Is it possible to get "tube sound" with just a tube preamp and chipamp output? - Page 2 - diyAudio
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Old 7th May 2006, 01:18 PM   #11
Tyimo is offline Tyimo  Hungary
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Thanks!!! I found it.

Greets:

Tyimo
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Old 7th May 2006, 03:32 PM   #12
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Quote:
Originally posted by Simpleton
That's odd... copy and paste the url, it should open then.
Still, if you can't find it, go to the 2nd or 3rd page of the Solid State forum, "Single mosfet amp"
Oh, if you want real tube distortion (16%) i can give you the values for the ECC86 (one of the reasons why i wanted to make a tube-power follower hybrid was a guitar amp)
That would be great. I'm not opposed to using a high-voltage tube, though; I'd like to try the trick with the carbon-composition resistors. On the other hand, I've got a 25VCT transformer handy, along with some 12000uf caps (36000uf should be enough, I'd think) and assorted other random components. I love the simplicity; I'd also think that it might be possible to overdrive the transistor with the tube to make the clipped distortion so desireable in an amp.

Out of curiousity, would it be possible to, using a (much) smaller transistor in the circuit you had shown, reduce the power use so that it could be used with a chipamp? I hate to be so narrow-minded, but I want to build something LOUD, without the high cost of a powerful class-A amp. (Those power transistors are danged pricey.)
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Old 7th May 2006, 05:14 PM   #13
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Quote:
Originally posted by Spasticteapot

That would be great. I'm not opposed to using a high-voltage tube, though; I'd like to try the trick with the carbon-composition resistors. On the other hand, I've got a 25VCT transformer handy, along with some 12000uf caps (36000uf should be enough, I'd think) and assorted other random components. I love the simplicity; I'd also think that it might be possible to overdrive the transistor with the tube to make the clipped distortion so desireable in an amp.



You seem to have it the wrong way round?, it's the TUBE/VALVE that needs to be overdriven, if you overdrive the transistor you get transistor distorion.

Quote:

Out of curiousity, would it be possible to, using a (much) smaller transistor in the circuit you had shown, reduce the power use so that it could be used with a chipamp? I hate to be so narrow-minded, but I want to build something LOUD, without the high cost of a powerful class-A amp. (Those power transistors are danged pricey.)
If you're wanting LOUD, you don't want class A, nor do you when you're looking for distortion anyway.

To recap, you're looking to build a LOUD guitar amplifier, and you're wanting to incorporate a valve stage to give the overdriven valve sound. A suitable size chipamp would do for the power amplifier, and use opamps for the preamp, with a valve stage added in the preamp (either switchable, or a seperate input) to give valve overdrive.

Perhaps a simpler option would be to copy the preamp stage of an old valve guitar amp?, a single double-triode should probably be enough, and feed that into a chipamp.
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Old 7th May 2006, 06:40 PM   #14
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Quote:
Originally posted by Nigel Goodwin


You seem to have it the wrong way round?, it's the TUBE/VALVE that needs to be overdriven, if you overdrive the transistor you get transistor distorion.



If you're wanting LOUD, you don't want class A, nor do you when you're looking for distortion anyway.

To recap, you're looking to build a LOUD guitar amplifier, and you're wanting to incorporate a valve stage to give the overdriven valve sound. A suitable size chipamp would do for the power amplifier, and use opamps for the preamp, with a valve stage added in the preamp (either switchable, or a seperate input) to give valve overdrive.

Perhaps a simpler option would be to copy the preamp stage of an old valve guitar amp?, a single double-triode should probably be enough, and feed that into a chipamp.
Which is what I intended to do in the first place! (Can you reccomend one in particular?)
Thanks for clarifying the overdriving thing, though; that had been confusing me for a while. (Sue me, I'm new to this).

That said, I think I'm going to try my hand at the amp design below, as I already have most of the parts. It's dead simple, and with a suitably efficient speaker, it might make a nice bass amp with a simple tone control section. Not loud, but I'd learn something about using tubes, and it would be cheap, too. (I might actually have one of those very tubes handy thanks to a lot I picked up from a garage sale!)

Also, could anyone link me to one of the Fender amps that uses a SS output stage?

Much thanks from a newbie,
Joe.
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Old 7th May 2006, 06:58 PM   #15
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Have a look at this existing thread which has a link to a Fender guitar amp - this uses a single tube as a double-diode for overdrive.
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Old 7th May 2006, 07:14 PM   #16
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Let me see my notes... ah, here they are!

For a low voltage valve line stage, with an ECC86 (you can try an ECC88 for more distortion), you have:

Grid signal excursion : 1Vpp
Idle voltage: 8V
Idle current: 0,9mA
Vout(rms): 3,18V
Rcathode: 5,6KOhm
Ranode: aprox 4,4KOhm
B+: 12V
Distortion (2nd harmonic): 16,6%

This, together with a chipamp that runs o at 12V should get you running

If you use a similar 2nd stage, fed from the 1st; the higher grid excursion will make even more distortion. Also consider that a guitar has nromally 1,5Vpp output when played strong, so the first stage distortion figures are only for a lower input
I advise to use an opamp buffer stage following the tube stage(s), before the power amp.
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Old 8th May 2006, 07:01 AM   #17
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Default Is it possible to get "tube sound" with just a tube preamp and chipamp output?

An interesting study, with blind tests indicate that you really can't tell a the difference between tube and SS:
http://milbert.com/articles/TvsT/tvtiega.html

And if you really want to get transformers in the circuit take a look at the results found here:
http://www.ssguitar.com/index.php?to....msg785#msg785

In any case, you can build a small tube amp, with xformers and build it in a box with a mic that you play into a big SS amp.

Or you can add in a speaker simulator to the tube amp, and run a direct out to your power amp.

Many preamps - have got it "right" and do have a "tube" sound that everybody wants.

Here's a popular theory on tube sound.
http://www.paia.com/tubesnd.htm
They always show sine waves, but a guitar is a complex waveform. The fundamental may clip, the the high frequency has reached clipping. The effect is bass compression and HF continuing to gain DBs. Tube amps don't amplify highs very well were a SS amp does. So a trick to make a SS amp sound better at clipping is to retard the highs.

Or better yet - round up a few amps and effects. Stick them behind a curtain and have some friends adjust the sounds and you try to pick what you actually hear as sounding best.

If you going to DIY - skip the tube and check out the many SS distortion schmatic. You'll have more fun, you might find or create your perfect sound that nobody else has.
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Old 8th May 2006, 07:40 AM   #18
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Quote:
An interesting study, with blind tests indicate that you really can't tell a the difference between tube and SS:
For clean sound, it is really10x hard to tell difference. But when playing with distortion, tubes and SS are very obvious.

As mentioned by others, tube crunch involved a lot in combination of the power tubes, output trans and cone breakup. Simply overdriving preamp section (like marshall valvestate) just doesnt cut it (to my ears).

However, if rock and roll is not your cuppa tea, hybrid can be more than statisfactory. Fender bassman is a good preamp to copy, IMHO.
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Old 8th May 2006, 07:53 AM   #19
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I agree with the previous post, simply overdriving a preamp tube just isn't going to cut it. There are at least three sources of main distortion in a guitar amp and you are only addressing the simplest one. Simply raking up the 2nd order harmonics is likely to produce a horrible sound.

My suggestion of introducing an interstage transformer is simple and will offer at least two types of the distortion you are looking for. It also gets around the fact that the output of your tube stage is likely to be much to high to drive a chip amp with the result of horrible chip amp distortion. Clipping a chip amp is not a good thing so you need to keep the input well bellow clipping the chip amp. The other alternative would be to use the valve as a cathode follower - but this reduces distortion rather than increasing it.

Using a 10VA mains transformer in a parafeed setup, with a 240V to 6V step down ratio is likely to saturate fairly easily, cost next to nothing and give a useable input to the chip amp for a sensible tube preamp output.

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Old 8th May 2006, 04:02 PM   #20
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Think of it like this.
You can play back a recording of a good "sounding" guitar on your home stereo and it will - "sound good". Your home stereo is a clean amp. You're hearing the signal in, but louder. Warm in = Warm out, crunch in = crunch out, clean in= clean out. No sense having the amp and speakers color the sound - they should just reproduce it.

Treat your guitar and signal processing as if it's the recording.
Get yourself a good power amp, like a hypex, and concentrate your efforts on the signal processing.

Also check out the software route which is popping up in every studio you can imagine.
IK "Guitar Rig"
NI "Amplitute 2"
Or the tons of freeware and shareware plugins, for example:
http://www.voxengo.com/downloads/?hi...=boogex#boogex

All IMHO, 2 cents worth, ...
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