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Post subject: Princeton 112 volume control
Posted: Wed Apr 06, 2011 11:35 am
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I am trying to find out if the two volume controls on a Princeton 112 amp are sensitive. Both volume controls go from nothing to loud between zero and one. The owner wants both potentiometers to be replaced. Since both potentiometers equally jack up the volume, I suspect this is normal operations.
Does anyone know if Princeton 112 amps are designed to be so loud at number one setting?
Doug
San Diego


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Post subject: Re: Princeton 112 volume control
Posted: Wed Apr 06, 2011 1:41 pm
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So many Princeton !!!!
Which one exactly ? For instance Princeton 112 plus is a solidstate amp !

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Post subject: Re: Princeton 112 volume control
Posted: Wed Apr 06, 2011 2:23 pm
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Tis-san wrote:
So many Princeton !!!!
Which one exactly ? For instance Princeton 112 plus is a solidstate amp !


The box says it is a Princeton 112, type PR 290
Doug


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Post subject: Re: Princeton 112 volume control
Posted: Fri Apr 08, 2011 4:40 am
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Here is the schematic:
http://support.fender.com/schematics/gu ... ematic.pdf
I don't know if you can tame this amp by a mod. May be the pot variation law (linear log antilog ) 8)

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Post subject: Re: Princeton 112 volume control
Posted: Fri Apr 08, 2011 7:19 am
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Thank you Tis-san for your reply. I downloaded the schematic earlier but it does not have a parts list. I was hoping someone had this amp and could tell me from personal usage if this is normal operation to go loud in one step.
Doug
Electronics Tech - not a musician
San Diego, USN (Ret)


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Post subject: Re: Princeton 112 volume control
Posted: Tue Apr 19, 2011 7:21 am
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I am an amp engineer in england and I quite often get these amps in for volume taming as my customers call it. Yes this is a modern Fender (businessmen not enthusiasts for their products) marketing ploy. They use linear volume pots so that when you play it in the shop it appears very loud at the low end of the dial which gives the impression it is going to be louder still at gig volumes. In reality when you crank it beyond 3 it doesn't really increase volume much but just gets more and more raunchy with a typical poor transistor pre-amp distortion. That said there are some great sounds to be found in both channels in this low range which is where the mod comes in. I replace the linear pots with audio or logarithmic to give them their correct name. The result is you now have a far more regulated control with a useable range upto 7 where it then starts to get nasty. My customers love it.

kenda47
Send Electronics UK


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Post subject: Re: Princeton 112 volume control
Posted: Tue Apr 19, 2011 9:50 am
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[quote="kenda47"]I am an amp engineer in england and I quite often get these amps in for volume taming as my customers call it. Yes this is a modern Fender (businessmen not enthusiasts for their products) marketing ploy. They use linear volume pots so that when you play it in the shop it appears very loud at the low end of the dial which gives the impression it is going to be louder still at gig volumes. In reality when you crank it beyond 3 it doesn't really increase volume much but just gets more and more raunchy with a typical poor transistor pre-amp distortion. That said there are some great sounds to be found in both channels in this low range which is where the mod comes in. I replace the linear pots with audio or logarithmic to give them their correct name. The result is you now have a far more regulated control with a useable range upto 7 where it then starts to get nasty. My customers love it.

kenda47
Send Electronics UK


Thank you for the great reply. I have informed the owner that his amp is working normally. I am glad you took the time to confirm what I was thinking.

In testing, I heard the distortion at the higher volume levels. My first guess was dirty volume pots, so I cleaned them but it did not change the distortion My final conclusion was a speaker problem. Now I understand what is really going on. I am indebted for your knowledge and help.

Doug, USN (Ret)
Electronics Tech
San Diego, CA.


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Post subject: Re: Princeton 112 volume control
Posted: Tue Apr 19, 2011 11:49 am
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Unwanted distortion, both harmonic and IM, are generally byproducts of the circuit design and the components used to execute it. A better speaker may help but as with anything else related to electronics (and I'm sure you learned this in "A-school"), garbage in - garbage out.

HTH

Arjay

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Post subject: Re: Princeton 112 volume control
Posted: Tue Apr 19, 2011 6:51 pm
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Retroverbial wrote:
Unwanted distortion, both harmonic and IM, are generally byproducts of the circuit design and the components used to execute it. A better speaker may help but as with anything else related to electronics (and I'm sure you learned this in "A-school"), garbage in - garbage out.

HTH

Arjay


I went to some of the most advanced 'C' level electronics schools run by the Navy.
I was under the impression that Fender only produced the best amps. So I did not consider a faulty design as the probable cause of the distortion. I did consider the very large jump in volume as normal operation since it was equal on both left and right.
Right from the start, I told the owner that changing the pots, as he wanted, would not change the volume control. He insisted I change the pots, so I found someone more knowledgeable than myself to convince him it was a waste of time and money. I am thankful there are people who would give me such good advice.
I am also thankful to Fender for its willingness to have such a forum.


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Post subject: Re: Princeton 112 volume control
Posted: Tue Apr 19, 2011 7:27 pm
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ic1doug wrote:
I was under the impression that Fender only produced the best amps.


Forty years ago you couldn't have been more right.

Unfortunately it's a whole new ballgame now, Doug.

:(

Arjay

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Post subject: Re: Princeton 112 volume control
Posted: Wed Apr 20, 2011 12:38 pm
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Retroverbial wrote:
ic1doug wrote:
I was under the impression that Fender only produced the best amps.


Forty years ago you couldn't have been more right.

Unfortunately it's a whole new ballgame now, Doug.

:(

Arjay


I am a dinosaur. The Navy schools I went to in the 1970s, taught us component level trouble-shooting and the math on how the circuit worked. The tests were full of mathematical equations and tested our knowledge of how the components interacted with each other.

Now, it is cheaper to buy another. It has been 25 years since I used an O'scope. So it was like deja-vu when someone wanted something fixed. Since it was not broken, I didn't get to use my years of training and experience. Unfortunately, it's a whole new ballgame now.

Doug


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Post subject: Re: Princeton 112 volume control
Posted: Wed Apr 20, 2011 12:58 pm
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Luddites like us are frequently castigated, ridiculed, and scorned by today's generation of "disposable economy" MTV addicts.

:lol:

I learned the biz (formally) at Keesler AFB, around the same time frame as you.

Arjay

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Post subject: Re: Princeton 112 volume control
Posted: Fri Apr 22, 2011 12:24 pm
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Luddites like us are frequently castigated, ridiculed, and scorned by today's generation of "disposable economy" MTV addicts.

:lol:

I learned the biz (formally) at Keesler AFB, around the same time frame as you.

Arjay

It is more than no knowledge needed. There is simply no way to repair a lot today's electronics. Even if you spent the time to figure out which board was bad, there are no spare parts sold. Even if the parts are available, they cost more than buying new. I had a great TV and the tube went out. I could buy another CRT for $900 and pay the shipping of $95.00, plus the tax of $85.00. Or I could buy a new and much larger TV which could play HD and had every format.

The company that has these CRTs must know nobody is ever going to buy them at that price.

It is a whole new world

Doug


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Post subject: Re: Princeton 112 volume control
Posted: Fri Apr 22, 2011 12:44 pm
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ic1doug wrote:
It is a whole new world


Which is why I'm driving a 25-year old pickup truck!

:lol:

Arjay

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