MikeC Princeton Deluxe

[olegmcnoleg]

For a change I'm building a hybrid - a Princeton Reverb mated with a Deluxe Reverb - a "Princeton Deluxe".
The preamp including the phase inverter is entirely PR but the power section is a DR's including the PT, OT & Choke.
It has a 4/8/16 ohm output impedance selector to correctly match with an extension cabinet.
So it will be a more powerful PR with no additional tubes and should be good for 20+ watts RMS.
It's all built into a PR chassis and will fit into a PR combo cab.
Progress pic below.

P.S. To those that are upset, apologies re the font!

This sounds like an amp I bought once, basically a Princeton (using old transformers & tubes & 12" speaker) with a bigger O/T, more power and a few mods to add versatility. I should have kept it. It is in a thread here somewhere (has a funky, hippy hand-painted cab).

[MikeC]

Think I've seen it!

[codedog]

For a change I'm building a hybrid - a Princeton Reverb mated with a Deluxe Reverb - a "Princeton Deluxe".
The preamp including the phase inverter is entirely PR but the power section is a DR's including the PT, OT & Choke.
It has a 4/8/16 ohm output impedance selector to correctly match with an extension cabinet.
So it will be a more powerful PR with no additional tubes and should be good for 20+ watts RMS.
It's all built into a PR chassis and will fit into a PR combo cab.
Progress pic below.

P.S. To those that are upset, apologies re the font!

This sounds like an amp I bought once, basically a Princeton (using old transformers & tubes & 12" speaker) with a bigger O/T, more power and a few mods to add versatility. I should have kept it. It is in a thread here somewhere (has a funky, hippy hand-painted cab).

It came to me... then went to Danny. That was a lovely amp, even if the reverb was a bit too subtle and quite noisy.

[Marshmallow]

Nice? When's the expected time of completion? I'm gonna have time in the next couple of weeks! Keen for a jam during the day haha

[MikeC]

Nice? When's the expected time of completion? I'm gonna have time in the next couple of weeks! Keen for a jam during the day haha

A week or so assuming it works lol! But I'm away from 5th December until 1st of Jan so will have to be before then (or after).

[olegmcnoleg]

Think I've seen it!

It was not the tidiest I've seen

IMG_1226.JPG (1.84 MiB) Viewed 946 times

[MikeC]

Think I've seen it!

It was not the tidiest I've seen

IMG_1226.JPG

Well... sometimes necessity is the mother of invention! Did it have a choke?
It's missing a tube too (compared to a usual PR).

[olegmcnoleg]

Yes to the choke--I think

yes also to the tube count. Put together from left-over parts I expect. It was housed in an old Marshall combo. No trem/vib circuit.

[MikeC]

Yes to the choke--I think

yes also to the tube count. Put together from left-over parts I expect. It was housed in an old Marshall combo. No trem/vib circuit.

I'd really need to see a schematic to see how "PR" that amp actually was!

[Slowy]

A question has emerged in my mind. This is a rare and momentous event.

Mike's Princeton Deluxe will have more power than a Princeton so probably greater headroom and increased SPL. Looking at SPL for a moment, how do you think it would sound compared to my standard Princeton driving a 100db 4x10 cab?

Which is actually something I'd love to hear.

[MikeC]

Here you go Bruce...

A common misunderstanding when it comes to audio is that doubling power (watts) will make it sound “twice as loud.” Doubling the power (or cutting it in half) actually provides very subtle changes to SPL levels. It will take a significant increase in power to sound "twice as loud". Lets take a deeper look into what increases in power are needed to make changes in SPL.

A 1 dB change in sound pressure level is the smallest difference perceptible by normal human hearing under very controlled conditions, using a pure tone (sine wave) stimulus. A 1 dB change in level is very difficult to hear when listening to dynamic music.

To produce an increase of +1 dB you need to increase power (watts) by a factor of 1.26. So, if you are getting 102 dB SPL from 100 watts and you want 103 dB SPL, you will need 126 watts of power. To produce a decrease of –1 dB you need to divide the reference power by 1.26, so you would reduce power from 100 watts to 79.4 watts.

A change of 3 dB is accepted as the smallest difference in level that is easily heard by most listeners listening to speech or music. It is a slight increase or decrease in volume.

To produce an increase of +3 dB you simply need to double power (watts).

So, if you are getting 102 dB SPL from 100 watts and you want 105 dB SPL, you will need 200 watts of power. To produce a decrease of –3 dB you need half the power, so you would reduce power from 100 watts to 50 watts.

Since this 3 dB plateau results in such a happy ratio, it is a very useful relationship to memorize:

“2 times the power = +3dB...

1/2 the power = –3dB”.

A change of 6 dB is accepted as a significant difference in level for any listener listening to speech or music. It is a quite noticeable increase or decrease in loudness.

To produce an increase of +6 dB you need to increase power (watts) by a factor of four. So, if you are getting 102 dB SPL from 100 watts and you want 108 dB SPL, you will need 400 watts of power (it adds up fast, doesn’t it?). To produce a decrease of –6 dB you need to divide the reference power by 4, so you would reduce power from 100 watts to 25 watts.

This 6dB plateau also results in happy ratios that should be memorized:

“4 times the power = +6dB…

1/4 power = –6dB”.

A change of 10 dB is accepted as the difference in level that is perceived by most listeners as “twice as loud” or “half as loud”.

To produce an increase of +10 dB you need to increase power (watts) by a factor of 10. Yes, to get twice as loud, you need ten times the power!!!

So, if you are getting 100 dB SPL from 100 watts and you want 110 dB

SPL, you will need 1000 watts of power. To produce a decrease of –10 dB you need to divide the reference power by 10, so you would reduce power from 100 watts to 10 watts.

The 10dB Rule should also be memorized:
“10 times the power = +10dB...

1/10 power = –10dB”.

Here is a handy summary table which also lists the change in voltage and speaker excursion for each change in level:

Increases in Power / Voltage / Decibels:
1.26 x power (watts) = 1.12 x voltage/excursion = +1dB
1.59 x power (watts) = 1.26 x voltage/excursion = +2dB
2.00 x power (watts) = 1.41 x voltage/excursion = +3dB
2.52 x power (watts) = 1.59 x voltage/excursion = +4dB
3.18 x power (watts) = 1.78 x voltage/excursion = +5dB
4.00 x power (watts) = 2.00 x voltage/excursion = +6dB
5.04 x power (watts) = 2.24 x voltage/excursion = +7dB
6.35 x power (watts) = 2.52 x voltage/excursion = +8dB
8.00 x power (watts) = 2.83 x voltage/excursion = +9dB
10.0 x power (watts) = 3.16 x voltage/excursion = +10dB

Decreases in Power / Voltage / Decibels:
0.79 x power (watts) = 0.89 x voltage/excursion = –1dB
0.63 x power (watts) = 0.79 x voltage/excursion = –2dB
0.50 x power (watts) = 0.71 x voltage/excursion = –3dB
0.40 x power (watts) = 0.63 x voltage/excursion = –4dB
0.31 x power (watts) = 0.56 x voltage/excursion = –5dB
0.25 x power (watts) = 0.50 x voltage/excursion = –6dB
0.20 x power (watts) = 0.45 x voltage/excursion = –7dB
0.16 x power (watts) = 0.40 x voltage/excursion = –8dB
0.13 x power (watts) = 0.35 x voltage/excursion = –9dB
0.10 x power (watts) = 0.32 x voltage/excursion = –10dB

As mentioned above, a +10dB increase in SPL is considered "twice as loud" and to do so power will need to increase by ten times.

[Slowy]

I read that before my coffee had finished brewing...
I survived!

I understand that principle but never before in such detail. In my simple mind, power = dynamics and headroom. Speaker efficiency is more related to volume. And yes, I know a 4x10 isn't 4 times louder than a 1x10.

Bottom line, I'd love to hear my amp through a 4x10 and I'm really looking forward to meeting yours.

[MikeC]

Yeah I understood that in principle too and with the explanation I posted (a copy/paste from the internet), I also now have a detailed explanation. I can't help with a 410 cab but will ensure you meet the PD!

[MikeC]

Taking shape - I hope to test this weekend

[StrummersOfThunder]

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