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previous: Matthew Springer Woot woot. Here's how to ca... -- 4/18/2003 9:37 PM

Re: woo hoo!

4/23/2003 12:26 PM
gazza	Re: woo hoo! Hi, I guess I could put separate cathode bias resistors for the power tubes to be on the safe side and spot any dodgy tubes. I haven't seen any glowing plates yet, but I haven't really cranked the amp yet due to the neighbours. I built a -15 dB attenuator on the weekend (L-pad) and I might make it -24 dB to try and allow some easier testing. I do have a 40W 8 ohm resistor load that I should use to check the current when the amp is on full ?? I was thinking of putting some inductors in series with the two resistances of the L-pad with such a high. What do people think fo trying some inductors that are in a discarded computer SMPS ? I'l post the question on the main discussion later. I'm now trying to tweak the amp, i've put a pot divider before the PI, and swapped the post master volume from a 1meg pot to 250k. I also tried some caps across the two pre stage anode loads and put 1 uF poly on the first stage cathode (10uF) bypass. the second stage now has a 3.3 uF bypass to maybe help with the overdriven sound ? It now got switchable negative feedback and a triode-pentode switch. Is there any danger in running EL84s as triodes with 280V on the plates ? Ive put the switch after the screen resistors so thier always present. The amp didn't work simply due to a silly layout mistake. every thing else is fine ! it's fairly quiet and no motorboating or oscillation problems yet. This is because I read all the great advice on ampage, ax84 and randall atkin sites about layout and grounding etc. I'll put some photos and the schematic on my website soon - but no sound clips - I'm far to poor a guitarist! gazza.

4/23/2003 12:26 PM

gazza

Re: woo hoo!

Hi,

I guess I could put separate cathode bias resistors for the power tubes to be on the safe side and spot any dodgy tubes.

I haven't seen any glowing plates yet, but I haven't really cranked the amp yet due to the neighbours.

I built a -15 dB attenuator on the weekend (L-pad) and I might make it -24 dB to try and allow some easier testing. I do have a 40W 8 ohm resistor load that I should use to check the current when the amp is on full ??

I was thinking of putting some inductors in series with the two resistances of the L-pad with such a high. What do people think fo trying some inductors that are in a discarded computer SMPS ? I'l post the question on the main discussion later.

I'm now trying to tweak the amp, i've put a pot divider before the PI, and swapped the post master volume from a 1meg pot to 250k.

I also tried some caps across the two pre stage anode loads and put 1 uF poly on the first stage cathode (10uF) bypass. the second stage now has a 3.3 uF bypass to maybe help with the overdriven sound ?

It now got switchable negative feedback and a triode-pentode switch. Is there any danger in running EL84s as triodes with 280V on the plates ? Ive put the switch after the screen resistors so thier always present.

The amp didn't work simply due to a silly layout mistake. every thing else is fine ! it's fairly quiet and no motorboating or oscillation problems yet. This is because I read all the great advice on ampage, ax84 and randall atkin sites about layout and grounding etc.

I'll put some photos and the schematic on my website soon - but no sound clips - I'm far to poor a guitarist!

gazza.

Replies:

Matthew Springer triode mode -- 4/25/2003 3:50 PM