Prowler <-> Valveking

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Prowler <-> Valveking

Postby Fael » Fri Nov 26, 2010 3:04 pm

I bought a used Peavey Prowler and I read that it was almost identical to the Valveking 112. I analyzed both schematics and there are very few differences. I'll note some of them:

Code: Select all
       Prowler - Valveking
R122 =  470k   -   220k
C105 =  2.2nF  -   absent
C149 =  820pF  -   1nF
R173 =   47k   -   3.9M
R148 =  100k   -   56 (marked as R4)
C134 =    1nF  -   270pF (marked as C2)
R150 =  220k   -   150k
R151 =  100k   -   330k


These seem easily replaceable. However, there is a part of the preamp that I did not fully understand and I would really appreciate if somebody could lend me a hand deciphering what are the differences between both schematics on that part. That tricky part is the tone stack on the distortion channel.

Prowler schematic:
Image

Valveking schematic:
Image

Apparently, the Prowler has semi-active EQ while the Valveking 112 has passive EQ. Is there a way to convert the Prowler's tone stack into the Valveking's?

Moreover, there is another difference near the end of the preamp. The difference is that the Prowler includes 4 extra diodes (all 1N4148). What are these diodes for?

Image



Schematics:
Peavey Prowler
Peavey Valveking 112
Fael
 
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Postby Geek » Fri Nov 26, 2010 5:08 pm

Hi,

The tone stacks are just a Baxandall in the Prowler w/notch filter that acts as a mid-boost in an active circuit (I do similar in my guitar amps), while the ValveKing is just a standard issue Marshall or Fender stack.

The diodes around the transistor keep voltages from gowing below ground or exceeding B+. A good thing in a guitar amp exposed to all sorts of I/O from people who know music, not device ratings ;)

Cheers!
-= Gregg =-
Fine wine comes in glass bottles, not plastic sacks. Therefore the finer electrons are also found in glass bottles.
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Postby Fael » Fri Nov 26, 2010 6:22 pm

Geek wrote:Hi,

The tone stacks are just a Baxandall in the Prowler w/notch filter that acts as a mid-boost in an active circuit (I do similar in my guitar amps), while the ValveKing is just a standard issue Marshall or Fender stack.

The diodes around the transistor keep voltages from gowing below ground or exceeding B+. A good thing in a guitar amp exposed to all sorts of I/O from people who know music, not device ratings ;)

Cheers!


Thank you very much for explaining that!

I have some more questions, then:

1.- If someone as knowledgeable as you (and Orange!) use this kind of tone stack, it cannot be bad. I'm not implying that it's better, just that it's not worse, only different.
What is the difference between a standard tone stack and a Baxandall tone stack? I read that it's the same difference between subtractive EQ (standard) and additive EQ (Baxandall). However, when mixing, subtractive EQ is almost always better as it doesn't load the signal.

2.- Those diodes seem like a good idea. Specially for newbies like me. What I'm not sure about is: why would Peavey take them out for the Valveking? Cost-cutting reasons or tone reasons? If it's the second one, how much tone loss are we talking about?

3.- Would the Valveking mods apply to the Prowler? (for example, taking R122 out, the bias mod, etc).

Again, thank you very much!
Fael
 
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Joined: Fri Nov 26, 2010 12:14 am

Postby Geek » Fri Nov 26, 2010 10:55 pm

1) Each stack is for a different tone. There is no one better than another. They all work similar in different ways.

Try this program and enjoy watching how they work:
http://www.duncanamps.com/tsc/


2) Beancounters pull them out, or perhaps over time they proved redundant in a particular stage.


3) Maybe. I'm only experienced with the Triple-X and 5150.


Cheers!
-= Gregg =-
Fine wine comes in glass bottles, not plastic sacks. Therefore the finer electrons are also found in glass bottles.
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