Vox ac 30 60's?

[d0z3r]

Please help me date my amp,it has matchoing serials on chasis and the board,has light green,grey control board,6 air vents ,im new to vox, the first numbers on the serial are 7410D if this helps.here is some pics.

[Robert M. Martinelli]

Hi and Welcome!

The double row vents and other cosmetic features indicate that the amp is an early STOLEC model. The square pilot (on) indicator seems to have been changed, as I have an identical amp (serial starts with 7411) with the traditional round indicator. It doesn't show, but I guess there is no GZ34/5AR4 rectifier valve inside, right?

If so, your amp is most likely a late 1969/early 1970 one. You're lucky, because it seems to be one of the last fitted with the silver AlNiCo speakers...the story goes that, after the Vox production premises went on fire in 1967, Celestion offered (cheaper) ceramic magnet speakers along with a massive price reduction so Vox phased out the (costly) Silver AlNiCos; after two years some Silver AlNiCo speakers (seems to me 100 or 200, but I can't seem to remember) were discovered in a warehouse, so a certain number of amplifiers (50 or 100) were, again, fitted with these speakers.

In the late 1970 STOLEC started to use PCBs, but these "proved fragile and awkward to service" (The Vox Story- Peterson-Denney). Your amp sports a PTP construction method, so it's surely older than that.

Sonically these amps are formidable, because the solid state rectifier is more efficient (it had to be so to compensate for the cheaper Ceramic speakers and their reduced efficiency), and the combination of a solid state rectifier and two Silver AlNiCo speakers is a powerful one, with an edge in terms of responsiveness/dynamics on the older AC30s (though your amp lacks the "sag" of the earlier ones' valve rectifier).

Hope this helps

Best regards

Bob

[pdf64]

What V B+ does that Si rectified amp have?
Didn't the later silver alnicos have a higher power rating? To cope with the AC50 and AC100. Thanks - Pete.

[R.G.]

(though your amp lacks the "sag" of the earlier ones' valve rectifier).

... which, fortunately, can be restored to a very large degree by inserting a power resistor after the rectifiers.

[Robert M. Martinelli]

Hi Pete, Hi R.G.!

@ Pete : AFAIK the power rating of the late Silver AlNiCo was 20W, and they have been used in the Jennings AC40 as well (built by Tom Jennings after resigning). As to the HT, in the STOLEC models it was slightly higher than in the older models, AFAICR it was in the 325-330 VDC range...anyway, soon I'll have to open mine, I'll take some measurements and I'll be back with the "real" figure. This particular model is known to be even rougher on the power tubes than the (already rough) older models.

@ R.G. - of course you're right, in all fairness, I should have said "it PARTLY lacks the sag..." because there's indeed a 47 Ohm resistor in series with the rectifier, though its main purpose was to drop some of the higher voltage coming from the SS rectifier...quite obviously, it introduces some sag, too (but the difference in responsiveness/dynamics still remains clearly audible, if I compare it with my late 1964 AC30T/B).

Cheers

Bob

[d0z3r]

thanks

and i have the numbers off of the valves,ive been told off previous owner it has not had
any modifications since new,everything is origional,and hes sure his grandad said its an early 60's model,everything here is exact same,regarding speakers and valves
The VOX Showroom - CBS/Dallas Arbiter Vox Hand Wired AC-30 Top Boost,
and it looks NEARLY exact too,where can i get a new vib/trem switch please as this is all thats the matter.Oh well id love to get some new black(matching covering for the couple of places wheree its worn,and whats the value of these?thanks
The VOX Showroom - Dallas Arbiter Vox Hand Wired AC-30 Top Boost is this the amp?innards and all look same to me,more pics when i get me camera,the literature for the speakers from the link is took from whats wrote on mine,the serials etc vox rola celestion 1088's,so idk what you were meaning the ceramicsilver AlNiCo ?is this same meaning as the vox rola celestion?

[d0z3r]

hi again,what would you value your identical ac30 at?im getting offers left right and centre,also if you pass me your email i can show you the insides via a photobook on my skydrive,but need your email so it lets you see them,thanks neil

Hi and Welcome!

The double row vents and other cosmetic features indicate that the amp is an early STOLEC model. The square pilot (on) indicator seems to have been changed, as I have an identical amp (serial starts with 7411) with the traditional round indicator. It doesn't show, but I guess there is no GZ34/5AR4 rectifier valve inside, right?

If so, your amp is most likely a late 1969/early 1970 one. You're lucky, because it seems to be one of the last fitted with the silver AlNiCo speakers...the story goes that, after the Vox production premises went on fire in 1967, Celestion offered (cheaper) ceramic magnet speakers along with a massive price reduction so Vox phased out the (costly) Silver AlNiCos; after two years some Silver AlNiCo speakers (seems to me 100 or 200, but I can't seem to remember) were discovered in a warehouse, so a certain number of amplifiers (50 or 100) were, again, fitted with these speakers.

In the late 1970 STOLEC started to use PCBs, but these "proved fragile and awkward to service" (The Vox Story- Peterson-Denney). Your amp sports a PTP construction method, so it's surely older than that.

Sonically these amps are formidable, because the solid state rectifier is more efficient (it had to be so to compensate for the cheaper Ceramic speakers and their reduced efficiency), and the combination of a solid state rectifier and two Silver AlNiCo speakers is a powerful one, with an edge in terms of responsiveness/dynamics on the older AC30s (though your amp lacks the "sag" of the earlier ones' valve rectifier).

Hope this helps

Best regards

Bob

[Steve Conner]

According to the blurb near the bottom of this page:

The VOX Showroom - Dallas Arbiter Vox Hand Wired AC-30 Top Boost

This amp is most probably a Dallas from after the Stolec era. It has the 6 vents and the birch ply cabinet instead of particle board. It is point-to-point wired, but that doesn't date it to the 60s: the above page says that Dallas went back to PTP after the stock of PCBs from Stolec ran out.

And, you mentioned that the serial number begins 7410, so it was made in October 1974.

Is it for sale? I can feel my gear acquisition syndrome acting up.

[d0z3r]

if you read the whole thing from that link,it says its exact same wiring,as the pcb amps were basicly a failure so they went back to the exact same way jmi built them,and i have that item,with the origional jmi speakers too,only thing missing is the
...The Dallas Vox AC-30 amp shows the evidence that the AC-30 was returned to the original Vox design with only one significant exception. The GZ-34 tube rectifier .However, the use of diodes in the power supply also has a benefit. The efficiency of the diode rectification in the Dallas produced AC-30 allowed the amp to produce over 40 watts of output power.My speakers have 1970 stamped on them from the inspectors mark,and a guy whos father worked at jmi/vox from 1958-1969 said its a late 69 model,yes its for sale.neil,and mine is that amp,not the pcb rubbish,might miss a little sag,but apart from some dust in 2 of the control knobs that if i had time and a can of air i would clean them.

[sprocket]

if you read the whole thing from that link,it says its exact same wiring,as the pcb amps were basicly a failure so they went back to the exact same way jmi built them,and i have that item,with the origional jmi speakers too,only thing missing is the
...The Dallas Vox AC-30 amp shows the evidence that the AC-30 was returned to the original Vox design with only one significant exception. The GZ-34 tube rectifier .However, the use of diodes in the power supply also has a benefit. The efficiency of the diode rectification in the Dallas produced AC-30 allowed the amp to produce over 40 watts of output power.My speakers have 1970 stamped on them from the inspectors mark,and a guy whos father worked at jmi/vox from 1958-1969 said its a late 69 model,yes its for sale.neil,and mine is that amp,not the pcb rubbish,might miss a little sag,but apart from some dust in 2 of the control knobs that if i had time and a can of air i would clean them.

Wonder how it compares to some new AC 30s

[diagrammatiks]

It's definitely later 60s.

The early 60s ac30s had different capacitors used throughout.

[d0z3r]

It's definitely later 60s.

The early 60s ac30s had different capacitors used throughout.

i have had many people telling me lots of diferent storys,i see what you say as i have a picture of an early1963 board,and see different colour but identical size and shape caps,thankyou for your input,the original reciept is being looked for too.

[diagrammatiks]

i have had many people telling me lots of diferent storys,i see what you say as i have a picture of an early1963 board,and see different colour but identical size and shape caps,thankyou for your input,the original reciept is being looked for too.

You have mustard caps in yours. The boards with all mustard caps didn't happen until the second half of the 60s. 68 at the latest.

In the 70s they stopped using the other caps all together and went to only Mustards.

[Bruce / Mission Amps]

Been a while since I had one in for a refurb but is that green filter cap an Erie and don't they have a date code on them? Gives you a decent idea of where you are...

[Steve Conner]

I don't see what all the debate is about. The OP started the thread by stating that the amp's serial number began 7410. And one of the pages linked says that the first four digits of the serial number are a date code.

So no matter how much you might like to pass it off as a more valuable 60s model, the fact is that it was made in 1974.

Still a pretty good amp. The alnico speakers and plywood cabinet would sell it for me, I hate particle board.