MikeC Princeton Deluxe

[MikeC]

Taking shape - I hope to test this weekend

Those MOD caps seem to get good reviews from the you tube techs Well priced too which is a change

Good to know, I want them to last!

[blackstratblues]

This sounds super interesting Mike, I'd be happy to make you a demo when it's ready.

[MikeC]

This sounds super interesting Mike, I'd be happy to make you a demo when it's ready.

Good idea Warren, cheers!

[MikeC]

Princeton Deluxe progress - the chassis is complete and I'm about to go through the first-time power up process. It's always fun!

[Mr Bungle]

Sounds interesting! PR has always been my favourite Fender amp, but the 12w has always meant it was not a great option live (3 on the dial and you've already hit max volume, just the breakup to come). I know we had this discussion when I went with the DR instead (which I've been very happy with), but if you pull it off (PR gloriousness at band volumes), colour me intrigued...!

My ‘66 isn’t like that. 3 is when it’s at a first up listenable volume. Between there and over 5 for volume adjustment. Breakup from 6 on. Fitted with a Weber 10F150T 25w light dope.

[MikeC]

Princeton Deluxe progress - the chassis is complete and I'm about to go through the first-time power up process. It's always fun!

The Princeton Deluxe lives. I had an initial issue with the negative feedback being positive which I've now fixed. Also a current issue with the bias - she's only making about 9W RMS (I'm expecting > 20). The bias pot sweep is not going higher than -46v and it needs to be around -35v. I don't have any of resistor values I need to fix it so I'll head off to Jaycar tomorrow morning.

[Cdog]

Princeton Deluxe progress - the chassis is complete and I'm about to go through the first-time power up process. It's always fun!

The Princeton Deluxe lives. I had an initial issue with the negative feedback being positive which I've now fixed. Also a current issue with the bias - she's only making about 9W RMS (I'm expecting > 20). The bias pot sweep is not going higher than -46v and it needs to be around -35v. I don't have any of resistor values I need to fix it so I'll head off to Jaycar tomorrow morning.

Congrats mate... That's cool

[MikeC]

Princeton Deluxe progress - the chassis is complete and I'm about to go through the first-time power up process. It's always fun!

The Princeton Deluxe lives. I had an initial issue with the negative feedback being positive which I've now fixed. Also a current issue with the bias - she's only making about 9W RMS (I'm expecting > 20). The bias pot sweep is not going higher than -46v and it needs to be around -35v. I don't have any of resistor values I need to fix it so I'll head off to Jaycar tomorrow morning.

Congrats mate... That's cool

I was very pleased it ran at all!

[Slowy]

The Princeton Deluxe lives. I had an initial issue with the negative feedback being positive which I've now fixed. Also a current issue with the bias - she's only making about 9W RMS (I'm expecting > 20). The bias pot sweep is not going higher than -46v and it needs to be around -35v. I don't have any of resistor values I need to fix it so I'll head off to Jaycar tomorrow morning.

Congrats mate... That's cool

I was very pleased it ran at all!

I'm completely in awe of what you guys do. It's a language I don't speak but my guitars and I are so grateful you're here!

[MikeC]

Congrats mate... That's cool

I was very pleased it ran at all!

I'm completely in awe of what you guys do. It's a language I don't speak but my guitars and I are so grateful you're here!

I must try and play guitar now & then too!

[jeremyb]

Congrats mate... That's cool

I was very pleased it ran at all!

I'm completely in awe of what you guys do. It's a language I don't speak but my guitars and I are so grateful you're here!

Me too, its high voltage shenanigans which somehow make beautiful tones, so amazing!

[MikeC]

So some progress on the PD - I've got the bias sorted and she's now making a solid 20W RMS. She's sounding nice and I'm doing some tuning and chasing a weakish reverb.

[jeremyb]

How do you measure the output wattage Mike?

[MikeC]

How do you measure the output wattage Mike?

Signal generator @ around 800Hz plugged into amp input.
8 ohm dummy load (it's a wire-wound resistor rated at 100 Watts) plugged into amp speaker jack.
Oscilloscope connected across the dummy load.
You wind amp volume up until the sine wave on the scope is just at the clipping point.
Then measure the RMS voltage of the output (my scope does this for me but so will a multimeter).
Then use the formula Power=Vrms squared/R.

[MikeC]

For the amp nerds I've got some interesting power results to share.

My "standard" Princeton Deluxe delivers 12W rms clean before the Cathodyne PI starts asymmetrically clipping. If I keep winding the volume up I can push the amp to about 27W rms nasty dirty.

Then I did the "Stokes mod" which simply increases the PI's plate voltage by around 60 volts giving it more headroom before asymmetric clipping occurs. Now the PD delivers 20W rms clean because the PI remains symmetrical for longer and keeps the output clean. I can still push it to about 27W rms nasty dirty.

A standard PR delivers approx. 12W rms clean at the point where the PI is starting to asymmetrically clip. Even winding up it's volume hardly delivers any more power because it's wimpy PT cannot provide any more, the voltage drops and the 6V6s clip.

After some reading I find that asymmetric clipping delivers a "warmth" to the tone because it generates even order harmonics. I've always preferred the PR pushed clean to the DR pushed clean and I think this is why. But people seem to prefer the DR over the PR when using a pedal for dirt which I suspect is because of the PR's asymmetric clipping. The PD with Stokes mod delivers 20W rms clean so it should be good with dirt pedals too.

So, I'm going to put a switch on the PD so you can choose.
"Standard" mode = no Stokes mod, "Power" mode = Stokes mod applied.

See attached pics of output waveform with & without the Stokes mod. Note that the RMS voltage is the same in both (ergo amp producing 20W rms).