My 2001 VH4 - I really wonder if anything is wrong (with photos!)

[Orvillain]

It doesn't really sound right. It sounds 'normal' as in, there's no weird frying bacon sounds or power tube drop outs or anything like that. But on channel 3 and 4 the overall tone is quite fuzzy, like there is too much low-end making it into the preamp distortion stages, something like that. It doesn't sound much like a lot of the Youtube demos I've heard, and I'm really wondering if there is anything wrong with the amp.

I know this is a 2001 model, and I also suspect from reading stuff on here that the circuit changed slightly throughout the 2010's or something, making the amp sound more modern. Modern is not how I'd describe this amp at all.

I've tried new preamp tubes, and new poweramp tubes, no difference really. I suspect it is either some resistors out of spec, or perhaps even the caps. Here are some photos:

To me the crinkles and slight bulging on the caps are suspect, but I really don't know for sure. Haven't looked at the other side of them under the board.


Here's some more general photos. You can see, it has had a hard life! I think the guy I bought it from on eBay might even be around here???

I feel like I should love this amp, and should want to play it all the time. But I generally don't, because of this tonal issue. I don't know if there is definitely something wrong, but I'd like to investigate.

 

[Techdeth]

Try different biasing . My vh4 changes drastically .

 

[Orvillain]

The service manual does say:

Here's some audio clips, first in drop B and then drop C:
https://www.dropbox.com/scl/fi/dk8q...ey=0eou1zqw564bunbhotj6vim50&st=po4r8mdy&dl=0

You can hear how there's no clarity, it is very fuzzy, and sounds like a fuzz pedal. The amp settings are:

Now I did dial the mids back on channel 3 as an experiment, and cranked the treble and presence. Bass at noon. Gain at noon. The amp is 'opened up' as much as I can get away with at home, and it just sounds fuzzy, tiny, and overall a bit shit. I've not checked the bias yet, and I haven't checked the power tubes but honestly they should be good. They were brand new and tested by my tech a year or so ago, and I've really not played the amp that much.

 

[Philhouse]

Did you have any success yet?

 

[Peter Diezel]

The amp has an issue. Would it be an idea to call a tech ?
Where are you located ?

 

[Orvillain]

Hey Peter, sorry for not responding. I was away from the internet for a week or so!

My tech has replaced the 3.3k resistor with the recommended 4.7k, and he has replaced the KT77's - which all checked out fine, but were more like two matched pairs, rather than a matched quad. Suspect when I bought them they were never a quad, and I put them in without checking. Oopsie number one. Then he said the bias was very high! I followed the service guide exactly, so I'm guessing it drifted at some point.

I had him put JJ 6L6GC's in there, and I'm loving how it sounds. Proper roaring "Marsha"-esque tones, but obviously with the Diezel flavour. It no longer sounds fuzzy and flubby, like a Big Muff!!!

He also moved the NFB to the 8ohm sockets. It was 4ohms from the factory from what we could tell.

Finally, I emailed you the other day about the channel switches being constantly lit up post-tech work. I just re-opened the amp up and reseated the midi chip, and now all is good. Must've come slightly loose during transit.

Amp roars like a demon now!