Mustard cap substitute!

[rp]

I like too, clean but not harsh. Fit everywhere easy too. But they look so pedestrian, I think it's the brown color.

[M Fowler]

I want to try them in a Dumble build

[billyoung]

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[billyoung]

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[Sone Aura]

Most polyesters are fairly close. Sozo pretty much nailed it though. I have this old 1983 Teague LCR that tests at 120 or so frequencies between 10Hz and 20KHz. Sozo caps had a better Q below 280Hz than Mullards. From about 300Hz up, they were spot on, but the Sozo caps are not metal cased, so they do not shield as well. I found some caps wound in Mexico I really like. I suspect that this winder may have made the Dijons for Mojo. I know this company has wound caps for the Mallory M150 series, General Electric, Plessey, and other several other companies. I spoke with a sales engineer, and 6000 pieces of .o1uF were around $360. o.1uF were around $600. I may have a bunch of them wound and start selling them. Their 600 volt polyester is very very close to a mustard cap. These are some old LCR caps. They were in need of reforming or replacing. When it came to the SOZOs I found them to have a little tighter bass, but still very very close to the Mullard Philips Bianchi made mustard caps. I have comparison pics of .047s on another computer, using this LCR. I need to go in and calibrate the LCR again. Pray for me! Replacing it, costs a lot. I let the Sozos age and retested them. Obviously every single mustard cap did not have a Q of 226 at 600Hz, but they would range between 200 and 260, with the average around 225. This machine is over 30 years old. It does a very good job though. In conclusion, Sozos, then Dijons, and then Mallory M150s, and then Sprague orange drop PS 225s (NOT THE 715 or 716). I think Weber also has a "yellow polyester cap too. Aside from the shielding issue, Sozo does a really great job. That minor drift at lower frequencies is an improvement to my ears, and for all I know maybe new vintage mustard caps had a higher Q at 100Hz. Until I get my time machine working, we may never know. [img2023]http://i.imgur.com/IsQtkwP.jpg[/img]

[sergio]

Sone Aura , what's the importance of the Q factor in the capacitors?

Thanks
S.

[billyoung]

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[gingertube]

Historically polyester caps where a lot cheaper than polypropylene so the latter were used only for critcal applications. There was also polycarbonate which were in between quality wise.

Today there is very little difference in price between polypropylene and polyester so I use polypropylene almost exclusively.

The old Polycarbonate were withdrawn from market about 5 to 10 years ago and replaced with PPS (polyphenylenesulphide). These are great too but generally not available in higher voltage rating required by tube amps. They do however have great temperature stabilty and superior temperature ratings. I do use 470nF, 1uF, 2u2 and 4u7 PPS caps in 63V or 100V rating in lieu of electrolytics for cathode bypasses.

So what do I use for those 25uF cathode bypasses? I don't do 25uF cathode bypasses anymore, they are simply not required. 4u7 is the most I ever use.

If I were to wish to attract multiple flames I would state that ceramic caps have no place in anything intended for audio, their dielectric absorbtion make them sound horrible (Oh I just did! ... ....INCOMING!!!).

Cheers,
Ian

[billyoung]

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[gingertube]

On the HIFI topic,

Caps introduce distortion mostly due to MECHANICAL stress (mechanical hysteresis) as the electric field reverses with the AC signal. This has to do with the "compressability" and mechanical strength of the dielectric. The cap "plates" are trying to have some "electric motor" action due to the electric field and the dielectric is trying to prevent those plates from moving .

If you design such that there is sufficent DC across the cap to prevent the electric field reversing (that is, the mechanical strain in the dielectric due to the electric field changes with the AC signal, but is always in the same direction) then I and others have been unable to tell the difference between a standard $1.50 polypropylene and a $50 piece of "audio jewellery". It is that zero crossing and teh mechanical hysteresis which does the "damage". YES we did blind AB listening tests.

Most coupling and bypass caps in a Guitar Amp have sufficient DC across them that we never see that electric field reversal and so the "audio jewellery" is a complete waste of money.

That is where there is a disconnect between the HIFI guys (mostly solid state) and the guitar amp tube guys. The capacitors are exposed to different conditions and where you might get some benefit from that "audio jewellery" in a SS circuit with effectively 0 DC bias on the cap we just don't see that condition in a tube Git Amp. So the discussion between the HIFI guys and teh tube Git Amp guys regarding capacitor "sound" is fundamentally flawed because the basic operating conditions are different.

So despite my arguement in my eaarlier post, the guys who say that in a tube guitar amp you will not notice any difference between Polyester and Polypropylene or between ceramic and silver mica do have some science on their side.

Where I can tell a difference is in my Tube HiFi Amps, Polypropylene main filter caps instead of electrolytics give gorgeous "loping" pace although most of this can be achieved by putting a 5 to 10uF film cap across the main B+ electrolytic rather than going full film cap B+ supplies.

Cheers,
Ian

[gingertube]

Can I give a tube amp example to illustrate the above?
Some guys advocate putting a DC blocking cap between the driving stage and the tone stack. The theory being that you can then use low voltage caps in the tone stack itself.I believe this to be a BAD idea as it just allows the tone stack caps to reveal their "warts" as they no longer have that DC bias preventing the electric field reversal.
Cheers,
Ian

[billyoung]

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[billyoung]

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[billyoung]

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