Vox ac50

Vox and Hiwatt Discussion

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Stevem
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Re: Vox ac50

Post by Stevem »

Yes, thanks!
When I die, I want to go like my Grandfather did, peacefully in his sleep.
Not screaming like the passengers in his car!😊

Cutting out a man's tongue does not mean he’s a liar, but it does show that you fear the truth he might speak about you!
Long Distance Call
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Re: Vox ac50

Post by Long Distance Call »

My pleasure. I get a lot out of this forum and hopefully I'll have more stuff to give back from time to time.

Best,

LDC
pdf64
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Re: Vox ac50

Post by pdf64 »

More AC50 info here, including layouts https://backfromthesixties-public.share ... m/vox_ac50
Here's some 'before' photos of a tube rectified AC50 I serviced http://s963.photobucket.com/user/pdf64/ ... t=3&page=1
Hepcat
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I've built three AC50 Mark 1s

Post by Hepcat »

I know the topic is about the mixed bias later versions but I can vouch for the wonderful sound of the original design. It's grounded cathodes, AC30 Top Boost preamp, no power amp feedback just like the schematic posted. I did adjust the gain structure to clean it up just a bit and make it more stable. (It used to oscillate easily). Also I use a solid state rectifier and of course fixed bias.The JJ EL34Ls are biased at 60%. The things sounds great! I use it here and there on gigs and I'm a Fender style player, so it really honks. In a solid wood cabinet with a Weber Blue Dog Ceramic speaker it's perfect!
Disclaimer: I'm also an amp builder and sell them.
Ken Zuercher.
If I can figure out the upload thing with my Mac I'll post some pictures if anyone is interested.
Stevem
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Re: Vox ac50

Post by Stevem »

This is all great info folks, thanks!
Also if I am not mistaken Vox made the first 100 watt tube amp for guitar, no?
When I die, I want to go like my Grandfather did, peacefully in his sleep.
Not screaming like the passengers in his car!😊

Cutting out a man's tongue does not mean he’s a liar, but it does show that you fear the truth he might speak about you!
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JoeCon
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Re: Vox ac50

Post by JoeCon »

Ken,

Yes pictures would be nice. Do you a a schematic of your build with SS recto and mods for making it more stable?

This could be my next build!!

Thanks....
In theory, theory is the same as practice. In practice it's different.
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rp
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Re: Vox ac50

Post by rp »

I've never seen some of these schematics either, much thanks. Any of you have a preference for V1 - orig 12AU7 or 12AX7? Hepcat? Read some peeps use a 12DW7 in these which seems clever.

pdf64 - nice looking AC50!
This could be my next build!!
I itch to do a Hiwatt, Orange, and AC50. Glad I don't have a lot of disposable income, as I need those amps like 3 holes in the head.
Hepcat
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Schematics for AC50 build

Post by Hepcat »

JoeCon, I'll be glad to post the schematic. I find the Vox amps to be a bit too high gain for a non-feedback type of amp. Reducing the level between stages and lowering the plate resistor from 220K to 100K on the last stage before the PI goes a long way to stabilizing the unit. Since the Schematic is a pencil drawing, I'll scan it to upload and include a few pictures.
Ken
Last edited by Hepcat on Wed May 13, 2015 9:12 pm, edited 1 time in total.
pdf64
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Re: Vox ac50

Post by pdf64 »

12AU7 in V1?
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rp
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Re: Vox ac50

Post by rp »

pdf64 wrote:12AU7 in V1?
AFAIK all versions of the AC50 had a 12AU7 in V1, after seeing the earliest schematics posted here that looks the case. These were pretty rare even when 'vintage' was called 'used' but the few I've seen had 12AX7s. Most people either goosed them up with a 12AX7 or I'd take a good guess and say they stuck a 12AX7 in V1 never even bothering to check either the chart or the writing on the tube. Obviously, trying a 12DW7 was beyond most musician's pay grade.

I just played around with them in friend's stores way back when, never lived with one so can't say what's best, that's why I'm curious. I hated a 12AU7 in anything I ever tried but that was from tube rolling not from an amp designed around it. Whenever you see old videos of bands using AC50s they sound fantastic, always wondered if they were stock or not.

An AC50 would be a fun build PTP, as it's got no 'crap' like tremolo, overdrive channels, presence etc to deal with. Should go together clean and quick and fire right up (for once).
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