Time for me to get with the program. What is the story on all of these 12AX7's that have emerged?
12AX7LP $14.30
Great for DC on filaments. Used by VHT.
12AX7LPS $15.50
"S" Spiral filament for no hum with AC heaters. Used by Mesa Boogie
12AX7WA/7025 $9.90
Used By Fender®, Hartke, SLM, Carvin, Trace Elliot, Orange
12AX7WB/7025 $11.20
Used By Rivera, VHT, Demeter, Kendrick
So What Is A 12AX7 These Days?
Moderator: jingle_jangle
So What Is A 12AX7 These Days?
Life, as with music, often requires one to let go of the melody and listen to the rhythm
Please join the Official RickResource Forum Facebook Page https://www.facebook.com/groups/379271585440277
Please join the Official RickResource Forum Facebook Page https://www.facebook.com/groups/379271585440277
The real news is the JJ Tesla ECC83S and Ei ECC83. I like the upper harmonics the best on the Ei ECC83, and it's the best tube for high end sound, but may be a bit microphonic in some guitar amps. The JJ ECC83S is the best all around (guitar or audiophile applications) and the one I fitted in my high gain Traynor YCV40 due to slightly less noticeable microphonics. I say slightly because the Ei ECC83 was still really nice in the Traynor. Sovtek 7025 tubes came in my Traynor, but the Ei ECC83, JJ ECC83S, and the E-H 12AX7 all clearly outperformed them. Watford Valves also says so in their tube test reports. I disagree with Watford Valves in that the Ei is a great guitar tube as long as you don't have a very high gain amp where microphonics can be a problem. Give it a try, because it is such a cheap tube from Angela Instruments. My father has used the shiny plate Ei ECC83 for several months in his Kustom Tube 12, and it has not gone microphonic from daily use. Angela Instruments sells the Ei ECC83 shiny plate tube at 10 for $45, and it is clearly the deal of the decade in a preamp tube. The E-H 12AX7 is the short plate version of the Sovtek 12AX7LP (LP = long plate, and therefore more microphonic). E-H is the premium branch of Sovtek. The E-H 12AX7 is the most rugged of the new crop of 12AX7/ECC83 preamp tubes from eastern Europe, and has a bit more gain and midrange punch than the JJ and Ei valves. The Sovtek 12AX7LP and 12AX7LPS would be best suited for audiophile applications, while the E-H 12AX7 is the premium guitar valve. I tried the E-H 12AX7 as well. My brother loved the gain it had in my Traynor. It was a bit much for me. The JJ ECC83S is a short plate tube like the E-H 12AX7. These are the best new guitar specific tubes. They are truly excellent to the point I see no need to ever buy NOS tubes at inflated prices ever again.
Go to the Watford Valve website for in-depth reports on all the above mentioned preamp tubes, as well as some notable NOS tubes. I generally agree with them, except the latest production version of the Ei ECC83 is a great tube. I believe Don Butler says the same about it. If it ends up a bit too microphonic for your guitar amp, your tube stereo gear should really love it.
I might be interested in snatching up a few Mullard M8137 tubes from any of you out there that might have some laying about.
Don't forget the Sovtek 5751 if you need to tame a hot gain section. SRV preferred the 5751 to the 12AX7 in the gain section his Fender amps. NOS GE 5751 tubes may still be available at decent prices. Gives a smoother distortion. Also, there are still NOS GE 12AY7A/6072A tubes available for your Fender reverb drivers at decent prices only slightly above recent imports.
Go to the Watford Valve website for in-depth reports on all the above mentioned preamp tubes, as well as some notable NOS tubes. I generally agree with them, except the latest production version of the Ei ECC83 is a great tube. I believe Don Butler says the same about it. If it ends up a bit too microphonic for your guitar amp, your tube stereo gear should really love it.
I might be interested in snatching up a few Mullard M8137 tubes from any of you out there that might have some laying about.
Don't forget the Sovtek 5751 if you need to tame a hot gain section. SRV preferred the 5751 to the 12AX7 in the gain section his Fender amps. NOS GE 5751 tubes may still be available at decent prices. Gives a smoother distortion. Also, there are still NOS GE 12AY7A/6072A tubes available for your Fender reverb drivers at decent prices only slightly above recent imports.
Robert,
Preamp tubes have never translated much into a difference in bass in any preamp I have ever used them in. They only provide voltage signal for phase splitter or output tubes. Any falloff in bass is usually due to undersized coupling capacitors in the signal path, especially the output coupling capacitor in the preamp. In my audiophile preamp, which drives a solid state 200W per channel power amp which drives audiophile loudspeakers with useful output down to 25 Hz, there is almost no difference in bass response among any tube I have used in it. It has flat response down to below 5 Hz into a 20k ohm load due to huge 4.4 uF output coupling capacitors. Noise, microphonics, and harmonic integrity are far more noticeable characteristics in preamp tubes. Power tubes need to put out more current when the impedance dips at low frequencies in loudspeakers, so strong power tubes with high emission do make a big difference. Solid state power amps tend to handle the wide impedance swings at low frequencies better than tube amps do. Tube bass amps need huge output transformers like audiophile tube amps use for good low frequency response. Ask any Ampeg SVT user that lugs that beast around. The question to ask would be: Does my tube preamp have a low enough output impedance and a large enough output coupling capacitor to drive a solid state power amp with a low input impedance? The "rule of thumb" in a voltage gain circuit is that the input impedance of the power amp be 10 times greater than the output impedance of the preamp. This results in over 90% of the voltage generated being dropped across the input of the power amp. A long run of highly capacitive interconnect cable between preamp and power amp will also roll off the high frequencies, especially if the output impedance of your preamp is much over 1k ohms.
If your power amp has 100k ohms or higher input impedance, almost any tubed preamp or preamp tube will drive it well. I am not familiar with your preamp or power amp, but these rules work for most all combinations, except for a few exotics such as Jeff Rowland amps that have 300 ohms output/input impedance on their preamp/poweramp combos and use 300 ohm interconnect cables for flat response from DC to radio frequencies (and are solid state anyway). Guitar amps never get that extreme in preserving fidelity.
Also, if your power amp has a coupling capacitor on the input, it will also roll off your low end response in conjunction with the output coupling capacitor in your preamp. If both caps were 1.0 uF, then the combined capacitance would be 0.5 uF. The combination of two series capacitors is always smaller than the smallest capacitor. If they are equal, the capacitance is halved. That causes your bass to roll off at a higer frequency than either capacitor alone would give.
The JJ ECC83S or Electro-Harmonix 12AX7 would be your safest bet. They are short plate tubes and can really take a pounding. If you separate your preamp from the bass cabinet, then the Ei ECC83 might work well also. The E-H 12AX7 is reputed to be extremely rugged, and should work very well in a bass combo amp or high gain guitar amp as well. All three tubes can be had for less than the price of many single NOS American or western European tubes, so it is economical to experiment. If finances keep you from experimenting, the E-H 12AX7 should work in any situation, for bass or guitar.
Preamp tubes have never translated much into a difference in bass in any preamp I have ever used them in. They only provide voltage signal for phase splitter or output tubes. Any falloff in bass is usually due to undersized coupling capacitors in the signal path, especially the output coupling capacitor in the preamp. In my audiophile preamp, which drives a solid state 200W per channel power amp which drives audiophile loudspeakers with useful output down to 25 Hz, there is almost no difference in bass response among any tube I have used in it. It has flat response down to below 5 Hz into a 20k ohm load due to huge 4.4 uF output coupling capacitors. Noise, microphonics, and harmonic integrity are far more noticeable characteristics in preamp tubes. Power tubes need to put out more current when the impedance dips at low frequencies in loudspeakers, so strong power tubes with high emission do make a big difference. Solid state power amps tend to handle the wide impedance swings at low frequencies better than tube amps do. Tube bass amps need huge output transformers like audiophile tube amps use for good low frequency response. Ask any Ampeg SVT user that lugs that beast around. The question to ask would be: Does my tube preamp have a low enough output impedance and a large enough output coupling capacitor to drive a solid state power amp with a low input impedance? The "rule of thumb" in a voltage gain circuit is that the input impedance of the power amp be 10 times greater than the output impedance of the preamp. This results in over 90% of the voltage generated being dropped across the input of the power amp. A long run of highly capacitive interconnect cable between preamp and power amp will also roll off the high frequencies, especially if the output impedance of your preamp is much over 1k ohms.
If your power amp has 100k ohms or higher input impedance, almost any tubed preamp or preamp tube will drive it well. I am not familiar with your preamp or power amp, but these rules work for most all combinations, except for a few exotics such as Jeff Rowland amps that have 300 ohms output/input impedance on their preamp/poweramp combos and use 300 ohm interconnect cables for flat response from DC to radio frequencies (and are solid state anyway). Guitar amps never get that extreme in preserving fidelity.
Also, if your power amp has a coupling capacitor on the input, it will also roll off your low end response in conjunction with the output coupling capacitor in your preamp. If both caps were 1.0 uF, then the combined capacitance would be 0.5 uF. The combination of two series capacitors is always smaller than the smallest capacitor. If they are equal, the capacitance is halved. That causes your bass to roll off at a higer frequency than either capacitor alone would give.
The JJ ECC83S or Electro-Harmonix 12AX7 would be your safest bet. They are short plate tubes and can really take a pounding. If you separate your preamp from the bass cabinet, then the Ei ECC83 might work well also. The E-H 12AX7 is reputed to be extremely rugged, and should work very well in a bass combo amp or high gain guitar amp as well. All three tubes can be had for less than the price of many single NOS American or western European tubes, so it is economical to experiment. If finances keep you from experimenting, the E-H 12AX7 should work in any situation, for bass or guitar.
Philip,
Thanks for the information. The Trace AH350SMX isn't a combo amp but a stand alone head. The preamp has both tube and solid state sections the outputs of which can be blended. The power amp section is FET driven and rated 350W RMS@4 ohms.
I know too well what it's like to lug an SVT around and I'm putting mine up for sale along with the 8x10 SVT cabinet. If there is anyone in the Seattle area interested please drop me a line.
Do you have any recommended online sources for tubes or is Watford the place to go?
Thanks for the information. The Trace AH350SMX isn't a combo amp but a stand alone head. The preamp has both tube and solid state sections the outputs of which can be blended. The power amp section is FET driven and rated 350W RMS@4 ohms.
I know too well what it's like to lug an SVT around and I'm putting mine up for sale along with the 8x10 SVT cabinet. If there is anyone in the Seattle area interested please drop me a line.
Do you have any recommended online sources for tubes or is Watford the place to go?
Angela Instruments (Maryland, new and NOS) is the place for Ei ECC83 tubes. Shiny plates are 10 for $45 or $5 each. Gray plates are $8 each. Same tube, but the gray plates dissipate heat better. Sound the same to me. Angela is also a great place for film capacitors, Riken Ohm resistors, Jensen oil caps, and Hammond transformers.
My other favorite places are The Tube Store (Canadian, mainly new tubes) and Triode Electronics (Chicago, new and NOS). Watford Valves is very good, but be prepared to pay shipping from England. It's THE PLACE if you live in the UK or Europe. Great website with reviews of Celestion speakers and popular guitar and audiophile tubes. I bought some great Mullard NOS M8080/CV4058/6C4 tubes from them for about half of what Conrad-Johnson charged for the exact same tube in matched pairs. These are the best 6C4 type tubes the world has ever produced (Ampeg amp and C-J PV-14L owners take note). They don't sell BS Chinese tubes with fancy lettering at jacked up prices like Groove Tubes does. Angela had NOS Philips 5881 tubes for only $15 each, about what a Russian 6L6 tube costs and almost as good as Tung-Sol.
My other favorite places are The Tube Store (Canadian, mainly new tubes) and Triode Electronics (Chicago, new and NOS). Watford Valves is very good, but be prepared to pay shipping from England. It's THE PLACE if you live in the UK or Europe. Great website with reviews of Celestion speakers and popular guitar and audiophile tubes. I bought some great Mullard NOS M8080/CV4058/6C4 tubes from them for about half of what Conrad-Johnson charged for the exact same tube in matched pairs. These are the best 6C4 type tubes the world has ever produced (Ampeg amp and C-J PV-14L owners take note). They don't sell BS Chinese tubes with fancy lettering at jacked up prices like Groove Tubes does. Angela had NOS Philips 5881 tubes for only $15 each, about what a Russian 6L6 tube costs and almost as good as Tung-Sol.