Other Amps

Stereo Guitar Amp Build

1

Finally have the amp part of this stereo guitar amp 99% finished. 20 watts a side using 7189s in pushpull.

Basically fender Ab763 (blackface) circuit except for an early 6G11 bias vary tremelo and a James(Baxandall) tone stack on the right channel.

Left Channel has tremelo and reverb and a mix pot to send a pre reverb and tremelo signal to the right power amp.

Right amp is straight up no effects.

This was set up to be used with my roland Re-150 space echo. Dry signal into left channel (then into both power amps). Echo signal gets sent to the right channel and just teh right power amp. Sounds great i have a cabinet I made waiting. Going to use 2 12" lightweight speakers with a slightly outward angled baffle for better stereo spread.

Amp is configured in a tweed sort of style(controls at back on top) in a homemade chassis using a Hammond organ AO-14 PT , hammond organ 20 watt OTs. A 10 henry choke that came from somewhere, reverb transformer and new components and tube sockets.

Still have to add the tiny footswitch panel9for reverb and trem) and then mount in cabinet. Should be under 45lbs.

4

Killer. We may have to talk.

5

Mind bending complexity!Way to go sir!

7

Thanks, it was bit of time in the planning and then execution. Kind of like advanced lego with soldering. It's usually the point where I have to start wiring up the board that I say to myself..'This is lot of work..I'm nuts!" However I've wanted a portable stereo rig for a while. To buy a custom one would cost lot's of money. This one costs maybe $300Can (about $5 US) in hard costs all in plus my time. I like to think I'm learning and in the end saving money being my own tech so that's cool. For those interested in this sort of geekery here's the schematic.

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Oh and a picture of the top. I did a mental oops and aligned the choke with the OTs. It's not as critical but I might fix that.

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Where is the schemo from? Did you draw it yourself?

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Where is the schemo from? Did you draw it yourself?

– GaryE

I used a program called Jschem. It's all fender stuff recreated in Jschem. Which is a fun program if you like that sort of thing. It's like a ab763 deluxe reverb (using 7189s)with bias vary trem(from a 6G11) and a plain deluxe (also 7189s) stuck together with one power supply, two bias adjustments, and a way to mix the one channel into the other. It took some figuring. I got some ideas from the Ampeg Stereo echo twin I had (basically the way one channel is fed to the other.) I credit Hoffmans amplifier forum with some help and guidance in most of my builds though I am growing more independant

13

This is a stereo amp I built about 10 years ago for TV Jones to demo his stereo pickups at NAMM. It's only 10 watts per channel and not as fancy as yours, but the Reverb and Tremolo are in Stereo. I have a Stereo Silver Jet to go with it. I haven't played it in years...maybe I should drag it out next week. It's kind of fun, but not much good for live shows...if you mic it in stereo, one side of the room hears the high strings, and the other side hears the low strings. Only those in the sweet spot get the full effect.

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Are both pickups stereo on the Silver Jet?

Is the amp for sale?

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This is a stereo amp I built about 10 years ago for TV Jones to demo his stereo pickups at NAMM. It's only 10 watts per channel and not as fancy as yours, but the Reverb and Tremolo are in Stereo. I have a Stereo Silver Jet to go with it. I haven't played it in years...maybe I should drag it out next week. It's kind of fun, but not much good for live shows...if you mic it in stereo, one side of the room hears the high strings, and the other side hears the low strings. Only those in the sweet spot get the full effect.

– Billy Zoom

Very cool. And very pretty! It's for split pickups? Mine will look a little more rough and ready. the cab is nice amber coloured baltic birch , but no fancy faceplate, corners etc.

I could have the tremelo on both sides of mine. But iit wouldn't oulse side to side. Is that what yours does? And how'd you do it? Does it have two tremolo circuits?

For me I typically use two amps, dry sound goes in both and echo in one. It makes the echo quite big. I like having reverb in just one side then because them you make a little more use (other than crazy surf reverb) out of the fender style reverb.

As I don't feel like making a new baffle and cutting up my pre-existing cab (from a past build) I'm doing a crazy experiment with these old Rola 12's to achieve a little more stereo spread on stage/outfront(when powering a smaller room) I was very careful not to warp the baskets....

16

I got to road test the amp today at volume. I finished mounting it this cab I've had kicking around for almost 10 years. First it housed a sherwood S-100 conversion with 2 12's then it had my first vibrolux in it with 2 x 10s (at that point the cutouts were done on the back panel) then it was a used as a 2 x 12" test cab. It's 26" wide by 18.5" high by 9.5" deep made of 1/2" baltic birch. I have to make a new back panel and the finish work hasn't been done on the top cutout enlargement. Entire amp weighs in at 45 lbs Pretty good for a 20 watt a side stereo rig with 2 12" speakers.

With the dry sound in both amps and the echo in one it holds up to my mono vibrolux ( I brought them both and was comparing) and would eat a deluxe alive. Definitely could cut it clean with the Colorifics (my original swing/latin band) and probably with the pop/rock band too.

You can hear the stereo effect but obviously it's not as pronounced as 2 amps a few feet apart. An angled baffle would help this. Also I'll be adding an extension jack for my mini leslie cabs so that should help too. I remembered a fake heater centertap at the last minute and that made it even quieter so it's very quiet now.

The 2 x 12" rolas did a good job but i think they're probably 20 watts tops and they're probably 50 years old. not sure how efficient they are. I have a Eminence little texas on it's way for the left amp 4 lbs 125 watt speaker and uber efficient. A Pair of those would probably make this amp into a monster

Over all I'm quite satisfied. it sounds really good.

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and back with old back panel which I need to replace

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Are both pickups stereo on the Silver Jet?

Is the amp for sale?

– Proteus

Yes, and maybe.

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Did some more messing around with this amp Silverfaced the PI. bahaha How often do you here that?! I also installed a Hammond EBZ290 PT. Same one that's used in the reissue 65 twin . The vintage hammond organ PT wasn't quite cutting it for current supply to the amp or heater supply and getting very very hot. Installed castors and maple tilt back arms made from old organ pedals. I also made a new back panel. It's up 50lbs now but still quite portable. I used my Super reverb at a gig last weekend for old times sake and after moving it around for a bit this amp feel like a lunch bucket.

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Any problem with the power transformer getting hot? That's a lot of tubes to handle.

Also what's up with that cap joining the cathodes of the two power tubes on the right channel?

I've never seen that before. Is it non-polar?

Edit: I didn't read your last post. Yea I was looking at that pic thinking there's no way that PT can handle all that current.


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