N-set wrote:

Looks like one more argument for the thesis that caps ssuck! Sorry for a naphtalene-smelling idea, but how about VR tubes *here*? It's an light-weight MF channel. The current variation VR's will see should be very small so perhaps charge redistribution time-lags become unimportant? Would/could you share your friend's views on the last cap operation (separate thread perhaps)? Thanks!

The caT

Thanks, jk

I have given a lot of thoughts to this topic lately and have a number of conversations with various people about the subject. A friend of mine from Europe, who is currently at fitness protection program, suggested that:

“.. in my "real" systems (that is not commercial) I have been running "electrolytic free" for the last nearly a decade and if I had to use them [commercial gear] I have always minimized their influence on the signal circuits as much as possible...”

He offers quite a few techniques how small film caps still might be used and does not screw sound. There were some other proposals and suggestions from different sources, which made me to think: why I ever need capacious? The single-stage Melquiades is as close to cap-free solution as it could be so why do not take it more racial – making PS capacitance free?

I spoke with Dima and asked him to suggest me solutions how it might be accomplished.  The PS caps do two duties: short signal to ground and kill ripples.  After a long conversation he came up with numerous options including those the Steve Bench proposes. The solution one is to use choke, then 600R series resistor (or a choke with 660R DCR) then a shunt of two back-to-back VR 105 tubes.  The 0B2 has very low impedance and will do a perfect path to ground for signal and will kill quite a lot of ripples. My idea was to run the Fundamental and HF channels from my current B+ and to use “no-caps supply” only for MF channel what 30mA the gas tubes will be able marginally to handle. The second that Dima proposed was to run 6C19P as default shunt regulator.

http://www.goodsoundclub.com/pdf/6C19p.pdf

.. having it’s cathode on ground, anode driving the output transformer and having approximately -33V on it’s grid. Of course we got carried away considering application a feedback from amp to drive the regulator’s grid. There were some further solutions that would keep private for now.

I most likely will try it all on my MF but I have an “ethical” problem with it. My usual rule is to make any changes ONLY if I specifically identified a specific sonic problem with the sound that I already have:

http://www.goodsoundclub.com/Forums/ShowPost.aspx?PostID=432

To be honest, I was playing the amp today with new dedicated power supplies on the single-stage channels and it was remarkably good, with me complaining about nothing. So, I might have some intellectual objectives to get rid of caps but I have no natural sonic temptation to pursue this direction. I know myself and I know that it is not the environment where my mind operates productively. So, I do not know where I will be staying on it.  The gas tube might be good, the shunt regulator might be good… but if the current cap sounds “properly” then what would be a definition of “better” for me? I am not a Moron from DiyAudio web site. Perhaps instead of experimenting with no-cap shunt I need to listen more my current MF channel and wait until I will be able to identify it’s weakness… and THEN to see if the no-cap solution would address those specific sonic faults.

Romy the Cat wrote:

3) There is an army of the 150V 7-pins gas tubes: 0A2, SG1P, STV150/30, StR150/30, 150C1, G150m 150C2, 150C4, CV10664, CV1832, CV2903, CV8161, HD51, M8223, QS1207, GD150/4K, QS1210, SR56. I did not try the larger octal 150V tubes (I very much would like to and I will)

Romy the Cat wrote:

Did anyone ever see the ready to do tube sockets adapaters that would let to pit the large gas tubes ingot the small sockets? Melquiades use 7-pin small 0A2 tubes but I would like to try the 0D3. They are the same 150V tubes but I got some VERY old 0D3 and I do not mind to try them on negative supply. The negative supply is bias line on driver tube and it is VERY critical as it sits right in grid. I would like to see what it would do with sound. The different 0A2 do affect sound as I described above, what not to try the larger or older gas tube?

This post is a derivation from the following post:

http://www.romythecat.com/Forums/ShowPost.aspx?postID=11797#11797

What is interesting is that I have a few the same types of shields for small 7 pin gas tubes and I have tried those shields on the gas regulators on my Melquiades. The shields on the gas tube do not damage sound at all. It is a common practice in past to use in measurement equipment the gas voltage regulators with external shields (in addition to an internal shield that any gas regulator has). Now I tried it on my gas tubes that serve Milq’s bias.

The positive supply gas tube had no difference between “with shields” and “without shields”. On the negative supply tube that cares grid bias the shield effect was auditable. The effect was very different then what it was on 6E5P and the effect was to much less degree. I would not even say that I bas better or worse – it was a tiny bit different but to a degree that I would argue if it was ever important.

Adding the external shields to 0A2 (the Amperex tube with doted internal shield - the best 0A2ever made) made sound a bit firm and a bit stiffer. Not a lot, juts a very little. I do not think that it has practical meaning however….

ghpicard wrote:

Hi Romy,   I wonder whether you could advance on the octal voltage regulator testing on the Milq, and what your conclusions were. As I have already seen Milq on your new home still with the 0A2s I can assume you weren't much satisfied but as I am going to try your Milq preamp stage (gas voltage regulator biasing included) in a SET of mine, it would be good to know if it's worth to try with 0D3s or if I should go straight to miniature tubes.Gaston