Hi everyone. I know this might sound silly and it is possible it has been discussed on some other thread, but... I am building a hybrid guitar amp and I want to put in some distortion in it, so I've built some simple triode preamp, but it only produces a clean sound. When looking for some overdrive circuits, I always found just some shcematics using about 12V of B+ voltage. So, is that the way I should reach the overdrive sound properly, or are those schematics made just so they can be powered from low voltage PSU?
My second question is about the output voltage, since the tubes have probably a lot more output voltage then regular solid state preamp, how do I convert those high voltages back to level appropriate for the solid state power amp?
Sorry for writing too much words on problems so simple, but I'm still learning stuff and it's hard for me to figure out those things, thanks for your replies.
My second question is about the output voltage, since the tubes have probably a lot more output voltage then regular solid state preamp, how do I convert those high voltages back to level appropriate for the solid state power amp?
Sorry for writing too much words on problems so simple, but I'm still learning stuff and it's hard for me to figure out those things, thanks for your replies.
Tubes do not magically produce distortion, you must overdrive them into clipping for that.
A 12AX7 with a 300V supply will produce up to 90V RMS before clipping and/or you need >1.5V RMS at its grid, to *start* clipping.
To get noticeable/useful guitar type distortion, you´ll need 10-20dB overdrive at least.
Second option.
]You´ll have to attenuate those >90V RMS to about 1V to drive a standard power amp.
As simple as a 220k/2k2 attenuator.
Please post the schematic of what you actually built so far.
Distortion circuits using low anode voltages are done to utilise triode characteristics not to save money on power supplies.If using a "standard" guitar amp the output from small signal dual triode will be fine to drive amp. ( I do it !!!). Can you post your schematic???? so we can see what you are doing. By the way a double triode should produce if anything too much distortion for most tastes when run flat out.NB hybrid amp will be fine.
Can you also post cct of your "custom" power amp as well as input impedance will make a big difference here.
In your case you need to make certain that all the distortion occurs in your distortion box as your power amp is solid state. With an all valve circuit the whole amplifier chain can be driven into overdrive to advantage.Transistor output stages generally Don`t sound "good" when overdriven
Can you also post cct of your "custom" power amp as well as input impedance will make a big difference here.
In your case you need to make certain that all the distortion occurs in your distortion box as your power amp is solid state. With an all valve circuit the whole amplifier chain can be driven into overdrive to advantage.Transistor output stages generally Don`t sound "good" when overdriven
Here is the schematic I'm using, nothing much to it yet. I used the triode section of EABC80, since I have a lot of them laying around.
An externally hosted image should be here but it was not working when we last tested it.
Here is the schematic for the power amplifier:
Yes, definetly, this is just the first version, that was making some sound. In future, I'll be adjusting those components including the cythode bypass cap.
Yes, it is, I know, and surely I'll be changing this in the final stage of making the circuit. For now it is laying on my test bench and I grabbed first caps that were laying around.
Dont know offhand the gain of this triode. May be better to use ECC83 high gain double triode (Many different triodes can have a huge gain range ie ECC83(high gain) V ECC82(low gain).Double triodes would let you with 1 off ECC83 get you to theoretically 10,000 gain!!!
Re:-DF96 he`s right. But I have NO idea how to move things around.
Re:-DF96 he`s right. But I have NO idea how to move things around.
According to the datasheet, this tube should be able to act in simmilar way as the ECC83, I think this tube was even used in radios for preamplification of the audio signal to the power pentode. By my judging, it doesnť have problem with gain, even in the datasheet there are really similar values.
As DF96 says, … wrong forum. But none-the-less, if you are trying to get “guitar lead distortion” out of a vacuum-tube amplifier, there are several principles usually employed.
[1] starved heater — running a “12 volt” filament at 8 volts with a series resistor is one useful hack. 22 Ω, for instance, on a nominal–12.6 V, 0.15 A drops roughly
Anyway, the 'fun thing' is that you can substitute the series resistors to your ear's content and test out all sorts of starved-filament tube sonics. You even might want to install a small rotary switch with a number of different values of resistors. Surprisingly, this is cheaper than buying a low-value potentiometer these days! (But…if you CAN find a 50 Ω one… for a buck… snap it up quick!!!)
[2] Starved anode … is another trick, already alluded to above by others. You don't run the “distortion section” off a 300 volt supply. More like a 12 to 20 volt anode supply, and a 4.7 µF capacitor in parallel with the 2.2 kΩ cathode resistor. Works wonders. Indeed… you might consider cobbling together a small variable B+ supply for the first stage with a high value pot (100 kΩ) acting as a B+ voltage divider … driving the gate of a hi-volt MOSFET, drain to B+, source as the 'variable B+' supply. Dial in anything from 10 volts to 250. Cost, less than $5 all in.
[3] saggy B+ supplies … several absurdly expensive, famous high-distortion guitar amps use B+ “nightmare” supplies. Long chains of resistor-drops, capacitors, each one driving yet-another front-end valve. When the guitar riff comes along, the insufficiency of the long chain results in all kinds of changing supply volts. Musical? To some ears, definitely. Big bucks, definitely. Just read up on them.
[4] Active distortion elements are yet another trick. Putting back-to-back (parallel, in series with low value resistor) "fuzz" bits in the audio chain really changes things up. The trick is to get low VON diodes. When dinosaurs were still designing things, we used germanium diodes. Nowadays, one might consider Schottky devices.
[5] positive grid excursions … and unbiased grid combinations also serve to distort the incoming signal beyond recognition. Musically… one assumes. Having a dial-a-cathode-resistor works wonders. Replace the 2.2 kΩ cathode bias resistor with a 10 kΩ pot. Trim to your heart's content.
[6] grid-leak bias … which you kind of have with that 10 MΩ resistor pinning grid to ground. Its high enough (maybe) to allow the grid to automagically “drift more negative” by picking up passing electrons. And being a signal-dependent system of values and potentialities, well … it too might change a bit with that mean guitar riff.
The reason I've gone to such great lengths here is because in my youth, I designed just such an amp front-end for a now-almost-famous guitar friend. Dunno if he's still using it, but I put everything in there. Germanium clamping diodes, starved filaments, starved anode, variable anode supply, absolute-bailing-wire-and-springs power supply and a whole lot of different front-end valves that could be SWITCHED on, with a large surplus 6 pole rotary switch. Had 10 input valves. A beast. And fun. Sounded awesome after about half-a-year of fiddling with it.
I ended up marking the top-panel with fluorescent red, green, yellow paint for different potentiometer settings that he liked. That way … literally … he could “dial in” the same crusty sound, performance to performance, song to song, riff to riff.
Good luck.
The above will address a lot of what you might be looking for.
Just saying,
GoatGuy ✓
[1] starved heater — running a “12 volt” filament at 8 volts with a series resistor is one useful hack. 22 Ω, for instance, on a nominal–12.6 V, 0.15 A drops roughly
E = I R …
12.6 = 0.15 * R
R = 12.6 ÷ 0.15 = 84 Ω when hot and normal.
RTOT = 84 + 22 (example) = 112 Ω
I = E/R = 12.6 ÷ 112
I = 0.113 A
E = I R … for the tube again
E = 0.113 × 84 Ω
E = 9.5 V
Easy enough, using Ohm's Law. It is also inaccurate since the filament's reduced power, causing it to heat less, also causes it to have less resistance. The actual voltage will likely be closer to 8 volts.12.6 = 0.15 * R
R = 12.6 ÷ 0.15 = 84 Ω when hot and normal.
RTOT = 84 + 22 (example) = 112 Ω
I = E/R = 12.6 ÷ 112
I = 0.113 A
E = I R … for the tube again
E = 0.113 × 84 Ω
E = 9.5 V
Anyway, the 'fun thing' is that you can substitute the series resistors to your ear's content and test out all sorts of starved-filament tube sonics. You even might want to install a small rotary switch with a number of different values of resistors. Surprisingly, this is cheaper than buying a low-value potentiometer these days! (But…if you CAN find a 50 Ω one… for a buck… snap it up quick!!!)
[2] Starved anode … is another trick, already alluded to above by others. You don't run the “distortion section” off a 300 volt supply. More like a 12 to 20 volt anode supply, and a 4.7 µF capacitor in parallel with the 2.2 kΩ cathode resistor. Works wonders. Indeed… you might consider cobbling together a small variable B+ supply for the first stage with a high value pot (100 kΩ) acting as a B+ voltage divider … driving the gate of a hi-volt MOSFET, drain to B+, source as the 'variable B+' supply. Dial in anything from 10 volts to 250. Cost, less than $5 all in.
[3] saggy B+ supplies … several absurdly expensive, famous high-distortion guitar amps use B+ “nightmare” supplies. Long chains of resistor-drops, capacitors, each one driving yet-another front-end valve. When the guitar riff comes along, the insufficiency of the long chain results in all kinds of changing supply volts. Musical? To some ears, definitely. Big bucks, definitely. Just read up on them.
[4] Active distortion elements are yet another trick. Putting back-to-back (parallel, in series with low value resistor) "fuzz" bits in the audio chain really changes things up. The trick is to get low VON diodes. When dinosaurs were still designing things, we used germanium diodes. Nowadays, one might consider Schottky devices.
[5] positive grid excursions … and unbiased grid combinations also serve to distort the incoming signal beyond recognition. Musically… one assumes. Having a dial-a-cathode-resistor works wonders. Replace the 2.2 kΩ cathode bias resistor with a 10 kΩ pot. Trim to your heart's content.
[6] grid-leak bias … which you kind of have with that 10 MΩ resistor pinning grid to ground. Its high enough (maybe) to allow the grid to automagically “drift more negative” by picking up passing electrons. And being a signal-dependent system of values and potentialities, well … it too might change a bit with that mean guitar riff.
The reason I've gone to such great lengths here is because in my youth, I designed just such an amp front-end for a now-almost-famous guitar friend. Dunno if he's still using it, but I put everything in there. Germanium clamping diodes, starved filaments, starved anode, variable anode supply, absolute-bailing-wire-and-springs power supply and a whole lot of different front-end valves that could be SWITCHED on, with a large surplus 6 pole rotary switch. Had 10 input valves. A beast. And fun. Sounded awesome after about half-a-year of fiddling with it.
I ended up marking the top-panel with fluorescent red, green, yellow paint for different potentiometer settings that he liked. That way … literally … he could “dial in” the same crusty sound, performance to performance, song to song, riff to riff.
Good luck.
The above will address a lot of what you might be looking for.
Just saying,
GoatGuy ✓
With ECC83 I would achieve gain about 73, with this tube about 54, which isn't such a difference. I would connect maybe three of them, or I can take a look on some other tubes.
And yes, I could use ECC83, no big deal, but I have some ECC83s prepared for my future projects and I'll rather use some unusuall tubes, than buy a new ones. I know, that this sounds dumb, but even if it won't work, I would have a certain prove of it.
Wow, now this is a huge piece of knowledge. Thank you for saving me from trying those things by myself. At least trying things, that probably won't work. I'm really excited about the fillament starvation method, since it's most simple to implement and hopefully easy to adjust. Still, this willl be a long journey, but I think you showed me a direction. Thanks
And yes, I could use ECC83, no big deal, but I have some ECC83s prepared for my future projects and I'll rather use some unusuall tubes, than buy a new ones. I know, that this sounds dumb, but even if it won't work, I would have a certain prove of it.
Wow, now this is a huge piece of knowledge. Thank you for saving me from trying those things by myself. At least trying things, that probably won't work. I'm really excited about the fillament starvation method, since it's most simple to implement and hopefully easy to adjust. Still, this willl be a long journey, but I think you showed me a direction. Thanks
PS: for "roadworthiness", I found some valve “cover cans” with twist-locks and internal springs (to keep valves pushed down against their sockets). Dunno if you still can buy these, but lemme tell you: when gigging in dark smokey venues, having a tube amplifier that you can drop, and which absolutely will … dozens of times… in its year-to-year life, is critical. This is frankly where solid state is superior. But the sound … of valves … well, just have to design them as if they're going to be deployed on a WW2 battle field. GoatGuy ✓
You're welcome. Use a large box for your experiment(s). That way, you can add stuff, remove stuff, change stuff … without too much trouble. As 'it' settles down to something you really like, well … then commit it to a much smaller, more durable, road-worthy enclosure. And re-read what I wrote. Yes, there's a lot there … and it would not at all be hard to do. I might even re-draw the schematic someday, if someone asks nicely AND intends to implement it. LOL … GoatGuy ✓
You're welcome. Use a large box for your experiment(s). That way, you can add stuff, remove stuff, change stuff … without too much trouble. As 'it' settles down to something you really like, well … then commit it to a much smaller, more durable, road-worthy enclosure. And re-read what I wrote. Yes, there's a lot there … and it would not at all be hard to do. I might even re-draw the schematic someday, if someone asks nicely AND intends to implement it. LOL … GoatGuy ✓
Yeah, I bought those covers some days ago, it works great. If I'm scared of anything, it's dropping those tubes and breaking them.
Here is my testbench. I use it for testing and building new circuits. It works great, for the chasis I of course have some more durable cases.
An externally hosted image should be here but it was not working when we last tested it.
Here is my testbench. I use it for testing and building new circuits. It works great, for the chasis I of course have some more durable cases.
I'm going to add my standard response: read the writings of the Valve Wizard and Rob Robinette on guitar amplifier design.
Yes, that's a lot of homework but just think of all the electrons you'll save.
Yes, that's a lot of homework but just think of all the electrons you'll save.
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BTW Try using LTspice its free from analogue devices it comes with a pretty full lib (solid state) but the valve models I got from this site.Still just playing with it at the moment but looks very very promising as my other hobby is hi-fi.Much faster than the test-bench + you can go into fantasy land without spending money
I'm using humbuckers with coil split and also every pickup has a different output signal. And this LTspice thing, oh man, I'm going to try it out right now, it looks very interesting. I also have some kinda "Hi-fi" projects, but I keep them for later, because now I'm very comfortable with and old Tesla NZC 420 Hi-fi amplifier, even though it's just a regular class AB amplifier, but the sound of it is irreplaceable.
With LT-spice you can graphically see the distortion and what actual harmonics are actually produced.Its a wee while since I downloaded the Valve models,But I am pretty sure it was from some-where on this site.(Passives res,cap,inductors,ect,ect,are included,as are semiconductors.).Sorry I cant` do a quick check as the machine they are on is down for re-building.You can also download transistor power amp ccts, from LTspice site,Also valve amp (mainly RB300 triode) from this site for ¬`tutorial`-purposes`.A lot to take in but WELL worth it !!!!
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