Garnet pa 5 channel head

[MikeR670]

Could anyone advise me on the possibility of modding this into something similar to a Liverpool? It uses a 12au7 for reverb and another for something else. Then four 12ax7s and two pairs of 6ca7s. I'm having trouble following it's signal paths, never built an amp before. Any thoughts or ideas much appreciated!

[xtian]

Wouldn't want to "mod" that into anything. Just strip it down and start whatever amp you want from scratch.

[MikeR670]

Thanks Xtian, I had a feeling that might be the response.......I guess I was looking for an easy route, having never built one before

It has tons of parts, good size transformers etc, I suppose they'll all be useful in a scratch build. Back to trying to learn to build something from a schematic! Thanks again, great to get an opinion from someone who knows how to do this stuff.

[David Root]

Those power tubes look like '70s GE 6CA7 "Fat Boys". If so, make sure you keep them, they are great sounding tubes! Assuming they are still OK, they are worth probably at least $50 each.

A 100W Plexi with those would be a worthwhile build!

[MikeR670]

Hey thanks for the info David, I'll have a closer look at them!

Here's my issue: I plugged it in to test all the inputs/ reverb etc and it sounds better than my 2010 fender super champ xd

It won't distort (I guess no one wants vocal distortion at any volume), and it doesn't go very loud. My xd is louder and this pa is called a "400" lol.

But with a little boost before it, the Garnet overdrives really warm, sweet and very musical.

I'm leaning towards rejuvenating it and using it. If I could get the loudness up and figure out a way to link a couple channels for additional gain, it might be good. Any ideas?

[David Root]

Since it's a PA its inputs likely need a good bit more voltage in for full power out than a guitar can provide.

Would need a schematic at least. I have the Garnet amps book that came out a few years ago, I'll see if I can find it.

[MikeR670]

That would be great, thanks! I've searched everywhere on the net but can't find a schematic. No schematic in or under the unit either. Tried to trace wiring using various net amp schematics, but it doesn't make sense to me.

I thought if I could find the power out of the preamp from channel one, I could feed it into the power in of channel two, etc. But it isn't wired that way, it seems to share tubes and I see that several channels appear to be linked across tone pots and then get mixed into the 12au7 reverb tube. Beginners nightmare ha.

[David Root]

I think I found the 5-input preamp schem w/ 12AU7 reverb. The 4x6CA7 w/6SN7 PI power amp schem is a bit less well-defined. There are several versions and none have the exact same name as your nameplate but I'll sort thru them and post 'em in the morning.

[MikeR670]

That's great! Much appreciated!

I really think this unit has great possibilities, the more I play it the more I hear. Thinking I could rip off the big faceplate and reorder the controls, deleting the unnecessary inputs/ channel designations etc - then build a new face and cab to suit.

I found a model number on the back, G400PAR, hope that helps. Anything close will help me get rolling. Thanks again!

[David Root]

OK G400 PAR 5 Channel Preamp is what I have. This appears to connect thru point Y to the power section. Power section shown is only 2x6CA7 and uses 12AU7 PI instead of 6SN7, but notes also refer to 400 models with 4x6CA7.
12AU7 is just a 9-pin version of the 6SN7.

I've also included the power section of the BTO 400 which shows a 4x6CA7 arrangement and the PI refers to "earlier models using 6SN7". May be helpful.

There are lots of other schems but these are the closest I think. Good luck! Garnet built solid stuff, similar in some ways to Traynor, also a Canadian builder.
Garnet built its name doing stuff for BTO including the famous Herzog for Randy Bachman.

[M Fowler]

That old Garnet PA of yours is a sweet unit, I would have a blast tearing into that. Enjoy.

[MikeR670]

Great detective work and thanks for your efforts David! Gives me lots to think about - and something to follow. My next move will probably be to see if I can drive Ch 1 into Ch 2.

Cool bit of history there, always admired Randy Bachman's tone, searing but thick and bluesy somehow. Maybe I could use part of the unit to build a Herzog circuit inside........label it Ch 2 and it just drives into one of the remaining clean channels......

[MikeR670]

Thanks M Fowler, it's really growing on me the more I play through it. It's a bit of a beast at around 60 lbs, but seems like something with decent possibilities - my first build/ mod attempt, so we'll see how that goes

[David Root]

Here's the official Randy Bachman's Herzog schem. No idea what the layout looks like, but there may be pix on the net.

Shouldn't be too hard to add on the existing chassis. Use one of the extra 12AX7s, and drill out another extra 12AX7 hole for an octal socket for the 6V6. You'll need a step drill with 1 3/16" step in it. Sounds tough but I found a cheap one, Chinese of course, boron nitride coated, OK for occasional use.

[MikeR670]

Perfect thanks! I have a step drill bit, picked up a two pack from Canadian tire the other day. They had it reduced from $60 to $17, my lucky day I guess. You know when you see a deal, no idea what you'll use it for but at that price you gotta have it lol

Let the mods begin! Doing some study on reading and interpreting schematics first. Downloaded a fender amp schematic plus the actual chassis layout so I can compare and learn. Thanks again David!