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Messages - Enzo

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Guitar speakers naturally roll off the highs, and I wouldn't think of them for piano, at least not as a first choice.   I would think a search of PA speakers might do better.  And if you are using a guitar AMP to drive the speaker, then double no.  A small PA system, and so many now include EQ, which provides any mid-scoop you might want.

Amplifier Discussion / Re: Crate G130C Amp
« on: July 23, 2020, 01:26:58 PM »
And the factory doesn't need to be there, ANY competent amp tech can repair this.  I bet you have a local shop.

I surely wouldn't assume the same zener needs replacement.  It MIGHT of course, but frankly it is more likely your FX loop jacks have dirty contacts.

Don't read too much into it.  A 4 ohm load on an 8 ohm rated amp won't automatically blow it up.  The poor thing will run out of gas if you push it, but polite play won't hurt.

Also, the load impedance will have no effect on the filter caps.

The compressor is basically just a compressor, the control is not a compression level or "amount" control.  The compressor control is the threshold.

The Newcomer's Forum / Re: early 90s Peavey Stereo Chorus 212
« on: July 20, 2020, 01:29:03 PM »
Refresh the connections to the DFX card.

Schematic please.

I could be way off base, so consider that.  But you have both 15v rails at the zeners, but do you get both rails right at the IC, IC8b?

Just thinking, but normally that IC sits between the two 15v rails and centers between them.  Well, the center between plus and minus 15 is zero.  And whatever appears coming out of that IC is what is going to output the amp.  At least at idle.

SO what if one of the power rails doesn't make it to the IC?  Then the poor thing tries to center between 15v and zero, which is 7.5v, and that is what is on the output.  Obscure, yes, but possible.

Amplifier Discussion / Re: Peavy 130 Special needs some TLC
« on: July 10, 2020, 08:21:17 PM »
It is rated down to 4 ohms, but an 8 ohm load will make it perfectly happy as well.  Take your pick.  What speaker is in it?  As far as I know the stock speaker in those is a 4 ohm Scorpion.

If I understand your concern:  the amp is rated for 4 ohms minimum load.  The internal speaker is plugged into the amp.  If the internal speaker is already 4 ohms, then there is no capability left for an external speaker.   If the internal speaker is 8 ohms, then you can ALSO use an external 8 ohm cab.  The two together make a 4 ohm total, and that is fine.

Or you can unplug the internal speaker and use an external 4 ohm cab of choice.

Amplifier Discussion / Re: Peavy 130 Special needs some TLC
« on: July 10, 2020, 06:15:50 PM »
It doesn't care about the reverb.

Look up "light bulb limiter" and make one and use it.

Amplifier Discussion / Re: Peavy 130 Special needs some TLC
« on: July 10, 2020, 02:26:39 PM »
Wire a plug to the speaker and plug it into the SPEAKER jack on the rear panel.

test the speaker with a 9v battery.

Reverb pan is 4EB2C1B.  or equivalent.

Amplifier Discussion / Re: Altec 770 Biamplifier
« on: July 09, 2020, 10:11:01 PM »
I wouldn't think so, maybe across R3 or R4.  Personally I do it by looking at crossover distortion.  Star at the coldest setting, apply a sine wave and watch it on the output.  Now advance the bias until the crossover notch JUST disappears.  Most adjustments by the current spec will be a little warmer than this.  I like it though.

Remember it was getting hot just idling?  That means it is turning power into heat.  SO a quick and dirty close enough method is to monitor mains current draw of the unit.  Start at coldest setting and start advancing the bias control.  At first the mains current stays low.  At some point (in fact, the point the crossover notch goes away) of a sudden, mains current starts to rise with the bias adjustment.  At that point, stop and back off ever so slightly.

people will make arguments for one way or another, but these methods will get you close enough.

Amplifier Discussion / Re: Altec 770 Biamplifier
« on: July 07, 2020, 07:52:35 PM »
So what happened when you turned down the bias?

Amplifier Discussion / Re: Speaker switching
« on: July 03, 2020, 10:42:28 PM »
For that matter, using the existing speakers in those two combos, a readily available ABY switch on the front end would work too, wouldn't it?

You are right, we need to isolate the speaker grounds.  The Peavey speaker return is NOT to ground, it has a current sense resistor there.  I don't have JC120 handy, but the similar JC77 does reference speakers to ground.  But still, even if both went to ground we might create a ground loop if connecting them.

When you described the project, I immediately got a mental picture of how I would do it, your inner vision is diffrent, but I bet yours will work too, and if it differs by one relay, so what.   I have a very lengthy history in relay systems - think old pinball machines and other control systems - and I think certain ways, but it ain't rocket surgery.

Amplifier Discussion / Re: Speaker switching
« on: July 03, 2020, 08:57:34 PM »
It shouldn't matter if either amp sits unloaded, so how about one DPDT relay per speaker?  Or for that matter a single 4PDT.

The commons go to the speaker terminals, then the throws go to jacks from either amp.

My personal view: seems kinda hard core to switch between those two amps in the middle of a song.

The Newcomer's Forum / Re: session 75
« on: July 01, 2020, 03:40:05 PM »
Clean the jacks and especially the cutout contacts in them.

Amplifier Discussion / Re: Rocktron Rampage R80
« on: June 23, 2020, 08:49:38 PM »
The return jack has a cutout contact.  It needs cleaning.  If that doesn't work, then replace the jack.

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