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If so, what were/are your impressions and opinions.
Follow Ups:
Allan Wright and even Eli Duttman have done this. Eli Duttman has some mods that include a mosfet follower output stage. You might even find Allan Wright's mods on the web. I don't think you can beat a 12ax7A for phono unless you get super sophisticated with cascodes and perfect power supplys. It's only drawback as drawn in the RCA tube manual is that it's output is not buffered and Eli's mod buffers it for reasonable long cable runs for people who have their phono preamp seperated from the rest of the chain (It needs to be close to the cartridge/tonearm). But if it's close to the rest of the preamp/volume control(within inches) then it doesn't need to be buffered. And avoiding a cathode follower at the output is a plus IMHO. It's RIAA EQ is essentially passive. But I would isolate the tube by mounting the tube socket screws with two sorbothane/rubber grommets, and use 6.3v DC for filament voltage by connecting pins 4&5 and use pin 9 as return.
"...the fool doth think he is wise but the wise man knows himself to be nothing but a fool." Will Shakespeare
His Master's Voice: This preamp used a D3a pentode along with an input transformer up front for a superior SN ratio. But it's designed for moving coil cartridges and you have to modify your tone arm for balanced (5 pin XLR) You could probably do this point to point. I would mount the D3A on sorbothane isolators. Moe
"...the fool doth think he is wise but the wise man knows himself to be nothing but a fool." Will Shakespeare
Thanks once again, but I try to stay with the KIS principle whenever possible. Looks a bit to complicated for me.
http://www.tubes4hifi.com/pre11.htm#PH16
I recall seeing another by SY on diyaudio. I'll try to find it and post it.
"...the fool doth think he is wise but the wise man knows himself to be nothing but a fool." Will Shakespeare
Very interesting I must admit, but a bit out of my price range and too much SS for me. I really like working with point to point wiring and assembly.
If it is as good as the reviews say though it probably is a good buy for the right person.
This might be an interesting read: His master's voice: A thoroughly modern phono preamp by Stuart Yaniger on diyandio forum. Stuart does by the nic-name SY. It uses an input transformer up front and an off the wall input tube. An input transformer up front SHOULD?? yield a superior SN ratio
My old mac wouldn't let me hyper-link it. Sorry. Moe
"...the fool doth think he is wise but the wise man knows himself to be nothing but a fool." Will Shakespeare
Short comments:
* The balance is a problem. There was once a "matched" 6SL7 version; otherwise a small pot between the cathodes would give some adjustment.
* By my quick calculations, the HF rolloff seems to be in error by about an octave, which would make it dull all right! Easily fixed though.
* The balanced amplification provides some PSRR as well as the ability to take a cartridge input in balanced mode for common-mode cancellation; these are not trivial issues.
Thanks Paul. Probably not quite what I am looking for.
I built both the one and two quite a few years back. I was not stable and would motorboat at times. This might have been resolved with even more power supply mods. But even when things where working well the sound was to dark. The bass was muddy etc. Nothing to special to say about it.
If you want a easy bread board do a Cornet. (Dan is still using one I think) I built it one platform and separate mono with both the 12ax7's and the 6sl7's. The octals have a little more noise but sound better.(a more full body sound) I also built it without grid stop resistors and took out the cathode follower last stage and put a interstage transformer and tried various tubes in the 3rd position. If you are not a noise freak dht in this position is great. (Low rp tube because you lose the cathode followers low output impedance)
The thing never got unstable no matter what I did to it. The cathode follower removal was big jump in dynamics. So if you do want to spend the money on a interstage transformer you could just do the normal gain stage for the 3rd tube but get rid of that cathode follower.
Phono stages are about as stable as the nitro. I built a lot of them in the past and some would not even work at all. I use separate power supplies for each tube now ( Which is way over the top) but if you don"t make sure you separate the tubes with some chokes and caps.
Enjoy Tom
Thanks for the info Tom. Doesn't sound like the best candidate for a bread board project. Is a schematic of the coronet available anywhere? I am not familiar with it.
Vinnie,
I have a copy of the octal coronet schematic as modified by DanL. It's based on Hagerman's original coronet. He posted it here many moons ago. If he had any "intellectual rights" issues with it, I'm sure he wouldn't have posted it.
You can email me if you'd like a copy.
.
Freak out...Far out...In out....
You are probably right about him not minding if people build a copy for themselves if he posted it. Going to do a search of what is out there before I try a breadboard. I have a pretty decent diy phono preamp that will carry me until I find one I think might be better. Thanks for the offer!
Hey Vinnie
Check Hagtech out. The link here is to the 1st one with the 12ax7's.
It is the whole manual. If you google around you might find the octal one he did, not much difference.
Have fun
Tom
Opps, I didn't know it was a commercial amp. Probably ought not be doing copies of it. Thanks just the same, I appreciate it.
.
Have Fun and Enjoy the Music
"Still Working the Problem"
I was referring to the previous post about the coronet....
Schematic was posted on public domain many times also by Jim so I don't see why you can't breadboard and try it out. From myself I can add that it's nothing special really , rather flat and on neutral side of things , boring comes to mind no matter what component quality one use. Octal version is a whole level better sounding to the point where in comparison 9 pin Cornet sounds like mono. 0f course, it's better than SS crap.
The design I would recommend is EAR 834 with Thorsten mods. Runs circles around most affordable phono units- bass, balls and highly musical. Also Audio Note M3-M8 phono is a nice one ,not as dynamic but maybe more nuanced. On a general note my understanding is once the designer or manufacturer post schematic or design on public domain it means it's free to copy it for private , non profit use , no additional note required.
.
Have Fun and Enjoy the Music
"Still Working the Problem"
"I didn't know it was a commercial amp. Probably ought not be doing copies of it. "
Why not?
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Buy Chinese. Bury freedom.
Same reason I don't copy other peoples designs unless there is a statement on the schem that says "it's ok to build one of these for your own use". Some folks mind and others don't.
"it's ok to build one of these for your own use"Of course it's OK. It's always OK. It's not as though designing a circuit entitles anyone to some sort of supralegal "first rights." You or I may not be allowed to publish a copyrighted schematic of the work, but that's an entirely different matter than constructing a working copy of the device for our own use. The latter has been done for centuries. It's the American way.
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Buy Chinese. Bury freedom.
Edits: 11/17/14
I agree with Paul that it is a moral obligation, if I understood his post correctly. Besides, even if it is the "American way", which I am not sure I agree it is, that doesn't make it right. If I designed a circuit I would expect people to recognize the intellectual property rights unless I specifically said they could make one for their own use. I also don't believe that pirating software or music for your own use is ok either.
That said, I don't think it would be particularly wise to post a schematic in the public domain if you did not want it used by others. Some people don't, they just put it in the construction manual.
Edits: 11/17/14
This is not an intellectual property issue, and no individual has any such moral obligation. It's all well and good that we want to be decent people, but you two have crossed the line between respect and altruism. I've seen a number of good people - like yourselves - fall victim to the same misplaced sense of honor over the years.
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Buy Chinese. Bury freedom.
And I have seen many people rationalize away what is the right thing to do because it does not fit what they wish to do. If intellectual property is not a product of someones mind, what the heck is it?
OK is not the same as legal. "OK with the designer" is a moral obligation IMHO; only the more egregious moral obligations become legal obligations.
Paul, help me out here. I'm trying to understand what you are saying.Does this moral obligation extend in perpetuity?
Even a patent runs out eventually and enters the public domain.
Look at all the manufactures making the pleated tweeter now that Heil's patents have all run out. Beyma, Mark & Danial, MartinLogan, etc.
Are each of them under moral obligation to the Heil estate not to do so?
I wasn't aware that even a standing patent prevented a person from making a design for their own use. I thought it only prevented them from making the design for profit?
I thought publishing a design (disclosing) before patenting a product prevents a patent from being obtainable?
Most of the published designs (setting aside the disclosure issue) would not be patentable in the first place since they contain only prior art.
A reshuffle of a bunch of old ideas is not (as far as I know) a new idea.
I know that the patent office hands out patents to anyone with a pulse these days but that doesn't mean those patents would stand up in court if it can be shown to be only prior art already in the public domain.
Tre'
Have Fun and Enjoy the Music
"Still Working the Problem"
Edits: 11/18/14 11/18/14
Trying decide if I want to bread board it.
A hedonist is a fun seeker. I think this article was written as a lark. I haven't built it or listened to it. I was taught that a difference amp was a noisy amp because of the summing effect of it's cathode connection and the attendant increase of the summed Johnson shot noise. Especially not recommended as the first stage of a very high gain preamp and there are two of them in series. The object it would seem IMHO is to get the gain up out of the noise and then monkey with the EQ. To get good CMMR which is why he is claiming to use two diff amps cascaded one after the other that they would entail quite a bit of tweaking because it's impossible to make both side of the tube that PERFECT. If you test most dual triodes then they vary as to transconductance. I didn't find any balancing measures to null out the imbalance. Just my 2 cents. Moe
"...the fool doth think he is wise but the wise man knows himself to be nothing but a fool." Will Shakespeare
You don't have to build it to know that octals are microphonic at phono levels. Caution is advised...
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Buy Chinese. Bury freedom.
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