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6/3/1999 7:00 AM
Hi there,  
Today is my lucky day: At the engineering department (where I study) they are dumping old valve stuff. Here's what I've saved so far:  
4 Mullard GZ34 NOS  
3 Mullar 5R4 NOS  
4 350V/250mA valve power supplies  
3 valve wave generators  
and the best of all:  
2, yes 2 Heathkit MA-12 Monoblock amplifiers with 2xEL84, GZ34, ECC83 splitter and EF86 preamp.  
This is not to make people envious, i just want to show how happy I am. Nobody here can understand me smiling all day after taking away 'some old junk'. It takes real gearheads to appreciate the joys of finding old valve stuff  
I need some advice on the Heathkits. They are in good condition and I am thinking about modding the as guitar heads (VOXAC15 with EF86 preamp and tweed deluxe w. EL84's).  
I feel a bit bad though because these babies are really nice and i could surely make 'em work for HIFI. Should I mod them or restore them, that's the question.  
6/3/1999 7:25 AM

Congrats, I've had similar luck here at work lately too... junk to one is treasure to another, eh?  
Sounds like you got an abundance of stuff to get started on a new project, but if it were me, I'd reserve those Heaths for HiFi.  
(you gotta listen AND play, right?)  
I'd bet Triode Electronics might have the schemes online for those units.  
... Whit
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6/3/1999 9:56 AM

Thanks (Bruce as well),  
Sorry about the double post. I can't believe my luck: I just found the original manuals which contain the schematic and complete building instructions for assembling the amps.  
The OT is ultra-linear (-3dB at 15Hz & 20 kHz, 12W @ 0.5% THD) and it would be a shame to use such nice HiFi equipment for a LoFi application as guitar. So I'm not going to hack up these amps. I'll put new filter & coupling caps in and check the valves. This will be such an upgrade from my shitty JVC mosfet amp. It looks 10 times cooler anyway.  
I will try and run my guitar through them as well, just want to see what happens.  
6/3/1999 12:10 PM

Nice score! It's rare to find a matching pair of old mono amps. The low power stuff with good transformers seem to have better high frequency detail than the high power amps of that era. You'll enjoy listening to them in your living room.  
Looks like you've also scored a lifetime supply of primo rectifier tubes. Bruce & I both like the 5V4s. The GZ34(5AR4) Mullards have no equal in performance and reliability. You can run those small mono amps with 5V4 rectifiers, and save the 5AR4s for other higher power amps & guitar amps running tubes like 6L6s.  
Bruce pointed you to a neat Heathkit site. The MA-12 amps aren't listed, but many others are, and some nice historical data. Also, I'd recommend you check out Sheldon Stokes' site at He's got some photos & schematics of a few Fisher & Heath EL84 amps similar to yours. You could e-mail him. He's a cool dude, and he may have some useful advice or info regarding upgrading your amps for more listening enjoyment.
6/5/1999 7:26 PM

Hey all;  
I'm with Doc and Bruce...5V4's are AMAZING!!! the Mullard GZ34's are making me drool!!! (ha, ha)  
I'm very happy for you!  
6/3/1999 9:06 AM

Here's a url that might get you pointed in the right direction.  
Mission Amps
6/3/1999 2:52 PM

Hey that's nifty. I posted twice by error, you replied to the 2nd message. Now you've ended up on the first thread. Is this tboy's excellent software or something else. Whoever it was, thanks for correcting my mistake
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