The Hundred-Buck Amp Challenge

[Printer2]

Originally Posted by jazbo8

Wouldn't running the PP OT in SE cause it to saturate, may be at low power level, it isn't too bad?

Jaz

No the OT does not saturate, well at least until the amp is into overdrive on bass notes. If you think about it, when there is no signal both tubes are idling with roughly equal current going through both legs of the transformer which cancels out the static magnetic field. Nothing changes that if both tubes are driven, or in the case of one tube being driven.

[tubelab.com]

multiple deaths in the family, a flooded home, and a spouse diagnosed with a chronic disease. Thankfully, the sh*tstorm has pretty much abated, and things are looking up.

I hope the storm is truly over, or at least subsiding. We are still dealing with the after effects.

Sorry to hear about the ordeal you had endure of late, glad to see your return, you should really be the one to get rewarded for creating one of the most successful threads in this forum, I have learned so much

Same here. It would be hard to imagine someone who really took the time to read and think about the posts in this thread who didn't learn something.

(can't remember his name), the one who builds guitars and posted a few recordings. Australian I think.

The Aussie that made the cool guitars was WDCW.

Tubelab, I know you like high voltage. How about a huge potted UTC transformer, and matching choke, rectifiers, and HV sockets to construct a 1600v, 2200mA power supply?

The events that I have gone through in the past three years has changed things quite a bit. After cleaning out the houses of both of our parents, the economic downturn, and the fact that I will be "retired" sometime in the next few years and will leave Florida, has convinced us to seriously downsize our "stuff". I have already sold or given away all of my high voltage stuff. I don't plan any more amps operating above 750 volts, the remaining parts will wind up on Ebay as soon as I have it all sorted out. I don't have room to keep it all, so I must decline your offer.

I now have two guitar amps that I didn't have before this thread started. They don't have proper cases yet, but that will change soon.

I was asked early on in this thread if I was going to offer a PC board for the amp I created here. My antics on this forum usually generates email. This thread and the two amps I made have generated exactly ZERO email, so I must assume that there isn't much interest in cheap guitar amps using oddball tubes. I think I will make a new version using the usual guitar amp tubes. Any interest?????

whats this years compition ?

Something we would all want to build at a reasonable price???? Prize to the design that keeps this tread alive for another year and another 1000+ posts???

Gentlemen, let me know your preferences, and a shipping address,

I am consent with the knowledge and fun that I got from doing all this (other than a few minor incidents) no prize is necessary. In fact I spent the day today at a hamfest SELLING my tubes and "stuff". I will do it again next weekend.

[scott17]

Welcome back bst! I'm very glad that the future is looking much better for you.

I certainly did not contribute to this thread at the level of many folks here. Your offer is very kind and generous.

Best regards,

Scott

[Cassiel]

Thread looks to be dead again. I'll take care of that. OK, cheap, cheap, looks like crap but it's not. I think my new amp fits the criteria of this thread. No schematic yet. All junk parts, good tubes though -the 717a rocks! Another great pentode to the list, my favorite so far. The OT is SE from vintage radio, the amp is push-pull. Paraphase PI.

This one is a keeper. The amp was great out of the box only thing I did was to lower the value of a coupling cap because bass was wrong now all it's OK. Sometimes you luck out, Frankenstein design process, just putting parts together and hoping for the best.

[jazbo8]

Originally Posted by Cassiel

Thread looks to be dead again. I'll take care of that. OK, cheap, cheap, looks like crap but it's not. I think my new amp fits the criteria of this thread. No schematic yet. All junk parts, good tubes though -the 717a rocks! Another great pentode to the list, my favorite so far. The OT is SE from vintage radio, the amp is push-pull. Paraphase PI.

This one is a keeper. The amp was great out of the box only thing I did was to lower the value of a coupling cap because bass was wrong now all it's OK. Sometimes you luck out, Frankenstein design process, just putting parts together and hoping for the best.

¡Mira qué Mono!
Schematic and clips, por favor!

Jaz

[tubelab.com]

Output tubes? 6K6???

Thread looks to be dead again.

No time for fun stuff now. Long work hours and two more hamfests in the outdoor season to clean out the warehouse.

I decided to ressurect the octal version of Amp 2.2 for a new round of experiments. Just fired off an order for a bunch of parts for this round of experiments that might fix the variable gain circuit that failed miserably in Amp 2.0. No mosfets this time.

Also cooking up a low powered tube amp that can run on batteries. OK, no big deal....so to make it a bit more challenging...it's got to fit INSIDE the guitar.

[Printer2]

Building a Princeton type amp, not in the $100 range. After that I think I will try my 15-20W Bassman/Marshall/Tweeker amp, maybe $200 range.

[Cassiel]

Originally Posted by jazbo8

¡Mira qué Mono!
Schematic and clips, por favor!

Jaz

Well, I think I should draw it; probably because there aren't many guitar amps out there with a 717A and a floating paraphase PI. Also, I'd love to post some clips, even though the recording process tends to be a nightmare. I still have bad memories of the last one. That amp was a lemon.

Output tubes? 6K6???

6V6.

Also cooking up a low powered tube amp that can run on batteries. OK, no big deal....so to make it a bit more challenging...it's got to fit INSIDE the guitar.

Sounds like fun to me.

[djgibson51]

Very nice Cassiel

[benb]

I hadn't heard of "floating paraphase" and wondered what it is, but a quick look found it here:
The Valve Wizard
That second tube, with Rg and Rf equal as the text states, looks a lot like a gain-of-one inverting op-amp circuit!

Google first got me to here, then I clicked the link at the bottom to get to the page above:
The Valve Wizard -Paraphase
Back when I was growing up all I had was the "RCA Receiving Tube Manual," and it's obvious I missed a lot of different circuits used in tube guitar amps, and surely tube hifi amps as well.