New Preamp Tubes for Fender Twin Reverb

[orri]

I've started to get some sporatic crackling sounds from my Fender Twin Reverb (75 silverface, with master volume).

I suspect it is a preamp tube that needs to be replaced.
(but I've run it 2 evenings now and it has just worked really well...).

JJs seem to be considered great quality for money but there are more expensive options.

Is there any reason to pay more? Are some tubes better suited to be over driven while others fit jazz better?
Are perhaps some of the tubes that are better suited to spend more money (V2 preamp tube and V6 phase inverter?)

I've been reading a bit and these is some interesting points I've found:

- tubes with larger plate can be beneficial as phase inverter tube (V6). (they however also tend to be more microphonic).
- using 12au7 (instead of 12at7) for the reverb driver tube (V3) can make the reverb easier to conrol. Most of the time I have the reverb around 1, and tiniest movement cause a vast differnce so this sound like something I would like a lot.
- using 12ay7 as preamp tube (v2, or v1) is an option to get a slightly different sound characteristics (some say smoother or warmer) but will lower the preamp gain.


What tubes have you tried in your Fender amps and what have you liked, disliked, or had good or bad expericences with?

[mad dog]

I've owned lots of different fenders, fender-equivalent amps, tried different pre-amp tubes in all of them. There are so many differences across models. Some things - such as the benefit from possible swapping in 12ay7 for 12ax7 in V1 or V2 spots - play very differently in different models. You can even pull V1 in some BF and SF Fenders, dispense with it completely, to slightly up gain in the vibrato channel. Which would not work in any Fender tweed.

Same thing with experimenting with different send/return preamp tubes for reverb. Really depends on the specific model, version of the amp, what the benefit would be. And of course, whether the preamp tubes in there now are the right ones to begin with.

One generalization I can make. For V1 and V2 - the preamp slots that typically affect tone the most - NOS almost always wins. Used to be always. But some new construction tubes such as the Tung Sol 12ax7 sound good enough to be seriously considered. I have yet to try a JJ anything in a tone-sensitive preamp slot where some NOS or other did not quite obviously make a better choice.

Some other preamp slots - mainly reverb driver - are hard duty for tubes. Here NOS can win just because they are generally so much more likely to last longer.

Just my experience. YMMV or course.

[Ray175]

A fascinating rabbithole to go down, where everyone hears different things because their ears are different.....

One great source to read up on the subject is on the site of Watford Valves in the UK. Read specifically their testing and reports sections where the tubes of a massive range of producers are fairly objectively compared. when I retuned my Princeton Recoding last year, I found this particular site invaluable and went down the NOS route with Gold Lion Genelex tubes - not cheap, but they give me clear headroom up to 12 o'clock and break up very progessively thereafter whilst staying fairly reactive to playing dynamics. YMMV

[Alder Statesman]

I like a 5751 in V1. It lowers the gain and really gives a warm and clean tone. You can find GE JAN 5751’s for about $70. These were made in the mid 80’s in Kentucky. Should last forever.

[whiskey02]

My vote is for JJ 5751.

[Longways to Go]

+1 on the NOS 5751 in V1.

I haven't owned a Twin Reverb, but the 5751 has worked great for me in a Hot Rod Deluxe, a PRRI, a 5E3 clone, and I have one in my current Pro Junior. It brings in a creamy quality that is just great for jazz IMO. Worth every penny.

I think guys who use a lot of distortion or like a lot of treble sparkle will prefer a high quality 12AX7 over the mellower 5751. Tube rolling is fun, and the variation in quality and sound characteristics among 12AX7 tubes is remarkable. Changing out the V1 produces the biggest change by far.

Does the Twin Reverb run on a quad of power tubes? If so, I think you can experiment with running 2 instead of 4 power tubes. My Musicman 210HD130 came with this configuration, and it really helps tame the beast for home playing. But you'd better check with other Twin Reverb owners to see if that amp works like that or not.

Some years ago I bought an amp at a pawnshop and discovered that it had a Mazda ECC83 in V1. Turns out this is a very expensive tube $$$$! It is a very lovely sounding tube, but more on the side of delicate and clear. I have found the 5751 much superior for my idea of jazz tone.

[wintermoon]

Yeah they're more expensive but I've found that NOS sound best and last much longer than current production you can just pony up the extra $ for peace of mind.
Mad dog is correct, and if you can't afford a full complement at least put one in V1 and V2.

[lawson-stone]

Assuming comparable quality, is there any difference between the 5751 and the 12AT7 other than a slight difference in gain?

[ugarte]

I'm glad I have a stash because prices aren't going down.

NOS Sylvania 12ax7's , I find the yellow labels are just fine, I do have a few RCA's (including 5751) of various flavors but no matched pairs. Tube rolling can be fun and expensive.

[Jabberwocky]

Tube Amp Doctor TAD 5751 is a nice selected-for-low-noise Chinese tube for under $20. I have found TAD tubes to be very good.

I put a 3-spring medium delay MOD reverb tank in my PR clone. $19.95 from Amplified Parts. Does the trick. It is not wet-surfy and sounds kind of dry and "controlled". But I can crank it up to 3 to get a hint of reverb. I like it when the reverb isn't obvious.

[jim777]

JJs are adequate and readily available fairly cheaply. That's about all you can say for them. I would also agree TAD, Jan-Philips, Tung-Sol, Svetlana and Gold Lion are a little to a lot better than JJs. JJs aren't awful, it's just that they're not at all amazing either. Thetubestore.com has a line called Preferred Series that aren't stupid expensive that are a fine compromise between cheap and ridiculously expensive.

Does the Twin Reverb run on a quad of power tubes? If so, I think you can experiment with running 2 instead of 4 power tubes. My Musicman 210HD130 came with this configuration, and it really helps tame the beast for home playing. But you'd better check with other Twin Reverb owners to see if that amp works like that or not.

It does yes, it runs on 4 6L6 tubes. It might work, but you would need to know if you used the two inside tubes, the two outside tubes, 1 and 3, or 2 and 4. Just yanking 2 tubes and turning it on would not be advisable Also, you would likely need to lower the impedance, from say 16 to 8 or 8 to 4 ohms. I would suggest, if you want to do this, that you bring it to an amp tech who has some experience with older Fenders, and not try it yourself on a nice vintage amp.

[BigDaddyLoveHandles]

I'm glad I have a stash because prices aren't going down.

NOS Sylvania 12ax7's , I find the yellow labels are just fine, I do have a few RCA's (including 5751) of various flavors but no matched pairs. Tube rolling can be fun and expensive.

Can you explain? I thought matching was for power tube pairs.

[orri]

Thanks everyone for your inputs so far.
Really appreciate it.

Can you explain? I thought matching was for power tube pairs.

You can also match preamp tubes but it is rarely relevant for guitar amps (as far as I understand).
I think it is more relevant for audiophile hifi stuff.

Some recommend that you select a balanced phase inverter tube (but I've also read that Fender designed their phase inverter stages so that it is not a bit issue), but that means that you check that the two triodes in a dual triode tube have negligible production variances.

[orri]

Assuming comparable quality, is there any difference between the 5751 and the 12AT7 other than a slight difference in gain?

The 12AT7 is most common in phase inverters and reverb drivers and not so common in preamp gain stages (such as V1 and V2 in 2 channel Fenders).

As far as I understand is that their "voice" or tonal qualities are not considered as good as 12ax7, 5751 and 12ay7 which are all more commonly used in preamp gain stages. But 12at7 can also work, and are sometimes used.

[Greentone]

FWIW, I have generally found sporadic crackling to be grounding issues. Typically, this can be tracked down to a dodgy ground at the input jack. Think about it--the input jack is mechanically where most of stress in the amp is associated. (i.e., plugging and unplugging cables, and the tug of the cable at the jack when you are standing ten feet or so from the amp with your guitar)

Try removing and re-seating the input jack, re-tightening the collar nut. Might do the trick.

OTOH, this problem is MUCH more likely to pop up on a post-1990 Fender amp than on a 1975 Silverface Twin Reverb. Reason: often the newer amp has board-mounted jacks. They develop loose joints at the board connections. I have repaired many Blues Juniors and DeVilles for this reason.

[orri]

Does the Twin Reverb run on a quad of power tubes? If so, I think you can experiment with running 2 instead of 4 power tubes. My Musicman 210HD130 came with this configuration, and it really helps tame the beast for home playing. But you'd better check with other Twin Reverb owners to see if that amp works like that or not.

yes it does have a quad of power tubes and can run on only two but then it has a 2:1 impedance mismatch which can be resolved by running only one speaker.

[ugarte]

Can you explain? I thought matching was for power tube pairs.

you are right, I was talking about my whole inventory pre and power, sorry to confuse.

[orri]

FWIW, I have generally found sporadic crackling to be grounding issues. Typically, this can be tracked down to a dodgy ground at the input jack. Think about it--the input jack is mechanically where most of stress in the amp is associated. (i.e., plugging and unplugging cables, and the tug of the cable at the jack when you are standing ten feet or so from the amp with your guitar)

Try removing and re-seating the input jack, re-tightening the collar nut. Might do the trick.

OTOH, this problem is MUCH more likely to pop up on a post-1990 Fender amp than on a 1975 Silverface Twin Reverb. Reason: often the newer amp has board-mounted jacks. They develop loose joints at the board connections. I have repaired many Blues Juniors and DeVilles for this reason.

Should I then be able to recreate it by fiddling with the cable around the input jack (or somewhere)?

It seems very sporadic, and not related to any movement of anything.
I've read that sporadic crackling is one symptom of bad preamp tubes (but sporadic squealing is more common than crackling).
I was also wondering if it could be the tube contacts, and that I could try spraying the sockets.

[mad dog]

Re: 12at7 vs 5751 ... I'm remembering that the 12at7 is much better suited to the hard use expected in the reverb driver slot. So you probably wouldn't want to sub a 5751 in those positions. (Could be similar for the PI tube, but I'm certainly no expert.)

I have tried 12at7 tubes in V1, V2. Sounds cold and nowhere. This is strictly my own taste: I've yet to swap a 5751 for a 12ax7 in V1 or V2 and like it enough to leave it there. Whereas a good NOS 12ay7, that's a different story. Who know's why. Probably more going on here than just the gain factor.

[pauln]

You can't judge a preamp tube by the brand stamped on the glass (they get tested and re-branded, you can often even see where the tube was branded and then stamped again with another subsequent brand). You can't judge by how it looks or how it is described; the test is how it sounds in your amp... the variability of results is huge.

Most of us with multiple tube amps (I have seven) will have spare preamp tubes (I have a box with over two dozen), and every once in a while (or when there is a problem) we do some swapping. In the long run it's the only way.

Although the signal path is serial, the multiple preamp tube triodes (two triodes per glass envelop) in an amp are provided with current for their heaters and cathodes in parallel (why you can remove one and the others still glow), which means simply removing V1 or V2 changes the operating characteristics of the other (this a safe modification).

Changing the type of tube within the same family (same pin-out configuration and electrical assignment) like swapping out a 12AX7 for lower gain tubes like 12AT7, 5171, 12AU7, etc. is also safe.

Removing either V1 or V2 and using a lessor gain tube in the remaining position is also safe.

Using a lower gain tube for the reverb driver may be preferred over using a lower gain tube for the reverb recovery if you use the amp's vibrato because too low a gain tube in the recovery position (like 12AU7) will sound great for the reverb but your vibrato will stop working.

The way to cut the power of a Twin Reverb in half by pulling two of the four power tubes is done by pulling either the inner two or the outer two. The impedance mismatch is within the safe range of the output transformer, but if this bugs you and you really want to match it, just pull one of the speaker connection wires off of the second speaker (and wrap the end in tape). The two speakers are in parallel so there is a first one in the chain, then the second... disconnect the second speaker.

Be careful... a lot of amps are taken to service techs for repair with stories that begin with, "So I was doing some tube swapping..."

[marcwhy]

Tube Amp Doctor TAD 5751 is a nice selected-for-low-noise Chinese tube for under $20. I have found TAD tubes to be very good.

I put a 3-spring medium delay MOD reverb tank in my PR clone. $19.95 from Amplified Parts. Does the trick. It is not wet-surfy and sounds kind of dry and "controlled". But I can crank it up to 3 to get a hint of reverb. I like it when the reverb isn't obvious.

+1 on the TAD 5751, or their 7025 (I also buy these from Amplified Parts!).

[Jimmy Mack]

I really like the 5751 in V1 in my Princeton Reverb II. Smooths it out, and gives better control of the OD function (a little tough to dial in with the 12ax7 I had in there). It is either a Sovtek, or a JJ, can't remember.

Buy a few inexpensive tubes, and enjoy!