Garnet pa 5 channel head

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MikeR670
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Re: Garnet pa 5 channel head

Post by MikeR670 »

Hey David, just wanted to report that I managed to run channel three into four and it sounds incredible. Huge overdrive with no muddiness. Very like "Jet - cold hard bitch". Roll back the guitar volume and it cleans right up! Stoked, and ready for band night tonight! Thanks for all your help, much appreciated :D
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RJ Guitars
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Re: Garnet pa 5 channel head

Post by RJ Guitars »

I'll join along just to see where it all ends up. I always thought the Garnet stuff was very cool although I think the engineering end of it was far more advanced than a Trainwreck
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MikeR670
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Re: Garnet pa 5 channel head

Post by MikeR670 »

So, as an update, I've stripped the unit down because I'd like to build a Single Ended small wattage head from it. Partly because in the schematics it looks like a parallel SE, but even if not, I'm hoping the OT could handle a single 6550. It came with 4 of those and a bunch of 12ax7s, and a couple 12au7s.

My intention is to end up with a small (but heavy lol) 8-12 watt unit that I'll run through my 2x12 cabinets. Really would like a lower volume but high clean headroom setup, with a creamy breakup when pushed. All without high volume levels.

Ideas much appreciated!!
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RJ Guitars
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Re: Garnet pa 5 channel head

Post by RJ Guitars »

I built a SE amp with a single KT88 (similar specs to your 6550) and it really had a good sound... plenty loud too.
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didit
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Re: Garnet pa 5 channel head

Post by didit »

It's Garnet's PA based on the Pro 400 chassis: http://www.garnetamps.com/400chassis.htm. There are schematics floating around. Look for LB200S. That's a >100W amp, hence the heavy iron. The last time I poked one it had ~530V at the plates. Attempts converting to SE will turn out badly. No gap etc., etc. One should easily be able convert to guitar or bass by removing the panel with all the PA controls and putting standard instrument controls on it.

It should have power to deafen you as is, or at least with general repairs a 40+ year old amp requires. The original main power caps are almost always failed and those do look stock original from '70s. Realize it's probably wired to drive 4ohm speaker load.

There is a Yahoo board for Garnet. Apparently many have migrated onto something called a Face Book page???

Best .. Ian
MikeR670
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Re: Garnet pa 5 channel head

Post by MikeR670 »

didit wrote: Wed Mar 15, 2017 10:15 pm It's Garnet's PA based on the Pro 400 chassis: http://www.garnetamps.com/400chassis.htm. There are schematics floating around. Look for LB200S. That's a >100W amp, hence the heavy iron. The last time I poked one it had ~530V at the plates. Attempts converting to SE will turn out badly. No gap etc., etc. One should easily be able convert to guitar or bass by removing the panel with all the PA controls and putting standard instrument controls on it.

It should have power to deafen you as is, or at least with general repairs a 40+ year old amp requires. The original main power caps are almost always failed and those do look stock original from '70s. Realize it's probably wired to drive 4ohm speaker load.

There is a Yahoo board for Garnet. Apparently many have migrated onto something called a Face Book page???

Best .. Ian
Hey thanks, I wanted to bring this topic up because I've come across some opinion conflicts here. This is quoted from a discussion on another forum, by Ronsonic (it's old and I hope it's ok to use it):

"While he is correct that the transformer is not designed for unbalanced operation and will be less than optimal, we are talking about using it in an application that severely derates it. Most transformers are not stacked that tightly and an oversized PP tranny will often work in a lighter loading SE application. We are talking about maybe 15W max from a 6550. So that's one option, just do it. Yeah, you'll probably get a crossover notch at any but very low power, but that isn't necessarily a bad thing. If the tranny is as overbuilt as you suggest this may work out well."

I even wondered about using only the 12ax7 and 12au7 tubes throughout, in some order that might give higher cleans before a relatively soft creamy breakup begins......
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didit
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Re: Garnet pa 5 channel head

Post by didit »

MikeR670 wrote: Thu Mar 16, 2017 4:04 am
Hey thanks, I wanted to bring this topic up because I've come across some opinion conflicts here. This is quoted from a discussion on another forum, by Ronsonic (it's old and I hope it's ok to use it):

"While he is correct that the transformer is not designed for unbalanced operation and will be less than optimal, we are talking about using it in an application that severely derates it. Most transformers are not stacked that tightly and an oversized PP tranny will often work in a lighter loading SE application. We are talking about maybe 15W max from a 6550. So that's one option, just do it. Yeah, you'll probably get a crossover notch at any but very low power, but that isn't necessarily a bad thing. If the tranny is as overbuilt as you suggest this may work out well."

I even wondered about using only the 12ax7 and 12au7 tubes throughout, in some order that might give higher cleans before a relatively soft creamy breakup begins......
You definitely will get sound out of it. Hard to do damage. Perhaps just frustrated getting what you have in your mind's ear. Suggestion was, make it work as designed with minor mods suiting taste. An easier path. Will watch with interest should you go either way.

Best .. Ian
MikeR670
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Joined: Sun Jul 10, 2016 7:56 pm
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Re: Garnet pa 5 channel head

Post by MikeR670 »

Thanks Ian! I really appreciate your knowledge and all suggestions. Having not built one before I see that without experience it will be a minefield. I have to start somewhere I guess, I'm contemplating buying a kit like the ax84 p1 type and work from there toward my own particular sonic goals.

I love the idea of creating it from the pieces I already have but trying to learn the rules and relationships from research alone may be a long ride ha.
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