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Post subject: Prosonic - How Clean is Clean
Posted: Fri Nov 18, 2016 8:23 pm
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I'm currently a Super Sonic player (22 and Twin) and quite happy with them . . . BUT I keep reading about the Prosonic and from what people say it must have some kind of magic mojo in there . . . SO I've been jonesing to try one and today I did. A nice 2x10 combo -- externally perfect as far as I can tell -- turned up on my local Craigslist and I so I drove across town to play it.

I could tell within the first 30 seconds that the gain channel was awesome. The tone sounded MUCH larger than 2x10s should be expected to deliver.

However, the "clean" channel did not resemble the "clean" that I'm used to. At very low volumes, clean was clean and sounded pretty good, albeit a bit thin. But if I turned it up at all - like to 1 or 1.5 - which was actually pretty darn loud - clean was no longer clean. Rather there was a buzzy, not so nice raspiness to the sustain. This distortion was very prominent and spoiled the clean tone in my opinion.

My question for those out there familiar with this amps - is it NORMAL to have a lot of distortion on the clean channel at reasonably loud volumes on a Prosonic?

Seller said the amp had very low hours and the immaculate looks certainly bore out that claim. Tubes appeared to be original though, so perhaps they were in need of a change. But the seller also had a Prosonic head sitting around (2 of them actually) so we plugged the head into the 2x10 speakers in the combo, and to my ears the head had exactly the same distortion on the clean channel as did the combo. (It didn't sound like bad speakers to me BTW.) So if it was a tube issue, the tubes in BOTH amps had the same poor condition, which would be surprising. (And of course also the gain channel sounded great - which seems unlikely with bad tubes.)

If clean on these amps is normally this raspy, the Prosonic is not for me --as I like a good clean clean to contrast my dirt. But if it is just a matter of old tubes, I might be willing to give it a try. Any thoughts out there from Prosonic fans? Are Prosonic cleans normally a bit dirty?

BTW I tried all the class and rectifier settings - A and A/B, tube and solid state - clean channel was equally distorted on each.


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Post subject: Re: Prosonic - How Clean is Clean
Posted: Sat Nov 19, 2016 2:48 am
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The amp need to see a qualified tech.


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Post subject: Re: Prosonic - How Clean is Clean
Posted: Sat Nov 19, 2016 4:32 am
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The Zinky-designed Pro-Sonic was never really intended to deliver traditional clean Fender tones. An examination of the schematic will reveal that the pre-amp features a total of four cascaded gain stages, with the tone-stack situated pretty far downstream between #3 and #4. As well, the master volume control is also uniquely positioned to favor a saturated input signal. Thus, the gain remains high regardless of the master volume setting. Switching the rectifier stage to the solid-state mode will prevent traditional power-supply sag but with the inherent signal already compressed and saturated, this is of little practical value when undistorted tone is desired. Thus, you'll never hear the classic cleans of a blackface or silverface from the Pro-Sonic.

http://www.thevintagesound.com/ffg/sche ... _schem.jpg

It's why I passed on buying one of these amps fifteen years ago when my primary rig (a silverface Twin Reverb) required some maintenance and I needed an immediate replacement. I ended up buying a TRRI instead. If I played hard rock, heavy metal, or grunge exclusively the Pro-Sonic would be ideal. But playing in a classic-rock cover band, I needed a jack-of-all-trades amp that could deliver a wide variety of tones.

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Post subject: Re: Prosonic - How Clean is Clean
Posted: Sat Nov 19, 2016 9:57 am
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Retro has it right.
My experience was a cold, glassy tone.
The long signal path almost guarantees it.
Then we put in some Bulge Boy and Telefunken preamp tubes.
Much improved clarity and some of the coldness was gone, but it still wasn't anything like a clean Fender tone.


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Post subject: Re: Prosonic - How Clean is Clean
Posted: Sat Nov 19, 2016 10:07 am
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I'll try a 12AT7 in V1


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Post subject: Re: Prosonic - How Clean is Clean
Posted: Sat Nov 19, 2016 10:32 am
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TimsAudio wrote:
Then we put in some Bulge Boy and Telefunken preamp tubes.
Much improved clarity and some of the coldness was gone, but it still wasn't anything like a clean Fender tone.


+1

A few years after I'd passed up the opportunity to buy one, a client of mine brought his Pro-Sonic (combo) to me for routine service and maintenance. He'd mentioned that the amp seemed excessively "muddy" at times so I experimented with different pre-amp tubes in an effort to clean it up. Significant success was achieved by replacing V1 and V2 with NOS mil-spec 5751's from my personal stash (the gentleman paid dearly for those bottles!). It wouldn't quite pass muster for surf music but it was substantially cleaner than with the stock tube array, albeit with some loss of gain and saturated OD. As well, I replaced the amp's OEM speakers with a new pair of Eminence Copperheads.

Arjay

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Post subject: Re: Prosonic - How Clean is Clean
Posted: Sun Nov 20, 2016 1:07 am
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There's clean and then there's Fender clean. When asking "how clean", most don't really want truly clean, but prefer the slightly ringing and slightly blended sound with chords that you get from a good Fender amp.

If you really want clean clean with no color, you need to either use a PA with HiFi speakers, or go for one of the metal amps that have clinically clean tones, like Diezel, Randall or ENGL. It may seem paradoxical that the amps used for the most heavy distortion also have the cleanest cleans, but when shredding without distortion in drop tuning, you really need it to avoid notes blending together.


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Post subject: Re: Prosonic - How Clean is Clean
Posted: Tue Nov 22, 2016 2:48 pm
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Thanks for the helpful responses. I infer from the comments that the Prosonic's preamp tends to send an overdriven signal to the output stage even in the "normal" mode at relatively low volumes (if there is such a thing with this amp), resulting in distortion. That explanation seems spot on.

I got curious and experimented with my Super Sonic 22, which normally has a good clean tone in the "vintage" channel, by opening up the vintage channel volume at 50% and higher while attenuating the amp's output using a volume pedal in the effects loop, which is between the preamp and power amp. The result was unpleasant (IMO) preamp distortion VERY similar to that which I observed in the Prosonic's normal mode at reasonably low volumes.

Also I've learned the concept of "clean" tone is very subjective. Online you can find many opinions that the Prosonic has a great clean tone. I think what this suggests is that many people enjoy the sound of a Prosonic in the normal mode (i.e., the "clean" mode), even though the tone is not really "clean" at all, in the Blackface sense. You can also find seemingly contradictory opinions that the Prosonic will not produce a good clean tone at all. These opinions may reflect an expectation that a Fender amp in "normal" mode will sound "clean" like a Blackface--and the Prosonic will not.

In any case, what I've learned is that the Prosonic is not for me, because the clean tones I want are along the lines of Blackface Fender. My Super Sonics already deliver those pretty well, and provide a good high-gain sound also--perhaps delivering some of original promise of the Prosonic. :wink:


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Post subject: Re: Prosonic - How Clean is Clean
Posted: Tue Nov 22, 2016 3:22 pm
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JDB2 wrote:
In any case, what I've learned is that the Prosonic is not for me, because the clean tones I want are along the lines of Blackface Fender.


+1

Which is precisely what I discovered fifteen years ago when seriously contemplating the purchase of a Pro-Sonic, unlike others here who weighed in on this topic who've never owned one, played one, or even seen one.

As well, many who commented elsewhere about the favorable clean-tone comparison between it and an actual blackface Fender have no frame of reference to proffer such an opinion simply because they've never owned or played a real blackface either. Absent some hands-on experience they're merely wasting some forum's bandwidth.

Arjay

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Post subject: Re: Prosonic - How Clean is Clean
Posted: Tue Nov 22, 2016 5:45 pm
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Something about that Prosonic tripped my wayback machine and when I was trying to figure out the Prosonic head I was working on.
I dug up these service bulletins for hum reduction and correcting a relay drive circuit.
The unit I worked on already had these mods, I believe, from the factory.
While you passed on the amp, someone else reading may find these useful.

Image


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Post subject: Re: Prosonic - How Clean is Clean
Posted: Sun Mar 12, 2017 9:52 am
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Well, I didn't give up on the Prosonic, and I'm glad I didn't. :) There is plenty of sparkly clean headroom in the head I picked up recently. :D Both clean and dirt sound huge with the matching 4x12 Tone Master cabinet. :mrgreen: Something must have been amiss with the combo I test-drove and posted about back in November. Or maybe it was breakup in the 2x10s? I was playing it pretty loud.

Image


Last edited by JDB2 on Sun Oct 29, 2017 7:32 am, edited 3 times in total.

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Post subject: Re: Prosonic - How Clean is Clean
Posted: Tue Mar 14, 2017 7:34 pm
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JDB2 wrote:
Image

A pre-90s Gibson Special, i.e. the oddball with an alder body instead of mahogany? Cool!


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Post subject: Re: Prosonic - How Clean is Clean
Posted: Tue Mar 14, 2017 8:08 pm
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From the schematic... the Prosonic doesn't appear to have global negative feedback. Plus, uses a 12AX7 instead of the traditional 12AT7 in phase inverter position. That, plus extra gain stages has to make this amp intended tone be different than the blackface dual-6L6GC Fender amp.

http://ampwares.com/schematics/prosonic.pdf


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Post subject: Re: Prosonic - How Clean is Clean
Posted: Tue Mar 14, 2017 10:35 pm
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I've played through a couple of them.
Guy I used to jam with about 15 years ago or so had 3 of them.
All were the 210 combo variety.

I wouldn't call them Marshalls.
Not saying that anyone here did but I've heard that said before elsewhere.
That they were Fender's Marshall.
I wouldn't call them Marshalls because you can often get a half decent clean tone out of a Marshall.
Prosonic, not so much.
I also wouldn't call them Marshalls because the cranked tone ain't very British.
Kind of a class by themselves.

Maybe that's a great thing.
Lotsa people looking for a different sound.

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Post subject: Re: Prosonic - How Clean is Clean
Posted: Tue Mar 14, 2017 11:02 pm
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BMW2002Ti wrote:
From the schematic... the Prosonic doesn't appear to have global negative feedback. Plus, uses a 12AX7 instead of the traditional 12AT7 in phase inverter position. That, plus extra gain stages has to make this amp intended tone be different than the blackface dual-6L6GC Fender amp.


+1

The Pro Sonic had a good tone......it just didn't have the traditional Fender blackface or silverface tone that experienced players are familiar with. That said, IMO it was a better amp in many respects than the line which replaced it -- better built, better S/N ratio, better reliability.

Arjay

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