Wangs VT15 review

Cirrus

So last week I met @thecolourbox in a dark and drizzly car park near Kerrang radio in Brum to give him money for his Wang. It was a surprisingly pleasant experience!

As a result of that exchange, I now have a little black box with an unfortunate name which I'm going to try to look past. It's a 15 watt 2x12 EL84 amp head with Hi and Low inputs, seperate 8 and 16 ohm speaker outs, and an effects loop that I've not tried out yet.

I got a chance to try it briefly before the weekend and had enough time to form a couple of conclusions;

- It seems like a reasonably solid amp - feels sturdy, controls feel good, and it's got plenty of gain on tap.

- It's brighter than the sun. With the bass on max and treble+presence off, it's a very bright amp. Any other setting and it gets painful. Looking past that though, the sound's got real potential.

So I decided to take it home and have a look inside - you know, pull back the foreskin, check the testicles for lumps, the usual. Here's what I found;

It's sturdily built. The headshell is ply, feels strong and looks neat. Chassis is strong and the transformers look decent. It's got 3x 12ax7 and two EL84s, solid state rectified. Every tube, even the EL84s, have shields. Not sure why the EL84s do, but there we go. I guess they are quite close to the transformers.

Flipping the chassis upside down to see the guts (Scrotum? Prostate?) it seems like it's built to a reasonably high quality. Certainly on a par with the Epiphone Jr amps, maybe a little better - Wima coupling caps and a mix of ceramic and polystyrene treble cabs. The PCBs themselves look sturdy and thick. Only criticisms would be that the board isn't very well supported along the side the preamp tubes are at - it wobbles a bit if you're trying to pull them out - and the transformer leads are all connected with spade terminals. In the long run, that might be less reliable than a firm soldered connection.

Cirrus

As to the circuit itself, I spent a bit of time applying my limited knowledge to what I could see, and managed to work out why it's so bright; It's based on the JCM800 preamp, except for a slight difference: The JCM800 preamp goes into some big ass power valves and transformer and is still quite bright, the Wangs preamp goes into two EL84s AND has smaller treble caps. Looks like it might be cathode bias too as there's a 180 ohm 5 watt resistor sitting at that end of the board, maybe @ICBM or @martinw could tell me how to find out for sure? The deal with the JCM preamp is that there's basically three bright cap arrangements in a row, but they're relatively big caps so they let through all that roaring midrange and increase the volume going between stages for more gain.

The Wangs didn't need more gain, and was too bright. So I clipped two of the bright caps - the one on the volume knob which was 1nf, and the one immediately after it which was a 470pf polystyrene. Someone on another forum has christened this the "Vasectomy Mod" which I think is fucking hilarious.

Last night I took it back to the studio to see what my tinkering had achieved. These clips are with a Gibson Explorer and through a 2x12 Roadkill cab with Celestion Greenbacks (G12c's), close miked with an sm57.

High input, gain at 11:00, master at 1:00;

Low input, gain at 12:00, master maxed;

Low input, gain at 10:00, master maxed;

And finally  through my Vox 2x12 with Celestion Blues with a Strat. Low input, gain at 2:00, master maxed;

I'm quite pleased with the sound. It's still bright and relatively bass light, but it's relatively responsive to pick attack, has pretty nice breakup, some clean(ish) headroom and the EQ controls are now much more useable. Bass is still maxed but treble and presence are around halfway in these clips.

I think it'd be interesting to see if it could be made a little more... ballsy. Maybe change the coupling caps which are all 22nf for something bigger to let a little more low end through? But I think it's a sweet little amp that's surprisingly well built, which is likely to be way too bright for most people unless it gets the snip.

ThePrettyDamned

Actually, that sounds really quite good! 

Nice wang, man

martinw

Cirrus said:

 Looks like it might be cathode bias too as there's a 180 ohm 5 watt resistor sitting at that end of the board, maybe @ICBM or @martinw could tell me how to find out for sure?

Yes, almost certainly cathode biased at 15W, and 180R 5W is probably the cathode resistor. Does it go to pin 3 of the EL84s, and have a bypass cap?

I think it'd be interesting to see if it could be made a little more... ballsy. Maybe change the coupling caps which are all 22nf for something bigger to let a little more low end through?

That will probably make the bass too flabby. 22nF is big enough. If it's still a bit thin, what are the cathode caps on the preamp gain stages?

thecolourbox

An excellent review my friend, and very happy to see my Wangs getting such close attention. Ahem. Also loving that you have kept up the somewhat dubious innuendo as well, particularly the Vasectomy mod haha i hardly felt a thing.
Interesting that its jcm based, that's a Marshall right? I felt it as more driven fender sounding, though that might be the brightness you mention. Plus i only played it through a Lil night train cab! Good to see the little fella getting some use (!!!) in any case. Cheers!

ecc83

Yes looks well made if a little "rat's nesty"!

Don't worry about the 6mm receptacles on the transformer leads, never known them to be a problem except for one daft maker that tried to put more amps of heater current thru' them than they were rated for!  

For the 3.5 amps that that amp's heaters will pull, not a problem.

Dave.

Cirrus

martinw said:

That will probably make the bass too flabby. 22nF is big enough. If it's still a bit thin, what are the cathode caps on the preamp gain stages?

I'll have a look inside later on and see. They're quite small bypass caps on the JCM800 though aren't they? It's not something I've messed with before, presumably a bigger cap would lower the frequency above which the gain gets a boost?

martinw

Cirrus said:

martinw said:

That will probably make the bass too flabby. 22nF is big enough. If it's still a bit thin, what are the cathode caps on the preamp gain stages?

I'll have a look inside later on and see. They're quite small bypass caps on the JCM800 though aren't they? It's not something I've messed with before, presumably a bigger cap would lower the frequency above which the gain gets a boost?

Yes, the first stage BP cap on the JCM is 0.68uF. Try increasing that to 1uF or 2.2uF. usually thickens the sound up nicely.

Cirrus

Ye have gain'd a wisdome.

Dave_Mc

Nice

kelv_w

those clips sounded pretty good to me. 

thecolourbox

Just a thought, less technical and presumably less fun but try an eq in the loop, i was surprised how much my cheap joyo eq improved the drive channel of my hot rod deluxe, might tame the trebly thing nicely

Cirrus

I like getting technical

Cirrus

Wangs update: Changed .68uf v1 cathode bypass cap for a 2.2 I had kicking around, muuuuch better to my ears. Distortion is thicker. Also changed the phase inverter output coupling caps from 22nf to 47. Not a huge difference, slightly deeper sounding. As a result of these changes I've partially reversed the vasectomy mod - put a 180pf cap back on the volume knob.

Next issues to deal with:

I'm getting quite a lot of noise (hum, crackle) that rises and falls with the master volume but is not affected by the preamp gain. It's still there when I take out V1 but dissapears when V2 comes out. Is V2 a cathode follower in a JCM pre? They're all sovtek 12ax7s, wondering if that might cause the noise.

The el84s are seeing 270v and biased with a 180 ohm resistor which according to weber's bias calculator is giving me 7 watts/ tube. This would explain why it seems relatively quiet for 15 watts. I'm going to try a 100 ohm to see where that puts me, maybe 120 if it gets a bit hot. Is there any reason this wouldn't be a good idea? eg Cheap transformers not actually rated for 15 watts?

Apart from noise and slight lack of power it's sounding great - very pleased with everything north of the edge of breakup!

drhodes13

Cirrus, I know this post is three years old, but there's not very many discussions on the web about any mods to the Wangs VT-15. Anyway, I read above that you said you clipped a "1NF" cap on the Vol knob, and a "470pf polystyrene" cap after that. I don't know if my VT-15 is built different, considering it's newer, or what, but on mine, there is no cap on the Vol pot. There is a WIMA 470 cap on the gain pot, and following it looks like a resistor. I've clipped bright caps before in a few other tube amps, but they were very obvious, and easy to find, but this all looks very confusing to me. I really want to love this amp, and you can tell that it could sound very desirable, but it's just too harsh when using the gain input. However, I do love the clean channel. Please help, thanks!