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Old 3rd February 2005, 02:38 AM   #1
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Default The T-Rex SET Amplifier DIY project

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/magazin.../0105/trex.htm

http://www.tubecad.com/2005/January/blog0031.htm
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Old 3rd February 2005, 03:45 AM   #2
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Default Re: The T-Rex SET Amplifier DIY project

Quote:
Originally posted by Peter Daniel
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/magazin.../0105/trex.htm

http://www.tubecad.com/2005/January/blog0031.htm
Too complex for my taste... i saw a thread on this amp somewhere thou where those with more experience than me were commenting.

dave
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Old 3rd February 2005, 04:20 AM   #3
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Default Re: The T-Rex SET Amplifier DIY project

Quote:
Originally posted by Peter Daniel
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
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?
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Old 3rd February 2005, 04:31 AM   #4
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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.
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Old 3rd February 2005, 04:45 AM   #5
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Default Re: Re: The T-Rex SET Amplifier DIY project

Quote:
Originally posted by jeff mai


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?
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.
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Old 3rd February 2005, 04:48 AM   #6
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Default Re: Re: The T-Rex SET Amplifier DIY project

Quote:
Originally posted by jeff mai
A circuit that uses all simple, grounded cathode gain stages would be better
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)

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Old 3rd February 2005, 04:58 AM   #7
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Quote:
Originally posted by serengetiplains
Survey peoples' opinions about regulated output supplies. You'll probably see a majority saying regulation works sonically.
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.
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Old 3rd February 2005, 05:03 AM   #8
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Default Re: Re: Re: The T-Rex SET Amplifier DIY project

Quote:
Originally posted by Peter Daniel
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.
In this case, go for it! It sounds like you've practically been commisioned!

If you become curious, build the simpler circuit later and compare.
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Old 3rd February 2005, 05:04 AM   #9
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Default Re: Re: Re: The T-Rex SET Amplifier DIY project

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Originally posted by planet10


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)
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]
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Old 3rd February 2005, 05:56 AM   #10
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Go for it then... still. like Jeff says, you should build a simple amp and compare...

dave
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