As I keep reading, I ran across two interesting sites. With apologies if you are already familiar with them:
Class A Analog EQ listening tests... - SH Forums, where Steve Hoffman shares his preferences in post #23, and
Classic Schematics, where there are several cool schematics for equalizers. Note the EAR 825 tube equalizer, and the Langevin EQ251A Passive, which I read is supposedly close to the old Universal 500-A EQ. Sowter still sells the inductors for some of the Gyraf and Pultec circuits.
There is one more request I would like to make, if I may, which is a healthy voltage swing at the output or the equalizer. My power amps are buffers (F4s) and it would be great if the equalizer could put out in the order of +/- 20 volts. My current preamp can feed it a comparable input voltage, so it is more voltage swing than gain I would seek.
Pierre
Class A Analog EQ listening tests... - SH Forums, where Steve Hoffman shares his preferences in post #23, and
Classic Schematics, where there are several cool schematics for equalizers. Note the EAR 825 tube equalizer, and the Langevin EQ251A Passive, which I read is supposedly close to the old Universal 500-A EQ. Sowter still sells the inductors for some of the Gyraf and Pultec circuits.
There is one more request I would like to make, if I may, which is a healthy voltage swing at the output or the equalizer. My power amps are buffers (F4s) and it would be great if the equalizer could put out in the order of +/- 20 volts. My current preamp can feed it a comparable input voltage, so it is more voltage swing than gain I would seek.
Pierre
Hi,
I don't need to. The parts are now discontinued and very expensive (and they have no cheap replacements) but they where never cheap, due the large die needed and the relative low volumes.
Well, it uses parallel filters and in the end is not much more complex fundamentally than the NTI EQ3.
I would suggest the EQ3 is for people who have to have Op-Amp's in their gear as they are not happy otherwise. As a project it is fully documented and your can of course alter the bands frequencies as needed. The patent that describes the operation is US Patent 5805716, easily accessed via (for example) pat2pdf.org.
The East German EQ is a bit more extreme minimilast, but over 20 years after discontinuation still has many fans over the more common Op-Amp Graves.
Inductors can be found at Mouser et al, quite a wide range. The very large values where always custom made, however you can use a circuit called a Gyrator (in the minimum one Transistor/Fet, three resistors and one cap) to make a "virtual" Inductor. It is covered in Post # 18 in thishere thread:
http://www.diyaudio.com/forums/analog-line-level/194119-high-end-tone-control.html#post2665167
How about you get some schematic drawing software and start on the re-work of the Nite EQ3D for "audiophile" use? It seems to have most of what you desire and can be made with more bands and so on.
My personal choice is in the Poll in the thread on building the thing (where this post should have been).
Software.
If I was to build a hardware unit, a variation of the East German EQ with tubes for signal path and either all inductors or mostly real inductors. Probably using some "Guru" Tubes that are hard to get and really expensive (but of which i have a stash), all 24-Pole stepped switches and output transformer.
For the project thread I'll probably propose a Fet Based version first, in the worst case (all virtual inductors - the PCB would be made to offer a choice between real inductors and Fet based gyrators) it would need 9pcs 2SK170/LSK170 per channel, use 10K linear potentiometers (PCB capable of holding Alps Blue) and split rails. For those who prefer tubes I'd include a section on how to replace some of the Solid State stuff with tubes.
Sure, have fun. I made those comparisons in the 1980's and I would not spend time on messing with the Op-Amp version myself, but "De gustibus non disputandum est".
Ciao T
I don't need to. The parts are now discontinued and very expensive (and they have no cheap replacements) but they where never cheap, due the large die needed and the relative low volumes.
Well, it uses parallel filters and in the end is not much more complex fundamentally than the NTI EQ3.
I would suggest the EQ3 is for people who have to have Op-Amp's in their gear as they are not happy otherwise. As a project it is fully documented and your can of course alter the bands frequencies as needed. The patent that describes the operation is US Patent 5805716, easily accessed via (for example) pat2pdf.org.
The East German EQ is a bit more extreme minimilast, but over 20 years after discontinuation still has many fans over the more common Op-Amp Graves.
Inductors can be found at Mouser et al, quite a wide range. The very large values where always custom made, however you can use a circuit called a Gyrator (in the minimum one Transistor/Fet, three resistors and one cap) to make a "virtual" Inductor. It is covered in Post # 18 in thishere thread:
http://www.diyaudio.com/forums/analog-line-level/194119-high-end-tone-control.html#post2665167
How about you get some schematic drawing software and start on the re-work of the Nite EQ3D for "audiophile" use? It seems to have most of what you desire and can be made with more bands and so on.
My personal choice is in the Poll in the thread on building the thing (where this post should have been).
Software.
If I was to build a hardware unit, a variation of the East German EQ with tubes for signal path and either all inductors or mostly real inductors. Probably using some "Guru" Tubes that are hard to get and really expensive (but of which i have a stash), all 24-Pole stepped switches and output transformer.
For the project thread I'll probably propose a Fet Based version first, in the worst case (all virtual inductors - the PCB would be made to offer a choice between real inductors and Fet based gyrators) it would need 9pcs 2SK170/LSK170 per channel, use 10K linear potentiometers (PCB capable of holding Alps Blue) and split rails. For those who prefer tubes I'd include a section on how to replace some of the Solid State stuff with tubes.
Sure, have fun. I made those comparisons in the 1980's and I would not spend time on messing with the Op-Amp version myself, but "De gustibus non disputandum est".
Ciao T
Hi,
Yet all the various EQ's that are (justly) legendary for sound quality under equalisation are not constant Q.
Constant Q makes sense from a technical viewpoint if we want to make sure the curve on the face of a graphic EQ resembles accurately the actual electrical equalisation, but has little advantage otherwise.
I would suggest that for the kind of EQ the Palette represents it is actually a drawback. If Bandwidth is retained but the gain varies the resulting EQ curves have a much better integration between bands.
It really depends on the application which is better. I would suggest constant Q for "technical EQ" (1/6th octave for speaker system EQ for example) and variable Q for "creative EQ" like mastering/re-mastering. The jobs are very different.
Ciao T
Yet all the various EQ's that are (justly) legendary for sound quality under equalisation are not constant Q.
Constant Q makes sense from a technical viewpoint if we want to make sure the curve on the face of a graphic EQ resembles accurately the actual electrical equalisation, but has little advantage otherwise.
I would suggest that for the kind of EQ the Palette represents it is actually a drawback. If Bandwidth is retained but the gain varies the resulting EQ curves have a much better integration between bands.
It really depends on the application which is better. I would suggest constant Q for "technical EQ" (1/6th octave for speaker system EQ for example) and variable Q for "creative EQ" like mastering/re-mastering. The jobs are very different.
Ciao T
Hi,
This uses a straightforward active Baxandall design, discrete circuits (non-op-amp style) for the actives. Nothing unusual.
I like what Luxman did in the Avance Z502 and the C-02 Preamps, where no additional circuitry (apart from the tone filters) are needed and they also featured selectable turnover frequencies.
Ciao T
This uses a straightforward active Baxandall design, discrete circuits (non-op-amp style) for the actives. Nothing unusual.
I like what Luxman did in the Avance Z502 and the C-02 Preamps, where no additional circuitry (apart from the tone filters) are needed and they also featured selectable turnover frequencies.
Ciao T
Hi,
Interesting that the old Sphere based EQ does best. Pretty generic circuitry, no surprises with Chandler as #2 and Manley as # 3 and while Avalon is rather good I'm not surprised in a blind preference test it ended up last.
This goes against simplicity. The EQ section will be unity gain aimed at -10dBV "0dBVU" levels.
Given that is a totally outlandish requirements for line-level electronics I'm not even going to think about it, sorry. Add a suitable linestage after the EQ with gain and enough output swing.
Ciao T
Interesting that the old Sphere based EQ does best. Pretty generic circuitry, no surprises with Chandler as #2 and Manley as # 3 and while Avalon is rather good I'm not surprised in a blind preference test it ended up last.
This goes against simplicity. The EQ section will be unity gain aimed at -10dBV "0dBVU" levels.
Given that is a totally outlandish requirements for line-level electronics I'm not even going to think about it, sorry. Add a suitable linestage after the EQ with gain and enough output swing.
Ciao T
Note that Tim de Paravicini designs his EQs with at least 28 dB / 25 volts output. Pultec and the EAR EQ's - Gearslutz.com. Granted, his are for mastering applications.
Since this is of little interest to you, I can put the EQ in a tape loop or add voltage gain in a separate stage.
That is an excellent idea! A project doable without expensive/discontinued parts? Nice!! Are you going to use the 6 Palette controls?
Hi,
This is called "headroom" and Tim's EQ's are for studio systems, that is +6dBU...
This would be a good choice.
Ciao T
This is called "headroom" and Tim's EQ's are for studio systems, that is +6dBU...
This would be a good choice.
Ciao T
Hi,
No, it has a buffer. This was the same circuit also sold as a standalone EQ but integrated into a Mixing Desk. This excerpt is from the mixing desk, as I could not find the one for the standalone one, they used the same PCB, the standalone one had also a 32Hz band.
Incidentally, I also owned this precise mixing desk, the stand alone EQ and so on.
They are in mH, it says on the schematic.
Ciao T
No, it has a buffer. This was the same circuit also sold as a standalone EQ but integrated into a Mixing Desk. This excerpt is from the mixing desk, as I could not find the one for the standalone one, they used the same PCB, the standalone one had also a 32Hz band.
Incidentally, I also owned this precise mixing desk, the stand alone EQ and so on.
They are in mH, it says on the schematic.
Ciao T
Hello Thorsten
Milihenry, on the schematic; 63hz would use a 1400 milihenry coil, quite big coil value.
Thank
Bye
Gaetan
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Hi,
Well, I have a fair few of these coils:
SteinMusic - Audio/HiFi-Spulen
Not all that difficult to make.
Ciao T
Well, I have a fair few of these coils:
SteinMusic - Audio/HiFi-Spulen
Not all that difficult to make.
Ciao T
Hi,
FWIW if i was making a tone control to account for various factors, e.g.
different old RIAA standards then I'd consider building it as a "Shuffler".
Basically at the input you add and substract the two channels, then EQ
them, and then at the output you add and subtract those two channels
again to restore left and right.
Two effects : One, the EQ of the mono signal of both channels will
exactly match. Two, by varying the gain of the sum and difference
channels before re-addition and re-subtraction you can vary the
effective stereo width, just like the tone controls, its the fact you
can make minor adjustments allows for possible improvements.
So it gives you an extra flexibility, and at the same time improves
channel matching of the EQ, what's not to like about the schema ?
rgds, sreten.
FWIW if i was making a tone control to account for various factors, e.g.
different old RIAA standards then I'd consider building it as a "Shuffler".
Basically at the input you add and substract the two channels, then EQ
them, and then at the output you add and subtract those two channels
again to restore left and right.
Two effects : One, the EQ of the mono signal of both channels will
exactly match. Two, by varying the gain of the sum and difference
channels before re-addition and re-subtraction you can vary the
effective stereo width, just like the tone controls, its the fact you
can make minor adjustments allows for possible improvements.
So it gives you an extra flexibility, and at the same time improves
channel matching of the EQ, what's not to like about the schema ?
rgds, sreten.
Hi,
There is only one RIAA standard, the other LP EQ's are not RIAA.
You might find that the Mono only EQ creates funky sounds when the Mono-signal is subject to substantial frequency dependent phases shifts, while the difference signal is not.
Ciao T
There is only one RIAA standard, the other LP EQ's are not RIAA.
You might find that the Mono only EQ creates funky sounds when the Mono-signal is subject to substantial frequency dependent phases shifts, while the difference signal is not.
Ciao T
That doesn't mean they don't exist, or that RIAA is always accurate.
I did not suggest Mono only signal EQ at all. You could "shuffle" post
EQ but then you'd be chucking away the better channel matching.
Its a better way of using two channel EQ and in this case dual
channel pots are mandatory, no-one would be able to set the
difference channel pots intuitively, and that is not the intention.
rgds, sreten.
Hi,
Not what I meant. I know how many LP EQ Curves are documented. Almost all are designed into the AMR Phonostage (by moi), but they are NOT RIAA curves. RIAA is unambigously defined with turnovers of 50, 500 and 2122Hz. Others cannot be called RIAA EQ, but need to be called suitable identifications, e.g. Decca or Columbia.
I know some people use RIAA and "LP EQ" as the same, but they are not, RIAA is the bunch who likes to sue their paying customers for more money, who also proposed the RCA Orthophonic EQ for adoption by the American Recording Industry in 1953...
Ah, I misunderstood. If you EQ both Mono and difference, yes that will work.
BTW, Spatial controls are possible without first creating M & S and then re-mixing them...
Ciao T
Not what I meant. I know how many LP EQ Curves are documented. Almost all are designed into the AMR Phonostage (by moi), but they are NOT RIAA curves. RIAA is unambigously defined with turnovers of 50, 500 and 2122Hz. Others cannot be called RIAA EQ, but need to be called suitable identifications, e.g. Decca or Columbia.
I know some people use RIAA and "LP EQ" as the same, but they are not, RIAA is the bunch who likes to sue their paying customers for more money, who also proposed the RCA Orthophonic EQ for adoption by the American Recording Industry in 1953...
Ah, I misunderstood. If you EQ both Mono and difference, yes that will work.
BTW, Spatial controls are possible without first creating M & S and then re-mixing them...
Ciao T
Hi,
Maybe, but it has to be the same principle, for headphones its frequency
selective. Anyway the point is not so much the spatial control, its the
arrangement guarantees perfect channel matching, for normal stereo.
(Differences in the two EQ channels are replicated in both channels as
differences in the EQ applied to the "stereo" part as opposed to "mono").
Whats not to like about that ? (As well as being able to tweak width ?)
rgds, sreten.
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Hi,
It does not use M/S as such. Stereo Width control was implemented widely in portable gear without using M/S.
But may screw up the stereo image otherwise...
All the unnecessary extra circuit is something I personally do not like. High Quality Potentiometers worth using usually track very well, if using stepped controls for tone (which has much to recommend it) tracking si down to what tolerance resistors you buy.
It seems we have very different goals. Mine is a maximum of sound quality both with and without tone controls, which in my personal experience precludes much added circuirt. Even adding an active Baxandal FUBAR's sound quality.
Ciao T
It does not use M/S as such. Stereo Width control was implemented widely in portable gear without using M/S.
But may screw up the stereo image otherwise...
All the unnecessary extra circuit is something I personally do not like. High Quality Potentiometers worth using usually track very well, if using stepped controls for tone (which has much to recommend it) tracking si down to what tolerance resistors you buy.
It seems we have very different goals. Mine is a maximum of sound quality both with and without tone controls, which in my personal experience precludes much added circuirt. Even adding an active Baxandal FUBAR's sound quality.
Ciao T