This is great stuff,
Rex, Thanks!
Rex, Thanks!
The "black beauty"capacitor phenomenon...
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Sound quality-When a friend of mine and me were servicing the AM stations we noticed how much better a high level plate modulated AM transmitter sounded on the air over solid state and PDM ones.The high level I am talking about are rigs that have push pull tubed modulators.Often the same tube as the RF PA.Again in the high level broadcast aM-and many SW transmitters the modulator is noting more than a very powerful PP audio amplifier.The modulator tubes have a bias adjust exactly like on a hi-fi amp or a guitar amp.When the tubes are good and bias adjusted right-the sound quality was almost magic.The Harris DTX transmittrers do sound much better than earlier SS transmitters.Remember Harris MW-1 AM broadcast(1Kw AM) the PA comprised of 6 power modules with standard TO-3 transistors.When they shorted-common---the circuit board traces must have glowed like toaster elements and blew before the board fuse did.Had to repair these with lots of wire jumpers.Liked the tubed 1Kw AM's better,4-400 tubes as RF amps and modulator or big glass 833 triode tubes as PA stage or modulators.One time we serviced a rig-Harris 1G the blower failed-Tx was still happyly playing away on air--tube plates really glowing-when we entered the building smelled REALLY "Hot Glass"The tube envelopes were sucked against the plates and they were still going.Fixed the blower and put in new tubes-all was right with the world again.Shows how tough those old 833's are!!Was a place in Baltimore.
'Nother thought for tubes-one other fellow that works with me at the transmitter can tell this-not sound quality,reliability,efficiency---but the SMELL of tubed stuff.The hot glass,dust on the glass.Now if the tube device is in a wood cabinet-like a radio,TV,or Hi-Fi console-the smell of the wood added to the hot tubes!Anyone else out there noticed? Take a good wiff next time you play your tubed device!
lordkenmore
Well-known member
Yes, I've noticed the tube smell on old radios. It was something my mother noted, as well. (She had grown up with tube technology in both radios and TVs.)
I remember the old tube radios and TV's very well. The sound was so much richer and natural, there was warmth if you will. I used to own a 55 Cadillac Coupe deVille in 1974 and it had a tube radio like all cars of this vintage did. After I would start the car it would take about 30 secs of so before the sound would come out of the speakers as the tubes warmed up, and it would almost swell, the volume gradually getting louder until it reached the set level. I think the song "Coming to You From Out of Nowhere" may have been based on the way the sound came out of the early radios.
My family had an RCA HiFi that my dad purchased in 1956. It had a beautiful cherry wood cabinet and the most beautiful sound I've ever heard out of any radio. I think that the vacuum tubes and the heavy wood cabinet combined with the huge speakers are what gave it such a rich sound.
Eddie[this post was last edited: 1/29/2017-01:48]
My family had an RCA HiFi that my dad purchased in 1956. It had a beautiful cherry wood cabinet and the most beautiful sound I've ever heard out of any radio. I think that the vacuum tubes and the heavy wood cabinet combined with the huge speakers are what gave it such a rich sound.
Eddie[this post was last edited: 1/29/2017-01:48]
Because HI-FI
was so gosh-darned expensive in the 1950's, manufacturers had no choice but to compete on quality. People invested the time to actually listen and look and work the devices. Today, I order a 12AX7 or a 12AX7A (low noise) and cross my fingers it won't be too awful at a price which is absurd.
Magnavox, back when it wasn't Philips cheap, bargain brand, put real engineering and applied acoustics into their consoles. The astro-sonic solid state amps had lousy high-frequency performance (among other flaws), so the unusual horns. The Micromatic turntables had rumble problems, so the channel separation at 100 Hz was very dampened.
I think the matter comes down to human hearing more than anything else. All people (even old folks) are really sensitive to transients. Tube amps of that era did enormously better than solid-state amps (hell, to this day rise time is one big measure of an amp's competence). Second, odd-order distortion is anathema to those of us cursed with perfect pitch, yes. But normal people without that hearing defect are also really attuned to it and don't like it. When poorly designed solid-state amps are pushed too hard, ouch - immediate third-order harmonics and other nasty clipping artifacts which hurt. Tubes fail gracefully when pushed up against their ceiling. The artifacts in the odd-order are much lower.
Finally, we can argue the lab. measurements. Take a well-designed, logic-controlled Class A tube amp and put it up against a well-designed, logic controlled Class A solid-state amp and what comes out of both is going to look great on paper. Very few of us can afford that level of quality.
I like classical music. It's a tough challenge to meet with anything but really high-quality solid-state. It's not so hard to do it with a good tube amp. Again, it's the transients (where measurements and perception line up) and the make up of the harmonic distortion (where they don't line up 1:1) which matters to our ears, not the 'facts' on paper.
Good discussion of the whole matter at the link.
www.theaudioarchive.com
was so gosh-darned expensive in the 1950's, manufacturers had no choice but to compete on quality. People invested the time to actually listen and look and work the devices. Today, I order a 12AX7 or a 12AX7A (low noise) and cross my fingers it won't be too awful at a price which is absurd.
Magnavox, back when it wasn't Philips cheap, bargain brand, put real engineering and applied acoustics into their consoles. The astro-sonic solid state amps had lousy high-frequency performance (among other flaws), so the unusual horns. The Micromatic turntables had rumble problems, so the channel separation at 100 Hz was very dampened.
I think the matter comes down to human hearing more than anything else. All people (even old folks) are really sensitive to transients. Tube amps of that era did enormously better than solid-state amps (hell, to this day rise time is one big measure of an amp's competence). Second, odd-order distortion is anathema to those of us cursed with perfect pitch, yes. But normal people without that hearing defect are also really attuned to it and don't like it. When poorly designed solid-state amps are pushed too hard, ouch - immediate third-order harmonics and other nasty clipping artifacts which hurt. Tubes fail gracefully when pushed up against their ceiling. The artifacts in the odd-order are much lower.
Finally, we can argue the lab. measurements. Take a well-designed, logic-controlled Class A tube amp and put it up against a well-designed, logic controlled Class A solid-state amp and what comes out of both is going to look great on paper. Very few of us can afford that level of quality.
I like classical music. It's a tough challenge to meet with anything but really high-quality solid-state. It's not so hard to do it with a good tube amp. Again, it's the transients (where measurements and perception line up) and the make up of the harmonic distortion (where they don't line up 1:1) which matters to our ears, not the 'facts' on paper.
Good discussion of the whole matter at the link.
Vacuum Tubes versus Solid-State Transistors
www.theaudioarchive.com
I believe the "A" suffix on a 12AX7 tube means controlled warm-up time so it can be used in series filament circuits. The low noise version of a 12AX7 is a 7025.
firedome
Well-known member
The IEEE Spectrum article...
"The Cool Sound of Tubes", referred to by me much earlier in this thread, and again just above, you will note was written by my friend Eric Barbour, the former Tech Editor of the magazine that I edited & wrote for back in the day: Vacuum Tube Valley. Eric was also Vacuum Tube Engineer for Svetlana, which is now part of the Russian tube manufacturing companies owned by Mike Matthews of Groove Tubes &c. IMO Eric probably knows more overall about vacuum tubes than possibly anyone in the world. His many tech articles about the history and development of numerous audio tube types are unmatched anywhere.
"The Cool Sound of Tubes", referred to by me much earlier in this thread, and again just above, you will note was written by my friend Eric Barbour, the former Tech Editor of the magazine that I edited & wrote for back in the day: Vacuum Tube Valley. Eric was also Vacuum Tube Engineer for Svetlana, which is now part of the Russian tube manufacturing companies owned by Mike Matthews of Groove Tubes &c. IMO Eric probably knows more overall about vacuum tubes than possibly anyone in the world. His many tech articles about the history and development of numerous audio tube types are unmatched anywhere.
firedome
Well-known member
memory glitch...
actually Eric was Senior Editor, mostly John Attwood was Tech Editor, followed by Lynn Olsen towards the end of the run... RIP our Founder/Publisher and my greatly missed good friend, Charlie Kittleson.
actually Eric was Senior Editor, mostly John Attwood was Tech Editor, followed by Lynn Olsen towards the end of the run... RIP our Founder/Publisher and my greatly missed good friend, Charlie Kittleson.
Ken,
The 12AX7A is a low-noise double-triode. Please reference the data sheet link. GE marketed them specifically for their low-hum and microphonics.
The 12AX7A is a low-noise double-triode. Please reference the data sheet link. GE marketed them specifically for their low-hum and microphonics.
Keven,
Ken is correct, the 7025 is a specially selected 12AX7A tube that was deemed to be lower noise and likely had more robust mechanical construction. I have had better luck with 7025's in the first preamp position in my Marshall guitar amp, I have never had a microphonic one.
The 12AX7A was an improvement that brought a different filament winding to try reduce hum induced from filament current.
Ken is correct, the 7025 is a specially selected 12AX7A tube that was deemed to be lower noise and likely had more robust mechanical construction. I have had better luck with 7025's in the first preamp position in my Marshall guitar amp, I have never had a microphonic one.
The 12AX7A was an improvement that brought a different filament winding to try reduce hum induced from filament current.
I didn't say
the 7025 wasn't a low-noise variation, but so is the 12AX7A. Says so right there in the data sheet.
There's an enormous number of variations on this tube, some I didn't even know existed until this thread.
As to the GE 12AX7A, it's about $80 a pop for NOS and the Shuguang about $10 for the 7025/12AX7 so there's not much to discuss. I just happened to recollect the GE 12AX7A as being a low-noise upgrade I made in the 1980's for an ancient moving-coil pre-amp I'd put together in 1969. If I were doing a guitar amp, the Shuguang would be the better choice for microphonics, clearly.
the 7025 wasn't a low-noise variation, but so is the 12AX7A. Says so right there in the data sheet.
There's an enormous number of variations on this tube, some I didn't even know existed until this thread.
As to the GE 12AX7A, it's about $80 a pop for NOS and the Shuguang about $10 for the 7025/12AX7 so there's not much to discuss. I just happened to recollect the GE 12AX7A as being a low-noise upgrade I made in the 1980's for an ancient moving-coil pre-amp I'd put together in 1969. If I were doing a guitar amp, the Shuguang would be the better choice for microphonics, clearly.
Type 5751 is a military-low noise version of the 12AX7.-Also this tube has lower microphonics-the elements are better reinforced.
Yes,the Astro-Sonic like other early solid state amps were TERRIBLE.The older TUBED Magnavox was best.I had no problems with the Magnavox Imperial and Micromatic TT's were good tables.The change mechanism was powered separetly off the motor.Also with some SS amps-you drive them into hard clipping---there goes your tweeters!Tweeters HATE clipped waveforms-blows them instantly!So that is the case of a low power amp being more dangerous than a higher powered one.Seen that several times.Even had to repair a tweeter horn from that.
At the transmitter we use Shuguang 845 tubes in the CEMCO modulators!Work great.
Yes,the Astro-Sonic like other early solid state amps were TERRIBLE.The older TUBED Magnavox was best.I had no problems with the Magnavox Imperial and Micromatic TT's were good tables.The change mechanism was powered separetly off the motor.Also with some SS amps-you drive them into hard clipping---there goes your tweeters!Tweeters HATE clipped waveforms-blows them instantly!So that is the case of a low power amp being more dangerous than a higher powered one.Seen that several times.Even had to repair a tweeter horn from that.
At the transmitter we use Shuguang 845 tubes in the CEMCO modulators!Work great.
12AX7 Family
This tube has been around so long, been so versatile and does it's job so well. This thread prompted me to do research on it. Impressive little high-voltage beasty.
The first electronic op-amps were realized with 12AX7 tube - pretty much only used for the war effort, of course. Wow. That was over 70 years ago!
This tube has been around so long, been so versatile and does it's job so well. This thread prompted me to do research on it. Impressive little high-voltage beasty.
The first electronic op-amps were realized with 12AX7 tube - pretty much only used for the war effort, of course. Wow. That was over 70 years ago!
firedome
Well-known member
the highly regarded 12ax712ax7a/ECC83 &c...
are the most popular audio tubes in the world, over 200 types being produced in 40 factories since introduction in March 1948 by RCA (see RCA tube manual RC-15), then shortly after by GE and Sylvania, later Tung-Sol, Nat. Union, CBS-Hytron, Raytheon, &c, followed by European ECC-83. They are essentially 2 x 6av6 triodes, mu = 100, in one tube. 12AU7/ECC82 and 12AT7/ECC81 are medium and low mu but very similar dual-triode tubes, the obsure 12AD7, 12BZ7, 12DF7, 6679, 6681, 6851 &c are also similar types.
High gain, low noise, and low hum, the 12ax7 types gained huge popularity mainly due to preamp use with the original GE Variable Reluctance low output magnetic phono cartridge. The original 12ax7 was found somewhat wanting so the military/industrial 5751 was introduced in 1950, a ruggedized mini 6SL7, and then a more cost effective 12ax7a for consumer (hi-fi) use. The superior Phillips/Miniwatt ECC83 with the precision grid winding of the 5751 and better cathode materials debuted around '52, followed by Telefunken, Mullard, Brimar, Valvo, MOV, Tungsram and other Euro versions. Most higher end US hi-fi mfrs such as Fisher, Scott, McIntosh &c used the Euro produced tubes re-branded with their own logos as they were truly superior (quieter) to the US tubes. The US competitor for the ECC-83 was the 7025, a std 12ax7a with coiled heater to reduce hum, more expensive, most were sold to guitar amp mnfrs.
All currently produced 12ax7 variants are Russian, East Europe or Chinese origin. Among the most desirable vintage variants are generally conceded to be the Telefunken smooth and ribbed plate ECC83 versions along with Amperex (Phillips) Bugle Boy, and the super rare Telefunken ECC803s gold pin, the latter bring over $1000 each on occasion!
are the most popular audio tubes in the world, over 200 types being produced in 40 factories since introduction in March 1948 by RCA (see RCA tube manual RC-15), then shortly after by GE and Sylvania, later Tung-Sol, Nat. Union, CBS-Hytron, Raytheon, &c, followed by European ECC-83. They are essentially 2 x 6av6 triodes, mu = 100, in one tube. 12AU7/ECC82 and 12AT7/ECC81 are medium and low mu but very similar dual-triode tubes, the obsure 12AD7, 12BZ7, 12DF7, 6679, 6681, 6851 &c are also similar types.
High gain, low noise, and low hum, the 12ax7 types gained huge popularity mainly due to preamp use with the original GE Variable Reluctance low output magnetic phono cartridge. The original 12ax7 was found somewhat wanting so the military/industrial 5751 was introduced in 1950, a ruggedized mini 6SL7, and then a more cost effective 12ax7a for consumer (hi-fi) use. The superior Phillips/Miniwatt ECC83 with the precision grid winding of the 5751 and better cathode materials debuted around '52, followed by Telefunken, Mullard, Brimar, Valvo, MOV, Tungsram and other Euro versions. Most higher end US hi-fi mfrs such as Fisher, Scott, McIntosh &c used the Euro produced tubes re-branded with their own logos as they were truly superior (quieter) to the US tubes. The US competitor for the ECC-83 was the 7025, a std 12ax7a with coiled heater to reduce hum, more expensive, most were sold to guitar amp mnfrs.
All currently produced 12ax7 variants are Russian, East Europe or Chinese origin. Among the most desirable vintage variants are generally conceded to be the Telefunken smooth and ribbed plate ECC83 versions along with Amperex (Phillips) Bugle Boy, and the super rare Telefunken ECC803s gold pin, the latter bring over $1000 each on occasion!
panthera wrote:
"The 12AX7A is a low-noise double-triode. Please reference the data sheet link. GE marketed them specifically for their low-hum and microphonics."
Can't argue with GE's data sheet. Thanks for the info!
"The 12AX7A is a low-noise double-triode. Please reference the data sheet link. GE marketed them specifically for their low-hum and microphonics."
Can't argue with GE's data sheet. Thanks for the info!
Ken,
Doesn't change the fact you may be right, too - goodness, there's supposedly a 12AX7HD from 2015 which is considerably better on noise/hum/THD. For a humble triode pushing 80 in it's original design, this sure has been a winner.
Doesn't change the fact you may be right, too - goodness, there's supposedly a 12AX7HD from 2015 which is considerably better on noise/hum/THD. For a humble triode pushing 80 in it's original design, this sure has been a winner.
The 12AX7--was a workhorse then-still is now!!May they live on!!The uses for that tube are just plain endless!The data sheet is just like what is in my GE tube manual.Have several RCA tube manuals and a Sylvania one around somewhere.Also the RCA master manuals that list transmitter tubes and large rectifier tubes.Mercury vapor ones,no less.The Audio nuts are discovering those!Liked them in older broadcast transmitters!
The GE book I have is the Essential Characteristic-but don't what date it is.In one of my MANY boxes and milkcrates of books!
