Tone controls are something of a no-no in high-price audio. But what is a high-price audio cable but a high-price tone control?
Now, you can buy or make cables to fit your system and taste. But regardless of what you do, it involves a lot of work that a tone control would solve in seconds. And it's not only that I want to save work, but I want to make the cable irrelevant. I want to get back to the days when cables didn't matter.
I remember that somebody mentioned how to make an "ideal" tone control here. It was quite some time ago. I did a search, but came up with nothing.
Does anyone know what this "ideal" tone control would be? It was nothing like traditional bass and treble controls, if I remember. Didn't give it much thought then.
Now, you can buy or make cables to fit your system and taste. But regardless of what you do, it involves a lot of work that a tone control would solve in seconds. And it's not only that I want to save work, but I want to make the cable irrelevant. I want to get back to the days when cables didn't matter.
I remember that somebody mentioned how to make an "ideal" tone control here. It was quite some time ago. I did a search, but came up with nothing.
Does anyone know what this "ideal" tone control would be? It was nothing like traditional bass and treble controls, if I remember. Didn't give it much thought then.
poobah, thanks.
I'm not quite sure what I look for or hope. Well, I hope for a revelation. But that might be to have a bit too high hopes.
mlloyd1, yes, I should put in more effort. I believe it was mentioned in passing and therefore hard to find. But, yes, it's out there. And it might turn out to be nothing.
I'm not quite sure what I look for or hope. Well, I hope for a revelation. But that might be to have a bit too high hopes.
mlloyd1, yes, I should put in more effort. I believe it was mentioned in passing and therefore hard to find. But, yes, it's out there. And it might turn out to be nothing.
Konnichiwa,
Try reading this:
http://www.enjoythemusic.com/magazine/equipment/0101/behringer8024.htm
If this is too complex consider the circuit (passive but 600 Ohm and 20db attenuation) from the pulse technology (PulTec) Equaliser, there are various arrangements, I would add an input buffer to the network in any technology (valves or solid state) you like.
http://www.gyraf.dk/gy_pd/pultec/pultec.htm
Finally, in my experience still ergonomically the best "program equaliser" is Cello Palette. A review of the "cut down" Palette Preamplifier is here:
Stereophile reviews the Palette
This shows the actual adjustment range on each control.
You could build something that goes a good way to emulate it's function using a circuit similar to the EAR 825 Equaliser:
http://www.gyraf.dk/schematics/Ear_825_EQ.GIF
This looks intimidating, but it is basically just a multiband EQ using a Valve Op-Amp. You could use just the Forsell Valve Op-Amp in this kind of circuit.
Just add a sixth control and set the controls LCR circuitry to match the Palette.
Sayonara
phn said:
Try reading this:
http://www.enjoythemusic.com/magazine/equipment/0101/behringer8024.htm
If this is too complex consider the circuit (passive but 600 Ohm and 20db attenuation) from the pulse technology (PulTec) Equaliser, there are various arrangements, I would add an input buffer to the network in any technology (valves or solid state) you like.
http://www.gyraf.dk/gy_pd/pultec/pultec.htm
Finally, in my experience still ergonomically the best "program equaliser" is Cello Palette. A review of the "cut down" Palette Preamplifier is here:
Stereophile reviews the Palette
This shows the actual adjustment range on each control.
You could build something that goes a good way to emulate it's function using a circuit similar to the EAR 825 Equaliser:
http://www.gyraf.dk/schematics/Ear_825_EQ.GIF
This looks intimidating, but it is basically just a multiband EQ using a Valve Op-Amp. You could use just the Forsell Valve Op-Amp in this kind of circuit.
Just add a sixth control and set the controls LCR circuitry to match the Palette.
Sayonara
Konnichiwa,
There was an article series by Richard Brice once in some mag or something, on the "Maximalist Preamplifier" republished on the web, which had a simplified Pultec Network....
I have a copy here, let me quote the relevant section:
"Rather than design a Baxandall tone-control based around a high gain op-amp or a discrete transistor stage (an option which I considered last month) I decided to look elsewhere for inspiration. I found it in a design of a vintage valve studio-equaliser, the Pultec Model EQP-1A. The blue-grey enamel fronted Pultec unit was first manufactured by Pulse Techniques Inc. of Englewood, New Jersey some thirty or forty years ago and this 'classic' design has spawned many derivatives, amongst which are some of the creme-de-la-creme studio equalisers of today."
"The Pultec's crucial power lies in the ability it affords to select independently the frequency range over which boost and cut may be applied, a degree of subtlety well beyond that of a standard tone-control circuit. Actually the EQP-1A in its original form is so complicated that it offers a bit too much of a good thing for domestic use. In the design for the preamplifier, I believe that I have succeeded in sacrificing unnecessary complexity whilst preserving the all important versatility."
"The diagram illustrates how the Pultec-inspired, Maximalist Preamplifier tone-control achieves all its equalisation in one entirely passive circuit of considerable complexity. The important detail to notice is that one may, for instance, cut bass frequencies below 100Hz and - at the same time - boost sub 30Hz frequencies. Using combination of controls such as this, it's possible to clean-up a 'boomy' recording (with a surfeit of energy in the 100 to 200Hz region) without emasculating the bass frequencies - a combination also extremely useful for correcting for the room resonance effects from which we all suffer to a various extent."
"The same advantages can be reaped at the top end where a conjunction of boost in the 5kHz region an treble-cut above 10kHz can help restore some sparkle to cassette tapes recorded with incorrect azimuth without introducing too much tape noise in the process."
"The only disadvantage of Pultec's passive approach is that the circuit introduces about 24dB of static attenuation at all frequencies when adjusted for a flat response. In the original circuit this loss was compensated by the introduction of a push-pull, valve amplifier constructed from a 12AX7, a 12AU7 and a couple of transformers. Beautiful, but a bit clumsy for the Maximalist Preamp - especially for stereo - where I have plumbed for an op-amp circuit instead."
"The design enjoys a couple of especially favourable characteristics; the first is that it cannot suffer from overloading problems or variable distortion characteristics due to reduction in feedback fraction - as is the case with a circuit like the Baxandall tone-control. Naturally, the other side of the coin is that the circuit does introduce some noise - however the impedances are very low so this is of no practical significance."
"The second advantage is that it does not require a bypass switch because, when the controls are set to 'flat', the reactive components are effectively out of circuit. The only possible source of distortion is that created by the following amplifier and that's very small indeed. Just one small technical detail, note that R2 controls the treble-boost characteristic Q. Set at 2K, the curve is pretty gentle. If you wish, you can increase or decrease the selectivity of the boost control by altering this value."
This might be usefull....
Sayonara
phn said:
There was an article series by Richard Brice once in some mag or something, on the "Maximalist Preamplifier" republished on the web, which had a simplified Pultec Network....
I have a copy here, let me quote the relevant section:
"Rather than design a Baxandall tone-control based around a high gain op-amp or a discrete transistor stage (an option which I considered last month) I decided to look elsewhere for inspiration. I found it in a design of a vintage valve studio-equaliser, the Pultec Model EQP-1A. The blue-grey enamel fronted Pultec unit was first manufactured by Pulse Techniques Inc. of Englewood, New Jersey some thirty or forty years ago and this 'classic' design has spawned many derivatives, amongst which are some of the creme-de-la-creme studio equalisers of today."
"The Pultec's crucial power lies in the ability it affords to select independently the frequency range over which boost and cut may be applied, a degree of subtlety well beyond that of a standard tone-control circuit. Actually the EQP-1A in its original form is so complicated that it offers a bit too much of a good thing for domestic use. In the design for the preamplifier, I believe that I have succeeded in sacrificing unnecessary complexity whilst preserving the all important versatility."
An externally hosted image should be here but it was not working when we last tested it.
"The diagram illustrates how the Pultec-inspired, Maximalist Preamplifier tone-control achieves all its equalisation in one entirely passive circuit of considerable complexity. The important detail to notice is that one may, for instance, cut bass frequencies below 100Hz and - at the same time - boost sub 30Hz frequencies. Using combination of controls such as this, it's possible to clean-up a 'boomy' recording (with a surfeit of energy in the 100 to 200Hz region) without emasculating the bass frequencies - a combination also extremely useful for correcting for the room resonance effects from which we all suffer to a various extent."
"The same advantages can be reaped at the top end where a conjunction of boost in the 5kHz region an treble-cut above 10kHz can help restore some sparkle to cassette tapes recorded with incorrect azimuth without introducing too much tape noise in the process."
"The only disadvantage of Pultec's passive approach is that the circuit introduces about 24dB of static attenuation at all frequencies when adjusted for a flat response. In the original circuit this loss was compensated by the introduction of a push-pull, valve amplifier constructed from a 12AX7, a 12AU7 and a couple of transformers. Beautiful, but a bit clumsy for the Maximalist Preamp - especially for stereo - where I have plumbed for an op-amp circuit instead."
"The design enjoys a couple of especially favourable characteristics; the first is that it cannot suffer from overloading problems or variable distortion characteristics due to reduction in feedback fraction - as is the case with a circuit like the Baxandall tone-control. Naturally, the other side of the coin is that the circuit does introduce some noise - however the impedances are very low so this is of no practical significance."
"The second advantage is that it does not require a bypass switch because, when the controls are set to 'flat', the reactive components are effectively out of circuit. The only possible source of distortion is that created by the following amplifier and that's very small indeed. Just one small technical detail, note that R2 controls the treble-boost characteristic Q. Set at 2K, the curve is pretty gentle. If you wish, you can increase or decrease the selectivity of the boost control by altering this value."
This might be usefull....
Sayonara
Even if I should have an ideal listening room and a system with perfect synergy (I doubt many of those are around), this Pultec would still be interesting, if just for the design. The high prices suddenly look justified.
I will have to get back to the drawing board. At least I have all the information I need to move forward.
Thanks again.
I will have to get back to the drawing board. At least I have all the information I need to move forward.
Thanks again.
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