Demeter TGP-3?

[pwurso]

Sean, thanks for the time you're putting into this and sharing it with us! I can't wait to see what you find.

[TUBEDUDE]

At least he used goop to stabilize components instead of trying to obscure components and circuitry like some other over hyped designer.

[pwurso]

Anything new to report?

[caphead]

*edit

[Vertigo]

I haven't done any poking around since I made my last post on this topic. Space it too tight at my house to keep it open for very long and time is too tight to do anything about it now. It'll likely be wintertime before I have enough time to open it up again.

I do have a new TGP-3 that he's supposed to send out next week. I'll pull the lid off that when I get it and maybe we'll get a couple of clues. I don't think it's changed much over the years according to Jim and on the up-side, he's building them again and in the grand scheme of things they're not terribly expensive.

[caphead]

*edit

[Wiseblood]

I'm really looking forward to seeing this one. Any more progress on the schematic?

[Vertigo]

I'm really looking forward to seeing this one. Any more progress on the schematic?

I'm making one and for now, I've decided to keep it to myself. James is still in business and is selling them, albeit slowly, so it doesn't seem right to publish the schematic. At the time I started the layout of the TGA and published what I had, his site stated that it was discontinued and putting the info out into the world seemed fair enough.

I'm going to be honest, the bottom end sounds really bad on the two high gain channels. It's super loose and any palm muting of notes lower than about the D3 are fuzzy and rumble for much longer than they should. I modified Ch2, which is sounding good now unless I hit the boost switch, and I'm currently trying to figure out how to tame it in Ch3.

[JD0x0]

I'm really looking forward to seeing this one. Any more progress on the schematic?

I'm making one and for now, I've decided to keep it to myself. James is still in business and is selling them, albeit slowly, so it doesn't seem right to publish the schematic. At the time I started the layout of the TGA and published what I had, his site stated that it was discontinued and putting the info out into the world seemed fair enough.

I'm going to be honest, the bottom end sounds really bad on the two high gain channels. It's super loose and any palm muting of notes lower than about the D3 are fuzzy and rumble for much longer than they should. I modified Ch2, which is sounding good now unless I hit the boost switch, and I'm currently trying to figure out how to tame it in Ch3.

If you don't mind sharing the schematic privately for academic reasons, I could probably suggest a few things to improve the bottom end.

[caphead]

Here's the Effects Loop section:

Demeter TGA3 Stereo FX Loops.jpg

And a cleaner version of the preamp schematic without component values (for the sake of clarity):

DemeterTGA-3 Blank Values.jpg

[caphead]

I'm making one and for now, I've decided to keep it to myself. James is still in business and is selling them, albeit slowly, so it doesn't seem right to publish the schematic. At the time I started the layout of the TGA and published what I had, his site stated that it was discontinued and putting the info out into the world seemed fair enough.

With all due respect, this is a 30+ year old design and while I am under no authority to be able to characterize where James Demeter's priorities are these days, a limited number reissue of a late 80s-90s rackmount guitar preamp with a modest cult following doesn't exactly scream top priority when compared to the other cool (and far more practical) stuff Demeter is making now, such as this: https://www.demeteramps.com/index.php?r ... duct_id=98
Or this guy here: https://www.demeteramps.com/index.php?r ... duct_id=82

I'm going to be honest, the bottom end sounds really bad on the two high gain channels. It's super loose and any palm muting of notes lower than about the D3 are fuzzy and rumble for much longer than they should. I modified Ch2, which is sounding good now unless I hit the boost switch, and I'm currently trying to figure out how to tame it in Ch3.

The flub, or most of it is due to that huge .12uF coupling cap coming off V1a. The easiest way to cut the flub would be to reduce the size of that cap to something more conventional like .022uF, although adding a series cap after the .12uF (like how I drew out CH2) would work just as good with the added benefit of better isolating that channel's gain control from the other 2. On the TGA-2, every channel gets it's own R/C branch after V1a whereas in the TGA-3 it looks like at least one resistor is being shared by CH1 and CH3; I drew out the schematic using the separate R/C path template of the TGA-2 for the sake of clarity but the (vast) range of values I used were based on pics of yours and 2 other TGA-3s and 2 Demeter Marshall mods.

If you don't mind sharing the schematic privately for academic reasons, I could probably suggest a few things to improve the bottom end.

The only people who benefit from this irrational allure of secrecy are collectors and even then it's not actually true, if it were, Dumbles would be worthless. I traced out the first Diezel Vh4 schematic about 10 years ago

Diezel_VH4_Preamp_rough_draft.jpg

despite that, they still sell for over $4,000, actually it's closer to $5k these days, so really the value has increased.

And, for anyone who's reading the TGA-3 schematic with a slight hint of dejavu and wondering where you've seen something like it before, let me refresh your memory:

CAE CAA-3+ SE.png

I see: the big input cap, effects loop driver (the Bob Bradshaw AC follower circuit, 680R-1M-47k cathode with 47k plate load resistor) and the 220-270p treble cap with 33k slope tone stack.

[Vertigo]

It's not my place to guess what James' priorities are. When I bought my TGP, he said he was working on eight of them concurrently and received orders for half a dozen more before he delivered mine. To me that says that he's still in the business of making them so it doesn't seem right for me to publish a schematic. I assumed wrongly, when I shared the layout of the TGA, that he wasn't doing them anymore (his website said as much at the time) which is why I felt it was OK to share. I left it up since it had been there for a year or more and if I took it down, undoubtedly someone else can post it again. People can figure out the majority of what's in the TGP from the layout I posted even though there are a few errors in it.

I get what you're saying, it's a 30 year old niche product and it borrowed from predecessors, but IMO, it's still his design, he's still making them and I'm not going to potentially take food off the guy's plate if he's still building them.

[caphead]

My theory on the issue is that specific circuitry and sound quality is far less important than brand and notoriety and it's assessed value in the retail/second hand market. This circuit sitting inside of a Ceriatone chassis built by some random Diy'er isn't going to turn it into a $3000 amp, what makes the TGA/P-3 valuable is that it's made by Demeter. It sounds like I'm saying something really obvious like "the sun rises every morning" but brand recognition is paramount above all other factors in almost every sector of the consumer economy. Take for example a heavily cloned/ripped off design like the SLO, despite it, a real Soldano is still worth more today than when it was new. On the other side of this you also have people who would never be able to afford something like a Demeter or Soldano. If that person buys a clone for a fraction of the cost, does that mean Soldano or Demeter lost out on a potential sale? No they didn't; that person would never have been able to afford the real thing and if not for the clone, they would have settled on something else within their limited budget. An interesting phenomenon I have seen happen is that someone playing a through a budget version of their favorite amp will be motivated to save up and buy the real thing. I had someone I did a Diezel-ish mod for who a few years later ended up buying a real Diezel, first a Herbert and then he sold it to buy an Einstein.

PS. If you want to make this all little less visible, we could move everything to the sloclone forum.

[Vertigo]

I get what you're saying and don't disagree with it. However, it doesn't seem ethical for me to post it when he's still clearly in the business of making them. He's approachable and friendly and his gear isn't outrageously expensive, especially considering that he's still going to great lengths to source US made components where possible and the thing is made in CA of all places. I work in a different industry and have had a handful of my designs copied in the past 15 years, by much bigger companies, buy people who should know better. It pissed, changed the way I do my job and I lost out on financial opportunities. I'm not going to do it to James, even though I believe what you wrote is true. When you look inside the amp, the individual stages aren't that different from things we've seen before, but he put it together into relatively unique package. As a wrote before, had I realized that he was still making them, I wouldn't have posted the partial layout. Knowing what I know now, I feel that it was a mistake but it's out there and there's not a lot that can be done about it.

[Reeltarded]

It's not ethical.