Preamp tubes question

I currently have a spax7 tube in the v1 position instead of the regular 12ax7.I got my V used on ebay and the seller said he had put a JJ tube in the v1 position, so after a few months i replaced it with the spax7.The amp seemed to have a lot less gain than before.To the point where even having the gain at 2-3 oclock on say mark 4 mode, it still feels like the sustain is very choked.There seemed to be a lot more sustain with the JJ, but i replaced it as i felt the clean channel was a little brittle with it.I had the wampler velvet fuzz back when i had the jj in the V and it sounded awful through mine, but through my mates V it sounded fine(another reason for changing the tube,although i had sold the wampler pedal before i changed the jj to the spax7 so couldnt compare).Im just wondering if the spax7 is the same type of tube as the regular 12ax7?Its meant to be less prone to microphonics and have less of a noise floor etc, but does that take some of the gain out of it?I think the amp sounds a bit better with the spax7 but the gain channels sound a bit choked now.Which tube has the most affect on the amps overall gain?I dont want to make the clean channel brittle again by any means but i feel the gain channels are suffering now.Is it a case of the spax7 just being poor quality,possibly one of the other preamp tubes going or even the power tubes going?But as i mentioned before the change in gain happened directly after taking the JJ out.Ill stick it back in tomorrow and see if it makes a difference.Just such a pain changing tubes in the V.Also is it ok to leave the chasis out of the shell while using it?Just be easier to move around some tubes that way.Thanks in advance

tung sol long plate reissue tubes are really nice and powerfull , lets try them ! ask balanced tubes

good luck

I buy a NOS Mullard 12AT7 ECC81 (equivalent spax7) having a gain of 60.
I put it in the V1 and I could think like you. It loses much the clean channel as the V1
if you put in the valve V7 (driver), it works best.
but for my taste, which really works in the V2 to Channel 2 warmer (cruch).
I have it on the V2 and I love the creaminess that gives the channel 2.

The V1 affects the completely amplifier and all its channels, I think the clean channel with gain needed a valve 100 to avoid losing strength and sound dark

So i stuck back in the old JJ that was in there originally.The difference is shocking.The gain channels feel looser and definitely have more gain so it feels nicer to play.Felt too stiff and unresponsive before with the spax7 in it.The amp is not as clear and punchy as it was with the spax7 in it though and has a quieter output overall.I dont think the clean is as nice either and maaaaan that JJ is so frickin noisey.Its very interesting though,how 1 tube can make such a difference.Im going to put a regular boogie 12ax7 in next and see if that sounds better.Due to the spax7 being lower noise etc does that take some of the gain out of it in comparison to a regular 12ax7.

I'm not a fan of SPAX's tonewise. For some reason, they do seem less musical than regular 12ax7's - I've found this to be true with the 1/2 dozen or so that I've had. I'm not a huge fan of JJ's either, but have also found that they can sound good in some amps. When I swapped-out most of the stock Mesa (JJ's ) in my Mark V, it was like a blanket had been lifted. The amp became more chimey and musical.

So, don't be afraid to try some other brands of 12ax7's in your amp. I rolled a few tubes a while back and ended up with an old Sylvania JAN12AX7 in V1, a Raytheon ECC83 (12,12ax7) in V2, and EH 12ax7 in V3 & V5, I kept the stock Mesa (JJ) in V4 & V6. For V7 (PI), I have an old GE JAN5751.

So i moved the jj to the v2 position and a regular mesa 12ax7 to v1.the amp is louder brighter and a tad stiffer than the jj in the v1.still quite noisey though compared to the spax7 in v1.the amp still feels gainier than when the spax was in v1.so v2 only affects channel 2 gain stage 2 according to the manual.thats why i put the jj in v2 as it supposedly has only one job instead of 2 like all the other tubes.i dont fancy tube rolling as its expensive and head wrecking.It is interesting though the affect it has on the overall tone.ill stick another mesa 12ax7 in to replace the JJ for now and see how it sounds.

Those are all JJ's. mesa12ax7= jj,,,,,,mesa spax7 = jj,,,,,,,,,,jj = jj.
Try some other brands, maybe a tung-sol in V1 will make more of a difference. They are a bit rounder and warmer IMO. Slight difference but it's there.

TRENCHLORD said:

Those are all JJ's. mesa12ax7= jj,,,,,,mesa spax7 = jj,,,,,,,,,,jj = jj.
Try some other brands, maybe a tung-sol in V1 will make more of a difference. They are a bit rounder and warmer IMO. Slight difference but it's there.

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Ya i have heard mesa tubes are rebranded JJ's alright.They seem to be a slightly higher quality though as they are clearer and a bit more punchy.A tad stiffer though.Do you use a tungsol in the V1 position?I definitely would prefer a smoother distortion as i have the presence at no more than 9 oclock ever.Id just be concerned about the clean channel.How does that sound with a tungsol?

I have been down this rabbit hole many times trying to tune the Mark V and tame the ice pick (as my amp was way too bright).

I actually like both the Mesa SPAX7 and or the JAN/GE 5751 in the V1 spot. The best tube I have used in V7 was a sovtek LPS as this seems to balance out the overall tone. What effects the clean channel is basically V1 and V3 (also what you install in V4, V5 and V6) may influence the character as the reverb circuit (half V4 and V5) along with the FX loop (half of V6) if you are using the master control for final output driver. I have loaded the entire amp with Tung Sol (medium plate, did not know the long plate is available) and was quite satisfied with all channels. However, I found the Tung sols created additional hum when used in V3, V4, V5. I have tried the Mullard reissue and had similar results (but had pining issues when changing channels) . The Mesa 12AX7 (JJ ECC83-S) does serve to be a dark tube (may serve well in the Roadster or Rectifier amp especially with the cathode follower circuits) tends to saturate the tone and gain character of the Mark V. CH3 compression can be dialed in or out with a change in V4 and V5, the cascade of gain stages for CH3 runs through the following sequence: V1A, V1B, V5A, V4B, V3A, V6A. Note that V1A is the driver for the tone controls for CH1 and CH3, V2 is a secondary gain for CH2 which also serves as a driver to the tone control of CH2. You can also adjust the compression CH3 compression with V3 and V6 but this will also effect character on CH1 and CH2 but not significantly. Preamp tubes are operated at different voltages for each channel and its associated voice switch setting. I feel that the most sensitive is the Tweed voice for CH1.

As far as the darkness in tonal character of the Mesa 12AX7A (JJ ECC83-S), the same can be said about the Mesa 6L6GC-str440 (Ruby 6L6GC-MSTR) which are both Chinese sourced tubes (also made by the Shuguang company). They are better served in the Rectifier type amp. Not bad in the Mark V, but there are better alternatives. SED =C= 6L6GC is my favorite but I refuse to shell out that kind of money for leftover tubes (quality of the SED that are still available may not be as good as you thing, I bought a quad before the price hike and they do rattle a bit, the NOS GT6L6GC-R2 from 1990 were excellent. TAD 6L6GC-STR were also great tubes and I have another set of quads on order.

I will definitely try a 12AT7 in V2, thanks for the suggestion. I have been using old Mesa 12AX7 (Shuguang 12AX7-A that have the square foil getter) in that position. Those are not the same as the current production tube.