2015 VOX Ac30c2 service manual

[pdf64]

So C2 has a solid state rectifier.. can recall many problems trying to get a decently made tube rectifier as well as possible problems with the filter capacitor load.

With tube rectifiers and the post '60's guises of Vox, my perception is that the failings may seem to be due to incompetent 'designers' rather than the device.
Unfortunately the tube rectifier is used as a scapegoat.

[J M Fahey]

Those tone stacks don't look right?
No bass caps,

???? ... the Bass cap is C2 .

and the Fender mid cap is shown as 10nF, rather than the regular BF 47nF (22nF on some models).

But this is not a BF tone stack !!!!!!!
Itīs a VOX/Gibson GA70/Fender Pro 6G5-6G7 one !!!!

Download TSC http://www.duncanamps.com/tsc/ to view and play with the more usual arrangements.

I suggest you do and check the VOX tone stack there compared to the one above ... you will be surprised

The only difference between the one I posted above and the TSC one is that TSC includes the .022uF coupling cap inside the Tone Stack and the one I copypasted has it outside the picture, coming from the earlier stage.
But that does not affect EQ at all.

Tom Phillips

Quote Originally Posted by pdf64 View Post
Those tone stacks don't look right?...

I agree. What's the source of those figures Juan?

Well, those come straight from the mouth of the horse: the Manufacturers themselves:

What I posted:


from VOX showroom (who are suppossed to know about VOX?) http://www.voxshowroom.com/uk/amp/ac30_tb_hood.html

Fender Pro 6G5 or 6G7 tone stack

As you see, that "mystery" tone stack is in fact way more known than most remember.

Important detail: many consider this very clever Tone Stack "a mistake" , plain "wrong", "an error which was mysteriously copypasted without analysis or correction" and similar demeaning designations; the fact is this is VERY CLEVER and you can check what I say by ... ummmm ..... playing with TSC.
Just move the Bass slider 0 to 10 and marvel.

Fact is this is a THREE pot, Bass/Mid/Treble control , where the Bass pot is also the Mid control.
Of course, since one pot (Bass) does the work of two, you can not set them separately, they are linked.

Let me show both pots (look at the schematics above):

* Bass pot: wiper-to-top section.
Its function is to more or less short the Bass Capacitor (.01 or .02uF) .
Fully shorted: minimum (0) Bass
Fully open: as much Bass as possible (10)

* Mid pot: wiper-to-ground
Fully shorted: 10k resistr shorted: no mids (notice Mid notch gets MUCH deeper, as much as 14 dB or so)
Fully open: Mid notch gets less dip, so "maximum Mids"

Please confirm this by playing with TSC Bass pot settings and see how it strongly adjusts Mids too.

But ... but .... isnīt having both controls linked a problem?

Not really.

With control on 5, you have a good balanced amount of Bass and Mids.

On 10: maximum Bass and 0 Mids (wiper shorts it), which gives the impression of even more Bass

On 0: zero Bass (Bass cap fully shorted). ... in principle this would sound unbearably thin BUT ... now "invisible in plain sight" 10k mid setting resistor is free to do its job.

VERY VERY clever and in no way a "lucky mistake" as VOX Showroom calls it.

[Dave H]

The only difference between the one I posted above and the TSC one is that TSC includes the .022uF coupling cap inside the Tone Stack and the one I copypasted has it outside the picture, coming from the earlier stage.
But that does not affect EQ at all.

So the circuits are different but their EQ is similar?