Well, you made your amp better, "more Hi Fi" .
Cool but then it will sound like a million others, and eventually same as if plugged straight in the board.
To give it "growl" you may insert a *pentode* , not a triode, between preamp and power amp, drive it hard so it clips and compresses.
You will have to tweak and EQ that output signal, it will NOT be the same as a full Tube power amp but if you are careful, let´s say you´ll get 90% of the sound with 10/20% the complication (and 10% the cost).
That´s the way to do it "the natural way".
Cool but then it will sound like a million others, and eventually same as if plugged straight in the board.
To give it "growl" you may insert a *pentode* , not a triode, between preamp and power amp, drive it hard so it clips and compresses.
You will have to tweak and EQ that output signal, it will NOT be the same as a full Tube power amp but if you are careful, let´s say you´ll get 90% of the sound with 10/20% the complication (and 10% the cost).
That´s the way to do it "the natural way".
Isn't that "bass amp" project merely introducing ideas and features, which tend to be commonplace in bass amps.
For example, Rod points out obvious stuff, like in rundown what "Distortion" feature does in an amplifier:
But he doesn't really introduce any techniques to "do it properly" and to get rid of that "harsh edge", to quote him.
In his projects I basically just see him using generic shunt diode clippers to introduce distortion, but these are always more or less limited to a single stage, symmetric by configuration, and hit the signal with the full effective bandwidth of the amplifier.
If you look at proper "distortion" circuit design in commercial amps - especially in the case of bass amps - you likely find more elaborate means to produce harmonic distortion. Ones that actually sound nice, and relate to what Rod was discussing about when he mentioned distortion as a musical effect. For example, it's quite typical that bass amps are designed to clip only higher frequencies because with bass amp excessive IM at low end would sound really, really bad.
I also understand Rod's point about tubes: He sees their function as mere "waveshapers", and as such their function is something that can be substituted with other circuitry that ahieves the same end result. If tubes are not used for clipping their small contribution to total harmonic distortion is negligible, and if tubes are employed for mere clipping one can substitute them with other devices/circuitry that has similar-enough clipping characteristics, yet higher reliability, better SNR, no requirement for using high-voltage parts, and no worries about supplying current-hungry filaments.
Also, if you look at it, the things that make tube-based circuit architectures great for guitar amplification are usually the same things that make them less great for bass amplification.
For example, Rod points out obvious stuff, like in rundown what "Distortion" feature does in an amplifier:
But he doesn't really introduce any techniques to "do it properly" and to get rid of that "harsh edge", to quote him.
In his projects I basically just see him using generic shunt diode clippers to introduce distortion, but these are always more or less limited to a single stage, symmetric by configuration, and hit the signal with the full effective bandwidth of the amplifier.
If you look at proper "distortion" circuit design in commercial amps - especially in the case of bass amps - you likely find more elaborate means to produce harmonic distortion. Ones that actually sound nice, and relate to what Rod was discussing about when he mentioned distortion as a musical effect. For example, it's quite typical that bass amps are designed to clip only higher frequencies because with bass amp excessive IM at low end would sound really, really bad.
I also understand Rod's point about tubes: He sees their function as mere "waveshapers", and as such their function is something that can be substituted with other circuitry that ahieves the same end result. If tubes are not used for clipping their small contribution to total harmonic distortion is negligible, and if tubes are employed for mere clipping one can substitute them with other devices/circuitry that has similar-enough clipping characteristics, yet higher reliability, better SNR, no requirement for using high-voltage parts, and no worries about supplying current-hungry filaments.
Also, if you look at it, the things that make tube-based circuit architectures great for guitar amplification are usually the same things that make them less great for bass amplification.
Wondering if you could point out specific examples of circuits that sound good, using "distortion as a musical effect"
RTFM
Arguably, the go-to article on how guitar amps is Tube Guitar Amp Overdrive by Rob Robinette
Note that one does not need to clip to use distortion to produce a musical effect. Plain ole' 2nd harmonic adds wonderful tone to otherwise thin music, as does a little microphonics and mechanical resonance (e.g. reverb springs or some speaker cone or voice coil misbehaviour). Throw in a little compression (dozens of ways to produce this) to add some more sustain and it "sounds better".
For those new to a concept, start with Wikipedia (in this case, here)
Arguably, the go-to article on how guitar amps is Tube Guitar Amp Overdrive by Rob Robinette
Note that one does not need to clip to use distortion to produce a musical effect. Plain ole' 2nd harmonic adds wonderful tone to otherwise thin music, as does a little microphonics and mechanical resonance (e.g. reverb springs or some speaker cone or voice coil misbehaviour). Throw in a little compression (dozens of ways to produce this) to add some more sustain and it "sounds better".
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I'm aware I'm posting on an antique thread, but hey, whatever. This might even be my first DIYaudio forum post.
I kept reading this thread hoping to find information, or at least peoples opinions on Elliotts bass pre-amp, but it's mostly people griping and replaying the valve vs solid state game.
Unfortunate.
However it does seem that we enjoy what we're doing and like ESP!
I've built/altered a number of his projects taking the schematics and laying them into EasyEDA or KiCad then etching. some are distinctly less than successful but I believe that's due to me altering the design or (more significantly) when I lay things out to test them without building them into an enclosure (which I rarely do, I play with my stuff more than I play through my stuff).
I have the input section of the bass pre sharing a PCB with the optical comp/limiter section and it's really cool and remarkably operational for something usually taped to a piece of wood with weights holding wiring down.
The parametric EQs have been giving me trouble. taking one out of a box and looking at my schemes/layouts after 18 months of neglect. Perhaps this time I'll achieve... something different.
The wonderful part to me is the modular nature of the pre-amp, and the entire site. I slowly build up a collection of modules, allowing me to modify or repair regular consumer gear.
So, to actually get address the original post: I've built the op amp input pre, bass and treble controls and the parametric (although as a part of separate projects, some have not worked as I intended), the high pass filter, the LED/LDR comp/limiter (love this piece, works great) and I've built a hoard of crossovers, which all work delightfully.
I kept reading this thread hoping to find information, or at least peoples opinions on Elliotts bass pre-amp, but it's mostly people griping and replaying the valve vs solid state game.
Unfortunate.
However it does seem that we enjoy what we're doing and like ESP!
I've built/altered a number of his projects taking the schematics and laying them into EasyEDA or KiCad then etching. some are distinctly less than successful but I believe that's due to me altering the design or (more significantly) when I lay things out to test them without building them into an enclosure (which I rarely do, I play with my stuff more than I play through my stuff).
I have the input section of the bass pre sharing a PCB with the optical comp/limiter section and it's really cool and remarkably operational for something usually taped to a piece of wood with weights holding wiring down.
The parametric EQs have been giving me trouble. taking one out of a box and looking at my schemes/layouts after 18 months of neglect. Perhaps this time I'll achieve... something different.
The wonderful part to me is the modular nature of the pre-amp, and the entire site. I slowly build up a collection of modules, allowing me to modify or repair regular consumer gear.
So, to actually get address the original post: I've built the op amp input pre, bass and treble controls and the parametric (although as a part of separate projects, some have not worked as I intended), the high pass filter, the LED/LDR comp/limiter (love this piece, works great) and I've built a hoard of crossovers, which all work delightfully.
Glad that you have good results. As JMF said, RE's site is full of no-nonsense stuff that works. As for the bickering, somewhat unavoidable. RE says a lot of bombastic, opinionated stuff. I mean he called one of his designs Death of Zen. I don't know how much his website generates, but it must be 5 or more orders of magnitude less than Pass Labs and First Watt 
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