Amp tinkerers and people who aren't afraid of 700 volts or so in here....

Moderators: Slowy, Capt. Black

BY godgrinder
#713428
It's usually intermediate/high school graduates in these Chinese electronics factories, and there are tons of them queuing up to do these jobs. It's quite risky to use little kids when you want to build up some scale, too easy to get fined.
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BY Molly
#713431
godgrinder wrote:It's usually intermediate/high school graduates in these Chinese electronics factories, and there are tons of them queuing up to do these jobs. It's quite risky to use little kids when you want to build up some scale, too easy to get fined.


S'OK. Didn't actually think Vox had an army of kids making the amps.

Recall reading twenty-odd years ago about the mobility of technology and how it moves around the globe depending on where the cheapest labour is to be found. I guess that's possible given how it has the potential to deskill.

Anyway, whoever did that Vox was certainly skilled if only in the business of making AC30s.
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BY hamo
#713445
I wish I understood what I was looking at when I look at this thread.
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BY Molly
#713456
hamo wrote:I wish I understood what I was looking at when I look at this thread.


Most usually about $300 worth of parts soldered together to make a $3,000 amp. :-)
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BY jeremyb
#713487
Mines probably the neatest looking build in this thread!

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BY sirvill
#713529
You're all still far too complicated.

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I haven't opened mine up myself (the voltage in that thing will be enough to take down an elephant) but I found this on the internet.
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BY sizzlingbadger
#750584
Ha, I see they put the bigger electrolytic cathode bypass caps back in on the input stages. I took em out, thought it was way better with smaller 1uF non electrolytic but we all have different tastes.
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BY Olderama
#750586
sizzlingbadger wrote:Ha, I see they put the bigger electrolytic cathode bypass caps back in on the input stages. I took em out, thought it was way better with smaller 1uF non electrolytic but we all have different tastes.

So at which point was this stock?
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BY Molly
#750587
Olderama wrote:
sizzlingbadger wrote:Ha, I see they put the bigger electrolytic cathode bypass caps back in on the input stages. I took em out, thought it was way better with smaller 1uF non electrolytic but we all have different tastes.

So at which point was this stock?


Before I got it back from Steve it had a visit to Danny (the tech guy down there) who put it back to stock. Nik, I'd be genuinely interested to know what part you changed / preferred since the above is double-Dutch to me.

The gain comes on more gradually now than when I first had it I think. I still keep the pre-amp around 3 though as I'm not after a massively saturated tone. Around 3 is pretty dynamic too. I can play gently and get a nicely clipped clean, back off for more clean, or beat it for a brown sound (it'll do great impression of EVH - even if I don't).

Demoed it at Gearfest with a P90 Les Paul and the pre-amp on just 3 but the master up a fair bit. God, it was good to hear it actually breathing properly through a decent 4x12. It's an incredible sounding amp. :thumbup:
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BY sizzlingbadger
#750593
It was a prototype so whether it was ever really stock is questionable.

When I first got the amp it had practically no clean headroom at all. I contacted Roy B himself and he was very helpful, he agreed it was a one trick pony in its current state. I showed him what I planned to do to reduce the gain and make it more flexible. He agreed and actually sent me the circuit for his current Plexi amp as it was practically identical to what I was going to do. I had based my changes on the original Marshall circuit.

After making the changes I felt the amp had a lot of low end so I reduced the two cathode bypass caps in the input section to 1uF each. this reduced some of the low end and stopped any flubbiness. It also means you can avoid using electrolytics which is always a good thing (Mike Soldano does this).

I also reversed the "Cut" control which is really a presence control so that the pot taper was useful and the knob actually did what it said on the front panel. I added a cap in series with the presence feedback loop to isolate the dc from the pot so it wasn't scratchy when you adjusted it.

Looking at the photo above I can see they have replaced the coupling caps (two big orange caps on the left), I expect they just changed them for nice ones and maybe changed the value slightly.

The electrolytic bypass caps are the two small blue caps strapped across the resistors on the very left of the main board.
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BY Molly
#750595
sizzlingbadger wrote:It was a prototype so whether it was ever really stock is questionable...


Thanks for the detailed reply. Hadn't realised it was a prototype but I guess that explains the blank serial number sticker thing. I'd be interested to keep a copy of the diagram Roy sent you with the amp (even if it doesn't mean anything to me). I guess that's the nice thing about simple PTP amps. Folk who know what they're doing can mod them to their heart's content.

I do think it sounds better than when I first had it. Definitely seems capable of lower gain tones than previously. Bottom end through the 4x12 is a visceral experience... ;-)
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