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a visit to THD and Andy Marshall

7/11/2003 1:57 AM
Greg Simon	a visit to THD and Andy Marshall Hello everyone. I had the opportunity yesterday to stop by THD Electronics in Seattle. (i.e. the makers of the Univalve in case you didn't know) I know a guy who knows Andy Marshall and so we went down there. I was VERY impressed by everyone there, and also by the product. The Univalve and Bivalve are made very well, using top notch components and methods of construction including steel plates inside the chassis isolating the various sections from each other as in Mil-spec stuff. We got a chance to listen to (and play) both amps in a test room with Ed Degenaro handling the guitar. (he's a fabulous player by the way) Very versitle amps, and they sound very nice too. I especially liked them with the KT66's. Andy Marshall was obviously very busy, but took a couple minutes to take a look at my project amp and offered some useful advice. I can't say enough about how gracious and knowledgeable he is. He lives and breathes amps from what I can tell! All in all, a very worthwhile trip, though if anyone else is planning one, I would be sure to call ahead as we did as they seem to be permanently very busy! Greg

7/11/2003 1:57 AM

Greg Simon

a visit to THD and Andy Marshall

Hello everyone. I had the opportunity yesterday to stop by THD Electronics in Seattle. (i.e. the makers of the Univalve in case you didn't know) I know a guy who knows Andy Marshall and so we went down there. I was VERY impressed by everyone there, and also by the product. The Univalve and Bivalve are made very well, using top notch components and methods of construction including steel plates inside the chassis isolating the various sections from each other as in Mil-spec stuff. We got a chance to listen to (and play) both amps in a test room with Ed Degenaro handling the guitar. (he's a fabulous player by the way) Very versitle amps, and they sound very nice too. I especially liked them with the KT66's.
Andy Marshall was obviously very busy, but took a couple minutes to take a look at my project amp and offered some useful advice. I can't say enough about how gracious and knowledgeable he is. He lives and breathes amps from what I can tell! All in all, a very worthwhile trip, though if anyone else is planning one, I would be sure to call ahead as we did as they seem to be permanently very busy!
Greg

7/11/2003 8:02 AM
Chris ( CMW amps )	Hi Greg That's a cool story . Let us know about your project amp ! Chris The Netherlands Ps Most of the time when I'm visiting a fellow amp-builder accidents do happen like fire and the 9-11 attacks while visiting VoodooAmps .

7/11/2003 2:06 PM
timf	Sounds cool. What type of tubes were they using? I figure their going high grade, but you were there and saw. Maybe you could explain the sound of the amps too. Thanks, Tim F

7/11/2003 5:55 PM
Greg Simon	Hi Tim. The KT66 they were using was one of the Chinese ones. I think the others (6L6, EL34, EL84)were JJ, and maybe a Sovtek too. There would be subtle differences if they were using different brands, but we were playing an amp in the test room, and I would think they would be more concerned with making sure the amp is working correctly. Not too much buzz and all that. Ed Degenaro was just grabbing tubes and switching them out...he didn't seem too interested in the brands per se. There wasn't any NOS tubes that I could see. It makes sense to me in a way because if you are designing a new amp for production, why use tubes that are not readily available in reliable quantities. Sound is subjective of course, but I'll try my best. The Univalve sounded very thick and articulate. It is Class A of course since it is single ended, so that makes sense. The Univalve has high and low voltage, and a hot plate incorporated into it, so there is a lot of versatility in the sounds you can get. It would clean up nicely if you backed off the volume no matter what the setting, and it really ripped when you turned the gain up, but was never harsh. I would give it a vibe somewhere between an AC30 without the high end chime, and a cranked Marshall Plexi getting into JCM800 range. The BiValve was very similar, except that because it was two power tubes, it had more grunt and authority in the bottom end. It was cool also in that you could use two different power tubes at the same time. Say one 6L6GC and one EL34 for example. Either amp is the perfect gigging amp because of the versatility and the hot plate incorporated into it, so you can vary how much of the signal you're sending to the speakers. If I had the dough I would be happy with either one of them! Greg

7/11/2003 5:55 PM

Greg Simon

Hi Tim. The KT66 they were using was one of the Chinese ones. I think the others (6L6, EL34, EL84)were JJ, and maybe a Sovtek too. There would be subtle differences if they were using different brands, but we were playing an amp in the test room, and I would think they would be more concerned with making sure the amp is working correctly. Not too much buzz and all that. Ed Degenaro was just grabbing tubes and switching them out...he didn't seem too interested in the brands per se. There wasn't any NOS tubes that I could see. It makes sense to me in a way because if you are designing a new amp for production, why use tubes that are not readily available in reliable quantities.

Sound is subjective of course, but I'll try my best. The Univalve sounded very thick and articulate. It is Class A of course since it is single ended, so that makes sense. The Univalve has high and low voltage, and a hot plate incorporated into it, so there is a lot of versatility in the sounds you can get. It would clean up nicely if you backed off the volume no matter what the setting, and it really ripped when you turned the gain up, but was never harsh. I would give it a vibe somewhere between an AC30 without the high end chime, and a cranked Marshall Plexi getting into JCM800 range. The BiValve was very similar, except that because it was two power tubes, it had more grunt and authority in the bottom end. It was cool also in that you could use two different power tubes at the same time. Say one 6L6GC and one EL34 for example. Either amp is the perfect gigging amp because of the versatility and the hot plate incorporated into it, so you can vary how much of the signal you're sending to the speakers.
If I had the dough I would be happy with either one of them!
Greg

7/11/2003 6:07 PM
Greg Simon	Hi Chris. No accidents happened on this visit thankfully! We were going to see Mike Soldano too, and we did stop by his shop which happens to be not very far away from THD, but Mike had to step out and we missed him. My project amp is one I've been working on off and on for the last 5 years or so. Teaching myself about everything at the same time. It started life as a Conn Organ power amp, which I am modding into a guitar amp. Or three guitar amps anyway! There are 3 power amps in the Conn chassis, which I am leaving stock for the moment. I am building three new preamps for it in a seperate chassis, but all in one head unit. Once I get the preamps done, then I'll tweak the power amps to suit. Originally, there were two power amps with a pair of 7027's, each with their own output transformer, and running around 450 volts on the plates. There was also a pair of 7868's with their own output transformer, running about 405 volts on the plates. I've changed things a bit and now have a 6L6GC pair, an EL34 pair, and the 7868 pair. A little more versatility perhaps. The preamps will be an assortment for versatility reasons. The first is a hodgepodge of different features from the Blackface Bassman/Silverface Bassman circuits, but it will also have the single triode bias modulating tremelo from the Princeton. This one will be fixed bias. The second section is using an EF86, into a cathode follower, into a 2nd Marshall gain stage, into a Vox tone stack, into a see saw inverter (it was already in there, but has different values from the norm), and then into the 7868 section, which will be cathode biased. The third section will be a 2204 Marshall circuit, with internal channel switching using Jfets. The output section will be EL34's, fixed bias, just like the Marshall. I'll tell you what thought....the next project I do will be simpler for sure! This one has taken me so long mostly because I've made it difficult by trying to do so many things with it. But it will be cool when I get it done for sure! What projects are you working on Chris? greg

7/11/2003 6:07 PM

Greg Simon

Hi Chris. No accidents happened on this visit thankfully! We were going to see Mike Soldano too, and we did stop by his shop which happens to be not very far away from THD, but Mike had to step out and we missed him.

My project amp is one I've been working on off and on for the last 5 years or so. Teaching myself about everything at the same time. It started life as a Conn Organ power amp, which I am modding into a guitar amp. Or three guitar amps anyway! There are 3 power amps in the Conn chassis, which I am leaving stock for the moment. I am building three new preamps for it in a seperate chassis, but all in one head unit. Once I get the preamps done, then I'll tweak the power amps to suit. Originally, there were two power amps with a pair of 7027's, each with their own output transformer, and running around 450 volts on the plates. There was also a pair of 7868's with their own output transformer, running about 405 volts on the plates. I've changed things a bit and now have a 6L6GC pair, an EL34 pair, and the 7868 pair. A little more versatility perhaps.
The preamps will be an assortment for versatility reasons. The first is a hodgepodge of different features from the Blackface Bassman/Silverface Bassman circuits, but it will also have the single triode bias modulating tremelo from the Princeton. This one will be fixed bias.
The second section is using an EF86, into a cathode follower, into a 2nd Marshall gain stage, into a Vox tone stack, into a see saw inverter (it was already in there, but has different values from the norm), and then into the 7868 section, which will be cathode biased.
The third section will be a 2204 Marshall circuit, with internal channel switching using Jfets. The output section will be EL34's, fixed bias, just like the Marshall.
I'll tell you what thought....the next project I do will be simpler for sure! This one has taken me so long mostly because I've made it difficult by trying to do so many things with it. But it will be cool when I get it done for sure!

What projects are you working on Chris?

greg

7/11/2003 7:09 PM
Chris ( CMW amps )	Hi Greg Seems to be very cool ; living in California . Your TripleAmpProject sounds wicked but I can truly understand it's a time consuming project . Many projects over here . Due to the bad economic situation over here in the Netherlands I did loose my dayjob some months ago . That was the reason for me to turn my on-the-side-amp-job into something "bigger" . Did start advertising ( repairs , mods and custom-builts ) and more and more people are bringing amps for repairs and mods . Did also make a deal with a guitarbuilder+shop to sell my "PaisleyWrecks" ( see http://home.hetnet.nl/~chrisdus/black_paisley.jpg for an example ) . When I'm rebuilding an amp I do always use a Paisley panel to make it kinda "special" ( a guy really wants to have a Paisley panel on his '70 Marshall too , no kidding ! ) . Some time ago I did meet a guy who did offer me to build some chassis and cabs to have some "new" amps . The plans are : plexi-based , 50 Watts with EL34s or KT66s and - of course - the famous OEI OT ) . Latest finished project : mini Plexi ( 2 x 6V6 ) , right now I was working on an old Selmer PA amp . Did paint the amp Ocean Blue and the front is gonna be Paisley - very 60/70s looking - . The circuit will be kinda like an SLO100 . Then I've another pa-amp ( probably 2x5881 with a high gain pre-amp ) and I really need/want to rebuild an old EL84 pp hifi amp with an EF86/EF184 pre and just one volume-control . back to my bench Chris

7/11/2003 7:09 PM

Chris ( CMW amps )

Hi Greg

Seems to be very cool ; living in California .
Your TripleAmpProject sounds wicked but I can truly understand it's a time consuming project

.

Many projects over here . Due to the bad economic situation over here in the Netherlands I did loose my dayjob some months ago . That was the reason for me to turn my on-the-side-amp-job into something "bigger" . Did start advertising ( repairs , mods and custom-builts ) and more and more people are bringing amps for repairs and mods . Did also make a deal with a guitarbuilder+shop to sell my "PaisleyWrecks" ( see http://home.hetnet.nl/~chrisdus/black_paisley.jpg for an example ) . When I'm rebuilding an amp I do always use a Paisley panel to make it kinda "special" ( a guy really wants to have a Paisley panel on his '70 Marshall too , no kidding ! ) .
Some time ago I did meet a guy who did offer me to build some chassis and cabs to have some "new" amps . The plans are : plexi-based , 50 Watts with EL34s or KT66s and - of course - the famous OEI OT ) .
Latest finished project : mini Plexi ( 2 x 6V6 ) , right now I was working on an old Selmer PA amp . Did paint the amp Ocean Blue and the front is gonna be Paisley - very 60/70s looking - . The circuit will be kinda like an SLO100 . Then I've another pa-amp ( probably 2x5881 with a high gain pre-amp ) and I really need/want to rebuild an old EL84 pp hifi amp with an EF86/EF184 pre and just one volume-control .

back to my bench

Chris

7/11/2003 6:09 PM
Sleebo_The_Beebo	Cool man! Andy Marshall is one of those people who truely is an innovator. It's OK to do nice clones of Fender and Mashall amps, but what THD is something totally different and something to be respected. They make original amps. Great stuff.

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