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re: matchless and other class A amps


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3/26/1999 4:56 AM
GFR

re: matchless and other class A amps
I've read that the old speakers are great. It seems that you can buy some not-so desirable old VOX transistor amps for a reasonable price just to get the speakers. I'll look for the article and post it.
 
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3/26/1999 7:55 AM
tg
"...modern speakers and trannies may not be able to capture the sound of the old ones..."  
 
Jump over to:  
http://www.celestion.com/pro/index.htm  
Then go to "Guitar" then "Download Soundfiles" and you'll be able to listen to a quick demo of Celestion's new Alnico Blue - possibly the closest you'll come to that original sound these days (with a new speaker anyway).
 
3/26/1999 9:34 AM
Benjamin Fargen
Subtle differences.......
Steve,  
I have an original Vox amp that is all stock including the original bulldog speaker(except for a cap job) and no other amp sounds quite like it. I would have to say it is a combination of all the things you mentioned.(trannies, speakers ect.)Even if you replicate the caps, resistors, ect. there is no way to actually know what Vox had in stock and used on their different amps  
throughout the years.  
 
I would also have to give some thought to G.Webers's article on the Bassman vs.JTM 45. These amps have the same layout and parts values, but the fact that the chassis material was different for each amp gave a different sound and response from the signal running to the chassis for ground. Not to mention the fact that the trannies and speakers were completely different manufactures.  
 
I think you nailed exactly why we all continue to build amps........ to see first hand how close you can come to the original and what makes the biggest differences in tone.  
Plus its a blast!!!!  
Benjamin.
 
3/28/1999 11:58 PM
Niek
AC30 schematic
Steve,  
 
I sent you a clear AC30 schematic by email. It is from a german tube amp book and seems OK. It probably is a later model AC30 since it lacks the tube rectifier but you should be able to work that out from the Pittman book. As far as I can see the rest of it is OK. It at least gives you a clue how the Top Boost section is wired into the amp.  
 
The Top Boost preamp is wired in the same way in the AC 15, which is nearly identical to AC30, just two power tubes less. Phase splitter is exactly the same, just put the Top Boost preamp before it. You can find the AC 15 at: http://www.triodeel.com/ac15.jpg  
 
If anybody else wants the AC30 schematic let me know, I'll mail it to you. I got it somewhere from the net ages ago and have completely forgotten from which site.  
 
Cheers,  
Niek
 
3/29/1999 3:20 PM
Bob S

If you're replying that the AC-15 in the schematic below you need to know that an AC-15 amp is a completely different amp than an AC-30 and that an AC-15 is not top-boosted. You have to modify an AC-15 in order to top-boost it.  
 
Bob S.
 
3/29/1999 4:25 PM
Bob S
re: matchless and other class A amps
Sorry it took me so long to get back to you but I was down in Dallas at the guitarshow. (That's gettin to be a bit of a joke).The first thing I must say is that I've worked on dozens of these things and everyone of them needed attention. You must make sure if someone is going to work on one that they know AC-30 amps, because it takes awhile to learn where the very specific places that these amps will fail. I'm not just talking about technical failure, I'm talking about tone failure. Unless a repair man really knows what an AC-30 should really sound like you will probably get short changed!  
I've changed several failed parts with modern parts including AC-30 reissue output trans into an old one and it still retained great tone. I've also used a New Sensor mop-50 marshall trans in an AC-30 with great results.I can say this with fact and confidence because at all times I've had aleast three AC-30's side by side for point of reference and tone comparison. So I think you can still build a great sounding AC-30 with today's available transformers and tubes, etc.  
I'm currently building an old AC-30 chassis with a rewound AC-30 pwr trans and a Matchless 15 watt output trans and will use a top-boost and complete AC-30 frontend into two EL-84's. I'll let you know how it turns out. If you have any other questions I can get very specific if need be!  
 
Bob S.
 
3/30/1999 12:15 AM
Carlo

I agree. I've built two of 'em from scratch w/ all new parts and they both sound extremely good. I used a Hammond power tranny and Hoffman's 30 watt output transformer. These amps are incredibly sweet sounding.  
 
Carlo
 

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