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Good or bad idea?

Started by xxRUZZTYxx, March 22, 2017, 02:46:13 AM

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xxRUZZTYxx

Hi all.forum noon here.
So I have this crappy little silvertone practice amp that was given to me. I like it for the fact it has O/D, reverb and an input effects loop.so it makes it a good starting point for my project (fingers crossed)
Part 2. I have an old TOA PA amp (1979 built)
It's 180 watt max and it's damn heavy and built properly.

Here's the hope bit.. do away with the pre amp on the PA (pretty much 1 circuit board to remove) do away with the power amp bit of the guitar amp and combine to make my own amp head so to speak.. is this at all possible? I know a decent amount about electronics to get me by.
I'm figuring somehow cutting the amp circuit on the guitar amp and then making this the "pre amp" board in place of the one removed from the PA?
Some pointers in the right direction would be much appreciated.
Some may ask why would I bother? I just recently had knee surgery and I have a lot of time on my hands.

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mexicanyella

#1
Some more knowledgeable people may come along and speak to specific electronic concerns, and probably ask that you post some schematics so that they have some specific info to base their answers on.

In the meantime, have you actually tried plugging your amp's FX send into a "FX return" or "Power amp in" jack on the TOA? Before physically trying to combine circuits, connect them electronically and evaluate whether it's even a good idea from a sonic standpoint. Silvertone as preamp, TOA as power amp, into as many different speaker cabs as you can get your hands on. You may find that it's an otherwise unobtainable killer tone, or that it's blah and not worth the effort or risk of trashing both the Silvertone and TOA past the point of reassembly.

There are a LOT of ways to provide OD and reverb, and using the Silvertone as preamp and TOA as power amp may well be one that flips your lid. But don't lock yourself into that just because it's what you have.

phatt


If you think it will fit then check the power supply voltages in the PA,,if same then yes it could power the silvertone preamp.

I agree with *mexicanyella* find out if it will fly before you take off,,  8|

Phil.

xxRUZZTYxx

Thanks for your input. It is just stuff that I have but it's also stuff that I'm happy to experiment with.meaning if I kill them no biggie.
The silvertone is only a little 15 watt ss thing that is "ok" and I think it may have  potential.
I believe this little amp was marketed under a couple of other brand names too. I will see what info I can dig up.

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xxRUZZTYxx



These are the 2

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mexicanyella

#5
Could be an interesting project. I am experimenting with the chassis of a Dean Markley K-20 guitar amp, a couple of pedals and a Peavey M-3000 mono power amp as a bass rig, but what I'll probably do is combine the K-20 and pedals on a pedal board and keep the M-3000 on top of the speaker cab(s). This way I have the option of carrying the pedalboard back and forth from home to practice space, using the power amp and cabs with the band and driving a small practice cab with the K-20's 15 watts @ 4 ohms output at home.

I'm running an Ibanez compressor pedal in front of the K-20 and a DOD Bi-Fet preamp after it to slightly boost the low-ish line out level before the power amp;  the DOD's tone knob allows me to subtly tilt the EQ post-tonestack too, which is useful since the tonestack's EQ points aren't quite optimum for my bass tone. I get the gain structure and tone in the ballpark with the K-20, then fine-tune with the DOD. 

xxRUZZTYxx

It's those who dare to push it and experiment and come up with a signature sound that others would like to emulate ☺️

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xxRUZZTYxx

Before any of my wild ideas with this I had gone back to basics playing around with pickup combos. 2 of my guitars I have played around with have similar direction but their own sound.
Dean MLXF - seymour Duncan dimebucker in the bridge and the original Dean DMT bridge humbucker in the neck position.

No name Les Paul - Bill Lawrence 500xl(neck) in the neck position and a DiMarzio crunch lab in the bridge..

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joecool85

I think it's a great idea personally.  If power supply voltages don't work out, if you have room you could always move the power supply from the guitar amp along with it's preamp section.  Then just tap everything into the mains voltage and away you go.
Life is what you make it.
Still rockin' the Dean Markley K-20X
thatraymond.com

J M Fahey

No big deal as far as Electrinics, but you´ll have a *packaging*  problem.

Not sure the Silvrtone front panel and presumably full width PCB will fit inside the TOA cabinet and viceversa with the TOA power amp, power supply, heavy transformer and heatsinks.

personally I would build a powered guitar cabinet since ypu will need some cabinet anyway: build a 2 x 12" cabinet, maybe a Twin Reverb like side by side which will be some 65/70 cm wide, or one on top of the other, this time the same width of the Silvertone which I estimate in 45 cm wide, or thereabouts.
Same width (or slightly more) is needed so the Silvertone sits nicely as a "tall head"  on top of the 212 cabinet.
Then in the bottom of the cabinet backside you mount the TOA amp, as is, hardwired to the speakers, and add an input jack which goes straight bto the power amp input or some suitable Aux one.

That way for home practice or easytravel toa friend´s home you just use thye light and handy Silvertone, and when rehearsing or playing LOUD you also bring the powered cabinet and join both with a Guitar cable. Of course each will need its own Mains connection, no big deal.

I suggest this because for Homebuilders the main problem is not the Electronics side but the "mechanicals" .

xxRUZZTYxx

Space inside the TOA probably won't be an issue..If need be I can drill holes in the base of the chassis and relocate things. Being from the 70s the circuitry is a lot more simple than today. The board inside the silvertone is the width of the input and controls but it's not very deep.i will put some pics up when I get everything opened up properly.

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J M Fahey

Yes, gut pictures will help a lot.
maybe you´d like to put them side by side in an extra picture to compare space needs or availability; but is suspect the long narrow guitar preamp PCB is longer than TOA chassis width.
You *might*  also build a "fat Twin" sized combo: 2 x 12" side by side, a slot cut on top for the Silvertone preamp and the TOA amp solidly bolted in the bottom, you may even "unify" mains connections and use only a single mins cable and turning everything ON with a switch mounted in the Silvertone (I guess you´d have to upgrade it though)
You use just the Silvertone preamp and disconnect its power amp, you may even pull its chipamp, no longer needed.

Polytone amps were conceptually the same, a bottom mounted powr amp and a top preamp, with speaker(s) filling the available space in a very compact package.

of course, mount the Silvertone preamp up front like it is now, forget the all-you-can-stuff crazy fiberglass filling, and your bottom mounted TOA will be in its own enclosure, while this one is a bare chassis, no big deal since it´s a sealed enclosure, but you´ll probably want an open back or semi open back cabinet.

But although not very common today (it was all the rage in the 40´s) , the idea is practical and thousands of Polytones keep working today, some over 40 years old.