Is this a good way to simulate the sound of tubes??

hugobross · 28th June 2002, 11:46 AM

Hi,

I've just designed this schematic, and I'm wondering if this is a good method to simulate the warm sound of tube amps. I've designed it for someone who has an electric guitar but no tube amp, so I ask you guys if this is a good method to make a "tubebox" before I'll deliver it to him.

with R3 you can adjust the "tube-distortion" and with R5 you can adjust the gain.

Thanks,
HB.

yeti · 28th June 2002, 12:15 PM

I'd work with one diode only, because this qill give you mainly even order harmonics,which are more like tube sound.
Your setup is similar to a so called "Fuzz Box",which gives odd harmonics,very harsh and ringing sound.

regards,

Arne

paulb · 28th June 2002, 02:31 PM

Some feel that the "warm sound of tubes" is just added distortion. Others (and probably most here) disagree.
But this is for a guitar, so fidelity is not the prime consideration. Try it.

tschrama · 28th June 2002, 03:20 PM

Hi,

I don't think you'll be satisfied with the sound of this schematic..

The output of a typical guitar will be around 200mV transient for humbuckers and about 100mV for single coils, so the diodes won't reach conductive state...

I can recommend the www.harmonycentral.com site! look for effects and then look for schematics... and a world of schematic information will be at your disposal..

personally I believe that the compression and bias shifting in tube amp is a key-factor of their signature sound.. the best way to accomplish that is by using single ended capacitive coupled stage without feedback ... try a cascade of N-JFET's, biased sub-optimal... reduce low-frequency transfer (to reduce intermodulation) to about -40dB at 1Khz and cut highs after the stage from about 1KHz ... for a nice sustained sound you'll need something like 40dB gain beyond headroom...

goodluck!

gr,
Thijs

MRehorst · 28th June 2002, 04:00 PM

Try simulating this circuit in SwCADIII and dump the output to a .wav file. Then you can listen to it and know what it will sound like.

If you want to go all-out, get any .wav file (rip it off a CD) of a guitar and use it as input to your circuit. Then you can see exactly what the circuit will do to the sound of a guitar.

MR

Nelson Pass · 28th June 2002, 08:23 PM

I've built a number of circuits that think along those lines,
and none of them sounded like tubes to me. I think people
trying to make tubes out of transistors are barking up the
wrong tree

tiroth · 28th June 2002, 08:38 PM

Yup. Why not lash together a simple line-level cathode follower or plate amp with a signal tube and go from there. Low plate voltage or low bias will definitely get you tube-induced distortion.

hugobross · 29th June 2002, 11:07 AM

Hey thanks guys,

Nelson, I was wrong: the schematic is not to make it sound like tubes, but to simulate a tube amp running into saturation (you'd better not try this with transistor amps huh, unless you are a squary heavy metal freak or something

)

tschrama, yes I know that the schematic won't work with that low voltages, I've forgotten two resistors in the input stage, it must be an amp with gain x20 instead of a buffer.

thanks for SwCADIII tip, I'll first give it a try with that.

Best regards,

HB...

Lisandro_P · 29th June 2002, 11:52 AM

I'd use the Tech21 (www.tech21nyc.com) approach; get an old tube amp schematic and replace the tube gain stages with jfet ones. Suposedly it works great.

hugobross · 29th June 2002, 01:04 PM

hmmm, tubes and fets, unfortunately I've never experienced with them before so I think that it will be something for the future.
That's the negative point about my education: I'm studying electronics but we've never seen anything about tubes and almost nothing about fets etc... But we've done a lot of researche and experiments with transistors and opamps, so schematics with transistors won't be a huge problem to me.

I'm going to get myself a good book of the local library here and start reading articles about fets and tubes, and then I'll try some liitle experiments to get started with them.

I remember something about fets: is it true that you may never touch the gate, otherwise it will be damaged because of it's very high input impedance or something like that. Is it true that a little wire is connected between the pins of fets to protect them in case that they aren't placed on a pcb?
Can anybody confirm this because I'm not sure about it...

HB.

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28th June 2002, 12:15 PM	#2
yeti diyAudio Member Join Date: Nov 2001 Location: Ewersbach	I'd work with one diode only, because this qill give you mainly even order harmonics,which are more like tube sound. Your setup is similar to a so called "Fuzz Box",which gives odd harmonics,very harsh and ringing sound. regards, Arne

28th June 2002, 02:31 PM	#3
paulb diyAudio Member Join Date: Jun 2001 Location: Calgary	Some feel that the "warm sound of tubes" is just added distortion. Others (and probably most here) disagree. But this is for a guitar, so fidelity is not the prime consideration. Try it.

28th June 2002, 03:20 PM	#4
tschrama diyAudio Member Join Date: Jul 2001 Location: The Netherlands	Hi, I don't think you'll be satisfied with the sound of this schematic.. The output of a typical guitar will be around 200mV transient for humbuckers and about 100mV for single coils, so the diodes won't reach conductive state... I can recommend the www.harmonycentral.com site! look for effects and then look for schematics... and a world of schematic information will be at your disposal.. personally I believe that the compression and bias shifting in tube amp is a key-factor of their signature sound.. the best way to accomplish that is by using single ended capacitive coupled stage without feedback ... try a cascade of N-JFET's, biased sub-optimal... reduce low-frequency transfer (to reduce intermodulation) to about -40dB at 1Khz and cut highs after the stage from about 1KHz ... for a nice sustained sound you'll need something like 40dB gain beyond headroom... goodluck! gr, Thijs

28th June 2002, 04:00 PM	#5
MRehorst diyAudio Member Join Date: May 2002	Try simulating this circuit in SwCADIII and dump the output to a .wav file. Then you can listen to it and know what it will sound like. If you want to go all-out, get any .wav file (rip it off a CD) of a guitar and use it as input to your circuit. Then you can see exactly what the circuit will do to the sound of a guitar. MR

28th June 2002, 08:23 PM	#6
Nelson Pass The one and only Join Date: Mar 2001	I've built a number of circuits that think along those lines, and none of them sounded like tubes to me. I think people trying to make tubes out of transistors are barking up the wrong tree

28th June 2002, 08:38 PM	#7
tiroth diyAudio Member Join Date: Dec 2001 Location: Pittsburgh, PA, USA	Yup. Why not lash together a simple line-level cathode follower or plate amp with a signal tube and go from there. Low plate voltage or low bias will definitely get you tube-induced distortion.

29th June 2002, 11:07 AM	#8
hugobross diyAudio Member Join Date: Jun 2001 Location: Flanders, Belgium	Hey thanks guys, Nelson, I was wrong: the schematic is not to make it sound like tubes, but to simulate a tube amp running into saturation (you'd better not try this with transistor amps huh, unless you are a squary heavy metal freak or something ) tschrama, yes I know that the schematic won't work with that low voltages, I've forgotten two resistors in the input stage, it must be an amp with gain x20 instead of a buffer. thanks for SwCADIII tip, I'll first give it a try with that. Best regards, HB...

29th June 2002, 11:52 AM	#9
Lisandro_P diyAudio Member Join Date: Oct 2000 Location: Argentina	I'd use the Tech21 (www.tech21nyc.com) approach; get an old tube amp schematic and replace the tube gain stages with jfet ones. Suposedly it works great.

29th June 2002, 01:04 PM	#10
hugobross diyAudio Member Join Date: Jun 2001 Location: Flanders, Belgium	hmmm, tubes and fets, unfortunately I've never experienced with them before so I think that it will be something for the future. That's the negative point about my education: I'm studying electronics but we've never seen anything about tubes and almost nothing about fets etc... But we've done a lot of researche and experiments with transistors and opamps, so schematics with transistors won't be a huge problem to me. I'm going to get myself a good book of the local library here and start reading articles about fets and tubes, and then I'll try some liitle experiments to get started with them. I remember something about fets: is it true that you may never touch the gate, otherwise it will be damaged because of it's very high input impedance or something like that. Is it true that a little wire is connected between the pins of fets to protect them in case that they aren't placed on a pcb? Can anybody confirm this because I'm not sure about it... HB.

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