Discussion in 'Amps and Cabs' started by SAVROHR, Jul 10, 2006.
If cost is no object, the Telefunken ECC801S - though it might be too much tube for a lowly reverb driver. I've used JAN Philips 12AT7WC with great success. Haven't tried Mullards.
It's a reverb driver tube. It's meant to induce a current into essentially a cheap 1950's style tonearm cartridge from an old record player and shake the "needle" which shakes a set of springs to another tonearm cartridge on the output side. Not exact, but approximate. Why would you spend good money on an audiophile grade tube to do this? Buy a JJ and be done with it. When people chime in talking about how much better the tone is from a $50+ tube than a $10 tube, you will know that they listen with their wallets rather than their ears. There's more to playing guitar than impressing people with how much money you spend needlessly on your gear.
My opinion, but those that disagree probably sell tubes.
I guess on some level, commenting on this thread does bespeak skewed priorities and too much idle time. My motivation was to explore why two BF fender amplifiers I owned had very different sounding reverbs. It shouldn't surprise anybody that the 12AT7 used for the reverb driver does make a difference. Out of the big box of tubes, and some are quite rare by today's standards, a humble Sylvania 12AT7 ended up giving consistently best results.
The reverb driver tube must be a reliable nonmicrophonic tube. At one time, current production 12AT7s were as squealy microphonic as can be. I have used JAN Philips for a long time - still reasonable at $10-12. I just bought a NOS quad off Ebay for $42 shipped.
JJs might be the ticket IF they are reliably nonmicrophonic. JJ 12AT7s I have not tried - JAN Philips I have and I am very happy with them.
In an outboard reverb unit, quality tubes impact the overall tone quite a bit because the entire circuit is dedicated to provide reverb tone - none of the tubes are shared for preamp or power. For an amp with onboard reverb, the impact would depend on the circuit.
I'm no tube snob, just replied with what I've found to be a rugged and reliable (and inexpensive by today's standards) tube.
The V3 spot in Fender amps with reverb can be hard on a tube.
Been playing guitar for about 43 years now so I'm well beyond the stage of "impressing people with how much money you spend needlessly on your gear."
Being a teacher I don't have all that much money with which to impress anybody.
Right, it's all a tube dealer conspiracy. After all, we have to protect our oil-barren-like incomes and lifestyles
I can't imagine why anyone would spend $10 on a piece of crap JJ 12AT7 (I'm not suggesting that all JJ tubes are crap, but the 12AT7s certainly are) when you could buy a Mullard for $22 and likely never have to replace it. Sheesh!
No offense to you, Mike, I've dealt with you in the past and find you to be one of the honest dealers that I'd recommend in a heartbeat to ANYONE looking for quality tubes. I would recommend a NOS 12AT7 for the PI/driver tube, and a good NOS tube for any other location. However, for the reverb driver, you're just looking for a lo-fi driver tube meant to be punished. The difference I could see would be in the gain levels; that would be the equivalent of different "dwell" settings, rather than a tone difference based on different manufacturers. I've found JJ to be very robust and durable, hence my recommendation for them. If you have Phillips 12AT7WC's for $22, than I'd say buy it. However, Mullards tend to cost much more, and other than the PI slot, or the input stage of a standalone, I wouldn't bother.
rooster, I think the Mullards are only $22 also, one of the reasons I like 'em.
The Philips are $12 and Mullards are $22. Mullard 12AX7s are much more expensive.
Contrary to popular, non tech, wisdom, the gain of a tube has virtually nothing to do with the gain of the circuit unless the tube is weak or has a gain less than what the circuit was designed to produce. IOW, since most 12AX7 gain stages are designed for a gain of 70, anything over 70 is wasted so using a "high gain" 12AX7 is of absolutely no consequence to the gain of the circuit.
The same can be said of reverb drivers. They're current drivers only, so voltage gain is a virtual non issue.
As for tone, if all of the signal (in this case, reverb signal) goes through the driver and none goes around it, the tube HAS to make a tonal difference. Imagine using a tube with a high frequency cut off of 500hz. Do you think that would sound different than one with full audio spectrum response? You bet your ass it would.
Mullards are WAY more durable than any new production 12AT7s. In general, all of the new production 12A*7 types with gains lower than 12AX7s are horrible. The good news is, for a few bucks more, you can get a high quality NOS tube for these types.
It appears I made a mistake - I bought a NOS 5 tube sleeve of JAN Philips 12AT7WCs off Ebay for $42 shipped - not a quad. My mistake... $8.40 each.
In that case, I'd say to buy one or 3 of the Phillips tubes from Mike and have some backups. That is only about $3 or $4 more than a JJ, and the durability will be better, much as I like JJ's. Mike, $12/ea. is NO way to make a profit!
As for the gain, I believe that the gain of the tube does play a part in the gain of the stage; not the whole thing, but the anode resistance is one factor in the gainstage response, IIRC, which I may not be doing. That gainstage would affect the drive level of the input to the cage, and a hotter tube would give you more "dwell" on a single-knob control.
I still don't think the frequency response of the reverb driver tube, taken by itself, would have nearly so much effect on the tone of the guitar amp as a whole, due to its application.
If it were my amp, I'd use a Mullard CV4024 (the early '80s version 12AT7WA, not the more expensive '60s version) because of its tonal qualities. This tube gives me the quintessential reverb tone I'd personally prefer: solid lows, rich low-mids, and open/airy highs that remain unobtrusive.
In my experience, the JJ 12AT7 is much too mushy, and lacks the clarity of the Mullard (or any other NOS version I've tried). The older ('60s) Mullard don't have the full lows that the later-production ones do, and neither do any of the other NOS 12AT7 or 6021 I've tried (including 3-mica Sylvania and GE) -they're noticeably more bright and dry.
I don't like an arid, spoingy reverb, but prefer a more viscous quality that the CV4024 can provide. Plus, they do last - I've never had one fail yet. Of course, I don't recommend turning up your reverb level so high that the tonal differences are that critical. But still, given the choice... CV4024!!
Just my opinion.