Vox AC15 layouts

[bnwitt]

HBP,
I'm reaching the limit of what I can squeeze into this chassis.  It is 20" W x 6.5" H x 2.5"D.  As far as the Top Boost is concerned, there may be a way to add it as originally it was an external add on kit before it was integrated into the AC30/6.  It basically needs an additional set of input jacks bass and treble controls and an extra ECC83 tube.  I do have room for those components.  What is tight is adding the additional support components.  I could probably add the inputs and controls and put everthing else in a box on the interior cabinet wall or do it just like it was done to the AC30/6.  See link below:

http://www.marshallforum.com/419422-post355.html

Barry

[drgonzonm]

bn--- referenced the freeinfo site.  please be careful, apparently some contributions to that site are not all that friendly.

I like the site, but have troubles getting on to it. because of malware problems. 

The schematic referenced by bn--- can also be found on this forum. 

[bnwitt]

Thanks for the heads up.  Evidently my virus protection is protecting me well.  I replaced the link in my post with the one from Doug's library.  On the virus front, I was searching for a website called guitaramplifierpcbs.com the other day and the actual website wasn't coming up in Google.  So I typed it in the url bar and bam!  Instant malware download which bypassed my virus protection and put my machine into a restart.  It took me 3 hours to get rid of it.  I've never seen anything that powerful before.

[Willabe]

On the virus front, I was searching for a website called guitaramplifierpcbs.com the other day and the actual website wasn't coming up in Google.  So I typed it in the url bar and bam!  Instant malware download which bypassed my virus protection and put my machine into a restart.  It took me 3 hours to get rid of it.  I've never seen anything that powerful before.

    

Glad you where able to fix it. I'm not sure I'd be able to figure out how to get ride of it.

I've always been dumbfounded at how people with the brains/gifting to do so much with a computer would use it just to hurt someone else, really as many as they can.            


                          Brad    

[bnwitt]

After doing some research on the different Vox AC series amplifiers I found the following:
1. The AC 15 was used by numerous British players with great satisfaction.  It was a great sounding amp but as venues got bigger more power was needed.  Two more power tubes were added hence the AC30/4
2. The EF86 versions of the AC15 and AC30/4 were altered to an ECC83 after "Bass" players complained about microphonics due to their bass frequencies.  This was not a guitarist complaint.
3. Along with this preamp tube change a third channel (Brilliance channel) was added since the dual triode allowed it hence the AC30/6.
4. After the preamp tube change, players noticed a change in tone.  There wasn't as much gain and clear tone in the new AC30/6
5. To satisfy the complaints on the AC30/6, the treble models were introduced (which had a treble boosting RC at each volume controll)
6. Shortly after that the Top Boost add on kit came out.  Eventually the Top boost circuit was made stock in AC30s.
6.  Most players of the AC30 amps consider the original circuit with the EF86 to be the best of the series in tone.

After reading all of this, I have decided not to add the top boost components or the 3rd channel to this amp layout  It seems to me that the original AC15 and AC30/4 with EF86 were the British gutarists' favorite of all models issued.  Of course it was common for guitarists and bass players to share an amp in those days and if the bass players had just had their own amp I wonder if good enough might have been left alone.  And of course if Public Address systems had existed back then I doubt there would have been a call for the AC30 at all.  So bottom line, I will be building the 1960 EF86 AC15 amp as it was originally issued and the layouts will be in both a combo and head style chassis.

[tubeswell]

Why not design the layout so that you can easily incorporate a top boost later if you change your mind? (I'm always fiddling with my builds down the line). Besides, in a gig/jam situation you'll probably be thankful for some mid-high freq boost - either that or some kind of rangemaster cloney thing in front. JM2CW

[bnwitt]

Tubeswell,
Putting in a Top Boost circuit later would be no problem, just like the original.  But, I'm after the orginal EF86 AC15-AC30/4 tone which is reported to have had excellent highs, great overall tone and great gain.  The Top Boost circuit came along after Denny changed the original circuit (which was considered awesome by guitarists) to try and bring the AC30/6 back toward the original tone.  Unfortunately not many of the original AC15-AC30/4 amps are still around since fewer were made than subsequent models.  There is a fellow out there who converts AC30/6 amps to the original AC30/4 circuit:

http://members.optusnet.com.au/~glen325/AC30convert.html

Evidently there is a market for that which is surprising.  To think that someone would do that to a valuable amplifier worth lots of moolah to achieve the tone of the very first original circuit tells me that the tone is worth it.  The oldest AC30 I have every played was a 90s reissue and I wasn't impressed.  I really want to hear for myself what the original circuit sounds like.  The way this is going I am going to be pretty darn close to the original layout and exactly on the circuit so I think it will be very close.  I've even got a UK made "Blue" speaker to put in the cabinet.

[moonbird]

Very interesting info -- sounds GREAT to me!!

[tubeswell]

There is a fellow out there who converts AC30/6 amps to the original AC30/4 circuit:

http://members.optusnet.com.au/~glen325/AC30convert.html

Evidently there is a market for that which is surprising. 

Yikes!

[bnwitt]

Yikes!

Yeah!  That's what I thought.

[carausius]

http://livinginthepast-audioweb.co.uk/index.php?p=xfrmrclassic

UK made Vintage style Vox transformers various models available.

Not sure if this link has been posted before but might be useful for European builders

[bnwitt]

 a bit pricey.  $45 for a $19 choke is a pretty heavy mark up but if it's all that's available in one's area.  I guess the OT and PT are fairly reasonable if one is after the vintage look.  Thanks Carausius

[carausius]

As always shop around, I doubt if a choke makes a large difference compared to an output or power transformer   Even if it's authentic   Non EU buyers would save 20% VAT on those prices.


EDIT More interesting stuff http://charliehall.proboards.com/index.cgi?board=project&action=display&thread=593

[sluckey]

I've been working on a single board layout for the AC-15. It will fit in a 20 x 6.5 x 2.5 chassis with a 'Marshall' style layout...

http://home.comcast.net/~seluckey/VAC15.pdf

[tubenit]

I think these SCH schematic and layout could be easily converted into what you guys are looking for.

With respect, Tubenit

[bnwitt]

Well I hope to have this preliminary layout done in the next week.  I have been slammed with PV design work and have had it back burnered.  Sluckey has been purusing the Steven Grosvenor layout and already found two mistakes so thank you thank you to him for his contributions.  I would appreciate it if after the preliminary layout is done all of you brainiacs would look at the 1960 AC15 schematic and the layout side by side to look for any other errors.  More heads are better for sure.

[SleepLess]

Hi.
Awesome topic and exactly the thing I'm looking at for my next personal amp project... Have you finished it? How does it compare to the real one you had before? Where did you source the various parts (mainly speaking about the chassis and faceplate!)?
Thanks!

[kagliostro]

Hi Bnwitt

I was thinking to your layout this days

Have you finish to plan it ?

Can you show us something ?

Thanks

K

[SleepLess]

Well I hope to have this preliminary layout done in the next week.  I have been slammed with PV design work and have had it back burnered.  Sluckey has been purusing the Steven Grosvenor layout and already found two mistakes so thank you thank you to him for his contributions.  I would appreciate it if after the preliminary layout is done all of you brainiacs would look at the 1960 AC15 schematic and the layout side by side to look for any other errors.  More heads are better for sure.

Hi bnwitt!
Have you finished this build? How has it turned out?
Thanks!

[Ed_Chambley]

I have been watching this as well.  Sluckey's layout says corrupted when I attempt to open it.  I am interested in building this in a Marshall chassis and make a head out of it.  Let us know how it is going.

[sluckey]

Sluckey's layout says corrupted when I attempt to open it. 

Actually, it says...

"Sorry, the page you were looking for could not be found."

I can put the file back online if there is any interest.

[SleepLess]

Sluckey's layout says corrupted when I attempt to open it. 

Actually, it says...

"Sorry, the page you were looking for could not be found."

I can put the file back online if there is any interest.

Well, I was more looking for a double chassis layout, just like on the original, but a single chassis layout would be a good start I guess... Thanks Sluckey!

[Willabe]

Well, I was more looking for a double chassis layout, just like on the original

Why? Their a pain. It was a big mistake on their part.


              Brad     

[sluckey]

My single board/chassis version of the 1960 Vox AC-15 is back online. No guarantees on how long it will remain online.

http://home.comcast.net/~seluckey/VAC15.pdf

[SleepLess]

My single board/chassis version of the 1960 Vox AC-15 is back online. No guarantees on how long it will remain online.

http://home.comcast.net/~seluckey/VAC15.pdf

Oh my... This is totally terrific Sluckey, thanks! So all I need now is to find the guy who can make the right faceplate to make it look like the original... 

[SleepLess]

Well, I was more looking for a double chassis layout, just like on the original

Why? Their a pain. It was a big mistake on their part.


              Brad     

Yeah, you're probably right, although Vox and the Vox fans assert that the double chassis actually helped reduce hum because of the two different metals used for the chassis (power section in the steel chassis, preamp section in the aluminum chassis)...
The other fact is that I have finally found someone who can build the double chassis... But nevermind, I trust Sluckey more than anyone else in this world when it comes to amps...

[Ed_Chambley]

The layout has a 12Ax7 in the normal preamp section, but the schematic has a EF86.  Excuse my ignorance, but why?

[Willabe]

Yeah, you're probably right, although Vox and the Vox fans assert that the double chassis actually helped reduce hum because of the two different metals used for the chassis (power section in the steel chassis, preamp section in the aluminum chassis)...

V hav other vays to kill hum you know.  


               Brad      

[SleepLess]

The layout has a 12Ax7 in the normal preamp section, but the schematic has a EF86.  Excuse my ignorance, but why?

Good point. And the rectifier (V8) in the schematic is present, but it's gone in the layout...

[sluckey]

The layout has a 12Ax7 in the normal preamp section, but the schematic has a EF86.  Excuse my ignorance, but why?

Because it's a labeling error on the board layout. Pins connections are correct for an EF86.

[sluckey]

Good point. And the rectifier (V8) in the schematic is present, but it's gone in the layout...

And same for transformers, filter caps, switches, fuse, etc. My layout is not a total layout. It's meant to show board construction and interconnections. You will have to refer to the schematic for any components or connections that do not interface directly with the board.

[Ed_Chambley]

The layout has a 12Ax7 in the normal preamp section, but the schematic has a EF86.  Excuse my ignorance, but why?

Because it's a labeling error on the board layout. Pins connections are correct for an EF86.

Thanks Sluckey.  I have always wanted one of these.  Do you know anyone who has built it?  I cannot see any reason why it would sound different.  This is my next project for me.

[kagliostro]

Hi Steve

I completely missed to see this layout

as always a fantastic one 

Franco

[sluckey]

I've built a VAC-15 Lite. It only has the EF86 preamp. I've never built the Vibrato channel but was sure close to pulling the trigger back in early September. Then I discovered that old RCA radio. Lost focus on the Vox. But it's not completely out of mind. If I do build it, I will use this board design rather than a dual chassis design.

BTW, the labeling error has been corrected on the board layout. If you spot any more errors, let me know. Thanks...

[SleepLess]

If one of you guys start a full VOX AC15 one-chassis build I want to see it... I'm too scared to be the first one to try it and report...
Where do you guys get the proper chassis for the one-chassis AC15 btw?
There's a model from 1960 up for sale on TGP right now, just shy of $4000 (and that's probably a good deal!)... We need clones out there, that's too darn expensive!
Thanks!

[sluckey]

I start with a blank chassis. There are some members here that can make them. Or you can buy blanks from several websites.