Here's a crappy sample. http://fatboy.ssguitar.com/index.php?dir=Samples/&file=Artist%20-%20red2.mp3
With Epi Les Paul. I'll do a better one soon.
Straight to computer through a PT-80 delay. There is some fluttery digital distortion there.

RDV

When I get it boxed up(hopefully today) I'll start with the samples & stuff.

The DB would make an excellent high-gain channel for a DIY SS amp. You'd have a lot of knobs between the 2 channels(My clean preamp I built has 5 knobs and a switch) so it'd be an 11 knob job + a switch. I'd need a huge chassis. I'm wondering(out loud) if a higher voltage would give a bigger output? I suppose it would have to. I run my Thomas/Vox pre at about 15v.

RDV

I put the Dr. Boogey together tonight in a marathon 5 hour session. It was a bit tedious wiring 6 pots but boy was it worth it. This is the best sounding high-gain DIY distortion yet. I'm not sure you could make it better unless a footswitchable cleaner sound could be made available. With that, you'd never need anything else. It really sounds good through my chipamps and I suspect a clean amp is where this will shine brightest. I always have trouble with super high gain circuits through my Marshall. The timbre of the distortion reminds me of my Fab-Metal but with less fizz and more meat!

A heartfelt DIY thanks to Electrotabs!

RDV

I believe this would be a good limiter between a preamp and an amp however it would be nice to be able to adjust the maximum output voltage by a pot or something so you could set it just below the point that a chipamp clips.

RDV

First of all, tranformers gots polarities. See those dots on the transformer schematic? All the leads with dots go positive (and negative, in turn) together.

Each winding used as a primary needs to be driven with its rated voltage. In the case of the dual 115V ones, you connect dot to dot, non-dot to non-dot, effectively paralleling the primaries.

If you get one winding reversed, you will see major smoke when you power it.

The transformer's rating is based on having enough amperes flowing into the core so the secondaries can take their designed current out. Dual primaries are made half the otherwise-required wire size each, so to get full power out, you must have the designed current flowing in each primary winding. You do this by paralleling for 115, or series for 230. Both situations give you equal current in each winding, and contribute each primary's fair share of ampere-turns to the M-field inside.

If you series two windings, you must connect a dot to a non-dot, and then put voltage across the series setup. again, if you connect it backwards, major smoke pours out, and the transformer is itself tranformed into a Darkness Emitting Diode (also called a DED).

You cannot get more power out of a tranformer than it's designed for by any means except running it at a higher frequency. So, no, hooking each secondary up individually will not help. What the spec is telling you is that each 18V secondary will do 1/2 of the specified 18V current when they are paralleled; this is the same current they will supply in series, which is shown as 36Vct. Same voltages, same currents, hooked in series instead of parallel.

You want primaries parallel, secondaries in series for your amp, since the LM3886 is designed for +/- power supplies.

I prefer a 42Vct 2A transformer for the 3886. Parts express used to sell one of these for $15, but I can't find it at their site now. Even better is a 115/115/22/22 toroid. I got a few of these on ebay.
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R. G. Keen

What's the application?

RDV

Do it do it do it.

RDV

Welcome Peter!

RDV

I had left the ground of the crossover out of the star. I rectified that and got rid of about 75% of the hum. I used one of my multi-output transformers for the x-over/subamp and it just didn't occur to me that I had to ground the x-over too since they were both running off the same transformer. What I didn't get was that this transformer is like 4 seperate in one, each with their own needs.

RDV

My stereo LM3886 amp has 0 noise of any kind but the subamp is another story. It's in a wooden box so there is no chassis ground as such. I did use star gounding techniques building it though. It doesn't hum till I plug it into the mixer. There's a chance I didn't filter the supply for the x-over enough. I'll probably poke around at it later, right now I'm burned out from a 3 gig weekend, but I got a pocket-full of dough so it's all good.

RDV

I've got a ground loop occurring with my subamp which I'm running from an aux out on my Mackie mixer, it goes from there to an active crossover, then into a chipamp into the sub. I disconnected the ground on the signal cable that goes from the mixer to the subamp. Doing this took the hum away from my near-fields but sort of increased it in the subamp, well either that or now that it only comes from there that's how I'm perceiving it, I don't know. Would a 1:1 isolation transformer be the way to go, leaving the signal ground unhooked still? I'd like a little advice before proceding.

TIA

RDV

That certainly makes sense because the LM4780 is just 2 LM3886 in a single die. It still sounds good though. I won another toroid on ebay. This one was a bargain. It's 20v + 20v 200VA.

RDV

The guitar amp really sounds good using the paralleled LM4780. I'm probably just in the "Honeymoon stage' but it deeper and less fizzy to my ears than the LM3886 ever did. We'll see when I can do some higher volume testing.

RDV

One of the 27 pins(#16) on the LM4780 was not soldered well which caused my rebuild not to work. I troubleshot for about 4 hours or better before I got it. 27 pins is a bunch of pins to be soldering. It's working wonderfully as a guitar amp at the moment replacing my blown LM3886. I've got another parallel LM4780 PCB to build and make a stereo LM4780 amp with a 20v + 20v 400VA tranny. I picked the lower voltage to make the amps run cooler (at the sacrifice of a bit of wattage). They'll still be a good 80 clean watts per channel, and I won't have to use as big of a heatsink methinks. It'll still be pretty good size.

RDV

I don't have any time. I fixed the non-working LM4780 board and put it in the guitar amp. I'll post more 2morrow.

RDV