The original champ only had some 8u's in there, plus it was all I had on hand
. If it's an issue I can always come back later and put some beefier ones in there. VVR is just one that's been widely circulated around (shown below). Only difference is on the same little proto board board I've got the filament float resistor divider.
The home of the magic pixes got installed tonight. Still waiting on the trafo's but I've got an extra PT that I'll be able to test the VVR out with in the meantime. Few last things to change on that board and then it'll go in too. Left the rectifying diodes long but after looking at it I might drill the rivets out and shorten it up some to preserve some room. I've also got a couple of tube recs that would work well, after some testing is done I may/may not put those in. There's some bigger plans for this guy but I got the bare-bones wired up first and will test from there!
As an edit, sorry about the lack of a VVR schema, must have forgotten to put that in when I posted I've got the output 4007 included in mine.
As an edit, sorry about the lack of a VVR schema, must have forgotten to put that in when I posted
I've got the output 4007 included in mine.An externally hosted image should be here but it was not working when we last tested it.
Last edited:
Want to tweak some values yet. Not really sure about the NFB, get a loss of highs and I figure that without NFB the higher output impedance of the amp is compensating for the impedance rise of the speaker. I was going to try a T filter instead of the feedback resistor to reduce the treble getting to the second stage. A lot of gain on tap so I could always put a Blackface treble and bass controls. Going to live with it a while before I decide what to do. Lot of other projects waiting for me anyway.
Funny, I had to say it, I have a new Champ. 5f1 but no feedback loop. Layout my own -- doesn't oscillate. What I'm saying is that I never thought of a layout, just the fancy of the moment. But these things oscillate easily. It strikes me in this moment, after reading J's post. I had forgotten the possibility of doing things by the book. My mind has no discipline. I will post a picture though I fear new infections coming my way. But even fools get bored of their foolishness.
I have to say this Champ has a special feature. It has two output sockets. One for 6V6, EL34 and 6L6 tubes and another for a 6SN7/5692. Right now there's a 5692.
I also have a new pickguard for my Telecaster. I have used wood, pretty thin wood...it's got a name but... Really original (and awesome). Not the wood, the pickguard. In short, I'm a creative guy and everything I build is awesome and if it's not, I throw it away. No kidding.
I have to say this Champ has a special feature. It has two output sockets. One for 6V6, EL34 and 6L6 tubes and another for a 6SN7/5692. Right now there's a 5692.
I also have a new pickguard for my Telecaster. I have used wood, pretty thin wood...it's got a name but... Really original (and awesome). Not the wood, the pickguard. In short, I'm a creative guy and everything I build is awesome and if it's not, I throw it away. No kidding.
Last edited:
I added tubelab's manifesto to the first post, slightly edited for length. I can't imagine anyone objecting, and if you want to post a design that was made under $100, just state that it is built for under $100 in your post! This is it:
Since this thread had pretty much run its course, the rules were loosened in early 2016:
"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?
Back then, several compromises 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!
tubelab.com"
Last edited:
I plan to revisit some of the ideas I had, just cheap and dirty builds, some just breadboarded just to see how viable they are. My latest one, which I envisioned during the challenge could probably do me just fine. But since I know it is a viable amp I think I may see what else I can make out of it.
I like the idea of a low loss tone control in the form that Fender used successfully, might just follow the path he laid out. I did not find the switched NFB all that useful, yes it changed the dynamics somewhat but with NFB there was a loss of treble. Not to let a switch go to waste I am thinking of including a bass control from the Tweed era.
I like the idea of a low loss tone control in the form that Fender used successfully, might just follow the path he laid out. I did not find the switched NFB all that useful, yes it changed the dynamics somewhat but with NFB there was a loss of treble. Not to let a switch go to waste I am thinking of including a bass control from the Tweed era.
I came away from the original challenge with two working amps, one that sorta worked, and a few more additions to the "box of broken dreams", boards or prototypes that didn't work, blew up, or otherwise sucked. They got tossed into a big box to be robbed for parts, or occasionally reborn into something else that may or may not work.
One of the working amps, Amp 1.4, was fully documented in the original challenge, and caused a disturbance over knobs of all things, but didn't see much use. It wound up in a box, and after moving twice, forgotten about until I opened the box while looking for something else. It took about 2 weeks for Amp 1.4 to become Amp 1.5. Amp 1.4 still exists, it will forever be a classic. Amp 1.5 is currently the only working amp I have, so I haven't made a cabinet or chassis for it yet.
Arthritis limits my playing time a lot, but I try to use the little amp for at least 15 minutes a day. I have discovered that I can play it full tilt with no load and nothing blows up. There is not enough power or B+ to blow the $4 OPT! This convinced me to put a 100 ohm pot in series with the speaker so I can crank it and turn down the racket.
The other working amp (2.something) made about 15 watts and still fit the $100 budget. It and it's stillborn sweep tube twin, have not been found. There is still a large stack of boxes that haven't been opened in two years to go through.
Still waiting on my OPT and PT but this is eventually the route I plan to go as well. Currently only a vol put between stages but I've got provisions for the necessary trb/bas pots. This wont get added however until I find an operating spot where both the amp and myself are happy. After that point, I've got some stuff for a 'fat' switch ah-la cathode bypass, thinking about adding a pentode/triode switch in as well.
This will be my main amp until proven otherwise. I had a modded out Blues Jr that was a real hot ticket but the 15W of output proved to be a bit too much for current living conditions. Why I'm going the route of the champ. This will also probably be a platform for some load emulation and output attenuation in the process.
Dern you edcor get those transformers done already!
Haha, I also have a similar box, dreams that came true and sucked. But you always find that out afterwards. There's 5 or 6 chassis in it, some with vital organs missing (of course).
I don't play everyday but I play often. Not a good player (never will be) but enough skills to have a good time. Maybe one day I'll hire somebody to teach me properly so I can reach the next level. I have a friend who plays great but he's selfish, he says go and practise more. Bastard.
*jlangholzj. I've seen your aikido preamp (been checking the tube gallery), I have two safe boxes. I was hesitant to use them for projects but now I'm thinking, hey, that look that says 'I don't give a **** about what you think' fits me. Nice idea.
Kind of my thought as well, still need to make a proper trafo cover for the damn thing. 50 cal boxes are pretty easy to come across as well (hint hint). After I get my hybrid amp done and tucked away in something I'm planning on using one for an evolution of my $100 amp. Going to just bump up what I learned/got working from this one and make a 15W or so head.
Hey hey
Here it is, my Champ. Best Champ of all. For some reason this one sounds better than the others.
OK, let's crunch some numbers, chassis free because it was from a SE EL34 amp that was being part of the decoration - not being played.
OT from Philips record player (also free). Power transformer 50 euros (ouch).
Resistors free - a Fisher amp donation.
Caps free, man that Ero-something coupling cap is over 40 years old and no leaks. Wish I could say the same.
Power supply caps, 6 euros.
Boy, I'm bored. Not much money, let's leave it at that.
Here it is, my Champ. Best Champ of all. For some reason this one sounds better than the others.
OK, let's crunch some numbers, chassis free because it was from a SE EL34 amp that was being part of the decoration - not being played.
OT from Philips record player (also free). Power transformer 50 euros (ouch).
Resistors free - a Fisher amp donation.
Caps free, man that Ero-something coupling cap is over 40 years old and no leaks. Wish I could say the same.
Power supply caps, 6 euros.
Boy, I'm bored. Not much money, let's leave it at that.
Attachments
Trafos came in yesterday! Layout of where it all will be going. Only thing I'm worried about is the orientation of the OPT. Would it be smart to rotate it 90* so I don't risk any interference with the tube? I've got room to turn it, this is just kind of how I plopped it on the test chassis. Afterwards I looked at it and though I may need to change that....
Switch on the right next to the input is for hi/lo/standby and the switch left of the vol control is for R,k bypass. I've got a 1M resistor in series with the 1st stage R,k. Switch will short out the resistor to enable R,k to be bypassed.
Switch on the right next to the input is for hi/lo/standby and the switch left of the vol control is for R,k bypass. I've got a 1M resistor in series with the 1st stage R,k. Switch will short out the resistor to enable R,k to be bypassed.
The OPT will not cause interference with an output tube. It can interfere with input wiring, but it should all be on the other side of the chassis. The orientation is correct to avoid hum pickup from the power transformer, but there appears to be enough distance between them to eliminate that possibility.
Well fired it up last night and well....issues
I'm getting some MAD 120Hz hum, which points me towards the PSU design. At first I thought it could be lead dress, so I gutted most everything to try and Isolate things and get some better routing with jumpers, but still the same annoying loud 120Hz hum. Only the output tube plugged in and with the pre-amp tube also plugged in it's not volume dependent.
I've got a C-R-C network, of 5u-220R-5u respectively. More specifically I've got a VVR in the (R) chunk of that that as well dropping out about ~100V from the rectifier. I was worried the VVR might be causing issues but after doing some prodding around in PSUD it looks as if I've got some HORRENDEOUS ripple (like...20V worth) with those values. I've got a couple 15u motor starter caps that I'll jumper in tonight to see if that resolves the issue or not.
I've got an LDO supplying the heater voltage to each of the tubes. I have a pair of 100 ohm resistors providing a virtual CT after the LDO. Tried these grounded and tied to the cathode of the tube....same nasty hum.
Also tried the transformers in various relations to each other, orientation and whatnot with no discernible effect. This is all really pointing me towards just a bad PSU design on my part. I figured the 5u was going to be close enough to the 8u in the 5e1 that I should at least get a usable result, which I'm afraid is not true. When I first powered it up sans tubes I measured sub 300mV of AC on the B+ (to try and quantify ripple) but as load increases (read the tube gets inserted) I'd expect ripple to maginfy. This was also backed up by playing around with a lighter/heavier load in PSUD.
TLDR: Power supply is noisy man, going to try more cap tonight.
I'm getting some MAD 120Hz hum, which points me towards the PSU design. At first I thought it could be lead dress, so I gutted most everything to try and Isolate things and get some better routing with jumpers, but still the same annoying loud 120Hz hum. Only the output tube plugged in and with the pre-amp tube also plugged in it's not volume dependent.
I've got a C-R-C network, of 5u-220R-5u respectively. More specifically I've got a VVR in the (R) chunk of that that as well dropping out about ~100V from the rectifier. I was worried the VVR might be causing issues but after doing some prodding around in PSUD it looks as if I've got some HORRENDEOUS ripple (like...20V worth) with those values. I've got a couple 15u motor starter caps that I'll jumper in tonight to see if that resolves the issue or not.
I've got an LDO supplying the heater voltage to each of the tubes. I have a pair of 100 ohm resistors providing a virtual CT after the LDO. Tried these grounded and tied to the cathode of the tube....same nasty hum.
Also tried the transformers in various relations to each other, orientation and whatnot with no discernible effect. This is all really pointing me towards just a bad PSU design on my part. I figured the 5u was going to be close enough to the 8u in the 5e1 that I should at least get a usable result, which I'm afraid is not true. When I first powered it up sans tubes I measured sub 300mV of AC on the B+ (to try and quantify ripple) but as load increases (read the tube gets inserted) I'd expect ripple to maginfy. This was also backed up by playing around with a lighter/heavier load in PSUD.
TLDR: Power supply is noisy man, going to try more cap tonight.
5uF? I start at 22uF and go up from there. Also the 5E1 has a choke that smooths out some ripple. I would bet the 220R resistor is no comparison to the choke.
Amp related, gave some advice to a feller not to put a 25L6 into his amp. Got me thinking about a add on reverb using one since I have a few. Then it got to using a 12AQ5 in the spot since the amp is already running two. Then I got to thinking of doing a Marshall inspired amp with the 12AQ5's. Heck, sub in some 12AB5's and run the heck out of them. I think you can see where this is going. (Well, why not some 12V6's?)
Then I thought, just do the 12AQ5's and for quieter times run some 6AK6's in the same amp. We'll see which one wins out.
Amp related, gave some advice to a feller not to put a 25L6 into his amp. Got me thinking about a add on reverb using one since I have a few. Then it got to using a 12AQ5 in the spot since the amp is already running two. Then I got to thinking of doing a Marshall inspired amp with the 12AQ5's. Heck, sub in some 12AB5's and run the heck out of them. I think you can see where this is going. (Well, why not some 12V6's?)
Then I thought, just do the 12AQ5's and for quieter times run some 6AK6's in the same amp. We'll see which one wins out.