cannot comment. Too bad they did not use the lower gain AU7's as those are so cheap and common in vintage iterations that you could play with them to your hearts content for not much money. You could find out what the higher grade hi fi tube amps are using these days, not the Chinese brand stuff but the botique amps with known western brands. They would probably not tolerate crappy tubes in their high priced amps. And I am sure they are not running vintage as that supply is unreliable for any production item. Here is an outfit that sells high end tube gear and also selected tubes for such purposes. Their preamp tubes category. https://upscaleaudio.com/collections/preamp-tubes

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 Post subject: Re: 12ax7 for Stereo Receivers—Which Brands?
PostPosted: Nov Sat 28, 2020 5:12 am 
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wazz wrote:
Vintage Mullard may be best, Telefunken second, then other Europeans may be close. Then you got vintage USA brands. As far as modern made AX tubes I cannot comment. Too bad they did not use the lower gain AU7's as those are so cheap and common in vintage iterations that you could play with them to your hearts content for not much money. You could find out what the higher grade hi fi tube amps are using these days, not the Chinese brand stuff but the botique amps with known western brands. They would probably not tolerate crappy tubes in their high priced amps. And I am sure they are not running vintage as that supply is unreliable for any production item. Here is an outfit that sells high end tube gear and also selected tubes for such purposes. Their preamp tubes category. https://upscaleaudio.com/collections/preamp-tubes


Yes, a 12AX7 is probably necessary/desirable for the phono stage, but for the line amp stage A 12AT7 or 12AU7 makes a lot more sense to me. You don't need the gain and you do want lower output impedance. It doesn't make that much difference when you are driving a tube power amp, I guess.

Brett


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