The Hundred-Buck Amp Challenge

[Printer2]

Originally Posted by Cassiel

We want no YouTube people wandering around here, he better post his schematic on Ebay.

The YouTube types are so easily distracted they will click on another video before they figure out who we are.

[tipetu]

I`m glad you enjoyed the vid! :P This is the amp only, no effect og distortion. It does sound better in real life. The camera I used was a Canon G7. The audio on the camera is crap, but as you can hear, the fuzz is there!

The speaker is a 3W RMS 6` Fullrange I bought of eBay. It looks like a vintage radio speaker I think. In my ears, the sound is perfect.
If I were to choose a different speaker, what would you guys suggest?

I have built several amps earlier and are familiar with schematics and basic tube theory. But I`m blown away over the amount of work this guy has put into the step by step instruction. EVERY single solder joint is well described, and it comes with a ton of pictures and tips and tricks.
I cannot stress that enough, it simply amazes me. Thanks!

[tipetu]

Originally Posted by Printer2

I would like to hear it with a different speaker, in a bigger box if possible. It does sound off, somehow it also sounds like there is some mid scoop happening but with the simple circuit I am not sure what is going on. Mind you an out of phase position on the guitar might do that. Probably sounds better live, in the middle of the clip the overdrive does get a bit wonky, might be the size of the output transformer. But for a low buck design not too bad.

I only have a 100W Celestion available. It`s in a bigger cabinet too. Think it would do the trick?

[Alvis]

Try it out, it will work good. That little amp can power 4 x 12" speakers as long as they are reasonably efficient.

I did not realize you had a 6" speaker in there, it looked smaller.

[Printer2]

WGS speakers are affordable and pretty good quality.

[tubelab.com]

In my ears, the sound is perfect.

If you like it, don't F#@* with it! Seriously, you are the only one who can hear the sound. We hear a "representation" of the sound after being processed and translated by the camera, two PC's and who knows what on YouTube's end.

But on the other hand, If you HAVE another speaker, by all means connect it up and try it. You might find a better "perfect". A 12 incher might fatten up the sound a bit.

in the middle of the clip the overdrive does get a bit wonky, might be the size of the output transformer.

The schematic that was posted here lists a Hammond power transformer being used as an SE OPT. A Class A SE amp is not Class A any more when it is driven past clipping. The tube current varies considerably as the guitar is played, causing variable OPT saturation. It imparts an ugly distortion, but I don't hear it on this recording.

I think that squeezing Voodo Chile through a $90 amp and getting this much sound is impressive indeed. Love the country twang too. I saw a black Strat in some of his other videos. I can understand how you get Voodo Chile from a Strat, but how do you get the twang?

[tipetu]

Originally Posted by tubelab.com

If you like it, don't F#@* with it! Seriously, you are the only one who can hear the sound. We hear a "representation" of the sound after being processed and translated by the camera, two PC's and who knows what on YouTube's end.

But on the other hand, If you HAVE another speaker, by all means connect it up and try it. You might find a better "perfect". A 12 incher might fatten up the sound a bit.



The schematic that was posted here lists a Hammond power transformer being used as an SE OPT. A Class A SE amp is not Class A any more when it is driven past clipping. The tube current varies considerably as the guitar is played, causing variable OPT saturation. It imparts an ugly distortion, but I don't hear it on this recording.

I think that squeezing Voodo Chile through a $90 amp and getting this much sound is impressive indeed. Love the country twang too. I saw a black Strat in some of his other videos. I can understand how you get Voodo Chile from a Strat, but how do you get the twang?

Agree. the other speaker and cabinet is a guitar tube amp I built some years ago. I would rather not part it out :P

The output transfomer is actually a 6.3V filament transfomer. 110/6.3V.
I never knew they could be used as a output tranny. I fancy that!

Yes I use the black strat here with standard USA pickups. Perhaps the twang comes from all the Cash/Luther Perkins I`ve been playing for so long :P

[MrResistor]

Hi Guys! I have been enjoying this thread for a while. I plan on building several of these amps. The first one I tried is Tubelab's 1.3. Im not nearly as knowledgeable as you are, so Im learning as I go. Im having some issues. The output transformer I assume is wired across the 70 volt taps, using the orange lead as the center tap, with the black and purple going to the power tubes. The amp works, but only with the volume cranked, and the tone all the way down. Otherwise it makes a terrible noise. I don't think its oscillation, but Im not sure. It hums quite a bit, too. I tried to go point to point, but it ended rather messy. Should I start over on a perf board? Opinions?

[flieslikeabeagl]

Originally Posted by benb

Many tone stacks had a mid frequency hump or depression.

However, guitarists got used to these primitive tone controls and we all grew up listening to the tone created by these primitive early attempts to shape tone.

The notch in the frequency response of the Fender tone stack was not an accident caused by a "primitive" design. In fact it was the opposite - Fender seems to have been the first to realise that a guitar pickup has a strong peak in its frequency response, and his amps were the first to attempt to compensate for this peak by having a corresponding notch in the amps own frequency response.

So the notch was actually put there to make the overall frequency response of amp + guitar flatter, and take away the midrange peak from the pickup. Other amps of the time had a tendency to sound more nasal or midrangey, because they didn't take out the peak in the guitars frequency response. You can still hear that more nasal tone in amps that don't use a Fender tone stack, for instance in some of the 18 W Marshall clones that use a one-knob tone control. (The one-knob tone control does not have a notch in the frequency response.)

Later Marshall amps modified Fender's tone stack for more gain, but kept the notch in the frequency response, though they shifted its frequency a little to get a somewhat different sound.

Guitar pickups have evolved over the years, so one unanswered question is whether the notch in the Fender tone stack response is in the right place to correct todays Fender guitar pickups or not. Of course all Fender pickups are not the same today, and there are also hundreds of other brands and models on the market. The notch in the amp cannot possibly be in the right place to compensate for all of these different pickups available today.

You can read more about the design and intention of the classic Fender tone-stack here (scroll down to the section on tone controls): GM Arts - Guitar Amplifiers

I've wondered whether a combination of a tunable notch (frequency and Q) and a Baxandall type control, one feeding the other, might make a good guitar amp tone control with the strengths of both Fender's stack and the Baxandall circuit, and more versatility than either one by itself.

-Flieslikeabeagle

[djgibson51]

Single knob tone stack in Post 1396 has mid-scoop. I designed it using the Duncan tone stack program.
Cheers,
JimG
PS. Ignore connection from OPT to ground - doh!