woody961
Tele-Meister
What is the best current production 12at7 tube for use as either a reverb driver or phase inverter application in a silverface Super Reverb or twin reverb??
THX!!
THX!!
12at7 tube question??
- Thread starter woody961
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vibrasonic
Tele-Afflicted
JJ, tung sol, TAD seem popular but you can get some really nice NOS 12at7's for pretty cheap that are a lot better for not a lot more than the new stuff.
StephaninMelb
Banned
Actually for a 12AT7 you are best off going on eBay and buying a NOS. There are fewer requirements for 12AT7 compared to 12AX7 type so 12AT7 type can be purchased at a price usually below new tubes. The NOS are also better quality than most new production, with exception of Genelex Gold and PSVANE.
The JAN Philips 12AT7WC is generally widely available as NOS and a very nice tube. This was a high-end tube developed for the USA military, which it has the JAN designation (Joint Army - Navy). There is tons of New Old Stock (NOS) always coming into the market. This would be my first "practical" choice for a good performing 12AT7.
You can also pick up NOS Mullard 12AT7WA (CV4024) for under $15. Other decent NOS 12AT7 types are:
With NOS 12AT7 so easily available I wouldn't bother with ones in current production. But if you prefer that Tung-Sol Reissue (NOS is best), Electro-Harmonix Gold 12AT7WC (ECC81) and JJ 12AT7 work "OK." Genalex 12AT7 (ECC81) would be best for guitar amp application, but expensive ($33 to $40/each) and Genalex Gold 12AT7 (around $80/ea). PSVANE (by Shuguang) are exceptional but expensive for guitar amp (about $40 - more for high-end HiFi). The Chinese have finally got it together with top quality tubes, but are focusing on the high-end audiophile market (what is sold into guitar amp market is older generation stuff).
Pass by on:
Pictures below - Top to Bottom
(1) JAN Philips 12AT7WC
(2) PSVANE 12AT7
(3) PSVANE Packaging (Tubes all have individual serial numbers and factory registration!)
The JAN Philips 12AT7WC is generally widely available as NOS and a very nice tube. This was a high-end tube developed for the USA military, which it has the JAN designation (Joint Army - Navy). There is tons of New Old Stock (NOS) always coming into the market. This would be my first "practical" choice for a good performing 12AT7.
You can also pick up NOS Mullard 12AT7WA (CV4024) for under $15. Other decent NOS 12AT7 types are:
- Mullard 12AT7WA (CV4024) < $15
- RCA 12AT7 (ECC81)
- Amperex 12AT7 (ECC81)
- GE 12AT7WA (6201)
- Telefunken 12AT7 (ECC81)
- Some of the NOS 12AT7 can be very expensive such as some of the Telefunken and RCA sub-types
With NOS 12AT7 so easily available I wouldn't bother with ones in current production. But if you prefer that Tung-Sol Reissue (NOS is best), Electro-Harmonix Gold 12AT7WC (ECC81) and JJ 12AT7 work "OK." Genalex 12AT7 (ECC81) would be best for guitar amp application, but expensive ($33 to $40/each) and Genalex Gold 12AT7 (around $80/ea). PSVANE (by Shuguang) are exceptional but expensive for guitar amp (about $40 - more for high-end HiFi). The Chinese have finally got it together with top quality tubes, but are focusing on the high-end audiophile market (what is sold into guitar amp market is older generation stuff).
Pass by on:
- Ruby 12AT7C
- Groove Tubes GT12AT7 (especially ones with sticker label ID on tubes - many relabelled Chinese fakes)
- 1st generation Shuguang (80s)
Pictures below - Top to Bottom
(1) JAN Philips 12AT7WC
(2) PSVANE 12AT7
(3) PSVANE Packaging (Tubes all have individual serial numbers and factory registration!)
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Fret Wilkes
Friend of Leo's
If a 12AX7 is used in place of a 12AT7 for the reverb driver, how does the greater gain effect the sound?
You are pushing that reverb route harder, when it comes back in the mix
it will be hotter. You will probably not be able to bump up your reverb
much past 2.
imho
StephaninMelb
Banned
The stock Fender tube reverb driver circuit is usually optimal with the 12AT7. The reverb driver (one triod of a 12AT7 / which is 1/2 of the tube) is combined with a reverb transformer to make a mini power amp. This is used to drive the tank. There are some people that do a mod of the reverb driver stage where they use a EL84 (power tube) as the reverb driver using a Fender 022921 reverb transformer.
These change takes a reconfiguration of the reverb circuit. A 470 ohm / 2W resistor is tapped from the preamp to the screen grid and the cathode resistor is around 820 ohms / 10W. Too much trouble for most people. If you think you need more gain you can go to 12AX7 which would change the mu factor from 60 mu to 100 mu.
You are better to make changes at the tank level with different models of Accutronic tanks that have different spring configurations and reverb decay. The best change is to use a Accutronics vertical mount - horizontal alignment tank on the lower rear panel. Changes to the reverb driver tube won't affect tone much - just raise or lower gain that hits the tank input.
These change takes a reconfiguration of the reverb circuit. A 470 ohm / 2W resistor is tapped from the preamp to the screen grid and the cathode resistor is around 820 ohms / 10W. Too much trouble for most people. If you think you need more gain you can go to 12AX7 which would change the mu factor from 60 mu to 100 mu.
You are better to make changes at the tank level with different models of Accutronic tanks that have different spring configurations and reverb decay. The best change is to use a Accutronics vertical mount - horizontal alignment tank on the lower rear panel. Changes to the reverb driver tube won't affect tone much - just raise or lower gain that hits the tank input.
jhundt
Doctor of Teleocity
I believe that most Fender built-in reverb systems use both sides of the tube, in parallel, to drive the reverb transformer.
NOS Mullard is the only 'AT7 I can recomend for audio use. It is the only one that has reasonable grid current onset. The grid current issue does not seem to be a problem in LTPPI duty, but everywhere else they load down the preceding stage to much to be acceptably to me
A 12ax7 as a reverb driver actually reduces the available reverb signal because it is so heavily loaded as a reverb driver that an AT7 will have more gain. This is a classic case of where lower plate impedance and Mu results in higher in circuit gain.
A 12ax7 as a reverb driver actually reduces the available reverb signal because it is so heavily loaded as a reverb driver that an AT7 will have more gain. This is a classic case of where lower plate impedance and Mu results in higher in circuit gain.
StephaninMelb
Banned
The Silverface Super Reverb & Twin Reverb use both dual triodes in a single 12AT7 (V3) as a reverb driver. For reverb return it uses one triode in a 12AX7 (V4B).
JJ is popular among newbies. 
There's plenty of better choices. If you're not going to order Tung Sol, consider a NOS - either Sylvania, RCA, or similar.
NOS = Old Tube that's never been put into service. It may have been tested, but is considered new condition, and may have been made before you were born!
Used tubes that are sold for near the price of a new tube are not worth the gamble. Don't believe everyone that says, it tested good, and is worthy being used in your equipment. There's plenty of opportunists around selling 'junk' that's not worth the cost of postage.
There's plenty of better choices. If you're not going to order Tung Sol, consider a NOS - either Sylvania, RCA, or similar.
NOS = Old Tube that's never been put into service. It may have been tested, but is considered new condition, and may have been made before you were born!
Used tubes that are sold for near the price of a new tube are not worth the gamble. Don't believe everyone that says, it tested good, and is worthy being used in your equipment.
There's plenty of opportunists around selling 'junk' that's not worth the cost of postage.BiggerJohn
Friend of Leo's
You are correct sir. FMIC hard wires both sections of the 12AT7 in parallel at the socket.
BiggerJohn
Friend of Leo's
Come on man get your facts straight. Not just the SF Super and Twin, but all the BF and SF amps with verb do it this way.
StephaninMelb
Banned
So what is your point Einstein
? This thread is specifically addressing the SF Super Reverb and Twin, not every amp ever built by Fender.So what is your point Einstein
I think the point is your google fed verbosity with seemingly no practical experience behind it got old long ago. At least two professional amp builders have given up on TDPRI since you have started posting. Your presence does not make up for that loss. If you don't like the pot shots, tone down your twaddle.
StephaninMelb
Banned
Gee are the Pro Amp builders losing business from TDPRI members because of my posts?
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6942
Poster Extraordinaire
With the exception of a few European-made tubes, most NOS 12at7 tubes are still relatively cheap.
Steve
Steve
Not likely, but far worse, the community is being denied access to data sets from real experience and practical knowledge. Something all your posts lack
StephaninMelb
Banned
I am sorry Ms. but you have no idea of my professional background or identity, so please keep quiet of your personal judgements. You really shouldn't assume. I am sorry if some of the tube distributors and whoever else runs commercial operations on TDPRI feels threatened because of little me. Unlike them I take NO financial benefit. What I write can be read if the person thinks it adds value or ignored. You might be surprised that the bulk of what I write is researched or based on experience. Do you care to make any other points? And what is your point following me around TDPRI and making public comments - there is a private email channel if you have an issue with me. That is the "polite way" to take issue with someone.
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