The VOX AC3 Top Boost

[tubelectron]

Hi All,

Here's my VOX AC3 Top Boost, named as a gimmick from his grandbrother the AC30TB... Probably the smallest VOX tube amp ?

[img:640:480]http://img10.hostingpics.net/pics/303590IMG_3367.jpg[/img]
[img:640:480]http://img10.hostingpics.net/pics/669128IMG_3368.jpg[/img]
[img:640:480]http://img10.hostingpics.net/pics/939517IMG_3369.jpg[/img]
[img:640:480]http://img10.hostingpics.net/pics/557420IMG_3485.jpg[/img]
[img:640:480]http://img10.hostingpics.net/pics/148604IMG_3296.jpg[/img]
[img:640:450]http://img10.hostingpics.net/pics/66860 ... ematic.jpg[/img]

A+!

[El_Martin]

Hi!

Now THAT'S a cutee - me likey small amps
How does it sound?

Ciao&have a nice x-mas
Martin

[tubelectron]

Thanks El Martin,

It sounds like a "miniature VOX"... I voiced it both in crunch and clean on a '76 VOX AC30 I had in hands at that time for restoration.

It's equal in loudness with the Gresch G5222 pictured (or a Fender Champion 600) but smoother sounding, particularly in crunch mode, due to a better quality speaker (Audax, discontinued).

A+!

[Kagliostro]

Very Nice Job

I like how it looks

have you a layout to share ?

Kagliostro

[tubelectron]

have you a layout to share ?

No, sorry - I quasily wired it directly from the schematic - All the occasional layout notes I took about are of no interest... At the back (not seen) of the chassis there is another PTP plate which is the PSU.

A+!

[Kagliostro]

Anyway Many Thanks for your attention

Have you closeup photos ?

Kagliostro

[FUCHSAUDIO]

A 50-W Champ.....2 EL-34's w/reverb....what was I thinking ? Dynaco MK-4 Power and outputs...it got warm...you realize there's a reason you DONT put this much power and a 10" speaker into something this teeny....lol

[tubelectron]

Kagliostro,

Here are some other pictures taken during construction :

[img:640:480]http://img15.hostingpics.net/pics/817823IMG3287.jpg[/img]
[img:640:480]http://img15.hostingpics.net/pics/536154IMG3291.jpg[/img]
[img:640:480]http://img15.hostingpics.net/pics/694022IMG3292.jpg[/img]
[img:640:480]http://img15.hostingpics.net/pics/114539IMG3293.jpg[/img]
[img:640:480]http://img15.hostingpics.net/pics/641566IMG3294.jpg[/img]

The basis of my AC3 Top Boost is a VOX Escort solidstate busker amp from the early 70's, in which the speaker and the circuit were out of duty, but the cabinet was nearly mint condition. I modified the closed back to open it for cooling and better tone. I also added a complement to the original chassis (see pics) to support the tubes.

I had this VOX Escort in a local flea market for only 5 Euros - but I know that I have been very lucky, as they sold for way much more, and not often in a so good condition...

A much cheaper alternative today would be considering the VOX Pathfinder 10 (used or even new) and built a tube circuit in it...

The speaker of the PF10 is a 6" and sounds good - I have made the test with my AC3 on a friend's one. Moreover, the cabinet is open-back, a bit larger and with a chassis of a better-suited shape for a tube circuit. The only drawback is that it's not the "real vintage" VOX look...

A+!

[FUCHSAUDIO]

tubelectron: You're a sick puppy, and I mean that in the highest way possible....

[tubelectron]

A 50-W Champ.....2 EL-34's w/reverb....what was I thinking ? Dynaco MK-4 Power and outputs...it got warm...you realize there's a reason you DONT put this much power and a 10" speaker into something this teeny....lol

FUCHSAUDIO,

I have made some trials in that field : Mine has 2x5881 25W rms clean sound, 8" Eminence speaker ME8-100 (97.5dB/W/m), padded reverb unit, UTC surplus transformers, is even smaller than a VibroChamp, and sounds suprisingly "big and good"...

But due to the size and power, it has some unwanted power tube vibration noises, inaudible on stage... but not at home, unfortunately ! So yes, you're right, "compactness and tubes and high ouptut" is a tough target to reach without some drawbacks. This stopped me from going further "à la Mini-Boogie MKII"...

[img:800:600]http://img15.hostingpics.net/pics/680404IMG9422.jpg[/img]
[img:800:600]http://img15.hostingpics.net/pics/852267IMG9426.jpg[/img]
[img:800:600]http://img15.hostingpics.net/pics/743565IMG9427.jpg[/img]
[img:800:600]http://img15.hostingpics.net/pics/269692IMG9429.jpg[/img]

A+!

[FUCHSAUDIO]

Very hip....you realize the limitations of the platform when the amp vibrates across a wooden floor at high volumes....lol. Nicely done.

[tubelectron]

FUCHSAUDIO,

Just for my information, have you any connection with the FUCHS company, which builds amps and pedals ?

http://www.fuchsaudiotechnology.com/

A+!

[John_P_WI]

Yes, they are the same.

[leadfootdriver]

That's a tiny little chassis; 'must have been hard to work on. You did a good job making it look nice.

[tubelectron]

Yes, they are the same.

Ah, OK - thanks - good products, indeed ! I was too in the amp and pedal design construction job for some time, but now I only concentrate on a part-time service, repair and mod business. May be I'll see a FUCHS amp coming one day on my bench... Who knows ?

you realize the limitations of the platform when the amp vibrates across a wooden floor at high volumes

My amps never vibrates like that (too good to be true !) : they are always too heavy regarding their size and power output...

The small wooden combo displayed before weights 15kg (circa 33lbs), and the VOX AC3 is 5.8Kg (circa 13lbs) for circa 4W rms. To give a comparison, a SF PR weights 16kg (35lbs).

A+!