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Sixty Cycle Blues


dude

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That's been my thinking lately, actually. So much of what is considered "desirable" in terms of tone is simply the result of cheap design. Been wondering lately if a bit more modern approach could be made to create "good" sounding guitar, albeit different.

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just remember most of what people think make a guitar sound "good" is based on what was happening in the 50's if the transistor had replaced tubes befor the electric guitar was invented our idea of what a electric guitar should should like would be completly different.

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just remember most of what people think make a guitar sound "good" is based on what was happening in the 50's if the transistor had replaced tubes befor the electric guitar was invented our idea of what a electric guitar should should like would be completly different.

very true very true. i actually shudder to think what that would sound like. but then again who knows some of the best transistor amps were cheap under built crappy things and they have some amazing tone. i have some little blue thing from the 70's and it is a killer sounding amp. natural breakup and all but the reason is cheap parts the powersupply can not keep up with the amps demands. so now i am building a clone of it. and then fixing the original. its interesting that you don't see more distortion circuits that have a better hi end response. have you noticed that. wouldn't it be lovely if we could have non harsh multi band distortion.
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I've found that my ears generally appreciate the later-60s to 70s tone more than the 50s and early 60s stuff. I'm not a fan of speaker distortion as it turns out, or just pure fuzz pedals. I much prefer tube distortion. As an example I love Hendrix's typical rhythm tone, but his fuzzed-out solos (a la Purple Haze) sound kind of unpleasant to me. Tone wise. Not playing wise.

Well, I've dialed back my revolutionize-everything idea and settled in on a design that I think will have a nice tone, with a smooth distortion at higher levels. I'll post the schematic when I get it.

Edited by dude
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well i think your on the right track. and really people have argued for years on what makes good amp tone there are guys out there that will argue that tweed coverings sound better than tolex, in the end its all up to you and what you like. i think your on the right track now you have got it narrowed down to a style sound that you like now look at what they where doing to get that sound and build a amp.

just remember most of what people think make a guitar sound "good" is based on what was happening in the 50's if the transistor had replaced tubes befor the electric guitar was invented our idea of what a electric guitar should should like would be completly different.

very true very true. i actually shudder to think what that would sound like. but then again who knows some of the best transistor amps were cheap under built crappy things and they have some amazing tone. i have some little blue thing from the 70's and it is a killer sounding amp. natural breakup and all but the reason is cheap parts the powersupply can not keep up with the amps demands. so now i am building a clone of it. and then fixing the original. its interesting that you don't see more distortion circuits that have a better hi end response. have you noticed that. wouldn't it be lovely if we could have non harsh multi band distortion.

until i messed the little amp up trying to make it a pedal i used to run a danelectro honey tone mini amp through a 1x10 open back cab. i would turn the gain all the way down turn the tone all the way up and crank the volume, it made some great bluey tones. dam i need to pick another one of those up.

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Right on. I'm still curious to try a 12" + 10" pairing or even a 15" and 8" pairing like a bass. You know - plenty of bass but with a crisp definition too. I bet it would be interesting if nothing else. Regardless of speakers I have an amp to build. Hopefully my parts will arrive soon.

I am debating buying new iron so I can do this build completely from scratch (you know, for that sense of accomplishment). I'm sorely tempted to build an el84-powered amp because my current 50W head is simply too much for my apartment at the moment (and when I play out I'm on keys these days), and this one would be the same way. We shall see.

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i wouldnt worry too much about the caps. theres a ton of mojo credited to caps thers better places to focus your attention

I agree, but some people seem to think it's a really big deal. You can get FAR more out of changing the speaker than one brand of coupling cap over another. And let's not forget about the output transformer. It can have a big influence on the sound too depending on how it saturates.

i have always though it would be fun to design a amp with 6v6 in the preamp section run a 12ax7 in to a 6v6 (much like a champ) then regulate that down then run in to a good clean power amp. use the 6v6 in the preamp section to create power tube distortion. if you could build something like that it should have a nice bluesy sound at managable volume levels.

I like the "Octal Fatness". It has a 6SJ7 on the input into a 12AX7 which feeds a single 6V6 as I built it (power tube section is flexible). It gets nice bluesy to mildly distorted sounds. It's the only DIY build I have left. I'll never sell it LOL.

I've found that my ears generally appreciate the later-60s to 70s tone more than the 50s and early 60s stuff. I'm not a fan of speaker distortion as it turns out, or just pure fuzz pedals. I much prefer tube distortion. As an example I love Hendrix's typical rhythm tone, but his fuzzed-out solos (a la Purple Haze) sound kind of unpleasant to me. Tone wise. Not playing wise.

I'm sort of like that too. But I like some of the heavier 80s sounds, like the dimed Marshall tone I guess. Or the EVH variac tone - "the brown sound". I generally don't like fuzz sounds when I'm playing, but a lot of times I like it when someone else is using one. I like a real smooth sounding distortion that still has a lot of dynamics and harmonics. I guess people would call that an "open sounding distortion".

Edited by Paul Marossy
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If your transformers are good i would just use them and save my money.

For a given cab to double the volume you need approximately 10x's the wattage. So a 5 watt amp is gonna give you half the volume of a 50pain watt amp through the same cab.

modded fender vibrochamp was what i was using for some time. that and a few pedals. i had a nice od sound that i could clean up with rolling the volume knob back a bit.and using my booster or my wah i could get metal grind out of it. of course it needed none of that later with almost 800 plate volts on the el34 lol. love those tiny little hammond transformers.

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I agree but lucky for me that isnt out of spec range

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That sounds like a similar principal to the variac "brown sound" Paul mentioned earlier. I would think with a weak PT that if you play loud enough, the current draw from the power tubes will saturate the power core. As a result, all of your plate voltages drop (same grid voltage, limited/lower plate current). Kind of like using a variac to drop your input line voltage so you saturate earlier, except without the incorrect heater voltage.

Thinking about it though, the current limiting in the PT would drop the voltage across both the tubes (anode to cathode) and their plate resistors (and the filter resistors in the power supply). So the "missing" voltage must drop across the PT itself. I bet that thing gets warm when you crank a Mig50.

I always wondered if you could just put a high-wattage resistor between the PT and the power supply in a JMP to drop the plate voltages and get the "brown sound" without wrecking your power tubes through incorrect heater voltages.

Edited by dude
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check out geofex for ways of dropping tube power supplies or tone lizards site

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  • 10 months later...

And here's a (bad) photo of my current schematic (without values for the most part) for your viewing pleasure.

schematic_zps10a47962.jpg

After some consideration I'm doing a one-channel amp. I have the vactrols I need to do channel switching, but I want to keep it simple for now. Well, sort of simple.

I've got an input buffer/gain stage driving a preamp volume control. Then we've got a cathode follower driving a 5-band eq for a tone stack. Then another gain stage driving a pentode gain stage. I'm thinking having the brunt of the distortion happening here is going to give me some really tasty pentode saturation. We'll see. Finally, I've got another cathode follower driving another 5-band eq (post-distortion). Then a master volume. I put another gain stage next in case the previous EQ kills my signal volume too much, but I don't think it is necesarry so I'm going to remove it. Then of course comes the phase splitter and power section. I'm doing a long tail phase splitter in case I want to add negative feedback now or in the future (I'll play it by ear based on sound).

The buffered EQ stages have approximately 0-1 dB of gain. This is a lot lower than the traditional TMB Fender-style tone stack, which has more like 7dB of gain. Also, the pentode (6AU6) has about half the gain of a 12ax7. I was worried I wouldn't have enough gain in the preamp, but I think I'll be okay. I've got basically the equivalent of 2.5 12ax7 gain stages, which is roughly the same as a JCM800 (plenty of gain). ALSO, the 5-band EQ has a gain of 0 when the bands are all at 10% (centered on a log pot). If I need more, I can always turn them up to get an additional 20dB.

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looks awesome, and very well thought out

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100K input resistor is pretty low for interfacing with high impedance guitar pickups. 1M is better suited in that position. Input cap should then be reduced by a factor of 10 to compensate for the increase in resistor to maintain the same cutoff frequency, or omitted altogether.

5-band EQ is an interesting idea, but may yield unpredictable results as each control will load the other. All controls at max will not necessarily result in an even response. Experimentation will be required. May work better if limited to 3 bands. My personal preference would be to simplify things to one EQ section (EQ before gain for early Boogie-style drive, or EQ after gain for Marshall), but for me that's more to do with having too many knobs to play with (oooerrrrr...)

6AU6s (and pentodes in general) have much more gain than a 12AX7. My gut feel is that with the circuit as shown (2x preamp stage, 2x boosted cathode followers, 2x pentode stages) you're going to have more than enough gain to the point where you'll probably find it a bit too over-cooked. Even the Soldano SLO100 only uses 3x voltage stages and 1x boosted cathode follower, and you couldn't call that amp mildly overdriven.

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Its a little more complicated, but have u ever thought of more unconventional tone controls? I'm driving now but I'll post again later

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ok sorry for the vague post i was at work and android phone is going south on me. i should have been more clear, curtisia i was actually addressing the topic starter, i actually agree the passive eq will indeed be tricky but doable.

what i was going to specify is that for bass control utilizing something like a couple of ldrs leds capacitors and a dual ganged pot to change the cut off point of the cathode filter section.of course this will affect the gain as well but not as much as you might think.

since i don't have the values for this amp i will use say a Marshall as my example. a typical plexi 2.7k and .68uf gives you a low end response around 86hz. if you were to say apply this with a larger bass cap similar to channel one which is usually around 220uf you would exponentially lower the freq range even beyond the guitars range which would help fill out the sound. this is easily done with a capacitor/ldr or cap/vactorol in series and that circuit paralleled with the original resistor cap. as you turn the pot up you increase the led brightness and blend the second cap in. increasing the bass. and decreasing it in reverse order.

mid range negative/positive feedback you can build a simple lrc bandpass filter and feed the output section through a larger power resistor into the circuit and then blend via a larger pot back into a positive or negative feedback stage. you can also set multiple ranges and filters and blend them accordingly.

high end trick, if you take your first tube stage and come off the cathode, into a mosfet or any gain device all we are trying to do here is boost up some of the original high end before clipping and feed it into a later stage in the same phase it was before, you can do this without the ss device but the fet keeps the negative feedback loop problems from coming into play as much. also you can use a typical Marshall filter like a 470pf/470k style filter for that 720hz push substitute your values in there and put a pot instead of a resistor or a pot and a resistor and you can tailor the high end to your liking. hope you have fun with it. i have never put all of these in one amp before but i have used every one of these in one amp or another. ciao

ed

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