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SET Asylum Single Ended Triodes (SETs), the ultimate tube lovers dream. |
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In Reply to: Interesting post. A few Qs posted by RioTubes on October 21, 2006 at 07:32:22:
Hello,I am glad you pointed out the tubed CD players. When I wrote CD players, I meant SS output stage players, which have very low output impedance, on the order of 100 ohms.
The tube output stage behaves impedance wise more similar to a phono preamp. Coincidentally, the phono I'm using also uses 6dj8 as the final stage...
The output impedance of the 6dj8 is much, much higher than that of the transistor-based DACs, and you definitively loose frequency extension. If the 6dj8 is operating as a cathode follower, you have much lower output impedance, but I have no experience with that. My 76 preamp has a 7193 cathode follower, which provides a low output impedance, that is sufficient to drive the AVC. So I guess, the 6dj8 CF would also be able to drive an AVC/TVC without problem.
I don't have phono, only digital. I've always heard that to use a TVC optimally, one has to have the right gain and voltage interface between source and amps, AND the digital source has to have a quality output stage.I agree wholeheartedly. These are all critical. If you want to experiment, put a small PP OPT after a cheap DVD player with mediocre sound, to decouple the digital ground from the rest of the system. The result is an output impedance in the 1 ohm range, and 100mV-range max output. If you have a preamp, that works excellent in that range, then you are for a surprise. But such preamps are rare, and you need loads of gain to compensate. The PP opt will behave as a TVC with 1 volume setting: very quiet... and the TVCs start having problems when the volume rises: the step-down ratio becomes smaller, impedance matching worse. However, I do not know if that is the cause for the thinning of the sound, or something else...
>Would either of the potential issues you mentioned above be addressed in the setup I described, and to what extend?I your case there is still plenty of HF noise coming from the CDs output stage. The 6dj8 is a frame grid tube, capable of working in the MHz range - plenty of opportunity for the nasties to go through. Having a separate transformers for the tubes is very good, but unless you decouple the ground, the tube is going to amplify the HF noise.
I would suggest to place an AVC after a preamp with a lot of current drive.
However, you should try out the TVC right after the CD. You might like it. It's not bad - that's not what I am saying. You loose freq extension, but the midrange and stereospace will be very nice, that fades as you increase the volume.
Good luck!Janos
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Follow Ups
- Re: Interesting post. A few Qs - Janos 20:34:07 10/21/06 (1)
- Thanks Janos, I just saw your post... - RioTubes 17:50:56 11/03/06 (0)
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