Vox AC 15 questions

[Leif H]

I'm going to do a vox ac 15-ish build.

is a choke going to help with the power supply?

It doesn't seem that I can get anything from my supplier but a hammond 5 henry for an AC30.
Is that going to do it?
Should I bother?

[black_labb]

that choke will work fine. you dont need as much current handling, but there isnt all that much difference as it is only the screens and the pre.

[otto pärt]

I recently built one without a choke. It's fine.

[Leif H]

So far, from what I've read, this will help keep the amp in more of a class "A" which is the charm of the amp's clean tones.

I think I'm going to give it a try, they're not a huge expense, and if it doesn't work out, I'll remove it from the amp.

If anyone can answer this, as far as mounting, should it be oriented 90 degrees to the Output transformer?

[d95err]

So far, from what I've read, this will help keep the amp in more of a class "A" which is the charm of the amp's clean tones.

That sounds like a myth. At least, I can't think of any way the choke would interfer with the operating class of the amp.

A choke will most likely have a lower resistance than a corresponding resistor. This will affect the screen voltage drop (screen "sag") when the amp goes into Class AB operation, and thus the amount of compression when the poweramp is pushed hard.

The character of the Vox AC15/30 amps is mainly defined by: lack of negative feedback, cathode bias and EL84s. As with any other push-pull amp, they operate in class A as long as the volume is low enough.

[otto pärt]

If anyone can answer this, as far as mounting, should it be oriented 90 degrees to the Output transformer?

Good question. Certainly the output transformer should be mounted at 90° to the power transformer, but how does a choke fit in? Seems like you'd want the OT 90° to both the PT and the choke.

[RWood]

I recently built a 6G6 Bassman, using a choke. I tried all different orientations of the choke, with the amp running, and could hear no difference between any of them.


RWood

[Bruce / Mission Amps]

And sometimes pointing the nulls at each other require not a 90 degree angle, but something much less.

[soundmasterg]

You should be able to order a vintage correct choke from Heyboer or Mercury Magnetics for an AC30.

greg

[Leif H]

You should be able to order a vintage correct choke from Heyboer or Mercury Magnetics for an AC30.

greg

Sadly our suppliers don't sell either Mercury or Heybouer, Hammond has the AC30 transformers, it's an AC15 I'm doing.
I'm going with the AC30 Choke.
I get them through work. Because of this being a personal purchase, my supplier will give me Hammond transformers at cost, and don't have to pay for shipping.

[Hardtailed]

Sadly our suppliers don't sell either Mercury or Heybouer, Hammond has the AC30 transformers, it's an AC15 I'm doing.
I'm going with the AC30 Choke.
I get them through work. Because of this being a personal purchase, my supplier will give me Hammond transformers at cost, and don't have to pay for shipping.

Hammond's universal chokes (153-159 series) have quite a variety of models.

Although I used their AC30 specific OT and PT for the AC30 build I did recently, I used a generic choke (159M). It was almost half the price.
And 15H seemed to be more in line with the vintage value, according to my research. (The AC30 specific parts are 5H or 30H)