The Amp Garage

Ah this calculator is perfect! Thanks:)

Hi guys I'd like to add DC elevated heaters to an AB763 circuit. I've hand drawn a tiny circuit attached. I am just a bit unsure how to calculate the "a" resistor and the "b" resistor values. The power supply node I was going to take it from has about 425vdc on it and I wanted to make the elevated h...

ah so is the louder and stronger signal the wrong phasing and the correct one is the less noisy but less strong?

Thanks Sluckey. So is it the case that any background hum/buzz can also make clear the phasing is wrong, just like the squealing in some amps is a give away?

Hi guys, could you let me now how I determine which wire orientation to use for a Hammond 15watt AB763 style output transformer? Normally the output transformer's colour code has a brown and blue wire (other than the centre tap) for the primaries. I realise however that unless you have the original ...

I You seem unconcerned about not knowing whether the power valves are conducting heavily or not? https://www.thetubestore.com/lib/thetubestore/schematics/Fender/Fender-65-Princeton-Reverb-Schematic.pdf Thanks PDF64. I'm not unconcerned, was just unclear how to do so. I'll now test from these two re...

Thanks PDF64 - I've responded below What’s the rationale for the zener diodes in the bias supply, especially for use as a high voltage rectifier? Just using the existing bias circuit that was on the Princeton PCB I pillaged. I removed the tremolo intensity pot that the Princeton's bias supply usuall...

Ok I've tried to attach my hand edited version of a Schematic that was floating around the web. I hope its readable. Basically it has a bias circuit that comes off the 325VAC HT secondary of the power supply and a solid state rectifier. I take your point PDF64 about the amp having high gain. Im actu...

Hi guys I've posted before bout my project 15 watt Ab763 (single channel without trememlo) based upon an existing Princeton reverb re-issue PCB. I thought I'd start a new thread if ok to ask for some help with my confounded noise issues. I also apologise in advance if I ask some really silly questio...

Thanks guys, lowering the resistor did the trick and I'm not biasing at 19ma cleanly.

Thanks Stevem I'm using a Hammond 15watt output transformer and these 14 watt Russian tubes. My power transformer has 325v@100ma specs and rectified with with the SS version and cap/resistor node comes out at about 440vdc on the first node, and about 405vdc on the second power node. I realise the SS...

Hi folks I have another novice question about lowering bias I'm wondering if I could confirm. I am making a low watt AB763 based upon a Princeton Reverb and I've also plugged in a generic solid state rectifier and some cheaper Russian 6p6s tubes (equivalents of 6v6 I understand but seem to have lowe...

Coming late to the party with this thread but my experience is that huge change can come from changing the first cathode bypass. To confirm this point, the link you provided is from Tyler Grund who made the same change (amongst others he did) based on Caeser Diaz's recommendation. Somewhere on the w...

Ah perfect thanks Martin!

Thanks Martin for your response.

Can I clarify, if I use the 2a 6.3v without the fan, would that be enough heater current for the circuit? I'm not sure why but I seemed to have calculated more than 2a required. Am I missing something?