Principle behind a tube buffer
Comments
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That's what I was thinking! Now I just need to sell the cables in the Flea Market to finish financing this build as the attenuator is $100 by itself.
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Tube input buffer + stepped attenuator + high powered Class D amp + fully balanced input to output = very cool .
Fred, I think you missed a few words behind very cool. Very Cool Disaster Recipe. :biggrin:Trying out Different Audio Cables is a Religious Affair. You don't discuss it with anyone. :redface::biggrin: -
Fred, I think you missed a few words behind very cool. Very Cool Disaster Recipe. :biggrin:
And what would you suggest good sir?
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And what would you suggest good sir?
Jake,
I was just kidding Fred since he wrote a formula. No harm intended.
Since this thread is about a Tube Buffer principle, it seems fitting to go with the route you selected.
But if you ask me, why high distortion Tube Buffer with High Distortion Class D amp?
I understand why one prefer the sounds of Tubes even when Tubes have high distortion. It's the Tube Magic and Tube Warmth that one is seeking with rolling and rolling Tubes. And I know you prefer to use Tube buffer.
But since you ask me, there are J-Fet BOZ (I think Fred uses BOZ) front end stage you can use instead of Tube Buffer. J-fets have pretty good sonic characteristics and sounds better than most Tubes without Tube distortion.
But using J-Fet front stage defeats the purpose of the Tube Buffer and this very thread.Trying out Different Audio Cables is a Religious Affair. You don't discuss it with anyone. :redface::biggrin: -
Jake,
I was just kidding Fred since he wrote a formula. No harm intended.
Since this thread is about a Tube Buffer principle, it seems fitting to go with the route you selected.
I assumed no harm was intended.
I've built Pass stuff before and like it; although I still need to get my ears on one of his amps...
The reason I am going with the concept of a tube buffered class D, is that I've only found one example of that design commercially available, and that isn't ICEpower either. Maybe this design isn't available for a reason? But I should find out soon enough and the physical project is 3/4 of the fun anyway. :cool: -
James most of the distortion and noise in a Class D amp reside above the audible range.THD in the 20hz-20khz range is similar to what you would find in a typical Class A/B design ,and distortion does not increase appreciably when driving lower impedances.(his ICE modules are stable to below 4 ohms)But if you ask me, why high distortion Tube Buffer with High Distortion Class D amp?
I think the tube buffer/Class D is an interesting combo(one I haven't seen yet)and could prove very sucessful if the tube sections noise and distortion is kept low.
Good luck Jake I'm interested in seeing how this project pans out for you. -
thought better of it :-P
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By all means share whats on your mind.mhardy6647 wrote: »thought better of it :-P -
By all means share whats on your mind.
Agreed; we are all in the pursuit of better audio and a good project, whatever direction that takes. -
mhardy6647 wrote: »thought better of it :-P
Please share."He who fights with monsters should look to it that he himself does not become a monster. And when you gaze long into an abyss the abyss also gazes into you." Friedrich Nietzsche -
I assumed no harm was intended.
I've built Pass stuff before and like it; although I still need to get my ears on one of his amps...
The reason I am going with the concept of a tube buffered class D, is that I've only found one example of that design commercially available, and that isn't ICEpower either. Maybe this design isn't available for a reason? But I should find out soon enough and the physical project is 3/4 of the fun anyway. :cool:
Good Luck and Have fun with the project!James most of the distortion and noise in a Class D amp reside above the audible range.THD in the 20hz-20khz range is similar to what you would find in a typical Class A/B design ,and distortion does not increase appreciably when driving lower impedances.(his ICE modules are stable to below 4 ohms)
I think the tube buffer/Class D is an interesting combo(one I haven't seen yet)and could prove very sucessful if the tube sections noise and distortion is kept low.
I agree about the disortion in the inaudible range. But I am old school and Class D amps are for the Radio Tower and Microwave Transmission. :biggrin:mhardy6647 wrote: »thought better of it :-P
I am all ears too. And stay warm! It's fricking feezing cold around your area? Trying out Different Audio Cables is a Religious Affair. You don't discuss it with anyone. :redface::biggrin: -
Class D amps are strange in that they love low impedance and difficult loads. Also, class D amps can produce large amounts of power (ICEpower ASP100 produces 1000W @ 0.01% THD+N (1kHz, 4Ω) with >50A), but for decreasingly shorter periods of time the higher the frequency. The best way to look at a class D amp like the ICEpower ASP1000 is not as a 1000W amplifier, but as a 100W amplifier with 20db of headroom.
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Would I be able to use two unbalanced tube buffers for a pair of balanced inputs? The board below accepts left, right, and ground, and outputs left, right, and ground; three connections ins and outs. That seems like it would work, even though I would have to use twice the boards and tubes. Any comments would be great, thanks!
http://cgi.ebay.com/High-End-Class-tube-buffer-6922-6N11-6DJ8-assembled-/160527006991?pt=LH_DefaultDomain_0&hash=item256027bd0f
I just ordered two of these, and the nice gent sold me them for $100 for the pair. I'll be interested to see the build quality and component matching as stated before, but I'm also interested to roll in my 6922 Gold Lion tubes. :cool:
As far as the balanced attenuator goes, I think it should best be placed between the buffers and the amp board, and it is available is values of 4k or 20k. If I read it right, and I think the output impedance of the buffers is 200 Ohm. Any suggestions? -
Have you checked out Goldpoint?As far as the balanced attenuator goes, I think it should best be placed between the buffers and the amp board, and it is available is values of 4k or 20k. If I read it right, and I think the output impedance of the buffers is 200 Ohm. Any suggestions?"He who fights with monsters should look to it that he himself does not become a monster. And when you gaze long into an abyss the abyss also gazes into you." Friedrich Nietzsche -
Have you checked out Goldpoint?
I have, but their balanced attenuator is a four board unit. I think I will be going with a two board, 24 step, shunt style, balanced attenuator from Endler Audio. I was chatting with Scott Endler, and his attenuators use the Elna switches (same ones as Gold Point), but his true balanced attenuator cannot be used with unbalanced inputs because of its design.
Now the question remaining is whether I use his 4k or 20k ohm attenuator. Is it true that you want the input impedance to be an order of magnitude (10 times) higher than the output (source) impedance? -
Restate:
The input impedance of the tube buffer is roughly 400K ohm and the output impedance is 200 ohm.
The input impedance of the amp module is 8k ohm.
I have a 4k or 20k ohm attenuator available, so which should I choose, and should I put it between the buffer and amp, or before the buffer which would then feed the amp directly?
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I don't know much about your buffer but I'm guessing the tube might prefer the lighter loading of the 20k pot. (if used at it's output).
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I think I've decided on the 20kΩ attenuator, and will be putting it at the signal input between the source and the tube buffers. With the rule of 10x when it comes to input impedance being higher than output impedance of components see if my math makes sense:
DAC output impedance 40Ω → Attenuator resistance 20kΩ → tube buffer input impedance 400kΩ → tube buffer output impedance 200Ω → amp module input impedance 8kΩ -
Update:
Received my attenuator from Endler Audio and the thing is amazing. I haven't been able to hook it up yet as I don't have all the parts for the amp, but to say the attenuator is over built is an understatement. The solder work is excellent, and the switches and boards are first rate. I'm excited to hear what it sounds like, and for $100, I know where I will be getting any future attenuators.
I also received my quad of Gold Lion 6922 tubes for the pair of buffers along with other misc. parts, and so now am only awaiting the buffers themselves (it takes way too long to ship from China these days...). Assembly on the tube buffered, ICEpower, integrated amp should begin shortly, and I will be wiring the whole thing with DH Labs BL-1 cabling. :biggrin: -
I am always interested to learn about the Passive Attenuators. Looking forward for your review on the Endler POT once you've done putting everything together.Trying out Different Audio Cables is a Religious Affair. You don't discuss it with anyone. :redface::biggrin:
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The forum has a "Technique of the Month" thread that allows members to disect and examine the self defense techniques of AK. What are your thoughts on having a "Principle of the Month" as well? The focus could be on one of the many principles of AK and open the floor to discussing those as well.
Use diet with acai berry to get rid of obesity -
The tube buffers finally arrived, so I believe I now have all the parts and I'm off to the races; once I have any time in my week. I don't have a chassis, but am not too worried about the ascetics right now as long as I can get the amp constructed well. The quad of tubes that came with the buffer are typical Chinese Military stock tubes, but I'll have to shelve them for the quad of Gold Lion 6922s that will be operating in the amp. :cool: The only issue I may run across is poorly matched components as I am running two stereo boards for two balanced channels, but a test with the LCR meter should illuminate any oddities.
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Do you plan on upgrading any of the components?"He who fights with monsters should look to it that he himself does not become a monster. And when you gaze long into an abyss the abyss also gazes into you." Friedrich Nietzsche
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It wouldn't be a bad idea to upgrade some of the caps. All the power caps are ELNA SILMIC II electrolytics which are decent, but the red WIMAs probably could be replaced with something higher quality. However, I do want to start by testing the caps and seeing exactly what specs they are and how well they are matched before I proceed. I would also need to restock my audio funds as this amp has already eaten up some dollars as I've gone premium with almost every part and component.
Any upgrade suggestions?
FYI: The RCA pig-tales will not be staying as they will be replaced by chassis mount RCA connectors fed via DH Labs BL-1 cable. -
