Wasn't Me,,,
And Dang!!
Its nice to see George back isn't it? Lot of water under the bridge since this thread started!
Maybe some new idea's will pop up as well!
Have some new ideas, not quite in the $100 vein. Would be nice to get to them in a month or so, drew up some schematics that I want to hear what they will sound like. But at the moment I am getting in the last bit of woodworking in the garage before winter arrives. Took a break from amps and got bitten by the acoustic guitar bug.
I have seen some of your pictures.....nice stuff. I started making some solid body electric stuff in my wood shop class in Florida, but that came to a rather abrupt end before any guitar was finished and I haven't had the time to go back to them.
I have a phone camera picture of one of them. Two of us got first (unamplified) sound out of our creations on the same day, so we sat around jamming one night after class. I left Florida shortly after that picture, but the other guy has built several electric Ukes since that one.
It was my birthday last Wednesday, and the weather was perfect, so Sherri and I just hopped in the car and took a 400 mile self guided tour of Amish country. Got back late last night. 3 days of wandering aimlessly looking at really old stuff......and a few tubes, sparked a few wild ideas.
Even though I was happy with the sound of the amp, I just couldn't leave it alone, so I ripped into it again. I added another layer of rats nest wiring over the furball that I made last week, but now it rocks, really rocks.....
I added a new knob. This one I will call the saturator, because when you turn it all the way up that's what you are gonna get. Even the deadest guitar comes alive. Can you get screamin feedback from a 4 watt amp through a pair of inefficient (91db) six inch speakers with a $50 flea market guitar?.....you bet. Turn it all the way down, and its a mild mannered amp that's clean enough for acoustic guitar or electric piano (3% distortion at 4 watts). BUT.......
Much to the dismay of some previous players in this thread, there are TWO pieces of sand directly in the path between the guitar and the speaker, in addition to the 6 diodes in the power supply.
I traced a schematic of the furball, then put it into Eagle. A new PCB layout is underway, but it will take a few days.....too much other stuff to do.
Here is the Eagle schematic I just made. No guarantee that it is correct.
The first stage is unique. Pentode voltage amp. The mosfet serves two functions. These cheap radio tubes are all over the place, and have a rather low Gm, so grain of sand #1. The mosfet will supply a constant voltage to the plate regardless of the Gm of the tube, it's condition, or drive level. The voltage divider on the gate sets the source at half supply. The mosfet is also a source follower for the plate signal, and the followed signal also bootstraps the 10K plate resistor so it appears infinite. The pot (and the parallel combination of the two voltage divider resistors) is the ONLY real plate load on the pentode, so the pot sets the gain.....and it goes WAY past 11! Here the mosfet wins out over a tube. You could make this circuit with a tube IF you had enough B+, but this whole amp gets 170 volts on a good day. Mosfets are better followers than tubes due to their Gm.
The buffered signal drives the unusual tone control which has a loss of 10 to 15 db depending on setting. The tone control uses phase shifting to move the break point through much of the guitar's frequency range. It goes from dark and muddy to really bright. There is some frequency shift with overdrive for a weird effect.
The triode is a typical voltage amp to recover the tone control loss. The volume pot drives a mosfet splitter. This could be made with a tube, and it almost was.....but I already have a chassis and I can't fit 5 tubes. This circuit will stuff 35 volts P-P cleanly into those poor output tubes, which just clip the tops off the drive as soon as the grid goes positive.
With three gain pots (counting the one on the guitar) you can get some good tone out of this thing. I am amazed at the differences I get just by flipping the pickup switch.
I'll have more info later. I plan on building at least two of these, one "little big head" and one combo. Both should fall way within the $100 parts limit. I have more budget amps planned....because I have more crazy circuits to try.......
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I'm thinking that my next little amp might use 6AQ5's since I have several hundred of them. I want to use tubes that I have a bunch of for every tube in the amp.
Nobody is enforcing the rules any more. This thread was about making a playable guitar amp for a budget of $100. Unless anybody cares, maybe it should now be about an amp you would really want to use for minimum $$$$. Several good ideas were spawned here and a few amps were made. How many of those amps still get used?
I know that my Amp 1.4 got built, and wound up in a box for about 3 years. Despite not even owning a working guitar amp, I never felt compelled to dig it out and play it. It didn't ROCK. Instead I just plugged my guitar into this PC and played it though an amp simulator. Between that and the arthritis in my hands, very little guitar playing has taken place.
I found Amp 1.4 a few weeks ago, and beat on it until I liked its tone.....quite a lot. I had no constraints, I just wanted a REAL guitar amp. I found myself playing the furball and clip lead mess quite a bit....so I set out to make a new one.
Back then, several compromised were made in our designs to fit the budget. Now that we aren't constrained, we can use the parts we like to get the tone we want...Bring on the 12AX7's and the real OPT's, if that's what works. Anyone and everyone is welcome to play along...rules, we ain't got no stinkin rules!
Try to keep the drama to a minimum.....We all realize that not everybody had the same definition of "tube amp". So what! If you don't like my amp, don't build one. If you have a better idea, post it!
Amp 1.4 was a MINIMUM $$$ design, but it has morphed into something that I like, AND it still uses cheap stuff like $4 worth of tubes and a $4 OPT, AND they are still available, so Amp 1.5 will go forth.
More will likely follow....I haven't found Amp 2.3 yet, but it's tubes are no longer widely available. It had killer tone since it was based on the "Marshall 18 watt" design, but used oddball low budget parts. My future designs will be more mainstream.
I did some checking and found out that some of the components used in Amp 1.4 have gone extinct, and others cost more than they did 3 years ago, especially transformers. The Amp 1.5 design has quite a few more parts than Amp 1.4, but will still fit well within the $100 range.
Amp 1.5 has been an exercise in frustration. I laid out a new PC board, and spent much of Monday making one only to find out when I drilled the first hole that the registration was too far off for it to work, so I tossed it in the trash.
I made a new one Tuesday...or tried to, and something bad happened. Many tracks disappeared, and the ones that remained were full of voids. I tossed it into the trash and decided to try again. I found out that I was out of toner transfer paper, so I rescued the bad one from the trash and started making jumpers for all the bad traces.
For reasons that I still don't understand solder won't stick to the copper very well either despite scrubbing with abrasive cleaner and Scotch Brite. Yesterday I started populating the board anyway, and I finished it this morning.
I popped in 4 tubes, wired up the transformers, plugged in a speaker and a guitar, stood back and plugged it into the wall outlet.....no bang, no smoke, no drama....it just works! Now I need to make a proper cabinet.
Two pictures of the ugliest PC board I have ever made......
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Drama! What do you mean no drama! Actually considering the number of pages and the target we did pretty well back then.
Going low buck again, using a 120V tho 120/240V isolation transformer, and a 70V line transformer for the output. I looked up the cost in town for a 8W P-P Hammond transformer and it was over $50, forget that. Did a massaging of the above schematic, changed the Big Muff values, used the Tweed values for the caps which got rid of one pole of the switch. Response still looks not bad but hearing it will be the judge. Once I get it up and running will post an updated schematic and a sort of layout.
We'll see if the NFB will survive the final design and reducing the screen and following preamp voltages. Tore up my shop to make it more dust friendly and can not (really should not) start building yet, hopefully soon.
Going low buck again, using a 120V tho 120/240V isolation transformer, and a 70V line transformer for the output. I looked up the cost in town for a 8W P-P Hammond transformer and it was over $50, forget that. Did a massaging of the above schematic, changed the Big Muff values, used the Tweed values for the caps which got rid of one pole of the switch. Response still looks not bad but hearing it will be the judge. Once I get it up and running will post an updated schematic and a sort of layout.
We'll see if the NFB will survive the final design and reducing the screen and following preamp voltages. Tore up my shop to make it more dust friendly and can not (really should not) start building yet, hopefully soon.
Printer2 makes a good point about the Hammond OT's and I am finding that their list prices are getting up there! I am starting to look at Edcor, Triode and Musical Power Supplies. The OT5PP from that last supplier caught my interest. Maybe you could explore that and reduce wattage slightly.
It bothers me that Hammond is becoming more expensive option (they are Canadian company, and I have good access) but for a budget amp that 50 bucks for an OT would kill it for me.
PS you guys did darn well on the initial challenge.
It bothers me that Hammond is becoming more expensive option (they are Canadian company, and I have good access) but for a budget amp that 50 bucks for an OT would kill it for me.
PS you guys did darn well on the initial challenge.
I've used musicalpowersupplies transformers on a few projects, including my last (Bassman Micro) amp which used an OT5PP. Good stuff, and Matt is helpful about keeping the shipping costs to Canada down as much as possible.
Still, the low $CAD is a budget problem these days, buying from the US.
ClassicTone is another company with some reasonable prices - a possibility for your budget list- but I've never bought from them.
Yeah overall it was OK, Sometimes a lot of energy was wasted arguing about stupid stuff....like mosfets or knobs.
That's where the money is saved in Amp 1.5. The power transformer is a Triad N-68X which is now about $16. I use series string radio tubes wired to a FW rectified, but unfiltered 125 volt secondary on the N-68X.
The OPT is a $4 70V line transformer from Parts Express. That OPT works about as well as a $20 Edcor that I have from about 8 years ago. The loss is about the same, and the low frequency response goes down to about 50Hz before some saturation is seen. Tested with random unmatched P-P 32ET5 tubes and zero feedback.
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It looked like Musical Power Supplies was planning in future to get the OT5PP wound in USA according to website. I don't know why Hammond is getting up there in price, they keep telling me their ''audio transfo's'' are wound in Canada, so should be cheaper now for US customers based on US-Canadian currency exchange. I'll mention that to their rep next time I speak to them ;-)
That is what got me, if they were made outside of Canada I could see them being more as our dollar is down right now. Not sure why they should cost much more than before. Not a major problem, just need to look for vintage gear to recycle.
As simple as the other one is this one will be, much more. Won't bother with its own thread, probably just post it when done. Want to add reverb or at least an effect loop to add reverb. Schematic is a work in progress.
This one will be built as a head using 12W6 tubes for the output for a home friendly roughly 8W. I am going with the 12W6 rather than use 12BK5 seven pin tubes like I originally planned. The reason being the 12W6 is an octal tube and it will be easier to convert this to 6V6 power (actually 12V6, I have a few of them). Real excited about this one, sort of a barn burner.
I have some acoustic guitars I need to make but I am going to fit building these two in along side the guitars. Hope to have them all done before Christmas. We'll have to see how that will go, some R&D needed to be done for all of them.
Plexi-JCM-Trainwreck
This one will be built as a head using 12W6 tubes for the output for a home friendly roughly 8W. I am going with the 12W6 rather than use 12BK5 seven pin tubes like I originally planned. The reason being the 12W6 is an octal tube and it will be easier to convert this to 6V6 power (actually 12V6, I have a few of them). Real excited about this one, sort of a barn burner.
I have some acoustic guitars I need to make but I am going to fit building these two in along side the guitars. Hope to have them all done before Christmas. We'll have to see how that will go, some R&D needed to be done for all of them.
Plexi-JCM-Trainwreck
The 12W6 is a sleeper amongst forgotten TV tubes. Respect the screen grid voltage rating (150 volts). The plate rating can be violated rather rudely without ill effects. I blew up a couple of tubes finding this out several years ago when AES had their tube sale and these were super cheap. They will randomly run away at screen voltages above 200 volts. I think I was getting over 20 watts from a pair of these things on somewhere near 400 plate volts. Your schematic shows triode operation, which I did not try, however.
I started playing guitar back in the 60's when surf music was king.....GOTTA HAVE REVERB!!!!!
I found a reverb tank while digging through boxes looking for more of my old amp designs. I vaguely remember ripping the tank out of a Kustom solid state PA amp that had been butchered. I don't even know if it works. Somewhere here I have a defunct Crate solid state amp. I believe it has a tank in it too. I saved it for the cabinet, tank, and speaker. It was a victim of the same "expert" that fried the Kustom. I got them both for $5 each.
I have not tried to make an acoustic guitar, nor will I any time soon. I am still looking for all of the parts for the guitar I started 2 years ago in Florida. That's likely a project for next year though.
I started playing guitar back in the 60's when surf music was king.....GOTTA HAVE REVERB!!!!!
I found a reverb tank while digging through boxes looking for more of my old amp designs. I vaguely remember ripping the tank out of a Kustom solid state PA amp that had been butchered. I don't even know if it works. Somewhere here I have a defunct Crate solid state amp. I believe it has a tank in it too. I saved it for the cabinet, tank, and speaker. It was a victim of the same "expert" that fried the Kustom. I got them both for $5 each.
I have not tried to make an acoustic guitar, nor will I any time soon. I am still looking for all of the parts for the guitar I started 2 years ago in Florida. That's likely a project for next year though.
No not triode operation, just a sloppy cut and paste. I was marrying two schematics and I put the screen supply line out of the working area of the screen. Not a complete schematic, the power supply needs to be worked out.
20W? Was not hopping for anything like that, maybe 10W on a good day. Any chance you remember what primary impedance you used?
I know I used a 6600 ohm OPT since I use these for most of my experiments that could go wrong (I have several).
I probably used it at that impedance. The same OPT's (at 6600 ohms) produce 25 to 30 watts from a pair of EL 84's on just over 400 volts......JJ or vintage 6BQ5's only. Chinese or Russian blow up!
I do use these at 3300 ohms, but that should produce about 70 watts on 400 volts if the tubes don't blow up.
I probably used it at that impedance. The same OPT's (at 6600 ohms) produce 25 to 30 watts from a pair of EL 84's on just over 400 volts......JJ or vintage 6BQ5's only. Chinese or Russian blow up!
I do use these at 3300 ohms, but that should produce about 70 watts on 400 volts if the tubes don't blow up.
I don't remember, this was about 5 years ago, but I use variable power supplies in my experiments, and I probably just kept twisting knobs until something fried. I usually start at a certain screen voltage (about half the max spec) and take the plate voltage up in 50 volt steps, then go back and repeat at a higher screen voltage, until I find a good operating point.
Most tubes give ample visual warning that it's time to turn things down, but some will just arc over, or spark out. The worse case is when a tube works perfectly with no signs of distress, then after hours, weeks, or months of happy life, just goes into a random runaway condition. This usually happens when violating the screen grid of a sweep tube!
I still have a dozen or so 6W6's, and a few other candidates for these type of experiments, so an octal breadboard is in my future. This will get revisited.
I built guitar amps as a kid using tubes from the local trash dump. Most were based on the Fender Champ 5C1 schematic since the tubes were rather common in old radios and HiFi sets. I started experimenting with other output tubes when I couldn't find and 6V6's. One of my best "designs" was a "Champ" with a 6BQ6 sweep tube in it. Lot's of them for free in dead TV's.
Of course, these are memories from over 50 years ago. Maybe those things really sucked, but I am going to go back to my youth and build one of those things to find out.
Note, by attaching a wire with a plate cap on it to pin 3 of the usual octal audio tube socket, a 6BQ6 and a 6DQ6 will drop right in. At the time I didn't understand why the little tubes (6BQ6) were louder and sounded better than the big tubes (6DQ6).....I didn't understand things like bias or impedance, so maybe it's time to try again?
Hi there. Building a guitar amp right now - just for entertaining. It's got to fit in this radio I just killed - speaker and all. I got to use my imagination. One has to figure out so many things.... ruler rules in cases like this. I want 2 watts, speaker dunno, got to be small. Too many unknowns. Just a heads up.
There's this thing in the back of my mind telling me 'it's just a waste of time you moron, you're not going to use it', also I can hear this 'you just killed a nice radio schmuck', thankfully I refuse to listen to these negative voices.
There's this thing in the back of my mind telling me 'it's just a waste of time you moron, you're not going to use it', also I can hear this 'you just killed a nice radio schmuck', thankfully I refuse to listen to these negative voices.
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I'd just make it a head. I mean sure there's some certain alure to having a mini amp but that looks like a pretty rad box and you could pretty easily maintain the stock look for a cool all around package.
What looks like a headphone out on the front can be the signal in from guitar, you've got 4 knobs for say vol, lo tone, hi tone, (then maybe mid, presence, brightness or something). AND you've got 3 switches in the front for a NFB in/out, a "FAT" switch and a one last one for whatever your heart desires.
Kind of jealous really as I've been scouring the thrift stores for something just like this to chunk my tubes into
What looks like a headphone out on the front can be the signal in from guitar, you've got 4 knobs for say vol, lo tone, hi tone, (then maybe mid, presence, brightness or something). AND you've got 3 switches in the front for a NFB in/out, a "FAT" switch and a one last one for whatever your heart desires.
Kind of jealous really as I've been scouring the thrift stores for something just like this to chunk my tubes into