Thanks for all the answers and ideas!!
I quite agree with all the comments abouit using ECC83/12AX7. Has anybody had a look at the pricing lately?? Im old and slow NOT stupid, and paying $100 yank bucks for a "supposed" NOS Mullard or AWV version has two problems!!
1. I need at least 10 of them.
2. I need at least a few replacements for failures.
I have tried the russian and chinese stuff and it makes more sense to me to use noise diodes instead, GAIN taken into account!!!.
I posted the link to the origional article using the 6BQ7A and I pay $2 for them Brand new in origional packaging, made in USA by Sylvania, and I have access to thousands of them.
6922/6DJ8 has similar problems to 12AX7/ECC83. I do have a SMALL stock of 6DJ8 and 12AX7, but I dont have sufficient quantity to remove the noisy ones, and that means I cant cover any failures down the track. As far as pentodes go, I am listening to EF86's at present and agreed they are not microphonic, but they do have hum problems. Admittedly they are probably my fault, as I made the whole amplifier integrated. I ALWAYS use DC heating in ANY low level circuitry!!. With the Golden ears amp project ( Im thinking my last amplifier for myself) I have done the following:
1. A separate power supply chassis.
2. Very underrated toroidal power transfomers with both pri/sec electrostatic screening, and an external flux band.
3. Large and very low ESR electrolytic capacitors.
4. Large and well screened filter chokes within the power supply.
1. Power amplifier will be at least 750 mm away from the power supply.
2. Additional filter capacitors to buffer the umbilical feed, and an additional choke for the minor HT levels within the amp, with associated big capacitor.
3. As logical as I could ( think ) make the layout.
4. All low level valves will be in screened cans.
5. DC heating for all but the 5B/254's.
Preamp design is still in progress, but will be the minimum required to work and drive the Golden Ears power amp.
As an addition, I want to add a small triode power stage to drive the "deaf as posts" digital garbage sound cards that are about, some requiring at least 5 volts of signal at about 2K input impedance. I have wound transformers specifically to this end.
I have many LP's that haven't, and probably never will be released onto a storage medium like a CD, and I constantly get requests to copy an LP onto digital media.
I dont use "tone controls" or loudness compensators on any of my amplifiers, as the superb Tannoy speakers I use do not require any. Even listening to early Beatles releases, which could be classed as "screetching treble" recordings.
Back to pre amps!! ( Sorry mods)
Some of you may have already worked out that I am willing to try new ideas!! Following along on this idea, I have spent about 3 years searching out any and all the information I can on this final designor plagiarised build. As far as how far back I go, is limited by RIAA specs. i.e. I dont play 78's although I have many hundreds.
I can design my own filters, but fitting switches to correct for the umteen dozen different recording characteristics is not worth it in my mind, considering of the 78's I do have, not many contain any "music" I am interested in.
Joseph Marshall also had cascode designs for preamps in the early 1950's, all in the search for lower noise. Hence my thought to try 6BQ7a's. It was already recognised back then, that some valves were more suitable than others for this class of service. Triode connected EF86's only deliver a low noise half of a 12AU7, in other words pretty low gain. Something in the vacinity of 20 rather than 60 or so for more suitable types which dont need extra amplification along the way.
I also have a large stash of 6BR7 which is Brimar's answer to GEC's EF86. In any case the 6BR7 is a much newer design than an EF86, albeit using similar design and construction techniques. I have not tried them in triode mode however. Twin triodes have both required elements in one bottle which simplifies heater wiring and reduces current required as an extra bonus.
GJ has an interesting idea re: a "rubber sheet" mounting idea!!. Its why I posted the question in the first place. Davids idea re: using some sand blobs is out!! Sorry David, the only concession I have made to sand in the whole power amp design is to use fast recovery diodes in the rectification circuit. Again because decent rectifiers have been priced out of this world. This new preamp has vacuum rectification though, as I have large stocks of Bendix Aircraft Company JG-6203 aka CV5009 rectifiers, again because I get them cheap, and there are hundreds available.
Thanks again to all for all the ideas and suggestions, and remember!! I am an aussie and I am very hard to offend
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Best regards
Joe