Concerning Valve and Speaker changes, i found this which was interesting...
Thrad
Post
I've just spent a happy afternoon trying various valve changes and a couple of speakers in an attempt to get some more clean(ish) volume out of my stereo AC4TV setup.
I set up both amps exactly the same, tried all the changes on one and kept the other stock for comparison:
Stock Sovtek 12AX7 swapped out for:
Used Mullard ECC83 - definitely more crunch, even at low volume, but less overall volume (est 1-2 dB). Sounds good, but not what I'm after (clean volume).
New Harma Diamond ECC83 STR - no improvement on stock. May last longer though.
Used Groove Tubes 12AX7 (out of Blues Jr). - no appreciable difference to stock.
DECISION - Put the stock Sovtek back in. Vox gets so far.
Stock Sovtek EL84 swapped for:
New Harma Diamond EL84L - according to the Watford Valves website, this valve has the most clean headroom of any of their EL84s. This one (of a pair) was rated at 30 / 7.2. I don't know how that relates to output performance, but I heard no appreciable difference to the stock.
New Electro-Harmonix EL84 - again, one of a pair rated at 32 / 8.0. I actually thought this was slightly quieter than the stock. As I say, I don't know how the ratings translate to sound, maybe the higher the number, the lower the output. Anyway, this one wasn't going to win.
Virtually unused JJ EL84 - about the same output as stock, but with a little more top end.
New Groove Tubes Silver Series EL84 - no appreciable difference from stock.
Another Harma Diamond EL84L - again, one of a pair, this pair rated slightly less than the first set I tried: 28 / 7.2 . However, this was the only power valve that had an audible increase in volume. Not huge, I estimate 1-2 dB and like the JJ, it seemed to have more top end.
DECISION - leave the Harma Diamond 28 / 7.2 in (cost £12 each). But again, good to see the stock valves holding their own against some pretty decent brands. Another for Vox.
(stock EL84 temporarily put back in to maintain parity with control amp)
Stock Celestion VX10 16 ohm swapped out for:
Used unbranded stock speaker from a Vox AD30VT Valvetronix - noticeably quieter (2-3 dB estimate), harsher top end, woolly bass. Wasn't expecting much from this, but just wanted to find out how the stock speaker compares with one from a similar price modelling amp. Not recommended!
New Celestion G10 Vintage - biggest improvement of the day. Estimate 2-3 dB increase in volume (it is rated at 97 dB sensitivity), distinctly tighter bass, more top end chime... just seems to give you 'more' of everything and at the highest volume on the 4W setting has less of a boxy quality. Build quality is excellent, the G10 magnet is nearly twice the size of the VX10. The G10's cone appears to be identical to the VX10, but has a smaller and lighter dustcap. Also note that this G10 is not yet fully broken in... can't wait until it is!
DECISION - G10 Vintage stays in (cost £42 each)
Summary:
I think the stock preamp valve is perfectly fine. The differences between the two Harma power valves are a bit puzzling, maybe someone can enlighten as to how the ratings affect things... only one EL84 from the five tried was appreciably better than the stock one. The stock speaker does not disgrace itself, it is a real cut above the one in the similarly priced Valvetronix and I would say it is actually a pretty good match for the AC4TV... another , Vox! But if you want to squeeze a bit more volume out of your AC4TV, a Celestion G10 speaker is the way to go... once it's broken in, I reckon I'll be getting 4 dB more.
Now to mod the other!
