prosonic mod question

[Alex D]

"IMPROVEMENTS- See all those little disc ceramic caps on the tube

sockets? cut them out with extreme prejudice. Not needed, and the

sustain and tone will improve. These do some funny business (Massive

local feedback) that does affect the audible signal. I don't know quite what I was thinking here."

 

Would anyone know what caps he is talking about? I open up my amp on the v1 there is a cap, but not where else. There are also two restistors on the power tubes. So I don't think those are it. Any ideas of what/where these cermanic caps are? Maybe a picture for me, I'm feeling really stupid since I can't find them

[Voodoo Amps]

"IMPROVEMENTS- See all those little disc ceramic caps on the tube

sockets? cut them out with extreme prejudice. Not needed, and the

sustain and tone will improve. These do some funny business (Massive

local feedback) that does affect the audible signal. I don't know quite what I was thinking here."

 

Would anyone know what caps he is talking about?

 

It's mod instructions such as these that you should be very careful about. We are only left to guess as to what caps he is exactly referring to as he has not provided any R/C board location numbers.

 

I open up my amp on the v1 there is a cap, but not where else.

 

There are two different versions of these amps any my guess (I say guess as there are no PC board designation numbers provided) is that you are referring to C301 (5pF cap) from pins 7 to 6 on V1B. This is removing highs from that stage that may be there to prevent HFO from happening (high frequency oscillation), which is something you do not want to contend with.

 

There are also two restistors on the power tubes. So I don't think those are it.

 

First, resistors are not the same as caps so you are correct in assuming that the resistors are not the caps the other person was referring to. Second, I would strongly recommend that you do not cut out any resistors that are connected to the power tubes as bad things will most likely happen. What exactly will happen? Hard to say for sure as you are not providing PCB designation numbers but unless you are willing to spend money on having a tech repair the amp I would not cut those resistors out.

 

Any ideas of what/where these cermanic caps are? Maybe a picture for me, I'm feeling really stupid since I can't find them

 

Email the guy and ask him to provide the PCB designation numbers for you. If he cannot provide them then my advice would be to not cut anything out of your amp unless you are prepared to take it to a tech to get it fixed because that is the gamble you are taking (not discouraging, just being honest)

 

 

Have a great day

Trace

[Alex D]

hey thanks, I got the info off of blue guitar web site. I searched the site for prosonic and it came up with the zinky mods, from zinky. I guess he used to do them but doesn't any more heres the link (edit: check below)

It also has the other mods like the power supply swap, but thats fine I know where that is and that it will have to be "fitted" to the prosonic as it doesn't just bolt in (amp tech job), but man if I could just figure out this easy mod, well not easy since I can't find it but if I did....

 

once again thanks for the reply and your help

[Alex D]

oops it doesn't direct link so here it is for the site

 

 

I recently acquired a Fender Prosonic Tube amp. The clean channel is very clean, but the distortion channel is giving me problems. Basically, there is a lot of crackling and popping and buzzing noise that is quite annoying, and the louder I turn it up, the worse it gets.

 

I don't have a lot of experience with amps, so my question is whether this is normal or whether something needs. The shop that sold it to me said that this is normal on a distortion channel. I play an Epiphone Les Paul with humbuckers.

 

Thanks,

 

Mike Wilson -- Mike

Mike Wilson

mchlwilson@hotmail.com

9/3/104 4:33 pm

A: Mike- Here is what Bruce Zinky had to say about the Prosonic amp (which he designed for Fender):

 

"PROSONIC POP

 

Caused by a few things:

1) Lousy relays. I have prototype #2 (Proto #1 went to the factory).

It only pops if...

2) Bad preamp tubes. Sovtek preamp tubes have a tendency to get

heater to cathode hum. Makes for a signal level difference when you

switch, which can give you the annoying "Pop". A spiral filament type, such as the Electro Harmonix 12AX7 is a good thing for the first two preamp tubes.

 

MAJOR CAUSE:

What you are getting is induced back EMF from the relays leaking into

the audio. R19 (on the Footswitch jack) was designed to always have

some signal flowing through the relays. Problem is, sometimes the value is too small and the relays hang, or sometimes it is too big and you get pop. Experiment with this value. 6.8k was the initial one, later changed to 9.1k (so the amps with abberent relays would still pass QC). [i now use very tiny low current 5V relays from NEC [ED2-5NJ] (mouser sells 'em).]

...

 

ALSO:

 

R13 Is 1 Meg. Reduce this value. This cap keeps the voltage at the

input of this tube [V2a] down when the relay is switching, and the circuit is otherwise open. A lower value will reduce the pop. Gain will be reduced slightly as well.

 

IMPROVEMENTS- See all those little disc ceramic caps on the tube

sockets? cut them out with extreme prejudice. Not needed, and the

sustain and tone will improve. These do some funny business (Massive

local feedback) that does affect the audible signal. I don't know quite what I was thinking here.

 

GAIN REDUCTION-

Some people like to remove some or all of the cathode caps in the preamp section to reduce the gain. If you never need the high gain, it's something to try.

 

...

 

Last Prosonic mod-

 

I would change the stock transformer to our Zinky unit, model

ZOT604816. This transformer will give much better bass response than

the original, AND the overdrive will not have any of the "Buzzy" or

"Fizzy" character you may hear with the stock one (Especially at low

volumes. Clean tones will be bright and airy, the big changes will be on overdriven tones). Does not fit the standard bolt pattern (Slightly larger), so you'll have to drill. $150 but well worth it. Has 4/8/16 Ohm taps. Will give you the liquid overdrive even at highest gain settings, even with high treble settings. Get dynamics AND tone....

 

Bruce Zinky"

 

http://www.blueguitar.org/new/schem/fender/modnotes/prosonic_notes.txt

 

- -- Steve

[Alex D]

here the scematic link. If your interested If you don't have the time that cools and thanks again for the help voodoo

 

http://blueguitar.org/schems.htm#Fender

[potaetoes]

i've tried all of these mods except the transformer.

 

the important modifications were all implemented at the factory by march 1997 (switch pop, reverb wire, etc.)

 

i'd leave the tube socket caps alone - better results can be had just swapping tubes around.

 

one thing bruce told me that would help balance tone between channels is to remove the treble-bypass cap from the drive channel (R6 or R7 or something, i forget which one and i don't have the schematic anymore). i didn't really like this, because i felt it added a little mud to the gain channel.

 

one thing i did that had great results was to add a treble bypass cap on the clean volume pot (experiment with values to find a good one), and change the clean channel's first coupling cap to a higher-quality poly cap. this helps brighten up the cleans without brightening up the dirt. messing with the value of the coupling cap doesn't work so well, because it affects the gain channel in a bad way. (when inactive, the clean channel is just grounded out, so there's some signal bleeding to ground through that coupling cap when you're on the gain channel, so... its value does have a noticeable effect on both channels and it's best left alone.)

 

bruce has stopped offering the upgrade transformers (and they are not available, period, from anyone), and he will no longer mod any prosonics, because of negative experiences he has had with a few people. he said this may change in the future, maybe, if he feels like it, but probably not. he points to the blue velvet amps as a better alternative to the prosonic.

[Alex D]

thanks alot with the help explaining and warning me about the mods, to bad about the transformer though Just so I can sleep at night could you exlain to me what the tube sockets caps are and what they look like? Their not the white discs that hold the tube in are they? I'm just a little confused and it's late Thanks again potaetoes you are a one

[potaetoes]

Originally posted by Alex D thanks alot with the help explaining and warning me about the mods, to bad about the transformer though Just so I can sleep at night could you exlain to me what the tube sockets caps are and what they look like? Their not the white discs that hold the tube in are they? I'm just a little confused and it's late Thanks again potaetoes you are a one

 

"caps" means capacitors. they're little tiny brown discs, some soldered directly to the sockets, some on the PCB. it would be pretty simple to clip a lead, try the amp out, and re-solder it if you didn't like the results. those amps are pretty easy to tinker with in general, everything is reasonably accessible and the circuit is pretty simple.

 

BUT, don't poke around in there if you're unfamiliar with the dangers of tube amp internals. you could get hurt.

[Voodoo Amps]

here the scematic link. If your interested If you don't have the time that cools and thanks again for the help voodoo

 

We have schematics but again there are no PCB designation numbers in Zinky's post.

 

 

Trace

[Grueller]

 

Originally posted by potaetoes the important modifications were all implemented at the factory by march 1997 (switch pop, reverb wire, etc.)

 

So if I have a Prosonic that was made after March 1997, there's no need for the mods? Where'd you get that info?

[Grueller]

 

Originally posted by innobidova So if I have a Prosonic that was made after March 1997, there's no need for the mods? Where'd you get that info?

 

bump

[potaetoes]

 

Originally posted by innobidova So if I have a Prosonic that was made after March 1997, there's no need for the mods? Where'd you get that info?

 

 

the reverb hum and switching pop updates were performed at the factory from 3/97 onward, according to fender and zinky.

[Loghead]

Very interesting.

[ghbaudio]

I have a 1996 Prosonic and cut the disc cap off the v1 preamp socket. It improved the top end of the amp. More treble seemed to be getting through to the speakers. Which I think the Prosonic needs. No problems what-so-ever.

 

Some silverface Fender amps had similar ceramic discs on the power tube sockets to deal with oscillation. but they bleed off high end & harmonics from the amp (the effect of the caps is -18 dB at 6 kHz). These were added because of problems with the lead dress that caused oscillation. Cutting them out improves top end and harmonics, but some amps won't run stable without them. Just have to give it a try.

 

Disc caps are dirt cheap and easy to replace.