Ok, got a chance to smoke check it and all is well. I was a little worried, as the amp has a line reversal switch that I wasn't sure about, but everyhing fired up on the limiter and I didn't get any nasty suprises. :tu:

The mod Roly suggested worked great! Nice clean tone till ya hit 6 on  the dial, and then nice fat crunch all the way to the end. I played it for the better part of an hour playing with all of the controls and finding the sweet spots and I'm really pleased with it. It does have a slight 60Hz hum that's there even in standby, so I'm figuring a cap job on the electrolytics is in order. It has three of the multi caps up on the top, but what's a few bucks more to get that nice clean sound.

While I was screwing around with the amp, a customer came by and checked out the amp. It turns out that he's a Harmony guitar collector, and he was blown away by the amp. He's offered up some enticing trades, but I don't know if I'm quite done playing with my new toy yet. We'll see what happend, but right now I don't see this amp getting out of my reach anytime soon.

Roly, you da man :dbtu: Thanks again for finding the killer sound in my garage sale head!

Baja

I'll be sure to post up the results tonight when I get home and fire it up. I was all set to give it the once over last night, and realized that I left my light bulb limiter at the shop. It wouldn't be a big deal, but I had all the tubes out and replaced the power cord while I was in there. I figure another 24 hours is better than finding out the hard way that I missed something.

Baja

  Sweet! I had some time this morning so I dumped in the 25uF cap across the cathode resistor. I slid the amp back together so I can fire it up and do a test run tonight, so I'll report back with the changes as soon as that happens.

  It was interesting to see that the 12AX7's had different values of cathode bypass caps here and there, from .2uF to 35uF. It'll be interesting to see the difference in the gain. Thanks again Roly, you da man!

Baja

Well, I spent some time looking last night and ran across a guy that made a post about having a schematic. I emailed him and got a much clearer copy in my inbox this morning. I'll still have to add in a few values that aren't real clear, but it's way better than starting off with the GIF image I had.



Baja

Yea, I had a feeling that was where I was headed.... looks like I'm gonna need an eye loupe and a bottle of asprin :grr

This point to point is kind of a pain to follow, but I should be able to trace it out and get a schematic up. Thanks for all of the help guys!

Baja

Well, I got my cap and opened it up. I'm now positive that the schematic posted is not the same at all. After tracing the inputs back a bit, there's no 68K in the circuits at all, and the placement of the the 12AX7's are different fron this amp to the one in the schematic. I looked online for an hour or two and the only schematic I can come up with so far is a GIF that is so blurry that I can't make out the component values. The schematic does however follow the circuit covention to a tee, so I'm positive that there's a good schematic out there.

Anyone got an idea where I might come up with a readable version?

Baja

Just got back! That's definitely the monster, good looking until you see all the spagetti inside. I'm going to run down to the parts store this afternoon and pick up some parts to give your idea a shot. Thanks Roly!

Baja

That makes sense. I'm on my way out for another few days, so I'll take the datasheet for the 2005 and play with the ducan calculator while im gone. I'm sure I'll have a bunch more questions by the time I get back... :cheesy:

Baja

Thanks Juan... Believe it or not, I have a distortion plus in the "box of doom". It's a great pedal, and I love it even more since I did the Wampler mods to it. I was just thinking that for only having a few bucks in it it might be cool to dial it up to where a guy has some nice crunch later in the dial. I know I can do it with a pedal, but it would be nice to do it without :tu:

Baja

I like the big muff stack, but I read that it was lossy and needed a recovery stage before the power amp. I like the way it looks on the stack calc, but will I need another gain stage to compensate?

Baja

I was on my way home this evening and spied a head unit sitting on a table at a garage sale. I pulled in and looked at it, and when the gal told me it worked and the price was $35, it followed me home :tu:

It's a Harmony 535 (tube), and is a loud 35 watts. The only thing I can say about it is it's way to clean, no crunch at all. Anyone know what forum might be the best to ask a few questions about hotrodding it a bit? I don't want to litter the SS forum up with a bunch of tube talk, but I trust the opinions on here and thought the question was worth asking.

Thanks,

Baja

Man, I want your job!

I was stuck in a hotel downwind of the dairy, with a train that came through every night at 2:30 am.

Your idea sounds way better.... :dbtu:

Baja

Just got back from 14 days on the road stuck in a hotel without internet

Had some time to do some screwing around while sitting in the hotel, so I changed up my preamp a bit to try to give the whole 1 knob tone stack thing a try. I used the stack out of a Matchless Lightning and tried my best to fold it in with what I already had. I ordered up some MPF102 and some BC549C, but found out this morning that they won't be here for another week. I had a couple of questions about this one:

I left the gain from the first circuit alone and added the matchless stack in behind it, do I need that second FET behind the circuit to buffer the impedance for the input of the TDA2005, or will it work fine the way it is drawn? I really like the way this tone control works on my buddy's tube amp (lots of fat tone), but I'm not sure if it will sound the same with the 2005?

Here's the circuit:


Thanks ahead for the input, man am I glad to be back in touch with the web!

Baja

Quote from: phatt on April 26, 2013, 11:30:03 PM
Re Pwr Amp?


Not sure about this but my understanding is that the + input of those black blobs (opamps) should have a ground ref or bias voltage ref. Head scratch?

Or maybe I've missed something?
Phil.

Man, I'm not saying I don't have it wrong, but I took the front end of that circuit right out of the spec sheet. I looked back through it and I can't find any of the circuits that aren't this way?

Quote from: Roly on April 26, 2013, 09:58:05 PM
um ... shouldn't the south end of the Zobel networks be grounded?

Yep, cleaned up one too many line on the schematic. Thanks for the catch.