Did you play with the order of the pentode/triode sections? e.g., t->p->t->p, or p->t->p->t... Like the LED bias, must be a nice light show when fired up.
Just hit 1,400 posts!!
Jaz
Thanks, also what is the switch on the plate of the PI for, sorry if this has already been covered before...
Jaz
The amp is running Class A so I disconnected the top output tube so the amp runs sort of single ended rather than push pull. I was more curious than anything, it cuts the power down by half, I think the amp sounds better in P-P, it gets a little ratty at higher levels but I hear adjusting the screen can help there. I had the hole for the switch already so it was something I had to try.
The prodigal returns.
I won't derail the thread with a detailed account of all that's gone on in the last several months. Suffice it to say, I must have signed up for a lot of work on karma in my last lifetime -- 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.
*********
Once again, I'm going to modify the 'rules' and rewards of this challenge. Rather than choosing one design as better than all the others (a flawed premise from the outset), I've tried to identify those who kept this thread going and growing. No, this isn't political correctness, where everyone gets a prize simply for showing up. I scanned many pages, and tried to pick out a dozen people who truly formed the core of this discussion.
Obviously, Tubelab and Tubekit were the source of this (almost always) friendly competition. Printer2 also puts a great amount of thought and time into his well-illustrated posts. TheGimp, Trout, Scitizen17, Djgibson51, Costis_n, Cassiel, ChrisA, Jonnyeye, and Wavebourn all kept the discussion lively and interesting. Kevinkr, with his moderator's hat on, rounds out this baker's dozen of worthies.
If other readers or participants feel I've overlooked someone, please chime in.
************
I too have 'magpie syndrome' -- except that my storage area looks like the last scene of 'Raiders of the Lost Ark'. So instead of paying the BOM tab for one 'winner', I'm going to ship a box of goodies worth at least $100 to each of the people listed above.
I have thousands of NOS tubes. hundreds of pounds of passive components, and many rare goodies to make A DIY tinkerer salivate. If you will tell me your preferences as to category of components, I'll try to oblige. Want sleeves of tubes? How about boxes of new aluminum knobs? Envelopes full of resistors, or bags full of polypropylene caps? 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?
Gentlemen, let me know your preferences, and a shipping address, in a PM. For those folks overseas, please be realistic -- I'll be glad to send you tubes or other lightweight components, but a box full of transformers isn't likely to come your way.
****************
I hope this twist is acceptable to all, and thanks for keeping things going while I dealt with much unpleasantness.
I won't derail the thread with a detailed account of all that's gone on in the last several months. Suffice it to say, I must have signed up for a lot of work on karma in my last lifetime -- 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.
*********
Once again, I'm going to modify the 'rules' and rewards of this challenge. Rather than choosing one design as better than all the others (a flawed premise from the outset), I've tried to identify those who kept this thread going and growing. No, this isn't political correctness, where everyone gets a prize simply for showing up. I scanned many pages, and tried to pick out a dozen people who truly formed the core of this discussion.
Obviously, Tubelab and Tubekit were the source of this (almost always) friendly competition. Printer2 also puts a great amount of thought and time into his well-illustrated posts. TheGimp, Trout, Scitizen17, Djgibson51, Costis_n, Cassiel, ChrisA, Jonnyeye, and Wavebourn all kept the discussion lively and interesting. Kevinkr, with his moderator's hat on, rounds out this baker's dozen of worthies.
If other readers or participants feel I've overlooked someone, please chime in.
************
I too have 'magpie syndrome' -- except that my storage area looks like the last scene of 'Raiders of the Lost Ark'. So instead of paying the BOM tab for one 'winner', I'm going to ship a box of goodies worth at least $100 to each of the people listed above.
I have thousands of NOS tubes. hundreds of pounds of passive components, and many rare goodies to make A DIY tinkerer salivate. If you will tell me your preferences as to category of components, I'll try to oblige. Want sleeves of tubes? How about boxes of new aluminum knobs? Envelopes full of resistors, or bags full of polypropylene caps? 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?
Gentlemen, let me know your preferences, and a shipping address, in a PM. For those folks overseas, please be realistic -- I'll be glad to send you tubes or other lightweight components, but a box full of transformers isn't likely to come your way.
****************
I hope this twist is acceptable to all, and thanks for keeping things going while I dealt with much unpleasantness.
Well, welcome back. Hopefully there would be no more sorrowful times for you, now that karma has done its nasty stuff .
Well, apart from me being at the bottom of the barrel sharing places with Costis and Johnnyeye *cough cough* I think Wavebourn left the game too early, I'd swap him with.......(can't remember his name), the one who builds guitars and posted a few recordings. Australian I think. Probably my 'peculiar' sense of humor put him off so I'm feeling a bit guilty. Never seen again.
Well, apart from me being at the bottom of the barrel sharing places with Costis and Johnnyeye *cough cough* I think Wavebourn left the game too early, I'd swap him with.......(can't remember his name), the one who builds guitars and posted a few recordings. Australian I think. Probably my 'peculiar' sense of humor put him off so I'm feeling a bit guilty. Never seen again.
Sorry to hear life has been throwing you a bunch of fast balls. Good to hear you are back. The challenge was fun in that it got us thinking and working on our projects. As far as I have looked at things the prize was to look at your design and see something to be proud of, that you might inspire someone else to pick up side cutters and iron to build or build upon your design, or at least learn from your mistakes.
While the concept of picking a winner and offering a prize seemed simple enough from the beginning, I would say now the practicality of it may not have been. So now we have a gracious offer of treats for all the good kids for participating in the fun. Well it just kind of knocks me over. You are being much too gracious.
While the concept of picking a winner and offering a prize seemed simple enough from the beginning, I would say now the practicality of it may not have been. So now we have a gracious offer of treats for all the good kids for participating in the fun. Well it just kind of knocks me over. You are being much too gracious.
Wouldn't running the PP OT in SE cause it to saturate, may be at low power level, it isn't too bad?
Jaz
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 just by reading and trying out the various designs that appeared in the thread, thanks again!
Jaz
I did try this arrangement.
RCA Receiving Tube Manual RC30 (resides on my iPad thanks to Pete Millett) gives a figure for input resistance at 50MHz.
So I have a lot of 100pF caps in the current circuit.
Using triode strapped pentode in the second stage I couldn't stop the oscillation without rolling everthing off above 1KHz - not a good sound. I don't have enough shed time to hunt down the possible layout cause of this so reverted to the posted schematic. A value of A=16 in the 1st stage was just too hairy, A=8 was just too polite, A=12 gave a sustained rude ballsy rock sound that had me grinning for days.
Cheers
JimG
See picture on Post 1321.
The 4 LEDs are 3ml items behind 2ml holes in the top of the chassis in a line between the two tubes.
Half my 6BL8's are used items and this way I can see at a glance if each tube section is at least passing current after everything has been buttoned up. LED in middle of front panel tells me heater circuit is also delivering.
Cheers
JimG
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.
I hope the storm is truly over, or at least subsiding. We are still dealing with the after effects.
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.
The Aussie that made the cool guitars was WDCW.
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?????
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???
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.
Attachments
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.
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.
Attachments
Output tubes? 6K6???
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.
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.
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.
6V6.
Sounds like fun to me.
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.
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.