I've been suggested to put together this amp. Since I don't have any experience whatsoever with tubes, I would be at least interested what do you think about the amp's concept. Is it worth the effort, considering that all the parts are practically available to me
http://www.enjoythemusic.com/magazine/equipment/0105/trex.htm
http://www.tubecad.com/2005/January/blog0031.htm
http://www.enjoythemusic.com/magazine/equipment/0105/trex.htm
http://www.tubecad.com/2005/January/blog0031.htm
Peter Daniel said:
As an introduction to tubes, I think this is a little complex. I don't think you'd have difficulty assembling it with your experience, Peter, but a complex design leaves less room for tweaking and learning. A circuit that uses all simple, grounded cathode gain stages would be better in that respect.
What brings you to this from the world of chip amps?
Peter, go for it! Survey peoples' opinions about regulated output supplies. You'll probably see a majority saying regulation works sonically. Here are thoughts I've had about this issue, which preceded Olsher publishing his new amp. Most amps regulate every other supply to evidently good effect. I suppose the reason output supplies are not regulated is due to added complexity which, if solvable, leaves the problems of added cost and heat. I also note that the Lamm SE amp is receiving accolades from people who sound to me like they know how to listen (J. Valin, among others). The Lamm uses (probably shunt) regulation in its output supply. Also check out the Audio Note comments on a shunt regulated preamp --- AN says "oooh" regarding it.
Perhaps Frank de Grove could relay his experience listening to a regulated-output OTL? I think I recall him saying it was p-r-e-t-t-y g-o-o-d.
Dick Olsher thinks he has a winner, but he might be project-biased, or diy-biased, but I doubt it.
As to the learning component, I have found there's nothing like a good challenge to really get the thinking gears working. Like, use Olsher's regulation with DCMB coupling.
Cheers.
Perhaps Frank de Grove could relay his experience listening to a regulated-output OTL? I think I recall him saying it was p-r-e-t-t-y g-o-o-d.
Dick Olsher thinks he has a winner, but he might be project-biased, or diy-biased, but I doubt it.
As to the learning component, I have found there's nothing like a good challenge to really get the thinking gears working. Like, use Olsher's regulation with DCMB coupling.
Cheers.
Re: Re: The T-Rex SET Amplifier DIY project
It's not that much of an introduction, but more of a challenge. I basically have all the parts in my basement, as Plitron is quite eager to see the completed amps and since Audio Oasis is involved here as well, I'm basically the first candidate to work on it.
Besides, I'm curious myself, and working on something like that should be rather interesting. I already have some ideas about tube amp chassis (the way it supposed to be, not the way everybody's doing it, and I'm quite disappointed with the chassis Plitron supplied: too big and too resonant).
If I see more comments that it's worth a try, I will go for it.
jeff mai said:
It's not that much of an introduction, but more of a challenge. I basically have all the parts in my basement, as Plitron is quite eager to see the completed amps and since Audio Oasis is involved here as well, I'm basically the first candidate to work on it.
Besides, I'm curious myself, and working on something like that should be rather interesting. I already have some ideas about tube amp chassis (the way it supposed to be, not the way everybody's doing it, and I'm quite disappointed with the chassis Plitron supplied: too big and too resonant).
If I see more comments that it's worth a try, I will go for it.
Re: Re: The T-Rex SET Amplifier DIY project
I'd hate to see you tackle something like this amp and have it turn out mediocre from lack of experience (on a pretty well un-excersized design)
Here is something you could throw together pretty quick to gain some tread.... a well worked out simple amp that sounds really good (as long as you have fairly efficient speakers without complex XOs)... went head-to-head with jasonLs redBoard 3875 amps last week and came out ahead (w Fostex FE108ES in B-Horns). If you can scare up Frugal-phile(tm) iron (or pick some of Plitrons EL84 SE iron), like my friends, you can put it together for a weeks or 2 worth of coffee money (the point is to gain some real-world experience with something simple)
dave
jeff mai said:
I'd hate to see you tackle something like this amp and have it turn out mediocre from lack of experience (on a pretty well un-excersized design)
Here is something you could throw together pretty quick to gain some tread.... a well worked out simple amp that sounds really good (as long as you have fairly efficient speakers without complex XOs)... went head-to-head with jasonLs redBoard 3875 amps last week and came out ahead (w Fostex FE108ES in B-Horns). If you can scare up Frugal-phile(tm) iron (or pick some of Plitrons EL84 SE iron), like my friends, you can put it together for a weeks or 2 worth of coffee money (the point is to gain some real-world experience with something simple)
dave
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serengetiplains said:
I'd be surprised if this is the case. There have been numerous and lengthy battles about this issue in other forums where the majority opinion was the opposite - and by a wide margin.
I don't know the answer, but I'm pretty comfortable in saying that it seems quite difficult to better a simple but competant, valve rectified, choke input filtered supply.
Re: Re: Re: The T-Rex SET Amplifier DIY project
I was under the impression that this is a complete and well tuned design. I'm not really planning to do any tweaking, just follow the schematic and parts choices used by the amp's designer:
"A working prototype was built by Ron Cox (RC), which then served as a test bed for various design ideas. Several input stage and driver circuit options were evaluated by RC and DO via listening tests before arriving at a final decision. Three output transformers were auditioned: the Plitron SE-3025 and SE-3050, and the Lundahl 1664. Of the two Plitron transformers, the SE-3025 gave the better impedance match with the T-Rex output stage and was selected for a head-to-head shootout against the Lundahl 1664. Both sets of transformers were mounted on the same chassis, which was wired with a switch and two sets of speaker binding posts that facilitated fairly quick A-B comparisons. The Lundahl was liked for its lush romantic sound, while the Plitron won us over on the basis of its deep bass extension and sonic refinement. For the past year and a half a final T-Rex prototype with Plitron SE-3025 output transformers has been auditioned and tweaked by DO in the context of his reference system. All of the voicing decisions were based entirely on the outstanding TJ Mesh Plate 300B. After much experimentation, DO reports that T-Rex lives up to its moniker in terms of musical passion and drama. "The most musically intense SET amp I've heard to date," reports DO. Not surprisingly, the T-Rex now serves as DO's reference low-power SET amplifier. "
I'll be commisioned to build it, so it's not even for my personal use, as I don't think it would be better than a properly implemented GC [joke]
planet10 said:
I was under the impression that this is a complete and well tuned design. I'm not really planning to do any tweaking, just follow the schematic and parts choices used by the amp's designer:
"A working prototype was built by Ron Cox (RC), which then served as a test bed for various design ideas. Several input stage and driver circuit options were evaluated by RC and DO via listening tests before arriving at a final decision. Three output transformers were auditioned: the Plitron SE-3025 and SE-3050, and the Lundahl 1664. Of the two Plitron transformers, the SE-3025 gave the better impedance match with the T-Rex output stage and was selected for a head-to-head shootout against the Lundahl 1664. Both sets of transformers were mounted on the same chassis, which was wired with a switch and two sets of speaker binding posts that facilitated fairly quick A-B comparisons. The Lundahl was liked for its lush romantic sound, while the Plitron won us over on the basis of its deep bass extension and sonic refinement. For the past year and a half a final T-Rex prototype with Plitron SE-3025 output transformers has been auditioned and tweaked by DO in the context of his reference system. All of the voicing decisions were based entirely on the outstanding TJ Mesh Plate 300B. After much experimentation, DO reports that T-Rex lives up to its moniker in terms of musical passion and drama. "The most musically intense SET amp I've heard to date," reports DO. Not surprisingly, the T-Rex now serves as DO's reference low-power SET amplifier. "
I'll be commisioned to build it, so it's not even for my personal use, as I don't think it would be better than a properly implemented GC [joke]
Peter, the T-Rex is somewhat complex, but not unreasonably so. The signal circuitry only consists of two 5687s and a 300B!
If you are really looking for a challenge, have a look at Steve Bench's 813 Matrix Amplifier. Basically regulated everything, cute magic-eye indicators dancing in time with the music, and the warm glow that only transmitter valves' W-Th filaments can provide
It is very well thought out - to the extent of making sure that the HV disappears if bias is lost, and ensuring the ambient light is sufficient for the gas regulator valves to mainatin a constant voltage drop. But it is extremely complex.
Oh, and it's no slouch when it comes to output power either: 66W per channel.
Of course there's the obligatory safety warning. This thing uses an 800V supply 
If you are really looking for a challenge, have a look at Steve Bench's 813 Matrix Amplifier. Basically regulated everything, cute magic-eye indicators dancing in time with the music, and the warm glow that only transmitter valves' W-Th filaments can provide
It is very well thought out - to the extent of making sure that the HV disappears if bias is lost, and ensuring the ambient light is sufficient for the gas regulator valves to mainatin a constant voltage drop. But it is extremely complex.
Oh, and it's no slouch when it comes to output power either: 66W per channel.
Of course there's the obligatory safety warning. This thing uses an 800V supply 
Peter Daniel said:
So, go for it.Peter Daniel said:
John Broskie is no fool when it comes to tube design, so I'd be surprised if it didn't work very well. And contrary to opinion, it's not that complex, no more so that something that sounds really mediocre like the Flesh and Blood. Shunt feedback works really well; I've been running a Pimm PP47 for a couple of years now and this amp, as well as a couple of others I've built to experiment with has completely changed my mind about FB and pentodes.Peter Daniel said:
If it were PP, I'd try one myself; don't have the iron for SE and I generally don't like SE amps (though I do have a parafeed 813 under construction - mainly because I have the parts and only 3 STC813's). It'd also be interesting to see whether the partial FB works to negate some of the value of the expensive 300B's, ie would a Sovtek be closer to a WE in this amp?
Shunt yes, series no.serengetiplains said:
Peter, I'm looking forward to seeing what sort of chassis you come up with for this amp
I have read the same article too few weeks ago. It sound very interesting but I won't consider to build it in near future.
I have an idea. I think it would be nice to build the amp with separate HT power supply unit. All filament transformer are kept inside the chassis.
Just my 2 cents.
Johnny
I have an idea. I think it would be nice to build the amp with separate HT power supply unit. All filament transformer are kept inside the chassis.
Just my 2 cents.
Johnny
Peter,
I was expecting one of these days you would try your hand at tubes.Anyway this amp seems to have the right pedigree.Of course there are some other ' advanced' set designs out there but then nobody will agree which is the best as always.
I am sure your chassis will be great although for me this guy here has done one of the best ever chassis I have ever seen:
http://www.jogis-roehrenbude.de/Leserbriefe/Drehko-Stefan-6C33C-Amp/Stefan-6C33-Amp.htm
But then who has access to big milling machines?
I was expecting one of these days you would try your hand at tubes.Anyway this amp seems to have the right pedigree.Of course there are some other ' advanced' set designs out there but then nobody will agree which is the best as always.
I am sure your chassis will be great although for me this guy here has done one of the best ever chassis I have ever seen:
http://www.jogis-roehrenbude.de/Leserbriefe/Drehko-Stefan-6C33C-Amp/Stefan-6C33-Amp.htm
But then who has access to big milling machines?
Peter, by all means go for it. I believe the T-REX design is one of the better "newish" designs. The power supply has much more thought behind it than several top of the line commercial and DIY tube amps out there. Also little noise cancellation techniques used will make it very special.
I've considered building it myself as well but was waiting for Audio Oassis to sell the PCB. They say it still not around the corner. Sounds like you have a good relationship with Piltron and AO so you are in a unique position because this no compromise amp will cost around $2K by my guess.
You will have a flag ship amp that deserves it's name. Don't forget all the man hours that has gone into this design by some very very respected names. I think they started thinking about it as fas back as 2001.
The parts list shows some very basic parts except for the Iron of course. Knowing you, you should tap into your pile of boutique caps and resistors.
Good luck and please keep us informed.
Paba
I've considered building it myself as well but was waiting for Audio Oassis to sell the PCB. They say it still not around the corner. Sounds like you have a good relationship with Piltron and AO so you are in a unique position because this no compromise amp will cost around $2K by my guess.
You will have a flag ship amp that deserves it's name. Don't forget all the man hours that has gone into this design by some very very respected names. I think they started thinking about it as fas back as 2001.
The parts list shows some very basic parts except for the Iron of course. Knowing you, you should tap into your pile of boutique caps and resistors.
Good luck and please keep us informed.
Paba
Konnichiwa,
I found the design interesting and an illustration of how you can use two very differnet pathways to attain the results.
I do see some oddities though, that would make me question the actual operation of some of the items and it appears a little as if someone took "building blocks" from a number of philosophies and strung them together somehow with a modest disregard for the inherent philosophies and principles behind the circuits.
Sort of like a horse designed by a comittee.
Some items that would concern me:
1) 300B Heater Supply. That particular approach taken is BAD. Even straight AC sounds better. AT THE VERY LEAST you should use Schottky Diodes and CRC Filtering, preferably some CMC Chokes as well.
2) Output Stage Feedback. Here a 47k feedback resistor sor shunt/parallel feedback is connected into the output of a 5687 SRPP (maybe 1K output), which means that other in terms of the textual writing virtually no NFB is actually present.
MUCH MORE milage and some actual sensible NFB use could be attained returning the 300B Cathode bypass capacitors to the output transformer secondary winding in the right polarity, then that particular cludge. Alternatively, returning the NFB (with the NFB resistor adjusted to suit) to the 5687 SRPP circuit cathode and leaving the bypass capacitor off there again would give some decent milage.
Alternatively you may omit the C8 & R15 with practically no change in measured and subjective performance (try it).
3) Main Powersupply. The signal return for our amplifier which is practically zero NFB is made through a high NFB circuit. In effect this makes the Amp more or less of a Push-Pull Amplifier in nature. Using such regulated supplies can nevertheless sound quite good, but usually requires some tweaking to get teh right sound, the regulators are often "too good" (and too non-linear) for their own good, managing to impose their own sound reliably on the signal.
I found that when comparing the (also noted and expounded by Broskie) optimised WE style output stage cathode decoupling the results where as good and/or better than any attained with extensive supply regulation.
Overall I think that the Amp could have done with a bit more "optimising and integrating the bits" which could have resulted in reducing the "material battle" this amp clearly is and at least based on my experience would have provided even better results. But that I have to agree is just me, so don't take me too serious.
If you like, you can build two pairs and I'll send you off-line some suggestions to "make it better" without departing too far from the spirit of the design.
Sayonara
Peter Daniel said:
I found the design interesting and an illustration of how you can use two very differnet pathways to attain the results.
I do see some oddities though, that would make me question the actual operation of some of the items and it appears a little as if someone took "building blocks" from a number of philosophies and strung them together somehow with a modest disregard for the inherent philosophies and principles behind the circuits.
Sort of like a horse designed by a comittee.
Some items that would concern me:
1) 300B Heater Supply. That particular approach taken is BAD. Even straight AC sounds better. AT THE VERY LEAST you should use Schottky Diodes and CRC Filtering, preferably some CMC Chokes as well.
2) Output Stage Feedback. Here a 47k feedback resistor sor shunt/parallel feedback is connected into the output of a 5687 SRPP (maybe 1K output), which means that other in terms of the textual writing virtually no NFB is actually present.
MUCH MORE milage and some actual sensible NFB use could be attained returning the 300B Cathode bypass capacitors to the output transformer secondary winding in the right polarity, then that particular cludge. Alternatively, returning the NFB (with the NFB resistor adjusted to suit) to the 5687 SRPP circuit cathode and leaving the bypass capacitor off there again would give some decent milage.
Alternatively you may omit the C8 & R15 with practically no change in measured and subjective performance (try it).
3) Main Powersupply. The signal return for our amplifier which is practically zero NFB is made through a high NFB circuit. In effect this makes the Amp more or less of a Push-Pull Amplifier in nature. Using such regulated supplies can nevertheless sound quite good, but usually requires some tweaking to get teh right sound, the regulators are often "too good" (and too non-linear) for their own good, managing to impose their own sound reliably on the signal.
I found that when comparing the (also noted and expounded by Broskie) optimised WE style output stage cathode decoupling the results where as good and/or better than any attained with extensive supply regulation.
Overall I think that the Amp could have done with a bit more "optimising and integrating the bits" which could have resulted in reducing the "material battle" this amp clearly is and at least based on my experience would have provided even better results. But that I have to agree is just me, so don't take me too serious.
If you like, you can build two pairs and I'll send you off-line some suggestions to "make it better" without departing too far from the spirit of the design.
Sayonara
Re: Re: The T-Rex SET Amplifier DIY project
I will be definitely interested in any suggestions. I don't neccessarily have to stick with the exact design, and if the changes bring improvement, I will surely implement them.
I was planning to build PS and the amp in separate enclosures. Should I go with monos or one chassis for the amp section?
If the boards will be offered by Audio Oasis, it will be based on my work here and I will be designing the layout. So again, any input is appreciated.
"The T-Rex is now in the public domain for the benefit of the DIY community", and since commercial rights are reserved, I will be not profiting on those boards.
Kuei Yang Wang said:
I will be definitely interested in any suggestions. I don't neccessarily have to stick with the exact design, and if the changes bring improvement, I will surely implement them.
I was planning to build PS and the amp in separate enclosures. Should I go with monos or one chassis for the amp section?
paba said:
If the boards will be offered by Audio Oasis, it will be based on my work here and I will be designing the layout. So again, any input is appreciated.
"The T-Rex is now in the public domain for the benefit of the DIY community", and since commercial rights are reserved, I will be not profiting on those boards.
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