New OPT Amp...

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Ray P
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#1 New OPT Amp...

Post by Ray P »

....coming from Bruce Rozenblit at Transcendent!

I thought one or two of you here might be tempted by this one;

Update;: I tried to post the link to the relevant document but kept getting a debug error so below is the text via copy/paste with a picture below.

"This will be project number 2 for the new book. It's a 1 watt monoblock amp that uses four 300B tubes for each channel. I am stunned as to how good it sounds. The sound is very rich and mellow. Hard to describe. Words like emotional and natural come to mind. The sound has a certain body and weight to it. Very addicting.

So far, I've only been able to listen in mono. Can't wait to build the second one and appreciate stereo sound with it. Even with only one channel, I'm sold.

The amp will be offered in monoblock configuration and it wont be cheap because of the tubes involved (eight 300B's). A pair with tubes will cost somewhere around $2500, maybe a little less. The driver is one 12AT7.

The Mini-Beast is truly wonderful and the new Son of Beast is also outstanding giving much more power at very low cost. This amp will be targeted to folks that must have the very best coupled with speakers that approach or exceed 100 dB for one watt. Many of these speakers are terribly expensive justifying the higher amplifier cost.


I originally thought this amp would be used as a treble amp in two way systems. Nope! It should be used in full range systems. The bass is incredibly powerful.

Bandwidth goes from 10 Hz to well beyond 100 kHz. Square wave response at 10 kHz is nearly perfect. The amp can resolve the most delicate nuances in the sound while being smooth as silk. There must be some magic in the 300B.

It uses AC filaments. DC wont work as it screws up the biasing of the output stage (long story). I was able to tune out the filament hum and nearly eliminate it. I can't hear it with my ear more than 6 inches from the speaker. The noise is mostly 60 Hz, no buzzing at all. The sound quality is so good that a minute hum wont matter. It's probably much quieter than most all of the transformer coupled SET amps on the market.

This will be the last amp in the new book. Next will be a couple of tube testers. One for general checking and tube life, the other will be for biasing and measuring parameters.
That's four projects for the book. Two blockbuster hi-end amps and two tube testers. Plus, all of the information on how tubes and circuits work. I want this book to become the must read for all that use and enjoy vacuum tubes. "



Ray
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#2

Post by Thermionic Idler »

:shock:

Interesting. I never thought I'd ever see B.R. come out with an amp which had 300B's in it. Anyone care to join me for a skiing holiday in Hell?

I'd assume this must be another single ended design given the power output. Surely if it is possible to use the 300B for an SE OTL it must also be possible to make a P/P OTL using them? Which would give more usable power maybe?

Cost of retubing either would be astronomical though.
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#3

Post by Ray P »

I've just received the latest Transcendent Sound Newsletter, which contains an update on his forthcoming 300B Output Transformerless (OPT) amp. The text from the newsletter follows;
Now that I have two amps up and running, I can better evaluate the performance. The bass is outstanding! Unbelievable for a 1 watt amp. The amp plays louder than the original SE OTL. This indicates that the 300B has a lots of peak power. My speakers are 95 db/1W and the amp has no problem driving them. It won't set up gut thumping pressure waves, but the bottom is there. After about 20 hours of break in, they sound smoother and richer. Due to the simple construction of a directly heated triode, tube failure problems should be eliminated.

The second prototype has an improved layout. The circuit is very simple and the chassis is big and spread out allowing for easy assembly as well as low cost. I never dreamed I would become a 300B fan. Am now.
Some pictures attached below. BR won't be selling a kit, the design will be included in his new book, due out very soon;
If the schedule holds, I should get the book back from the editor by July 1. It may take a little longer because it's so technical. That's OK, better to do a good job. It should then be available for sale by around Aug.1.

I'm going to use the new print-on-demand technology. It will be primarily distributed through Amazon. I'm not going to stock and sell it directly. The list price will be $34.95.
I use BR's SE-OTL amp and it is very good so this looks like a tempting project.

Ray
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#4

Post by jack »

Anyone got a paper copy of Audio Reality for sale at a reasonable price?

Ta
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#5

Post by Ray P »

Bruce's new book, with the 300B design (and others) is now available.

Ray

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#6

Post by jack »

Ray P wrote:Bruce's new book, with the 300B design (and others) is now available.

Ray

Indeed - ordered it yesterday... Due on the 25th July...
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#7

Post by jack »

(this should probably be in its own thread)

Been reading this for that last few days.

Disclaimer - I'm thick (but with a really strong maths & physics background... :shock: )

First 110 pages (out of 268) are basic maths & physice - vectors, imaginary nos, usual stuff, introduction to inductors, resistors & capacitors, theory of impedence/reactance etc.

Next 48 pages are introduction to valve theory - construction, chemistry, physics.

At page 159 we get to tube circuits... - 54 page on the basics of that, using the maths & physics covered before.

Eventually, on page 213 we get to the first project (basic 15W/chan OTL) - very well analysed. Then a 300B SE OTL, a simple valve tester, a simple rectifier tester, and lastly a valve analyser...

Interesting read, but gave me nothing I hadn't already got from other books like BVA (MJ) in, I would argue, a more accessible style - I am a bit biassed - I prefer MJ's style and the balance he has between practice & theory - I did all the theory years ago and its, IMHO, questionable that most readers would need anything like the coverage of basic maths etc.

40% of the book is basic maths, the next 18% basic valve circuits theory, 12% on the two amp projects and the rest on other stuff.

Of course, percentages don't tell the whole story and there are a few really interesting bits in there, but not much that adds to the generic tube oeuvre. I expected (and hoped for) more...

My vote is still with MJ or "The Ultimate Tone" (great stuff), even NEETS (which is excellent AND free) etc.
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#8

Post by Ray P »

I've not had my copy for quite as long but have managed a read through today. I think my requirements are different to Nick's; I wouldn't claim to be thick but maths and physics (and electronic theory in particular) aren't my strong points. I found the book quite readable and, for me more importantly, it presented technical stuff in a way I can get a grasp of. If you're an 'expert' already I don't think you'll get much from the book, other than some of BR's circuits, but I would recommend it as a useful investment for mere mortals.

Ray
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#9

Post by jack »

Ray P wrote:I've not had my copy for quite as long but have managed a read through today. I think my requirements are different to Nick's; I wouldn't claim to be thick but maths and physics (and electronic theory in particular) aren't my strong points. I found the book quite readable and, for me more importantly, it presented technical stuff in a way I can get a grasp of. If you're an 'expert' already I don't think you'll get much from the book, other than some of BR's circuits, but I would recommend it as a useful investment for mere mortals.
Tchhh ! I wasn't trying to be rude... :)

My chief gripe is that in a £23 book entitled "Tube Circuits" there is not a bunch on tube circuits (which I take to mean amplifiers) - only 30% (by volume) or two projects - there are also a couple of test kit projects (not rocket science) - and that's being generous - 60% of that section was on basic (available all over the place) modules of tube amp design.

But 40% of the book on basic electronics-related maths? Seriously? This is not "Tube Circuits" - this is mostly electronics 101 and there are dozens of excellent books out there which cover that, including some, like NEETS, which are free.

NEETS: http://www.hnsa.org/doc/neets/mod06.pdf (change the digit in "mod0n.pdf" for the other modules)

I really wanted this book to offer more - the author is a top man - but apart from the two designs, what's in there that's even vaguely new?
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#10

Post by Ray P »

Hey Nick, I didn't read anything that I construed as rude and hope I didn't come across like that myself? :D

Being a bit of a pedant, can I point out that the book is actually entitled "Tubes and Circuits" and from that perspective maybe it isn't very realistic to expect it to be stuffed full of amplifier schematics?

Anyway, it works for me but I'll also check out the link you included.

Ray
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#11

Post by Paul Barker »

nickds1 wrote: I really wanted this book to offer more - the author is a top man - but apart from the two designs, what's in there that's even vaguely new?
Out of interest, is the design of this new amp based on Steve Benches SE OTL design in which he use multiple tubes in inverted operation?
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#12

Post by Ray P »

Paul Barker wrote:Out of interest, is the design of this new amp based on Steve Benches SE OTL design in which he use multiple tubes in inverted operation?
Hi Paul. It's a long time since I looked out Steve Bench's OTL design; I think the answer is no from memory but if I get time over the weekend I'll try to confirm that.

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#13

Post by steve s »

I've never quite 'got' these otl amps, we heard one at the first eggfest, and i was not veryimpressed.

like everything in hifi.. it appears a compromise ?, i assume it works sort of as a 4 valve parallel SE with all the know issues of sound thickening and reducing detail from parallel operation. then removing the output transformer to improve that sound?

he's not even using the likes of vitavox s2 or the like so he can really hear whats going on.. who's to say his better bass is not just the valves thickening things..
or have i got the wrong end of the stick?
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#14

Post by Ray P »

Steve, of course all hifi is a compromise in some way or another - in my experience it hasn't yet bettered hearing real musicians.

I bought my Transcendent SE-OTL along to an Eggfest around the end of 2010 and it performed disappointingly, however, this wasn't because it was an OTL amp but because, with an output of only around 1.5W, it had insufficient power to drive the speakers it was used with in the room.

My experience at home is that it is significantly better than the well-regarded 2A3 SET amp I was using previously; contrary to your expectations it is more delicate with greater resolution of detail and better bass. Maybe you should try one?

Ray
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#15

Post by Ali Tait »

They can certainly throw a huge soundstage.
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