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Topics - phatt

Preamps and Effects / PhAbb SS AmpDemo
January 06, 2010, 12:40:25 AM
Hi everyone,
                Could not decide where to put this but as there is no actual *PowerAmp* being used to generate the audio then this seems the most logical place.
Well I figured enough talk why not a little demo of my PhAbb SSAmp Setup.

As just about any bit of gear these days (including mine) can produce copious amounts of distortion then why not demo those in between dynamics that are probably harder to reproduce with all SS equipment.

Tube Amps have an area which is on the edge of distortion and this was my aim, to nail/capture that in between *Rattle* that a lot of those famous tube amps where able to do so easily.
The Knophler sound is often a tricky one so I tried it out, see what you think.

First track is done with a bog stock Chinese Strat copy, I like it for this stuff because the Pup's are low winding only 4k DCR.
The second bit is Recorded with my other guitar (real 60's era Strat pup's)

(Maxiverb is a stand alone Spring Rev unit I desiged and built about 10 years ago,, and still going strong.)

Signal path;
Maxiverb > My PhAbbTone box > DDC (My Dynamic Distortion Control)
> A Realistic HiFi GraphicEQ > signal into Line mixer> Into Audigy SCard.
Adding no post efx of any kind.

There is very little difference between the line rec out sound and a real 100Watt power amp driving a guitar speakerbox (To my ears at least) but your speakers will colour the sound to some degree no doubt.

If any interest I will post more short demos and all the setup schematics, might give you some ideas to work on.
Sorry the file is short but only 500kb allowed.

Hope you enjoy, Phil.
Edit 2011
> Reloaded the files and Dloaded back to myself and it seems to be working OK now.<
Schematics and Layouts / Passive Tone Circuit
May 24, 2009, 10:18:18 AM
My effort at tone controls.
Ok "Zappacat and sergscar" have asked for this one so here it is;
The "Tonemender circuit" has been mentioned more than once on these pages and although it works it could be quite easily improved. No disrespect to ROG but I get the impression not much effort goes into "Refining" there ideas. Nearly all these old styled passive tone circuits are quite prone to picking up noise but if you know your way around it they can be greatly improved. At the very least this will give DIYer's some other options to choose from that
I think most will find superior.

HiWatt tone does not get much mention (probably because it looks a little tricky) even though it was the best of all the famous tone stacks. In fairness it's no better than the classic Fender in regard to the Amount of bass and treble but the midrange cut leaves fender types for dead.
I doubt many will read all this but I have built a lot of these old circuits both Valve and SState so I'm fairly confident in stating how well they actually DO or Do Not perform.
If you are just hell bent on replicating a specific tone circuit then It should become obvious that you can use most of the old tone stacks in place of mine if you so wish.
For those that wish to replicate the EXact HiWatt circuit be aware that the bass pot was a *TRUE LOG* 500k unit and you may have trouble sourcing those nowadays.  What is often sold today has a psudo log curve and will be very disappointing in use.

I've tweaked the components for what I think is the best mid freq Q point and max cut, it's around 400hZ.
Play around with the values if you so wish but what you gain at some place you may loose out elsewhere. Like all the other tree type tone circuits the controls are very much interactive. There is No Gain/Boost with passive tone stacks so the game plan is all about making the biggest difference between frequencies. A deep notch cut is what you want as shallow scoops tend to sound unconvincing or bland.
Side note;
My Alesis Micro EQ cannot deliver the 30/35Db difference at 400hZ when compared to the passive HiWatt even though the Alesis is an Active parametric device,,, and yes I A/B tested this many times.

This schematic is version 2, which is better than the original circuit that I've already posted on this board. I've built 8 of these units for mostly working musicians and over time it became apparent that the noise/hiss
was an issue with some Hi gain Amps. This is all good because it forces me to work harder and find better ways to implement the circuit.
Very low noise opamps might help in extreme situations, I've used both TL072 and LM883 and you can hardly pick the difference by ear.

Be aware that altering or deleting R5(10k) will just increase the noise in quite a dramatic fashion but not the gain.
I discovered from some in-depth reading that this is how to do it and keeps the noise down. The 10k/10k voltage divider network (R5 and R6) seems to deliver the best results. Some here may have even better ideas so feel free to comment.
Also make VR4 100k lin or log if you need more power to drive your amp but don't go mad here as the noise will climb fast. The intention here was to just use this to balance the bypassed sound level and is not intended as a high gain section,, there are plenty of those around so use them for gain.

A good understanding of wiring up high impedance circuits helps as well. For those that may not fully understand,, Everything above R1 R2 R3 R4 in the tone stack is going to be prone to picking up unwanted crap,,
so just use metal film R's for the whole circuit and be done with it.

What! No active input? :duh
One of the not so obvious subtleties of famous valve driven tone stages was the simple fact that the output of the tone stage had a natural roll off in the high freq response.
With an active opamp buffer stage front-end this may not happen so by using the tone passively you are likely getting closer to the original Valve Tone effect. The passive tone stack input imp is plenty high enough for the magnetic PU's used in electric guitars.
Feel free to use a buffer in front but don't expect it to be vastly
When players first hear this box there is often a comment about the presence/brightness,, so again attaining more hi freq will likely render it more SState sounding which is the very thing your probably trying to avoid. so your call.
And for those that think it can't work passively you need to go way way back as this was how it was done in some early equipment.

How to use;
The treble dominates the tone in old standard fenders and I wanted to avoid that as much as I could. So if you want the treble to sparkle with this one,, just turn down the mid as it is now the dominant control.
I've deliberately tilted the output slightly to the treble freq but without loosing to much bass.
If you want more bass make R1 smaller, try 56k. Lower values will likely upset the mid cut ability.
Now I've bored you long enough so here's The schematic and some pictures that might give you some ideas of how to build it. I use the old printer selector boxes, you can pick them up for next to nothing as they are of no use anymore.
I do this cause someone may as well benifit from all my frustrations of trying to get a decent sound.
After 20 plus years of fiddlin with circuits,,, on rare occasions you have a win and I think this is one time I did pull something off that actually worked.
Have fun with it, Phil.

*Edit*  Just a note, Scroll down for the up to date SCHEMATIC. Cheers, Phil.