About amp "immediacy"

[pdf64]

...I also had asked for someone to explain the electrical differences between presence and treble tone control. so far, none have taken that up. To answer nosaj, I will be using it for guitar but I don't want it limited to that...

Generally, treble controls operate in the preamp, presence controls operate in the global negative feedback loop of the power amp. They act to remove the NFB at high frequencies when set to max, thereby allowing full interaction between power amp and speaker in that freq range.
So treble and presence sound different.
Obviously, such presence controls can only be used with power amps that incorporate a global NFB loop, eg not a 5E3.

Guitar amps, like guitar speakers, are a pretty specific thing, the opposite of hifi; what other applications were you hoping to use it for?

My perception is that whatever speaker is used, due to sag, squish and bias shift, a heavily overdriven 5E3 will get pretty garbled and notes may get 'lost', hence it may not fit with the requirements of 'immediacy'.

The Celestion Blue and Gold are very similar speakers; I guess that the 90W Cream may use more heavyweight parts, which may explain the more muffled response folks report.

[netfences]

I'm pretty sure nosaj was the first to introduce the contribution of the instrument here which includes the strings. I'm aware of the interactive nature of all the elements but lets concentrate on the amp since I've already defined a general use cab. The theory behind this cab selection is the same as the one some sound engineers use in their choice of monitors. Get the flattest and most obtuse speakers you can find and get the best sound you can out of them. Once you achieve that, the playback can only improve on other speakers. Since my desired amp will be FX free, a slightly modified hifi amp seems like a good choice. We'll need it to have good phase and gain margins and sufficient headroom along with the ability to drive a wide range of impedance. The SKA seems like a good starting point. It's a public domain design too which relieves us of any IP obligation. Another interesting suggestion was emailed to me and that was the F4 by Nelson Pass. It is not an amp but a power buffer. It takes whatever signal you present it and just supplies the amps to drive the cab. This would seem an ideal solution for anyone using a modeler, rack or pedals.

The point pdf64 makes above reconciles what nosaj says about certain amps for certain types of music with the change of immediacy likely to happen with changes in the nature of the signal. This is why I prefer to design around any music style target. The notion of touch sensitivity is definitely related to immediacy but that is mostly in the instrument domain. The amp isn't "touching" anything. Adding to the confusion of introducing this term is what happens when you add compression to a signal. In that case, you begin to hear the note the minute you fret it. No, immediacy should be restricted to the reaction of the amp to the signal so as to avoid confusion and meandering purpose. Big thanks to escherton for his slightly different look at slew rate and to pdf64 for affirming the reason I like NGNF. Does anyone think damping factor is relevant here?

[Helmholtz]

Regarding SS guitar amps one of the best reads is Teemu Kyttälä's book "Solid-State Guitar Amplifiers" (can be found on the internet as pdf>30MB). I am sure this will answer at least some of your questions. See page 48 for damping factor.

[nosaj]

You're going for a sterile sounding amp if your going for flat response, to me that means your going to loose musicality if the amp.
The amp as far as guitars color the sound. Where you come from is a whole difference. More of a reference amp. You gotta change your thinking for this problem im afraid.
nosaj

[netfences]

I don't think so, we're only starting with a characterless amp which we'll be tweaking for immediacy. The signal processor and instrument will be responsible for the majority of the tone. This makes more sense than the unexpected and often unpleasant sounds we'd get changing parameters on the shaped signal going into an amp with too strong a character (cough, cough, Marshall).

[rjb]

If "immediacy" means touch sensitivity, isn't putting a signal processor between the instrument & amp analogous to wearing a condom?

[Jazz P Bass]

Just my opinion: the OP should sit down and play his signal processor set into a power amplifier.

From there we can move on.

As no one, especially the OP, can define this "immediacy" thingie, circuit wise, I tend to believe that this thread is a waste of time.

[Leo_Gnardo]

Just my opinion: the OP should sit down and play his signal processor set into a power amplifier.

From there we can move on.

As no one, especially the OP, can define this "immediacy" thingie, circuit wise,

Exactly, guitar > digital food processor > and run that power amp thru that 2x8 + horn PA cab. I'm sure it will be THRILLING! What's left to "design???"

I tend to believe that this thread is a waste of time also, as far as coming up with something new and amazing.

It has been fun at times kicking around semi-useful concepts like slew rate, and learning the AMAZING FACT that electrons start out fast but settle down quickly to 35 miles an hour on their cruise down the copper highway. Simply astounding!

Yes we should move on but I have a feeling this thread will continue another 1000 entries at least, in the grand tradition of Sea Chief and the eternally bewildered Wil from Belgium.

Old Irish proverb: there is not much point in teaching the pig to whistle. It's clearly waste of your time, and it annoys the pig.

Have a nice weekend folks. I'll be whistling whilst I sizzle up some bacon.

[Dave H]

I tend to believe that this thread is a waste of time.

Yes, I'm sure that was the intent.

[netfences]

What a bunch of sourpusses Why do you believe an amp with a full array of effects built in will be more immediate than an external modeler feeding a made for purpose immediate amp? Don't you want an amp that'll be fast with any cabinet so why grouse on developing that amp with a dull cab? I don't think you guys are hip to good product development strategies. Your way might lead to a very specialized one trick pony that has immediacy but I don't think whatever is achieved is worth the loss in functionality.

[nosaj]

What a bunch of sourpusses Why do you believe an amp with a full array of effects built in will be more immediate than an external modeler feeding a made for purpose immediate amp? Don't you want an amp that'll be fast with any cabinet so why grouse on developing that amp with a dull cab? I don't think you guys are hip to good product development strategies. Your way might lead to a very specialized one trick pony that has immediacy but I don't think whatever is achieved is worth the loss in functionality.

When your done with your way let us know how it turns out. My guess even if everyone was doing your work for you, it would still be in thread form next year.
If you came in my shop you would be one I'd probably have to charge double, because your twice the amount of work as others are.

And as far a good product development strategies I think that statement really turned me off to you. I just get this feeling that if you did come out of this with an amp you'd claim it as all your own development and sell it as such.

We all support each other here in one way or another, but you new guys seem to be all take or tie up everyones time. And people get tired of that stuff.

Maybe personality cafe will have you back to discuss amp design.

Goodbye

nosaj

[gmaslin]

Evan, I sent you a little present for your project. Let me know when you get it.

[netfences]

Thanks, I got it this morning. For those wondering, I was sent two GB150D amp circuit boards for the amp section of my killer music amp. I will get the schematic and upload it for an analysis of its potential. For all those interested in participating, get your SIM software and models ready

[gmaslin]

You may have noticed that the website of the original designer is gone. If that's the reason why you haven't posted the schematic, I linked it here.

SKA GB150D Public Domain sch 1.pdf

The boards I sent probably will work better with a KSC1845/KSA99a pair. Key is high hFe.

[R.G.]

If you're thinking about power amp designs as magic, I suggest that you read Doug Self's power amplifier design book. Doug's a wizard - but he can back up each magic trick with a sound theoretical basis and proof by testing. I think you'd be interested in some of the evaluations of the circuit sections in that power amp in this light.