AMPLIFIERS

VOX AC 30 Signed by Dick Denney

This is my own VOX AC 30 it dates from 1963 signed for me on the top right by its designer the late Dick Denney. This he did on the occasion of his 80th birthday party on the 24th February 2001 at the sports and leisure centre Hastings. He was taken ill on the night, and sadly passed away just a few months later on the 6th June 2001. It reads, " To John, Best wishes, Dick Denney" My guess is this is the last amp he ever signed.

I have owned and gigged this VOX AC 30 for a good number of years now. It used to belong to Jim Green, the rhythm guitarist in my old band " The Soundimension" . He paid £25 for it around 1968, I can vouch for its history ever since then.

When he had this VOX  first, it had one leather handle on one end of the amp. That one was worn through on one end, the other two were missing, the brackets having broken.

I restored this AC 30 as it is now around about 1995

I recently read somewhere that the AC stood for the fact that it was for operation from an AC power supply.  I do not believe this to be correct I always understood it originally stood for Amplifier Combination  even though AC30 and AC50 Heads later became available. 

1959 FENDER BASSMAN

Back in May of this year 2010 I got a phone call that went something like this.

Hi my name's Steve, wondering if you could take a look at my amp, an old 59 Bassman it's not sounding so good, a little fizzy if you know what I mean.

(Me) Yea ok bring it in an we'll have a look at it.
(S) Can I drop it in tomorrow)
(Me) Umm yes that'll be ok , what did you say your name was?
S) It's Steve, I'll see you around eleven tomorrow then, ok.
(Me) Ok Steve, I'll look out for you.

 

 

When he turned up the following day he brought in a really scruffy been everywhere 59 Bassman. My camera has actually done it justice because it looks much worse then the pictures show. The grill cloth and tweed top was/is filthy, but Steve said don't clean it up too much I'm a little superstitious about things like that, they never seem to sound the same afterwards. We took it in to the workshop and Steve plugged in a beat up old guitar, played a few low notes, not loud and sure enough there was a fizzy noise as the notes died down. A sort of ghosting but there was something else about it. Steve said he didn't think it was the speakers, but something was telling me the speakers weren't all they could be. But Steve said he didn't want them re-coned or anything like that. Also he told me not to change the sound or replace anything that wasn't necessary! Now this amp was about to get the the hell gigged out of it, and had to be reliable. After he had gone I turned it up and gave it some stick that was when it really began to show its age. This old thing you can imagine has had no easy life, and isn't about to be pensioned off either. It had been patched up over the years, was full of dry solder joints, components had been stuck down with silicone because everywhere you touched the board it would crackle and cut out, but that dodgy joint just couldn't be found from the top side of the board. The output valve sockets were intermittent and the bias was so hot the valves had almost set fire to the rear panel. The filter caps were original and bursting out of their casings, here was an amp in need of some serious refurbishment, but I was almost forbidden to touch anything. What the hell do you do in a case like this? After a general look, tightening of screws etc and testing I decided to have a look at the old Jensen speakers first.

On removal of the speakers, all four had splits in the cones and the dust caps. All four had at some time had new voice coils fitted and one had been re-coned, rather poorly in my opinion. They looked a bit messy with glue spread everywhere. I know a man who would do a really good job of re-coning these.

Steve, all your speakers need re-coning etc etc. Reply. Oh no I'm kind a superstious about things like that, they never sound too good afterwards.
Me. Well they have been done before and don't sound too good now do they? Steve. No leave em as they are. Me. Ok but I will need to glue up the splits otherwise the way you play they'll soon get worse, then you'll have to get them done. Steve. Um yea well ok just do the minimum you think necessary. So I glued up the cones on both sides of the splits with Evo-stick, and also the coil dust covers.  The mess you see around the voice coil was done by whoever fitted the new coils, not by me!!


Speakers back in place.

Note that there are no bell covers fitted to the top pair, this is the way they are to avoid fowling the amp chassis, which comes pretty close.

Sorry Steve I cleaned out all the dust and shit because it was making me sneeze!

Having done this the amp still sounded crap, just like you might expect an amp that has had next to nothing done to it for fifty one years to sound.

You could never run a vintage car without fitting a few new tyres and maintaining it , so why do people expect old amps to be at their best after a lifetime of abuse?

Ah, but that's the original tyres officer, and the blue smoke looks really cool, the lights they'll come on if you give the wing a bump.

Mr. Plod. Been drinking have we Sir? Mmm I think you'd better come along with me.

As for the chassis, it was riddled with dry joints and someone had glued up several components with silicone sealer to stop them moving and causing crackles bangs and pops! This is an amp that could be worth something like three grand should it ever come up for sale!

Here you can see the silicone glue someone had applied to several components in a botched attempt to cure the annoying noises within this amp. Pretty near anywhere you touched the board would cause it to crackle and fizz. Most of which was obviously dry solder joints. (For those who don't understand what a dry joint is. It's a solder joint that may or may not look perfectly sound, but one to which the solder has not adhered properly to one or more of the connecting leads or terminals, causing intermittent contact) I cleaned all the messy glue away and attempted to find the offending dry joint/s by heating suspect joints and running in some fresh solder. All to no avail, in fact if anything it just made matters worse. I had to de-solder several joints remove the components and scrape clean the ends of the leads with a craft knife blade, tin the leads with fresh solder, refit the components and solder in place.

Having done that the board was no longer intermittent but the output valve octal bases certainly were. A clean up with IPA fluid and re-soldering the connections made little difference. As they had been replaced before with inferior quality ones, there was only one thing for it, (don't tell Steve) replace the dammed things with some decent ones! Oh heck now all the valves are showing up noisy, where is this going now? Old Steve's gon'a hit the roof, but so much needs to be sorted once and for all if he wants this amp back on song and gig worthy.

I thought to hell with it, this amp is about to get it's ass gigged off from here to Australia and back again, and in a way few amps have ever been gigged before, so it just has to be reliable. I just can't make it reliable unless I change a few things. I happened to have a nice quad of original USA Sylvania 6L6G valves / tubes that had seen very little use, that were just waiting for the right amp to come along. If ever there was a right amp, this was it, a pair for now and a pair for fifty years time! Having made my decision, experience was telling me I couldn't possibly leave the original Astron filter caps in there, so out they all came, and in went new ones, including the two 8uf bias caps on the left and the 16uf Mallory cap in the centre of the eyelet board.

In typical Fender style the main filters are housed under a metal cover on top the chassis. These are actually mounted in the cover rather than on a chassis mounted board, more commonly found on Fender amps.

You will notice the grounds of the capacitors are soldered to the outside edge of the cover, having passed trough adjacent holes. I snipped off the wires close to the old caps and soldered the replacement caps directly to the remaining wires leaving the original external solder joints intact purely for cosmetic appearance only.

One other thing about this amp was that it ran hot, so hot that the 6L6's left burn marks on the inside of the rear panel.  Each valve was pulling about 100ma even after replacement of the bias capacitors.  I decided I would convert to adjustable bias and discreetly installed a preset trim pot for the purpose. The bias was set at 30ma per valve, the amp now running much cooler and sounding real good.

Unfortunately I didn't photograph the after work appearance as time was stacked against me, due to all the issues with the amp and the fact that Steve wanted to come and collect it as soon as he could. Despite having done all this work, the amp was still left with an annoying fizz on decaying low notes, and I just had to put Steve off collecting it for another day.

The Fizz!!

If you look at the picture of the chassis, under the two 8uf bias capacitors is a 1 watt 4.7k resistor. Something about that resistor was niggling me all the way through the repair process of this amp, to the extent that at one stage I actually removed it before replacing any capacitors, for testing out of circuit. It tested fine well within tolerance. As Steve wanted nothing replaced, I foolishly put it back.

Nothing to do with the crackles and pops but it was the cause of the low note decaying fizz! Funny how instincts are so often right.

So what do you think of the amp now then Steve?

 


Man that's amazing it sounds much better than before.

(Me) Better, but you said don't change anything because you like the sound as it is / was!!

 

STEVE

Yea but now it's better.

 

If you look at this year's Glastonbury clips on YouTube, you can see Steve using this amp on the main stage 2010

 

Besides the bill, I handed Steve a bag of fifty one - year old bits, saying "if you ever decide you don't like the sound of the amp as it is now, and the way it should sound, I can refit the bits and nobody will be any the wiser" .  :-)

 

 

 

SEASICK STEVE     Glastonbury 2010 

GLASTONBURY 2010

The Pinkpop festival 2012 Landgraaf in The Netherlands several good close ups of Steve's old 59 Fender Bassman, and the music's pretty good, too.

PINKPOP

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Many of you have asked about the S M F amplifier shown in a previous workshop picture of the home page.   This is an "S M F 30 Watter" ( yes that is its model name) As its name suggests it is a 30 watt class A amp from the Mark Sampson stable of Matchless & Badcat .   S M F stands for" Sonic Machine Factory" .  Just like Matchless & Badcat amps, it is built like the proverbial brick outhouse, over engineered with the massive transformers and top class components.  I think these were made during a spell of, shall we say between jobs, if you get my gist!

Below are some pictures of the amplifier the owner is Dan Anderson.  Dan also has a Matchless DC50 he plays in a local band Motel 6.

Front view, the SMF logo has a revolving array of led's
which stop when in standby mode.
 
Front panel removed
 
Three images of the unusual rear opening flap, attached at the bottom with a piano hinge, and locking side catch giving the choice of a closed or open back.
 
Chassis top view, valves mounted inside.
 
Neat PCB 5 X 12AX7 & 2 X EL34 Note the dark grey cathode bias resistors
 
The four diodes of the solid state rectifier as fitted to this amplifier.
 
A hole has been pre - cut for an optional valve rectifier
 

I will load a picture soon of the chassis mounted in its new cab as it is now.

I have no schematics or any service information for this S M F 30 Watter amplifier.  One thing I will say is, that is gets very hot!  Needs a cooling fan.

 

This is an unusual cast brass logo I removed from a 1961/2 AC30 many years ago.  In all my years in this business, I have never seen another like it.  I wonder if Jennings had a run made, and found they were just too expensive.  I would be interested to know if you may have one, or seen one like it.  This is no home made effort, it is a really professional part.

Have a look at the front and back images.

 

Copyright (C) John Beer     Jan 2007 All rights reserved

   

                                      

                                                                                               Old time muso,  just loves this line sexy modelling amp!!!

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