The Amp Garage

Thanks guys, especially you, rg. Your expertise is shining, and the generous dose of common sense makes the task far less daunting.

I'll let you know what I find.

I just finished another "Dilla" - 50 watts, EL34s, etc. They usually come out quiet as church mice; with nothing plugged in there's no hum and only the tiniest bit of hiss with everything dimed. But this one, well it doesn't have any hum but the hiss is way out of hand, very loud. Even if it only sh...

So, while you guys were answering my question without me knowing (I get no notification even though I checked the box to), I figured out that I needed a full bridge rectifier. It works great!

Thanks. The thread has some interesting stuff about particles and things. So, good stuff and things!

Hello, I have a Classictone 40-18015 power transformer. Its secondary has 300v at 200mA between the red leads, but has no center tap. Can I do without it? Or should be derived with resistors to ground as in many heater wire instances? I'm only noticing this now that I have it in my hands or I might ...

Thanks Mark! The cab was a fun build. When heating and bending the steel bars I tried them on the box while they were still hot, thus the burns. On this one I tried using transformers by Musical Power Supplies Inc. I usually use Edcor, at least for the OT and sometimes for both. But these are less e...

More pics
So, that's my latest.

Thanks everybody for your help. It got it done.

Okay, finally got it sussed. There were two ground connections that were crappy, one not connected at all. But moreover, this is cathode biased (EL84s). The resistors have Very tiny print and I accidentally put a 150K instead of a 150R. Boy, what a Duh! But now it sounds Great. Cranked all the way w...

Nope. Not the problem. I tried chopsticking everything to no avail, but I didn't expect much. The plate wire to the OT carry a lot of voltage but it's DC, not AC. However, while I was messing around in there I discovered some more odd behavior. I mean really weird. I'm going to scope it all out and ...

Good point! I checked to make sure no wires had compromised insulation, no shorts, but didn't think of a field effect. I'll check it out. Thanks!

Mr Fowler: here's a wider view of the schematic - LTP.jpg @jjman: it measures about 70v AC across the plates of the PI. Again, this vanishes if either of the plate feeds is lifted. There is no voltage to ground at the junction of Rp10 & Rp12. In fact, there is no input voltage at all either to the L...

@nworbetan: I tried a known good tube - the voltage was very slightly lower but still there. This amp design has no NFB. @ pdf64: I'm ashamed to admit it but it's been awhile since I was doing serious studying of LTPs. Been more about power supplies of late and mostly just putting together designs I...

Hello, I'm building the third of this design, a Coyote (by me), and have run into something Weird. It was making a horrible noise from the first time I tried it. A little poking around revealed that there is a 60 cycle AC voltage in the signal path that varies from 45 to 51 volts! I made some pics o...

Mr. Fowler - I'm not sure exactly what you mean but across the top, where the handle mounts, there are 2 straps of 1/8" X 3/4" steel that connect the sides together. It's plenty solid. To get into it there are pocket screws on the bottom. Loosen them and the whole top, cage and sides come off. pd64 ...

Here's a gut shot.

That was just the prototype. I tossed it together to see how it would do and it sold right away. Here's the full on production model: the Activax - A20 Coyote. It sounds really nice and is plenty loud enough for most clubs. This is the "Cage" style. It also comes in a "Hanging" style in a cab with t...