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pre amp tube ques?

gtrplr71

Member
can I mix preamp tube in v1 and v2 or do they need to be a matched set
example I have a EH 12ax7 in v1 and a tung-sol 12ax7 in the phase inverter is this going to hurt my amp?
 

tonehead

Member
can I mix preamp tube in v1 and v2 or do they need to be a matched set
example I have a EH 12ax7 in v1 and a tung-sol 12ax7 in the phase inverter is this going to hurt my amp?

If it is a two channel Fender like a Deluxe or Super Reverb then it will not matter if the preamp tubes are matched. Probably no other tube amp either, as far as I know.

Here is the layout for a standard two channel Fender amp like a Deluxe Reverb or Super Reverb. You may already know all this, but if not, hope this helps:

V1: For the first, or "normal" (non-reverb, non-vibrato) channel. If you do not use this channel you can take out the preamp tube from the V1 position to get a bit more gain and better compression in the reverb/vibrato channel. You won't be able to use the normal channel; who does? V2 now becomes the critical tube.

V2: Get a really good preamp tube into this position. This tube is more critical for shaping your tone than any other, and even moreso if you take out V1.

Tubes I have come to like:

Penta Labs Chinese 12AX7 tube made at the Shuguang factory (about 12 bucks on most sites). Shimmering and chimey.

JJ ECC83S (9 dollars). Sweet, sparkly.

Tung Sol 12AX7 reissue. Very round and sturdy tube. I like it especially in the V4 position, but try it in V2 as well. About 15 bucks.

Best Option: JanPhilips 80's military stock 12AX7. You will find a noticeable difference in the sweetness of your tone with one of these in V2. Still quite affordable. Compare Tube Depot, Tube Store, Dougs Tubes and other sites for prices.

Other option: a JanPhilipps military stock 5751, which you can get for between 17 and 19 dollars. This is a great tube and it will calm that amp down a bit. A little less gain, but sweet and round.

V3: This is the reverb driver. Best to have a 12AT7 or 5751 here. The Jan military stock 12AT7 is very affordable, as is the Mullard reissue 12AT7. This will give you real control over your reverb and make is sound more lush, less clangly.

V4: second in importance for tone among the preamp tubes. See above recommendations for V2, any of them will work here.

V5: least important preamp tube for tone, it works with the vibrato. Any good 12AX7 will do here.

V6: this is the phase inverter, and it calls for a good 12AT7 (a 5751 will work here as well). I like the Mullard 12AT7 reissue.

Hope this helps.
 

tonehead

Member
Yea, I got mine from Doug's Tubes as well. I think he has them for about 40 buicks, last I checked. Check out his prices on the Jan and the Mullard 12AT7, if you need one of these. Also, either Tube Depot or the Tube Store have some good deals on the Jan 5751s, an awesome tube for calming the amp down a bit and sort of focusing your tone.
 

candid_x

Supporting Member
I've found the JAN 12AX7 can also be a bit microphonic in combos. I bought an NOS set of 4 from 1966 (not from Doug), 2 weren't usable in my combo, in the V1.
 
C

clamdip7714

V3: This is the reverb driver. Best to have a 12AT7 or 5751 here. The Jan military stock 12AT7 is very affordable, as is the Mullard reissue 12AT7. This will give you real control over your reverb and make is sound more lush, less clangly.

V6: this is the phase inverter, and it calls for a good 12AT7 (a 5751 will work here as well). I like the Mullard 12AT7 reissue.
Or even a 12AZ7 which I am using and seems to be a great value atm.
 

tonehead

Member
I've found the JAN 12AX7 can also be a bit microphonic in combos. I bought an NOS set of 4 from 1966 (not from Doug), 2 weren't usable in my combo, in the V1.
Point well taken; you may find one of these to be microphonic. The ones to which I am referring are 80s military stock Jan 12AX7s. Same thing happens with Ei ECC83s which are very close to NOS Telfunkens and have a very rich tone. With most suppliers you can return tubes if you get a bad one, but this is a hassle for sure. Have never had this problem with a new Tung Sol 12AX7 or JJ ECC83S.
 

Timbre Wolf

GoldMember Supporter
Gold Supporting Member
Ei ECC83s which are very close to NOS Telfunkens and have a very rich tone.
Gotta disagree with you on this one - they looked sort of similar inside, but Ei didn't ever sound like Telefunken to me. I can find merits in both, and you're correct about the microphonic issue, but, from my experience, the two tubes are tonally quite different. Ei's brightness can be quite harsh, whereas Telefunken's is sweet, and never harsh.

- Thom
 

telebuck

Member
Hello all,

I am just getting into trying out different tubes. I picked up a Marshall 1974x in a trade.

It calls for three preamp tubes. V1 is non-trem, V2 is PI, and V3 is trem side.

Previous owner had installed some nice JAN Phillips 12AT7s, but it sounded a little bright and thinner to me. I put in some JJ 12AX7s across the board. Sounds better to me.. much louder, more gain, a little darker, but a little boomy on the bass. Would also like a bit more swirl and chime.

I've seen many say the PI should have a 12AT7. I'll give this a try tonight, but what change in tone should I expect going from an AX7 to AT7 in the PI?

Any other suggestions?

Thanks
 

Timbre Wolf

GoldMember Supporter
Gold Supporting Member
what change in tone should I expect going from an AX7 to AT7 in the PI?
Tone change depends on which 12AT7 you're going to use. But you should have a less distorted signal, with same amp settings, as you go from the X7 to T7. Why not try the JAN Philips 12AT7 you've got, and find out?

Would also like a bit more swirl and chime.
Swirl is not something that preamp tube changes can provide. Chime is. Depending on your budget, you may choose NOS options, such as long-plate Mullard 12AX7, long black-plate Raytheon 12AX7A, Tesla (not JJ) E83CC, or long black-plate Sylvania 12AX7. I'll let others discuss current-production options for chime.

- Thom
 

candid_x

Supporting Member
Point well taken; you may find one of these to be microphonic. The ones to which I am referring are 80s military stock Jan 12AX7s. Same thing happens with Ei ECC83s which are very close to NOS Telfunkens and have a very rich tone. With most suppliers you can return tubes if you get a bad one, but this is a hassle for sure. Have never had this problem with a new Tung Sol 12AX7 or JJ ECC83S.
You know, I wondered about that, the 80's mil stock being tougher somehow. Had no mic problems with the 80's JAN from Doug. Cool, thanks for confirming that.

I'm using the JAN in V1, and JJ ECC83S's in the rest of the spots. Was funny, when I got the '66 JANs, I loaded them across the board, thinking, if one sounded good, five oughta sound great! lol.. wrong, sounded awful. Back in went the JJ's except for in V1.
 
Or even a 12AZ7 which I am using and seems to be a great value atm.
I have a bunch of 12AZ7s and 12AV7s. I've found them to be pretty microphonic. I later learned they were designed to be used in computers and other industrial electronics and were never meant for audio. But if you can find a quiet one, they can sound pretty good.

I'm going to have to disagree with recommendations to put 5751s in reverb driver positions. You can use a 12AU7 to help tame the reverb, but a 5751 is not necessarily a good idea (and has a similar mu to the 12AT7 anyway). The reason is the lower plate impedance of the 12AT7 is matched to the reverb transformer to yield an 8-10 Ohm output impedance for the reverb tank. Swapping the tubes creates a mismatch that can actually fry the reverb tank over time.
 


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