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Tube Recommendations - SVT-4

isher1992

isher1992

Nov 27, 2008
1,209
200
Little Rock, Arkansas
#1
So, I managed to score an SVT-4PRO at a decent price used, and I'm waiting for it to come in...

...So, I'm already preparing to want to change the tubes. Luckily, I've got a pretty good stash laying around.

According to Ampeg, the preamp only has 3 12AX7 tubes. I thought it had a fourth 12AU7, but I guess that's only on the SVP preamp. As for their function, I'm not sure of V3, only V1 (input gain) and V2 (EQ). I'm guessing V3 is for the output or graphic EQ?

In my stash, I have these:

2x Tung-Sol 12AX7 (Current production, matched set and balanced)
1x Tung-Sol 12AU7 (Current production)
2x Chinese 12AX7 (Marshall pull-outs, pretty sure they are Shuguang)
2x Sovtek 12AX7-LPS
1x Sovtek 12AX7WC
2x GE 5751's (matched)
Bunches of GE 12AU7A's of varying age

I'm just curious what some other guys have tried. I know a few people like GE's. Personally, I'm not a big of JJ's...they seem a little too dark for me. I've tried a few RCA's and not been too thrilled with them. Maybe they were just worn out, I don't know.

I understand from reading on these forums that V1 will make the most tonal impact, so I was thinking of just using the matched Tung Sol's for V2 and V3 and use either a GE 5751 or the EHX 12AX7WC in that position.
 
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#3
We used EHX tubes in a Marshall Haze 15W head, and had pretty good results, but I think they compliment the amp's tone well. I've always felt like Ampegs were pretty round with the ability to be punchy or gutsy. Although, I have tried the new Ampeg SVT-7 with a JJ 12AX7 and I wasn't a huge fan of it. It just felt too dark.
 
#4
Okay, I found a schematic and I see what each tube functions for. V1 is first gain stage, V2 is Bass/Treble control, and V3 is Mid control. Got it!

I think that settles what I will try where. I'll probably just use the two matched Tung-Sol 12AX7's for the EQ section since they're a matched set, and play with V1 to taste. I think I will probably like the 12AU7A there, but I'll try some of my other 12AX7's and 5751's first.
 
#6
degonzalez2000 said:
I have tried Tung Sol and JJ on my SVT4-Pro.
Now I have Ruby12AX7AC5HG+ in the three positions.
The Ruby's are sweeter and more clear.
Doug, from Dougstubes.com recommend it.
Click to expand...

I might try that. It may seem counter-intiutive, but I'm not so interested in getting overdrive from the preamp as much as I just want some grit. That's what made me think about trying a 5751 in V1. I may order a Tung-Sol 5751 and another 12AX7, and order maybe a Ruby. I thought Ruby's were JJ's.
 
#9
Believe it or not, in any newer Ampeg that I've changed V1, tube or hybrid, without fail I have liked the regular JJ 12ax7's over any other tubes I've tried, including new Tung Sol and a small handful of nice but unspectacular NOS tubes. In any other socket I've not really noticed any differences, but in V1, the Tung Sol and NOS tubes all made them sound too bright. That said, I don't have a 4 Pro to experiment on.
 
#11
isher1992 said:
Was waiting for you to chime in, Jimmy.

Bright may work for me, since most of my basses have overwound pickups. But good to know, i ordered a JJ 5751 to have on hand in case.
Click to expand...
At least they're cheap :D Well if you're looking for bright, a newer Tung Sol is really good at it. Going to run them in my Fender Super Reverb once these tubes in it croak. Easily as good as the last of the NOS stuff I have on hand...a GE, a couple Raytheons made in Japan on old Mullard gear...but I'm done with NOS power tubes and 12a_7's. I refuse to pay the prices they want for a bottom of the barrel GE or Sylvania 12ax7. With some tubes, I think NOS is necessary, but not the common ones IMHO.
 

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