princetone reverb master volume

[phsyconoodler]

I've tried nearly every version of master volumes in a Princeton circuit and have never been happy with the tones.They always compromise the tone or have lousy tapers.
  Well I tried the type 4 trainwreck style master and it works flawlessly.
It was absolutely the best in my experience so far.

[sluckey]

Makes no sense to me. Why would you put a MV pot between the treble pot and volume pot? Look at this PR schematic...

http://www.el34world.com/charts/Schematics/files/fender/PRINCETON_REVERB_AA1164.pdf

[macula56]

I use this a lot and it always sounds great. however, i don't put it between the treble pot and the volume pot. i use it after the mixing resistors and it works very well for me. i do notice, however, that as i turn down it gets a little muffled so i was thinking about a treble bleed network like i use on my guitars. just to see if it helps any. anyone ever do that?

[phsyconoodler]

Sluckey wrote:"Makes no sense to me"
  May not make sense but it works flawlessly.you can get the preamp wound up and the master control feeds it rather nicely into the rest of the circuit.
  I put it on an amp I just did after struggling to get a good tone out of the 'bootstrapped version'. It works so well I'm going to use it on more Princeton amps in the future.

[stratele52]

Look on your Book 2 pages before, ( 194, or Trainwreck 42 )  the Master volume type 2. A friend of mine a good tech an guitar player said this is the best master volume . He try some.

[tubenit]

Can someone draw the master volume that physconoodler is recommending into a PR schematic?

I am not able to envision what is going on with that?  The directions in the Trainwreck picture don't make sense to me.

Not saying they're wrong. I'm saying that I don't understand them?

with respect, Tubenit

[sluckey]

May not make sense but it works flawlessly

      Of course it works flawlessly. It does exactly what the original volume control does! You just have one volume control feeding directly into another volume control. That MV was meant to be used like the Marshall 2204 MV, between the treble wiper and the LTP PI input cap.

[phsyconoodler]

The idea is the same as a volume control,yes,but it allows you to crank the preamp and lower the volume.Like a MASTER volume is supposed to do.
  The lo channel on a 2204 is the same and it works very well too.Yes it's like having two volume controls,I know this.All I can say is it works for what i want it to do.

[sluckey]

...

[tubenit]

Thanks Sluckey! I appreciate the drawing.

Of course it works flawlessly. It does exactly what the original volume control does! You just have one volume control feeding directly into another volume control.

With respect, Tubenit

[phsyconoodler]

regardless of how it looks,it works.It allows you to crank up the volume and get preamp grind at a lower overall volume.

It's like adding a second pressure valve in a water supply.The first valve(volume) is cranked up,allowing the pressure to rise to maximum and the second valve restricts the flow to the rest of the system,in this case the phase inverter.
  With two controls in place the pressure remains constant but the flow is controlled.Remember there is no pressure unless the first valve is opened all the way,or little pressure.I look at the volume control as the 'pump' and the second volume control as the flow control valve.
  the pump needs to be opened up before the pressure is there.

[sluckey]

pure snake oil!

[phsyconoodler]

ah but I love snake oil! It keeps the snake smooth to the touch!

It works.Try it first before condemning it as snake oil.And futhermore,why would it NOT work?What's the difference between this method and a volume further downstream?Both allow the preamp to output the maximum before sending that signal along it's merry way.
 

[sluckey]

If you don't get it from looking at that simple schematic, then there's nothing I can say to convince you. 

[phsyconoodler]

I do see what you see,it's just in the amp it works.and quite well too.I'm not trying to argue or doubt what your eyes are telling you.
The ears on the other hand..........

Take a look at the portion I've circled on your schematic.Now picture that as the 'pump' and the master as the bleed valve.With just the pump you have no increase in the pressure,but with the pump cranked and the bleed valve as the control it makes perfect sense to me.
  This would work great with a pedal in front of the amp as the stock preamp doesn't have a huge amount of gain.It still grinds a bit without a pedal.This is the most pedal-friendly master I've found for the Princeton circuit.

[pullshocks]

Isn't that MV meant for the Marshall or tweed bassman preamp circuit with the tone stack at the end of the chain and fed by the cathode follower?

[sluckey]

Yes. Here's a page from the Trainwreck book...

[chocopower]

Maybe i´m wrong, but that second volumen is like if you change the old 1M vol. pot fot a 500k one. isn´t?

 

[weege]

If I may be so bold, I think what is missing is an explanation of what a master volume does.
Distortion is created by a series of gain stages boosting the signal level to a point well beyond what the last stage(s) can accurately reproduce and then an attenuator is inserted to reduce the distorted signal to the desired SPL. The implementation being discussed can't possibly achieve that because it's not at the END of a series of gain stages.
 

[alerich]

I don't see how this mod really does anything useful. Without the mod the tone control wiper goes directly to the original volume pot with nothing dropping any signal in between. With the mod in place you have an added 1M resistor to ground in the circuit. Not a huge load/drop but a load nonetheless. So even with both volume controls maxed you should still be dropping a bit of signal across the added 1M to ground which should really cut the gain a touch compared to the un-modded circuit. It's nothing but one voltage divider directly feeding a second voltage divider. Seems like the conventional raw control in place of the 6K8 mid resistor would be a better choice.

Having said that, I have not tried this. The only Fender amp I have is a Vibro Champ. No PI so it would not be an accurate comparison. psychonoodler has installed it and digs it. Perhaps something is happening that defies conventional electronics logic. Perhaps it's installed differently than the diagram (i.e. wrong, per se) and that is what is yielding the favorable result.

[phsyconoodler]

Ok lets look at it a different way.We all know what happens when you crank the normal volume.It maxes the preamp and the power section at the same time,right?You get a combination of preamp distortion(not much in this case)and power amp distortion.If the Princeton is set up right it sounds really nice,right?
  So you crank up the volume with the 'master' installed and it maxes the preamp in the same way,right?Then you choke it off with the second volume control before it goes to the rest of the circuit.The preamp is still maxed but it has the extra 'valve' to bleed it slowly to the rest of the circuit.You don't get the power amp distortion but the preamp is maxed out.
  It works incredibly well with a pedal in front of the amp.Not so well with just the amp.But most Princeton owners complain about the amp not being pedal friendly like a Deluxe or Super.This makes it VERY pedal friendly.

If your search is for a master volume that works like a PPIMV then this isn't it,but it is soooo good with pedals that I'm never going to fart around with other masters with the Princeton PI.
  It's 'phsyco' approved.

[sluckey]

So you crank up the volume with the 'master' installed and it maxes the preamp in the same way,right?Then you choke it off with the second volume control before it goes to the rest of the circuit.The preamp is still maxed but it has the extra 'valve' to bleed it slowly to the rest of the circuit.You don't get the power amp distortion but the preamp is maxed out.

I can't believe you're saying that!

[tubenit]

The first preamp gain stage is MAXED already prior to the second gain stage. Volume control has nothing to do with reducing the gain in the V1a.
V1a is full tilt and not impacted by tone or volume.

Tone or volume impacts the V1a gain going into V1b.

The volume control and your "master volume" is simply controlling the gain between the first and second gain stages. The volume pot alone will control that.

OR you can add a second volume pot (master volume) which will do exactly what the volume alone does.

However ..............

The second volume pot does create more resistance going into the regular volume pot. So at some level it adds more volume "control" ala resistance. You could add a 330k resistor between the treble and volume pot to accomplish a reduction in volume (& perhaps some frequency range)  also but it would not be adjustable.

The two volume pots in series is like adding a second resistor in series.

If you like the tone and the impact on tone, I think that is a reason to use it.


With respect, Tubenit

[alerich]

I had an old SF Princeton Reverb that was very pedal friendly totally stock. I got some great recordings of that amp in the late 80s. BOSS Turbo Overdrive -> SFPR -> Marshall 4x10 cabinet miked up with a Shure SM57. Fender amps are pedal friendly with the right pedal and the right person adjusting the knobs.

[phsyconoodler]

I know you guys are right and I see the mechanics of adding a series resistor to an already existing adjustable resistor.
  I'm trying to convince myself that this is working and it's putting blinders on me.
I guess I want it more than need it after the frustrating problem with master volumes on the princeton circuit.
  they simply all sound like crap to me.

[sluckey]

I never doubted what you hear. But your explanation is a bit slippery.   

[phsyconoodler]

Well there is lots of snow and ice on the ground up here and my coffee is just kicking in............
 It's like the 'master volume' you state side people put on the sun up here.He He.

[jerrydyer]

Ok lets look at it a different way.We all know what happens when you crank the normal volume.It maxes the preamp and the power section at the same time,right?You get a combination of preamp distortion(not much in this case)and power amp distortion.If the Princeton is set up right it sounds really nice,right?
  So you crank up the volume with the 'master' installed and it maxes the preamp in the same way,right?Then you choke it off with the second volume control before it goes to the rest of the circuit.The preamp is still maxed but it has the extra 'valve' to bleed it slowly to the rest of the circuit.You don't get the power amp distortion but the preamp is maxed out.
  It works incredibly well with a pedal in front of the amp.Not so well with just the amp.But most Princeton owners complain about the amp not being pedal friendly like a Deluxe or Super.This makes it VERY pedal friendly.

If your search is for a master volume that works like a PPIMV then this isn't it,but it is soooo good with pedals that I'm never going to fart around with other masters with the Princeton PI.

  It's 'phsyco' approved.
the preamp is maxed after the treble control then attenuated with the Volume Control. you now have two 1megs in a row allowing more to bleed to ground so you could prob find what you need in a 500k audio taper??
confusing post for sure but this is how I learn.

[phsyconoodler]

Ok,so your rubbing my face in it now?

[jerrydyer]

not at all sir. I did not know it was resolved.

[phsyconoodler]

Resolved? Hmmmm.........

  I think I'll have to get my face rubbed in it a few more times to really get it.

[phsyconoodler]

Take a look at this one.It's basically the same and the master is inserted right at the PI.Still pre-PI

[sluckey]

OK grasshopper. Now you're making sense. That's 100% pure type 4 MV.

[tubenit]

ALOT of amp building is mental because we're always searching for the perfect tone. I personally find the mental piece as challenging as the electronics.

Perseverance, commitment, contentment, willingness to venture out, planning well, learning how to problem solve, setting realistic goals ................ all part of what makes great amps, IMO.

Most of us have experienced something of a honey moon period with a new tweak. After the honey moon period, hopefully ....  we still experience it as a great mod/tweak ............ and other times, maybe we re-classify it as only "OK" and only sometimes or somewhat useful.

The fact is that Physconoodler makes incredibly toneful and beautiful amps! Check out his website and the sound clips on it. Excellent stuff!!!!!

It's quite a collection of impressive amps.

AND, some of the amps are truly unique and innovative, IMO. He was the first person I heard of trying cathode bias D-style amps  and his own vibrato design on one amp is phenomenol & it has sort of a vibrato/swirly uni-vibe tone.

Maybe this "mod" is proving to be just sorta useful?  BUT, I sure like it that you are willing to color outside the lines and try new stuff. Very cool!

 

With respect, Tubenit

[sluckey]

The fact is that Physconoodler makes incredibly toneful and beautiful amps!

And that's exactly why I've been poking at him.   

[tubenit]

And that's exactly why I've been poking at him. 

 

Well said!   

Tubenit
 

[phsyconoodler]

Sometimes easy concepts are hard for my limited intellect to grasp.That's why the sober minds on this forum are so helpful!
 I think we should bottle and sell 'Sluckey sweat' .Rub some on in the morning and you're good for the whole day.

One thing about me is that I'm not afraid to try anything,even if I burn the amp to ashes doing it.Nothing ventured nothing gained.

[macula56]

man, i love this place. you guys are the best.

[sluckey]

I think we should bottle and sell 'Sluckey sweat' .

Ha! Someone beat you to it. It's called Icehouse beer. Available at a super center near you for $7.97 per 12 pack of bottles. I highly recommend it!   

[PRR]

> in a Princeton circuit

There's two or three very different "Princeton"s. Which One is that first diagram supposed to apply to??

Can't be the AA1164.

[phsyconoodler]

Yes it's in an AA1164. i also have an extra gain stage in front of the first stage in this amp.It seems to work quite well.I dunno,maybe I did something different.All I know is that it's working well.

  I've tried the bootstrapped master in a few other AA1164's and they suck the hind tit IMHO.

[kagliostro]

If the added pot is wired like Sluckey supposed



have you think that the second pot connected that way acts like this resistor



that way you alter the linearity of the potentiometer and have a different response

http://www.geofex.com/article_folders/potsecrets/potscret.htm

may be what you note is an interaction between the two pots giving a different response in % of level in accordance with the different position of the same (two pots) ?

Kagliostro

[Fresh_Start]

i also have an extra gain stage in front of the first stage in this amp

If your "normal" volume is between the first and second gain stages and the "master" volume is between the tone stack and your 3rd gain stage, then it's Type 4 all the way and makes complete sense to me.  Not a Princeton, but a very cool circuit 

Cheers,

Chip

P.S.  Thanks a lot guys - I'm not sure that I'll ever be able to drink Icehouse beer again... "sluckey sweat"!!!

[sluckey]

I'm not sure that I'll ever be able to drink Icehouse beer again...

I thought I was their only customer!

[phsyconoodler]

quote:"If your "normal" volume is between the first and second gain stages and the "master" volume is between the tone stack and your 3rd gain stage, then it's Type 4 all the way and makes complete sense to me."

Yes the normal volume is between the first stage and the master is after that.i have a gain control for the first stage.It works pretty awesome.Ihave to lift the tremolo out of the circuit with a pot or it oscillates when the gain is high.With the trem disengaged completely the amp rocks.So it has a gain control for the first stage,a volume control inbetween and a master after the volume control.
 I crank up the gain where I want it,feed it in with the volume control that acts like another gain control,and then the overall level is done with the master.It does not just sound like having an extra pot that does nothing.
  I look at it in the schematic and I see that it should do nothing more than the existing volume control does now,but it doesn't act that way at all.
  No,I haven't been drinking.......yet.

[sluckey]

Arrrrgh! So I've been poking you for 3 days now and this ain't even a Princeton Reverb! I thought you were talking about a Fender AA1164 Princeton Reverb. Could you show us a schematic for the amp we've been talking about? It could be that nothing I've said is even relevant to your amp.

[phsyconoodler]

It is a Princeton Reverb that a guy wanted more gain from.(long story)I added a top boost like module to the amp and ran the wiring to the existing Princeton circuit.
 I just used a universal gain stage and put it in front of the existing amp.The input goes to the module first and I used a 1 meg grid to ground grid reference on the existing gain stage.
  I added a gain control to throttle the module down.There is a picture in the media section.
 The guy flat out loves it.It took a while to get it working properly but the end result sounds like a Marshall.It has tons of gain but can get somewhat of the original Princeton sound if you throttle the gain control way down.I used a 12AY7 to get the gain under control,as a 12AX7 was too much and it oscillated.
  So imagine this:gain module > gain control > first stock input stage > volume > master volume.Sort of like Peavey pre and post gain control. It actually seems to work just like that.With a hot set of humbuckers it does some nice rectifier-like tones and with low output pickups it's much mellower.
  I fiddled with the cathode resistors/caps until it sounds ok. I'm not a huge fan of what I'm hearing but the customer loves it to pieces.
My own personal Jam Amp is my 'little bastard' with a pair of 6L6's and a G12M celestion speaker.