non-HRM Findings

[groovtubin]

old school regulation of screens

[jelle]

LOL.... totally OT but very cool! Thanks, I never noticed that.

Jelle

[groovtubin]

LOL.... totally OT but very cool! Thanks, I never noticed that.

Jelle

everyone needs a lile REGULATION every now and then! Hope you are well man!

jim

[jelle]

Hey Jim, you know us Dutchies...we do not like too much regulation! LOL!


PM sent.

And Gil, sorry about the hijack....

Jelle

[talbany]

Here is the one you want. Uses Ionized gas to regulate voltage. will also drop 100 volts. This shows the screens as well as the PI tube regulated you can try it like this and see if you like it though I just regulate the screens. One other thing you need to do is filter it before the regulator and after it 20uf on both sides should do.

[groovtubin]

Here is the one you want. Uses Ionized gas to regulate voltage. will also drop 100 volts. This shows the screens as well as the PI tube regulated you can try it like this and see if you like it though I just regulate the screens. One other thing you need to do is filter it before the regulator and after it 20uf on both sides should do.

will that thing handle B+ of my Dual showman tranny? ( 440 roughly) I`ve got 4 x EL-34`s a going.

[roberto]

Hi all,
I noticed someone attached cathode bypass roll-offs.
Time ago I wrote a xls about that. This is a print-friendly pdf version of it.
Enjoy!

[odourboy]

Pardon my ignorance, but in these charts, what's the Rk' signify under the Rp?

[roberto]

Rk' is cathode resistance of 12ax7 due to plate load.
The combination of that internal resistance and cathode resistor Rk (seen as a parallel) and cathode bypass cap Ck, changes low frequency cut-off of that stage. Ck in uF, Rk in kOhm and F in Hz.

[odourboy]

Thanks! Another dumb question - how do you determine which value of Rk' is applicable?

[jelle]

Talbany,

Thanks for the file!

I just saw it.

jelle

[roberto]

Hi,
please read this, you'll understand better my pdf.

[odourboy]

Or if you just want to give the man a damn fish...

Rk'=(Rp+62.5k)/101

where the constants used are based on 'typical' 12AX7 values.

Thanks for the link (and the chart)!

[roberto]

Yes, that's the smelling fish
but reading the whole link, you can predict how a never used brand of 12ax7 will sound in your amp, or just understand why substitute a 12AX7 with a 12AT7 sounds that way. As I find it, I'll post the plate bypass' cap cut-off. Just another old pdf of mine.

[butwhatif]

Thanks Ayan, for posting on this subject, as I have never liked the grainy
sound of the clean with the biased hi cathodes. And I'm sure that your experience with these amps and in the clone community, the idea will be received with renewed thought. The larger plate resistors can make for a robust difference in tone, I think, to taste, but the higher biased cathodes get too dry and 'hard' for my ear. I think that the 1.5k resistor places the tube in it's warm working range, imho. I like these in OD1 and OD 2 also, but more care needs to be done here to get a good sound. Also, the power supply for the amp can be tweaked for varied sound, as well. I have a Mesa Mk III that has been rebuilt for a clone sound, and the nice thing with these is there's a platform for a d'ator already inside, although it needs much rework as the original wiring of it sounds not well. This internal interface also can be tweaked for variations of tone, and done right can really add to the overall sound.