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Old 10th October 2013, 04:43 PM   #21
shanx is offline shanx  Canada
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There are commercial overdrives that use the CD4007, but looks like they typically tie all the stages to a common VDD rail supply..I would think that it would be neat to be able to dial in the headroom each stage.
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Old 15th October 2013, 02:15 AM   #22
hewo is offline hewo  United States
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thank you all for your responses - i have been away for rehab, yes i am an old man, barely enough stamina to leverage the lever of the hydraulic jack to change my car's lubes to save gasoline money (35 increased to 40 using amsoil! both tranny and engine lubes)

back to theme: i did manage to successfully create the smt but it is cumbersome having all those bjourn micro sized multi-turn trimmers. so i thought if there was a programmer who'd know how to resolve this partial differential equation. as it is now i can only vary one parameter at a time to observe signature impact (scope documents waveform response). this approach is caveman, rather empirical. it'd be proficient to run a computer programmer's program that varies all parameters until the equation is resolved - since we know all of the boundary conditions, right? they are output waveform, input waveform and battery tension. circuitry must accomodate by either over-emphasizing or under-emphasizing characteristics of the waveform that in turn interacts with reactive amplification components (OT/spkr, lesser extent tele stock pickups). the tele has exceptionally pure waveform, that of a sinusoid. but when we look closely at some of this world's sought after tone, e.g., dumble, we find the waveform is intentionally skewed because of the reactive component to which it will interface to. this is the black magic in a nutshell. it is so coveted creators expend more effort protecting their derivations than developing it, so called intellictual property.
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Old 1st November 2013, 01:58 AM   #23
JMFahey is offline JMFahey  Argentina
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Sorry to hear that.
I think that the goal of the original designers who used it to distort was rounded clipping (they got it), very low cost (idem) and ***simplicity*** which applies to a 2 resistor per gain stage device.

Once you start complicating it, even a little bit ..... forget it, there's much better (and still simple) available.

Laney made good use of them, even in clean gain stages (Bass amps), etc.
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Old 3rd November 2013, 07:21 PM   #24
hewo is offline hewo  United States
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must look at laney's application
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Old 12th November 2013, 05:12 AM   #25
JMFahey is offline JMFahey  Argentina
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Startwith this good example.
The Laney Hardcore HC25X, a 25W 1x10" amp designed for Hardcore (imagine a Punk band which *LOVES* Heavy Metal) .
The distortion channel uses 4 stages for a staggering 9000X block gain (besides what the input TL072 provides) and does not use (nor need) diodes for clipping, relying in loaded gates swing limitation.
The amp does actually sound good (for its intended audince)
LANEY HC25 SCH Service Manual free download, schematics, eeprom, repair info for electronics
Here's a live sample.
There's 2 Laney SS heads (wict cascading gates ) driving those Marshall cabinets.
Extremely distorted compressed guitar sound.
Manhole - Respect Yourself - YouTube
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Old 14th November 2013, 08:59 PM   #26
hewo is offline hewo  United States
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Default thankyou JMFahey

will start on clean first - need to affirm cleanliness sine preservation tele stock pups

then migrate over threshold your recommend schematic laney four cascade - recall excessive gains in single jump will blunt bandwidth, right? isn't this why signature gets mooshee on low end and muffled on highs? so prudence dictates small jumps over many cascaded stages - is this correct?
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Old 19th November 2013, 06:35 PM   #27
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Here is an interesting article on using CMOS Logic chips as building blocks in a opamp design,

A true op-amp made from inverters | EDN

jer
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Old 19th November 2013, 07:28 PM   #28
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My first job in California was with a company that made radio test gear. Some of the guys took a Non-Linear Systems micro-oscilloscope (a 1 or 2" screen using an ultra-sensitive Telefunken CRT) apart to see if there were any good ideas that could be used. The found that some of the amplifier circuits inside were implemented using CMOS gates. This was back in 1981.
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Old 19th November 2013, 10:40 PM   #29
hewo is offline hewo  United States
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Default thankyou both gerald fry jr and wrench one

1. okay i will examine and utilize the intellectual materials to arrive at desired round clip waveform high harmonics (even not odd) content of desired frequency spectrum (hollowed sounds sassy and appeals)
2. the trouble comes from the macroscopic feedback discrete bjourn multi-turn trimmers because of the lead dressing umbilical antennae inviting unwanted parasytic and runaway (constructive) interferences, crosstalk
3. trimmers necessitated for taming gain thru cascaded stages - i don't believe fixed resistors would facilitate mission objective round clip high even harmonics content
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