I stand corrected.
The LM3886 will run on that transformer.
The 18v min is a [v+] + [v-] value which could even be 18vct.

RDV

Quote from: joecool85 on May 26, 2006, 07:26:29 AM
I think thats +/-18 not that it needs 18v per rail.

Those are one and the same.

RDV

That transformer will work for an LM3886.

Gain Bandwidth    3 MHz
SupplyCurrent Per Channel    50 mA
Supply Min    18 Volt which is a [v+] + [v-] value
Supply Max    84 Volt
Output Current    11500 mA

Gotta have at least 9v per rail.

RDV

I had to fix this. I was wrong.

R.G. did the math, I'm not that smart! That's probably a conservative figure because it was every bit as loud as it's been with more powerful transformers.

RDV

My 36vct 56VA only made 30 watts with an LM3886. It was loud though.

RDV

I actually tried my Les Paul Jr. Special(w/P-100 pickups) with it last night and got the midrange pot oscillation that I've read about.

Bummer.

The circuit only seems to work right with full sized humbuckers. I also got a lot of noise with it that I couldn't identify.
I think this circuit is a little too high gain to be reliable as a preamp. I also doubt that there's enough voltage gain running at 9volts to run an amp to it's full potential unless you use a higher FB resistor.

I'm gigging this weekend too, which will limit the time I'll have available to fool with the circuit.

RDV

Quote from: javacody on May 23, 2006, 09:36:17 PM
I love my minibooster. I added RG's mods, and the pedal has way more oomph.

Me too & me too.

RDV

You know me, just email me the paypal bill once you know what it will be. I'm most interested in the LM1875, but I've got 2 toroids just ready to power something. The 20 + 20 200VA would work for the LM1875 one for sure. If that's not enough, I've got the 400VA one too.

RDV

Check yer email.

Quote from: joecool85 on May 17, 2006, 07:30:24 PM
I haven't even built one yet, but I keep hearing people rave about how great booster pedals are...whats the hype about?  Doesn't it just make your guitar louder?  Couldn't you just turn up the amp?

It makes the guitar bigger and makes the front end of an amp produce more distortion.

Let's say you have a single channel amp and a fuzz pedal, that's 2 sounds, add a boost and now you've got a 4 channel amp.

It's just another tool in the box.

I can send you a really good schem for one if you'd like, only takes a few parts.

RDV

The ebayer emailed with a correction, he now says the yellow wires are the primary. At least he owned up.

RDV

Quote from: joecool85 on May 16, 2006, 09:24:24 AM
Does he still check this board?

Every now and then I think, but I'm hedging my bets, I've posted this EVERYWHERE. I value everyone's input. I've learned some key stuff like the DC resistance being higher on the primary because of there being more windings there. That's huge.

RDV

I think everybody's right but the f**ker that sold me the toroid. Of course the smoke test will be the final judge. I wanna hear from dear Uncle R.G. before I try that though.

RDV

I asked the guy a bought it off of and he told me the black & white were the primaries but I don't think he ever hooked one up. He just got continuity between them and assumed. He sold about 4 of them and if others follow his advice they're going to burn up their trannys. No way would the secondaries be two different kinds of wire. I bought this one for the LM1875 kit when it comes along.

RDV

I just picked a 20v + 20v @ 5amps(200VA) Talema transformer. It's supposed to be a single primary and dual secondary. I guess it's a few years old NOS so I can't find any info on any website.

There are two double insulated(orange covered by yellow) stranded wires, and there are four solid wires(black, white, red, & green).

Would anyone know the deal with these? Would the two stranded wires be the primary? That's the only thing that makes sense if this is a single primary/dual secondary transformer.

What's strange to me is the lighter(though double insulated) wires being the line voltage & the heavier being the 20v.

I also searched the net for the word Talema and the only diagram I saw was not like this transformer.

I got continuity between the two yellow wires, between the black & white, and between the red & green.

I measured the resistance between the three pairs and got 3.3 ohms between the two yellow wires.

.8 ohms between the other two pairs.

Does this mean the two yellow wires are the primary? I got a response at DIYaudio saying that the larger resistance would be the primary, but I'd like an R.G. opinion on that one.

Please advise.

RDV