Vox AC15HW1 Hand Wired Mods

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sizzlingbadger
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Vox AC15HW1 Hand Wired Mods

Post by sizzlingbadger »

I have completed the mods to my AC15 and have documented it here http://www.nikplayer.com/2012/01/ac15hw ... tions.html if anyone is interested.
Tube amp and guitar tones straight from 1958… amazing how believable the sounds were back then, even without the modellers...

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Re: Vox AC15HW1 Hand Wired Mods

Post by GrantB »

Wow - thanks for the info! What sort of characteristics (other than the "less stiff" you mention) tonally do these mods deliver?
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Re: Vox AC15HW1 Hand Wired Mods

Post by sizzlingbadger »

It has a softer attack and sounds a bit more squashy and less harsh a little bit like the old Fender tweed amps. Its still has its Vox character, it just sounds a bit more like a vintage AC15 if that makes any sense. These amps are very touch sensitive you can go from clean to really dirty by just digging in hard with the pick.

Ryan at CAB supplied all the caps.
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Re: Vox AC15HW1 Hand Wired Mods

Post by AmpShop »

Looking good Nik! Glad to hear it made an appreciable difference too.

7K5 seems a little low for grid stoppers? Did you calculate the HF rolloff or just go by listening?
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Re: Vox AC15HW1 Hand Wired Mods

Post by sizzlingbadger »

My gut feeling was to use around 10K but I didn't have any 10K resistors left. There aren't any in the original circuit and there were no signs of any extraneous noise so I thought 10K would be fine just to help a little. 7.5K was all I had in the shed at the time so I used them. They could probably go a fair bit higher without any noticeable HF roll off. The next size up I had was 470K which was way too high. I may try some bigger ones but I don't think it will make that much difference audibly to be honest.

The reduced filtering and replacing the really cheap single layer ceramic signal caps with Mica made the biggest difference overall.
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Re: Vox AC15HW1 Hand Wired Mods

Post by GrantB »

sizzlingbadger wrote: These amps are very touch sensitive you can go from clean to really dirty by just digging in hard with the pick..
Sounds a lot like my JMI 30...compression kicks in with the dirt. The sound sort of blooms afterwards...great for big power chords. I used it for a punk show reunion recently (with a Gretsch Duo Jet) and it cooked. One thing I did was add a PPIMV and a London Power VVR type setup. It's very flexible in terms of tone at any volume. Do these newer HW's have a master? My original HW Ac15 didn't and tonally it was fantastic - just too loud to get the tone I wanted. I should have put a VVR type solution in that.
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Re: Vox AC15HW1 Hand Wired Mods

Post by AmpShop »

sizzlingbadger wrote:My gut feeling was to use around 10K but I didn't have any 10K resistors left. There aren't any in the original circuit and there were no signs of any extraneous noise so I thought 10K would be fine just to help a little. 7.5K was all I had in the shed at the time so I used them. They could probably go a fair bit higher without any noticeable HF roll off. The next size up I had was 470K which was way too high. I may try some bigger ones but I don't think it will make that much difference audibly to be honest.

The reduced filtering and replacing the really cheap single layer ceramic signal caps with Mica made the biggest difference overall.
Sure, I suppose 10K is a good standard, 7K5 isn't too far off. I've been getting into large grid stoppers on some of my builds/protos recently, but these are mainly for higher gain amps, whereas I guess you're walking the line trying to not to rob the amp of chime, vintage vibe etc. Still, you might be surprised how much the larger ones can smooth things out even in more vintage-style amps.

Anyway, great blog and a nice tidy job! :)
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Re: Vox AC15HW1 Hand Wired Mods

Post by sizzlingbadger »

*UNIQUE* wrote: Sounds a lot like my JMI 30...compression kicks in with the dirt. The sound sort of blooms afterwards...great for big power chords. I used it for a punk show reunion recently (with a Gretsch Duo Jet) and it cooked. One thing I did was add a PPIMV and a London Power VVR type setup. It's very flexible in terms of tone at any volume. Do these newer HW's have a master? My original HW Ac15 didn't and tonally it was fantastic - just too loud to get the tone I wanted. I should have put a VVR type solution in that.
I based the filter cap values from the old 60's JMI schematic which shows 8uF for a lot of them. These new amps have an MV and a bypass switch.
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Re: Vox AC15HW1 Hand Wired Mods

Post by sizzlingbadger »

I just picked up some 27K, 39K & 68K resistors today so may have a play with the grid stoppers further !
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Re: Vox AC15HW1 Hand Wired Mods

Post by mr_sooty »

I reckon that particualr amp's pretty freakin incredible stock, so it'd be awesome to hear an improved version.

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Re: Vox AC15HW1 Hand Wired Mods

Post by tubeswell »

I prefer the micas for the small signal caps. They are definitely smoother sounding
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Re: Vox AC15HW1 Hand Wired Mods

Post by MogwaiBoy »

Alas, how long is a piece of string indeed. Hehehehe :D I adore my AC30 Hand-wired Head... please don't give me ideas on improving it. My wife will slaughter me. For good reason!

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Re: Vox AC15HW1 Hand Wired Mods

Post by AmpShop »

That's the joy of modding, you can take it at step at a time, as funds allow :wink:
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Re: Vox AC15HW1 Hand Wired Mods

Post by MogwaiBoy »

Yep. Can you slot me in for tomorrow at 2:25? hehe JK :)

Been using the Hand-wired Head in the studio and will hopefully have some sounds to show soonish.

I usually dabble in modding by experimenting with tube swapping first. But since you have to remove the whole chassis to get at the tubes (I think, unless there's an easier way) I feel pretty reluctant to mess with it. Have you heard of the 'McAllister fix' though Ryan? My AC30HWH will need that eventually if I want to use anything other than Ruby EL84s.

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Re: Vox AC15HW1 Hand Wired Mods

Post by AmpShop »

MogwaiBoy wrote:Yep. Can you slot me in for tomorrow at 2:25? hehe JK :)

Been using the Hand-wired Head in the studio and will hopefully have some sounds to show soonish.

I usually dabble in modding by experimenting with tube swapping first. But since you have to remove the whole chassis to get at the tubes (I think, unless there's an easier way) I feel pretty reluctant to mess with it. Have you heard of the 'McAllister fix' though Ryan? My AC30HWH will need that eventually if I want to use anything other than Ruby EL84s.
Moving the grid stoppers? Yeah, it's good practice in any amp, even if they do look tidier being on the board.
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