What's your favorite 12ax7 and why?
- Thread starter pilotputz
- Start date
FalconEddy
Audio Mastering Engineer
pilotputz,
Kegger reinforces my point.
Gear, circuit design, and component selection can make a small, or huge difference in how a distinct sounding tube responds. They can, and will, exhibit entirely different characteristics between different amps; or identical model amps with different components.
Many people select metallized polypropelene caps these days when restoring vintage amps. These caps will generally brighten the sound, to a greater or lesser degree between manufacturers; and sometimes makes the amp sound harsh and/or thin in the upper register.
It is obviously not the original sound intended by the amp designer, so the original tube choice may sound terrible in those altered circuits.
The 5751 has only 70% of the gain in a 12AX7, but its a very linear tube with lots of headroom.
. . Falcon
Not to sound flippant, but my favorite 12AX7 is a 12AT7. At least in any circuit that I can adjust to work with (resistors for gain and bias changes, etc) the operating point of the 12AT7. Usually, bandwidth, gain and linearity are improved by the swap, IME. The 12AT7 can handle much more plate current (and is much more linear as a result, by being able to get "above" the curvature at the bottom of the plate curves), and is much more robust compared to either the 12AX7 or 12AU7.
Of 12AX7s, I have had the best luck with the Telefunkens that were included as original equipment in my Harman A300. That amp was one of the more "modern sounding" amps of its era (designed to be "voiced right" with higher bandwidth than was normal for that era), and the Telefunkens are right at home in it. Other tubes sound somewhat "dead" or "slow" in it, by comparison...
Regards,
Gordon.
Of 12AX7s, I have had the best luck with the Telefunkens that were included as original equipment in my Harman A300. That amp was one of the more "modern sounding" amps of its era (designed to be "voiced right" with higher bandwidth than was normal for that era), and the Telefunkens are right at home in it. Other tubes sound somewhat "dead" or "slow" in it, by comparison...
Regards,
Gordon.
The A300 should not have a cathode resistor for the outputs! IN those, the heaters of the two 12AX7s in the phono stage are connected in series, and THOSE act as the cathode bias resistor (24v drop). These should have a 200uf cap across the heaters of those tubes (between ground and the output tube cathode connection).
Here's a link to the schematic- it SAYS it's the link for the A500, but it's NOT... it's actually the schematic for the A300. We've been pestering Harman about this error for years, and they've never corrected the file name/location error.
http://manuals.harman.com/HK/Service Manual/A500 schematic.pdf
Regards,
Gordon.
Dave C
Super Member
Thanks for the link Gordon, I'm not at home to look at the amp right now but as I recall there is a wire tying all 4 tubes together and something else. (Capacitor??) and it has a single resistor to ground which I can't determine the color code because of heat. I wouldn't think it had been modified, I've owned it for about 20 years. Maybe the previous owner.
VinylRob
Vinylphile
Sounds good to me!
Ok, my golden earred friend. I have to pretty well agree right down the line with you. There are always exceptions, and thanks for that quad of smooth plate Tele's that grace my phono's first gain stage. They are magic.
Happy Listening!
Ok, my golden earred friend. I have to pretty well agree right down the line with you. There are always exceptions, and thanks for that quad of smooth plate Tele's that grace my phono's first gain stage. They are magic.
Happy Listening!
FalconEddy
Audio Mastering Engineer
The linearity I'm referring to is its frequency response, although this varies a bit from manufacturer to manufacturer. Some are a bit sweeter at the top end.
Their headroom factor makes them a really nice fit for many guitar amps, especially when there's a 2nd stage in the amp.
The mid to late 1950's produced GE 5751WA black plates are generally an outstanding variant of the 12AX7. I also like the early Raytheon and Tungsol versions of the 5751.
. . Falcon
RWFE
Well-Known Member
My preamp calls for 4 5751s. I have four National 5751s which sound good, four Five Star GE two mica 5751s that sound better, then four Grey plate 3 Mica GE 5751s that sound very good and finally four 3 mica black plate GE 5751s that are in my preamp now and sound the best so far. The black plates are very expensive though. I personally think that the gray plate 3 mica 5751s sound just about as good to me. Knowing then what I know now I probably would not buy the black plates again but would look for the 3 mica gray plates and save a few bucks but at this point I am just going to keep them all.
PakProtector
AK member
hey-Hey!!!,
The preference is quite system dependant. However, the older RCA 12AX7 has served me well. Black plates on these early ones. In truth the circuit can usually stand a 3 dB reduction in gain and with slight adjustment in values a 12AY7 goes right in. Type 6072 is the mil version. These tubes are used in mic pre's and are quite nice. Even in direct coupled amps like the McIntosh the 12AY7 goes right in...
cheers,
Douglas
The preference is quite system dependant. However, the older RCA 12AX7 has served me well. Black plates on these early ones. In truth the circuit can usually stand a 3 dB reduction in gain and with slight adjustment in values a 12AY7 goes right in. Type 6072 is the mil version. These tubes are used in mic pre's and are quite nice. Even in direct coupled amps like the McIntosh the 12AY7 goes right in...
cheers,
Douglas
Hi, first post here, but long time audionut/tube fan. Sorry for the cross-post/link, but I found this to be a fantastic article, and also a big recommendation for the 5751:
http://www.audioasylum.com/scripts/d.pl?audio/faq/joes-tubes.html#12AX7
Seems that once the word got out that 5751s were good substitute for 12AX7 (as long as you can live with less gain), everyone's jacked up the price.
Kegger - Any specific 5751 recommendations?
jaymanaa
RIP 1961-2018
GE 5 Star Triples are pretty nice too.:yes:
modge
Super Member
My favourite 12AX7s
pilotputz,
In 9 pieces of tube gear, I use 28- 12AX7s. The interesting aspect of 12AX7 choice ofr me is the nature of the gear using it: in my case I have vintage- McIntosh MX110 and MC240, Dynaco PAS3, Fisher 800, EICO HF-12 and then an important piece for me, the modern Audio Research SP8,a nd finally a Peavey VMP-2 microphone preamplifier which uses 6-12AX7s and 2-12AT7s.
Since 2000, I've collected about 80- mostly NOS 12AX7s and have experimented most in the SP8 and the VMP2 mic pre.
1. My favourite overall 12AX7 has gravitated to the Siemens and Halske triple mica E83CC. This is an amazingly energetic with great natural timbre, dynamics and the kind of authoritative but open and tranparent bass I like- also very quiet. This tube can both wake up sleepy vintage and in the SP8 phono really give it life with fantastic imaging. The Siemens E83CC is though a "revealing" tube and I can conceive of cases where it might be too punchy or agressive.
2. The best all-rounder I've found is the ordinary Philips / Amperex / Valvo ECC83 from the early to late 60's. By reputation, the early D-getters are even better, but a good example of this tube just does everything well- balanced top to bottom never harsh and the imgaing and detail is just fine. There were millions made too and if you watch they don't have to be astronomically ecpesinsive. The good feature is that I've been pleased with the sound of these everywhere I've tried them- vintage and modern.
3. Next is a kind of specialty tube, the Sylvania black plate, square getter of the mid to late 50's. These wre often labelled as organ tubes and they are amazingly lush and deep, but still with good detail and imaging. These might be too sweet and liquid in some vintage gear and I only use them in my mic pre when I want that kind of slightly dark sound. However, I'd be interested to try them in a CD player with a tube output stage as these might be useful to tame any digital flatness tendencies by introducing some air.
4. A tube that really really impresses me, the Sylvania triple mica, black plate, square getter 5751. These are for me just the ultimate in refined sound- dynamic and detailed with fantastic discretion between sounds, astounding imaging, and for me the best bass I can imagine- a very "non-electronic" tube. I use these in my mic pre along with the ordinary grey plate GE- which is not bad at all. In the future, the Sylvania 5751 will be the line stage tubes in the SP8.
Others that I think are very good: RCA 7025- quiet, beautifully balanced and the Tesla ECC803S, the early frame grid version that copies the Telefunken. This is the 12AX7 for people who like the 6DJ8 and has a great kind of nimbleness and can be both delicate and punchy. In the future I'll use these to replace the smooth plate Telefunkens in the Fisher 800.
The 12AX7 is a tube I quite like, epseically as it has such a wide range of sounds and there are so many around. By contrast, I find the 6DJ8 family very tough to get right and the prices and availability have all but ended my buying of NOS.
Cheers,
Bambi B
pilotputz,
In 9 pieces of tube gear, I use 28- 12AX7s. The interesting aspect of 12AX7 choice ofr me is the nature of the gear using it: in my case I have vintage- McIntosh MX110 and MC240, Dynaco PAS3, Fisher 800, EICO HF-12 and then an important piece for me, the modern Audio Research SP8,a nd finally a Peavey VMP-2 microphone preamplifier which uses 6-12AX7s and 2-12AT7s.
Since 2000, I've collected about 80- mostly NOS 12AX7s and have experimented most in the SP8 and the VMP2 mic pre.
1. My favourite overall 12AX7 has gravitated to the Siemens and Halske triple mica E83CC. This is an amazingly energetic with great natural timbre, dynamics and the kind of authoritative but open and tranparent bass I like- also very quiet. This tube can both wake up sleepy vintage and in the SP8 phono really give it life with fantastic imaging. The Siemens E83CC is though a "revealing" tube and I can conceive of cases where it might be too punchy or agressive.
2. The best all-rounder I've found is the ordinary Philips / Amperex / Valvo ECC83 from the early to late 60's. By reputation, the early D-getters are even better, but a good example of this tube just does everything well- balanced top to bottom never harsh and the imgaing and detail is just fine. There were millions made too and if you watch they don't have to be astronomically ecpesinsive. The good feature is that I've been pleased with the sound of these everywhere I've tried them- vintage and modern.
3. Next is a kind of specialty tube, the Sylvania black plate, square getter of the mid to late 50's. These wre often labelled as organ tubes and they are amazingly lush and deep, but still with good detail and imaging. These might be too sweet and liquid in some vintage gear and I only use them in my mic pre when I want that kind of slightly dark sound. However, I'd be interested to try them in a CD player with a tube output stage as these might be useful to tame any digital flatness tendencies by introducing some air.
4. A tube that really really impresses me, the Sylvania triple mica, black plate, square getter 5751. These are for me just the ultimate in refined sound- dynamic and detailed with fantastic discretion between sounds, astounding imaging, and for me the best bass I can imagine- a very "non-electronic" tube. I use these in my mic pre along with the ordinary grey plate GE- which is not bad at all. In the future, the Sylvania 5751 will be the line stage tubes in the SP8.
Others that I think are very good: RCA 7025- quiet, beautifully balanced and the Tesla ECC803S, the early frame grid version that copies the Telefunken. This is the 12AX7 for people who like the 6DJ8 and has a great kind of nimbleness and can be both delicate and punchy. In the future I'll use these to replace the smooth plate Telefunkens in the Fisher 800.
The 12AX7 is a tube I quite like, epseically as it has such a wide range of sounds and there are so many around. By contrast, I find the 6DJ8 family very tough to get right and the prices and availability have all but ended my buying of NOS.
Cheers,
Bambi B