Vox AC-30 Reissues

admin · Post by **admin** » Tue Apr 15, 2003 1:24 pm

From a technical point of view how close is the Vox AC-30 reissue of the 1990s to the 1960s Vox AC-30?

glen_l · Post by **glen_l** » Tue Apr 15, 2003 2:49 pm

The AC30TBX produced by Korg from the early 90's to the present is about the closest you can get to an early 60's AC30/6 with Topboost option. The only thing closer would be the New AC30TBX/HW (Hand wired with point to point wiring). However the Standard Korg AC30TBX (X indicates Blue Speaker option)is an amp that is a big pleaser, and if you can get one at a good price it's well worth getting.

Some poeple have had modifications done to the standard AC30TBX. Like retro style Output Transformer (Now available from Korg) and old style caps in the audio path and power supply, but these aren't essential for the amp to sound great.

ricnvolved · Post by **ricnvolved** » Tue Apr 15, 2003 10:36 pm

While the Vox AC-30TB produces my all-time favorite guitar amp tone, I've heard muted rumblings from various forum participants that the AC-30 is notoriously unreliable and scarily prone to near constant breakdown. I'd like to know Don's experience with these amps and any insights he may have.

Even though I'm a bass player, I was tempted several times in the past 8 years to purchase one of the Korg re-issues of the AC-30TB. However, my sixth sense warned that even these weren't worth the price. In light of what I've heard recently, I'm glad now that I didn't get one. This has led me to plan on taking a good hard look at the Cage Audio 18/00 amp at some future time. Supposedly this Cage amp model has a distinctive "Vox like character", and I feel reasonably certain that it far surpasses any of the Vox models in quality materials and construction. Whether it gets enough of that Vox AC-30TB flavor to suit my tastes remains to be seen.

toneman · Post by **toneman** » Sun Apr 20, 2003 9:57 am

O.K. we might open a can of worms here but here's my take on the current pc board version AC-30 that Korg offers.
First off, Mitch Colby is a good friend and really GREAT Guy!!! He, almost single-handedly is responsible for the new "Hand Wired" AC-30 which in my opinion is a fab amp. I had the pleasure of being inside one yesterday for a couple hours.
O.K. on to the PC board version that Korg has made for the last 10 years.
What I replace and Why:
Output tranny- this is 40% of every tube amps sound/tone. The Drake and now Dagnell made one's are just o.k. in my book. They lack alot of chime and depth. They don't have what I call the "IT Factor". I use the Axiom clones from Mercury Magnetics. These are hand made/ hand wound repros of the original Haddon's (`59-`61), Woden (`61-`63/`64) and Albion's (`63/`64-`67). The most desired one's are the Woden and Albion(which is the version of output tranny that Vox has set on for their current handwired series-although the Korg one is not made by Mercury). It's also the era from which more AC-30's were produced than previous years by JMI so that sound is the one most heard by everyone in general.

Needless to say that in any manufacturing situation that almost all parts are supplied by "lowest bidder" to keep costs down and profits up.

Filter Caps: these affect the way your amp responds. Sum it up like this;
High filtering= tight bass and stiff response. Amp sounds a bit constipated.
Low filtering= looser sound, more open, more touch sensitive. Amp breaths more.
I lower them down to JMI era specs as close as possible. Some values are different now than what was used nearly 40 years ago.

Choke: What's it do? Mainly acts as a humbucking coil for the power tranny and comes right after the first filter stage in the power supply.
Why's it important? Well, since they are mainly made from copper wire and iron cores they affect the way your power supply acts. The way they are made, the amount of inductance and even the way they are mounted to the chassis will have an effect on the way your amp functions and sounds. Alot of lower powered and budget amps don't even have a choke but use a large wattage/low value resistor that costs about a dollar. I replace the Korg one with an exact JMI era clone from Mercury.

Signal path componets: To alot of electronics engineers a resistor is a resistor and a cap is a cap and they're not any different tonally.
I say ********!
There's a big difference in a carbon film resistor vs. a carbon comp resistor in your signal path.
Basically JMI used Carbon comps in their original amps. They offer better harmonics and more detail in your notes.
Carbon film is great in voltage paths because of their lower noise factor/higher tolerences.
I replace all the 1/2 a penny a piece carbon film resistors in the Korg version with carbon comp in all signal path locations.
Caps: JMI/Vox used Wima's and later what everyone now refers to as "Mustard Caps" that were made in the Czech Republic by a company called Iskra and imported to the U.K. and Western Europe by Phillips. Phillips was a huge vast electronics parts empire that owned alot of companies including Mullard Valves (tubes).
Basically both these caps were polyester film types that have a nice warm harmonic sound to them.
I use polyester caps in all signal applications except for pico farad caps. For those I use silver mica for their superior tonal response. Some companies use ceramic caps. I personally don't think a ceramic cap has got any business in any guitar amp. They sound harsh & brittle and make your high end sound shrill.

toneman · Post by **toneman** » Sun Apr 20, 2003 9:59 am

So to sum it up, I replace output tranny, choke, filters and signal path componets to get the Korg's to sound as close as possible to what the JMI made one's sound like.
I think Korg did an excellent job reproducing the AC-30 in a modern factory production facility(Made in the Marshall Amp Factory) but tonally was only about 65% there vs. a JMI version. These changes get you at least 30%+ closer.

admin · Post by **admin** » Sun Apr 20, 2003 11:29 am

Don: In looking at the inside of the Vox-AC30, what distinguishing feature allows the "average" user to identify if it is PC version or a hand-wired version.

toneman · Post by **toneman** » Mon Apr 21, 2003 5:44 am

Peter; You can pop the back off the Korg combo with 4 screws and see inside without having to remove the four stove bolt screws located on the sides(two on each side) that remove the chassis itself.
I would say that 99% of the Korg amps you'll see right now are the pcb reissue combo's. The Hand Wired one's are a very limited production and the U.S. market will only get around 200. These are being built in the U.K. @ the Marshall Factory on an extremly limited basis. I'll have to ask Mitch Colby the exact amount coming over here, but needless to say it's a small amount as I think between the head/cab combination and the straight combo's there will only be around 500 total world wide.

toneman · Post by **toneman** » Mon Apr 21, 2003 5:55 am

I should have added that with the pc board model you'll see alot of small parts mount to a large pcb and on the "Handwired" you'll find a long 2" wide phenolic strip with turret mountings that the componets are mounted and soldered on. The pots and preamp tube sockets are mounted to the pcb on the standard reissue. On the "Handwired" version the pots are mounted to the top of the chassis and wired to the strip and the tube sockets are mounted along the bottom section of the chassis facing out horzontially. The standard pcb version has six inputs w/three channels and the "Handwired" has only one channel with 2 inputs(but has a great reverb and the best sounding tremelo you've heard).

ricnvolved · Post by **ricnvolved** » Mon Apr 21, 2003 9:06 am

Don-- What about the Cage 18/00 combo amp? Have you ever had the opportunity to hear one of these or check out the electronics & construction?

toneman · Post by **toneman** » Tue Apr 22, 2003 6:40 am

Jeffery; Sorry, but I haven't heard of them. I'll check into finding out more about them. Do they have a website with info, etc. that I could look at?
Thanks!

sir_andrew_of_left_coast · Tue Apr 22, 2003 7:28 am

http://www.audiocage.com

toneman · Post by **toneman** » Thu Apr 24, 2003 7:57 am

Thanks Andrew!!! I'll check them out! I appreciate the link.

ricnvolved · Post by **ricnvolved** » Wed Jun 04, 2003 8:25 pm

Don-- Have you had an opportunity to check out the Audio Cage guitar amps yet?

toneman · Post by **toneman** » Thu Jun 05, 2003 6:19 am

Jeffery; Yes! Nice amps. Appear to be well thought out and well laid out and quality componets.

ricnvolved · Post by **ricnvolved** » Thu Jun 05, 2003 9:18 am

Cool! Now, how about the tone as compared to the classic Vox AC-30TB?