FastEddy said:" I am just suggesting that a Valve pre-amp might handle any clipping (harshness) better than a solid state pre-amp, resulting in a "smoothing" of any clipped audio. (The SqueezeBox's simulated VU meters indicate regular clipping from many of the lower resolution Internet sources = check out Virgin Radio's audio streams = 32 bit/44k stereo with lots of clipping & compression. Same, same for heavily clipped & compressed MP3 / WAV files of "CD quality", quality being the inoperative word here.)
BB = Burr Brown (TI), I assume. (The SqueezeBox supposedly has a BurrBrown 24bit/96k D to A on board and out through those RCA connectors ... but the implimentation may not be as good as your DAC.)
commuter = computer? In the case of the SqueezeBox and some other digital sources, I try to limit the various digital manipulations between the digital sources and the analog inputs ... believing that in many cases the data (the music) gets transposed through too many compression and expansion scenarios ... direct connect between the SqueezeBox (and others) producing the best audio results, generally.
Pictures to follow ...
No, I mean the rca's connect directly to the valve preamp (I have the chance of other incoming signals, cdplayer and so on, so I have a selector)
Line Amp
Here I will post a couple of pics of my line stage amp.
Very simple design.
It uses 2 12au7's for a stereo setup. One tube per channel.
Constant current sources for both gain stage and cathode follower.
These constant current sources replace the Plate and cathode resistors to effectively completely isolated the loading effect of the power supply. (Effective impeadance will be 10's of megaohms).
This will reduce distortion enormously and also reduce hum from the power supply. Cathode follower output impeadance is low (around 200 ohms) to drive solid state inputs. If you want a single tube to be used for stereo you can substitute the cthode follower with mosfet as a source follower. This will reduce the output impeadance to about 30 ohms. (Enough to drive headphones)
Billy D.
Here I will post a couple of pics of my line stage amp.
Very simple design.
It uses 2 12au7's for a stereo setup. One tube per channel.
Constant current sources for both gain stage and cathode follower.
These constant current sources replace the Plate and cathode resistors to effectively completely isolated the loading effect of the power supply. (Effective impeadance will be 10's of megaohms).
This will reduce distortion enormously and also reduce hum from the power supply. Cathode follower output impeadance is low (around 200 ohms) to drive solid state inputs. If you want a single tube to be used for stereo you can substitute the cthode follower with mosfet as a source follower. This will reduce the output impeadance to about 30 ohms. (Enough to drive headphones)
Billy D.
Attachments
Ok, at the moment the sound is very good. I tried to put everything in the case (not a second case with power supply), and I was a little scared of zzzz coming from the toroidal trafo (feeding the squeezebox) a little too close to the output, but that does not happen (tested with a pair of Klipsch Heresy with 99db of sensitivity: a good test...) . At the moment I have a little too much gain, and t 1/4 of potentiometer I already have a big volume, but I will fix it, these are not problems...
I also had a problem with (probably) a "mass loop", hence you see a disconnected wire there: even that is not a problem...
I also had a problem with (probably) a "mass loop", hence you see a disconnected wire there: even that is not a problem...
artQuake's pre 1.1
it began in 2005 with an tube output stage from a tube tuner
1.) Backward engineering stuff to learn
2.) Soldering practice
3.) at the end of practice ... now i did understand that the amplifiing faktor was 1
(so this wasn't a preamplifier ....
4.) Further a few surfings and study brought me thru This
with further work on mixing my first impressions (1.) to my final Sovtec 6H30 Tube preamp ...
This Preamp is really great and i can really recommend to rebuild
this paeg design ... you will be suprised !
regards
artQuake
it began in 2005 with an tube output stage from a tube tuner
1.) Backward engineering stuff to learn
An externally hosted image should be here but it was not working when we last tested it.
2.) Soldering practice
An externally hosted image should be here but it was not working when we last tested it.
3.) at the end of practice ... now i did understand that the amplifiing faktor was 1
(so this wasn't a preamplifier ....An externally hosted image should be here but it was not working when we last tested it.
4.) Further a few surfings and study brought me thru This
with further work on mixing my first impressions (1.) to my final Sovtec 6H30 Tube preamp ...
An externally hosted image should be here but it was not working when we last tested it.
An externally hosted image should be here but it was not working when we last tested it.
An externally hosted image should be here but it was not working when we last tested it.
An externally hosted image should be here but it was not working when we last tested it.
An externally hosted image should be here but it was not working when we last tested it.
An externally hosted image should be here but it was not working when we last tested it.
This Preamp is really great and i can really recommend to rebuild
this paeg design ... you will be suprised !
regards
artQuake
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