New amp build - AC30/4 w/pics

[fzfwyv]

Here is an EF86 4xEL84 build I just completed.

I used this schematic: http://www.blueguitar.org/new/schem/vox/ac34ef86.pdf

A few minor modifications - .047 for PI coupling caps, 8.2K power resistor to the PI to give it a little more ooomph, and I put the 1st filter cap before the standby ala' Tranwreck style. I used the PRP's for resistors and Sozo caps (not the hand wound ones). Also added a bright switch with a 50pf and a 330pf. The tone control is just a 3 position bypass cap switch .01 (stock value). .0047, .001. I upped the filter caps a bit to 22uf-22uf-10uf-10uf which gives a really great feel to the amp and no ghosting that I can hear so far.

I built a few of these previous with spare parts or what was on hand. This one, I spec'd out all the parts just for this amp. This thing is totally Vox! It chimes & grinds and it never loses it's character. It's quiet as hell and rings, chimes, glassiness, or whatever stupid adjective you want to use. It really is great.

Front & Rear plates are from BNP and I bought the blue power cord sleeve from wirecarre (.com). A cool thing if you want to dress up some cables. There are lots of options.

I'll have to make a vid & post on youtube because I have to say I'm proud of myself for this one. I'm really impressed with the sound and it does all the classis Vox stuff in spades!

[img1224]http://home.comcast.net/~rszmagaj/ac30_front_01.jpg[/img]

[img1224]http://home.comcast.net/~rszmagaj/ac30_rear_01.jpg[/img]

[img1224]http://home.comcast.net/~rszmagaj/ac30_top_01.jpg[/img]

[img1224]http://home.comcast.net/~rszmagaj/ac30_guts_01.jpg[/img]

I always have to thank the guys here who've helped me along...you know who you are!!!... you guys rock.

-Rich

[Structo]

Very nice and clean build.

How do you like the EF86 tube?

I keep reading conflicting reports on these tubes as in they are noisy, prone to failure, etc.

Do you use new production tubes or NOS?

[MBD115]

Beautiful build!!!! Looks like a piece of art.

Thats some 'heavy-duty-iron' on there!!!!

Waiting for the clips.

[Colossal]

Looks great. Very nice work!

What brand of GZ34 and EL84s are you using? Also, what speaker(s) are you playing this amp through?

[FunkyE9th]

Very nice! Would love to hear clips.

Is that a standard Dynaco 470 clone or a special modded version? Toneslut PT?

[fzfwyv]

Thanks for the good words guys. To answer a few Q's:

- PT is Moose standard PT using the 260 tap
- OT is the Dynaco clone HTS-8093-1
-Tubes are a NOS Mullard EF86 Smooth Plate, 1 ANOS GE Long Plate (circa 1958...one in the pic is a 60's RCA), (4) Saratov EL84's (circa 1984) and 1 good ol' Chinese Sino GZ34. SgtOD provided the EL84's & GZ34. The Power tubes are really nice for a very reasonable cost.
- Power cord & wire stuff is here: https://www.wirecare.com/products.asp?prodline=PTN

As far as the EF86 being prone to noise & microphonics, the answer is yes. But if you build a head and not a combo, and go with a quality NOS tube (or a newer e80F works great too) then you will avoid most of those issues. The amp sounds just awesome. I'm using my R9 Les Paul. I have a friend who is going to rip a nice Tele through it. Can't wait.

-Rich

[M Fowler]

Very nice amp and glad she sound good too. I love all the room one gets building it in this style.

Mark

[jelle]

Very sweet! I like it!

[UR12]

Awesome looking amp!! Congrats!!!

[jjman]

The preamp's cathode bypass cap is in backwards, no? Also it looks big for a 25/25, not that there’s anything wrong with that.

Very nice and clean layout.

[jjman]

dbl post

[fzfwyv]

The preamp's cathode bypass cap is in backwards, no? Also it looks big for a 25/25, not that there’s anything wrong with that.

Very nice and clean layout.

Holy crap..you are right. Wow. Tunnel vision on my part. The cap is a 22uf 450v (it's what I had on hand) other than the black Spragues which I've had a few bad ones lately.

-Rich

[CapnCrunch]

Hey Rich,

I thought I recognized the front plate on that amp. Looks a lot like the Rocket chassis and plate that I bought from you a while back. Cool looking amp! I've had a busy summer and haven't had a chance to complete the Rocket yet. I've built and Tolexed a head cab and Dumble style 2x12 cab for it though. The Blues go into the cab tonight and I'm going to get started building the amp in the next couple of weeks.

Why did you do this build rather then the Rocket? Just curious. Also, have you compared this build with a Rocket clone? Curious how they compare. If you have a chance, can you post some clips? I'd love to compare with some of the Rocket clips on the forum.

[fzfwyv]

Hey, good eye! The amp bug bit me and I decided to do another build. I actually spent some time thinking about which build to do. The circuits are different, but essentially the similar layouts can be used.

I like the grind of the EF86 and it is a bit more aggressive, IMO. Previously I built a Matchless Lightning clone and tweaked the pre to match the Rocket. While it was a nice sounding amp, I prefer a little more angry character to my amps but I still wanted that Vox chime.

So, in comes the AC30/4. It's filtered less than the Rocket (22-22-10-10) so it has a more vintage feel to it. I did up the PI coupling caps to match the Rocket for a bit more oomph. I also like the minimalist tone layout. The tone control is nothing more than a 3 position bypass cap and the standard Vox/Rocket cut control. The little switch is a 2 position bright cap which acts like a "glassiness" control, if that makes any sense.

Overall I am really happy with this amp. I plays perfectly with my Les Paul and it has every single Vox tone adjective in it.

-Rich

[CapnCrunch]

Rich

Cool! I was wondering about the tone control. I have an AC-15 clone, and I have to agree with you on the ef-86. The additional gain vs. the 12ax7 is noticeable, and it has a character that I've always had a tough time describing. Aggressive is definitely a good description, especially with humbuckers. I was surprised at how inexpensive (relatively speaking) NOS or ANOS ef86's can be. I picked up a NOS Mullard for about $20. I've never had issues with it being microphonic, and it sounds superb.