Balanced LDR
Hi Ondesx,
The pdf shows the shunt connected to + and -. How will that change the sound of the balanced ldr pre? Is the shunt controlled by the pot? That doesnt make sense to me. I am looking for circuits to improve the ps of the ldr preamp. The 2 posts you point to do not have any circuit info. I am not that knowledgable about this stuff but am willing to learn. I find the single end ldr pre I made sounds very good and would like to finish the balanced one someday soon.
Hi Ondesx,
The pdf shows the shunt connected to + and -. How will that change the sound of the balanced ldr pre? Is the shunt controlled by the pot? That doesnt make sense to me. I am looking for circuits to improve the ps of the ldr preamp. The 2 posts you point to do not have any circuit info. I am not that knowledgable about this stuff but am willing to learn. I find the single end ldr pre I made sounds very good and would like to finish the balanced one someday soon.
Well, there are two different ways to go balanced. One is the schematics you already have, the second is the so-called "floating balanced" which is represented on my figure.
The two series and the shunt are controlled as they are in your own circuit, i. e. series in one polarization and shunt in another. In this approach not only you'll save 2 "matched" components but it is easier to control.
You have to "imagine" that "a virtual ground" is somewhere in between the bridge figured by the shunt LDR.
Perhaps to help you understand the things in a very simplistic way, please go do it with "fixed resistor values" (not LDRs) for a given attenuation factor... You'll see that the voltage of the +/- input side is really attenuated by the expected value at the output side...
The best way to understand is to experiment...
I'm afraid that even if I provided the circuit this wouldn't help you unfortunately, because the heart of this attenuator is something not easy to deal with in fact...
Suffice to say that the "linearity" and "stability" of LDRs are far from to be the "better parameters" of these components. As you probably are aware, it's necessary to always give an adapted current to the LDRs for ALL the attenuation steps. There is no "analog method" which delivers "continuously" the correct currents for all the working range (this is what was tempted through the potentiometer method...). Then you must either "manually" or "automatically" determine these values. Last, all these data are stored and used for each required attenuation.
It'll be near impossible to derive a correct working balanced device for all the attenuation range by the use of a good potentiometer, even a very good one and even by the use of the "floating balanced" approach... Unfortunately.
Hi bikerboy,
I have not tried the balanced version of the Warpspeed as I don't have a balanced source and amp to really go fully balanced. I can't find any reason though that it won't work as presented on the simplified schematic. The Warpsquid can source enough current and will work with just one along with one precision pot. You probably can use the matched LDRs you have, as these are what are common to all the designs, but not sure if these are matched at the Warpspeed's listening range (response curves on article). If you really want to try I can provide just the Warpspeed and the control pot. Please pm me if you do.
Yeah, it's only late fall we have already ran the full gauntlet of winter weather here in the PNW...including thunder and lightning!
Could you please start your own Thread so we can discuss your designs separately. Thanks...
Oh sorry I didn't realize it's a "private thread". And the circuit I suggested isn't "my own design" but a well known balanced design. Anyway...
Btw, this is already up...http://www.diyaudio.com/forums/swap...tocoupler-volume-control-kit.html#post2396418
Ok, I looked at the pdf.
Now please explain to me what's so special about it?
To me it looks like standard series/shunt configuration with current sources?
I'm doing current sources as well, I have a big knob (well actually two since I have balance as well) and distortion due to a psu shouldn't be a problem if you know how to design a psu?
It's possible I'm missing something here but I'm just not seeing anything special?
I don't want to be a bad sport, I'm just not seeing it? Please explain?
Now please explain to me what's so special about it?
To me it looks like standard series/shunt configuration with current sources?
I'm doing current sources as well, I have a big knob (well actually two since I have balance as well) and distortion due to a psu shouldn't be a problem if you know how to design a psu?
It's possible I'm missing something here but I'm just not seeing anything special?
I don't want to be a bad sport, I'm just not seeing it? Please explain?
...but I'm talking about the circuitry.
It's just me being curious.
I like to understand why something is supposed to be better.
At this time there are 2 ways you can satisfy your curiousity -get a kit and build it or wait for the early birds to complete their kits and hear from them.
You sound like you didn't really read the postings and the article...? Please don't hold your breath about the circuit.
Badge, the attachment on post #38 lets you play with the various variables and see how it fits in a system. Music peaks measured from my amp's output at 3.5Vrms (~5Vpk) is already very loud on my 88dB loudspeakers. Keeping that peak value in mind try your system's parameters and see where the volume level knob will be.
As an example a standard CD out of 2.83Vpk, 200R output impedance; an F5 amp with 100k input impedance, 5 gain; and 85dB loudspeakers...3.5Vrms will be at 12:00.
Changing the amp's input impedance to 10k will need it to go past 12:00. Of course all these are approximation and guide. There are a lot of possible permutations it's tough to cover all in reality.
It doesn't have a buffer...
As an example a standard CD out of 2.83Vpk, 200R output impedance; an F5 amp with 100k input impedance, 5 gain; and 85dB loudspeakers...3.5Vrms will be at 12:00.
Changing the amp's input impedance to 10k will need it to go past 12:00. Of course all these are approximation and guide. There are a lot of possible permutations it's tough to cover all in reality.
It doesn't have a buffer...
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Just an update...http://www.diyaudio.com/forums/swap-meet/178839-warpspeed-optocoupler-volume-control-kit-2.html
Merry Christmas to all!
Merry Christmas to all!
I picked up several genre of music from my local library and found the albums amazingly enjoyable in every musical sense...even Bela Fleck's banjo playing! Here are the selections:
Love's Been Rough On Me -Etta James
The Great American Songbook Vol. II -Rod Stewart
A Wonderful World -Tony Bennett and k.d. lang
Perpetual Motion -Bela Fleck
John Williams Conducts John Williams' Star Wars Trilogy -with The Skywalker Ranch Symphony
Appalachian Spring/Billy The Kid -Aaron Copland/Boston Symphony; Eugene Ormandy/Philadelphia Orchestra; Arthur Fiedler/Boston Pops Orchestra
Copland Symphony No. 3 -Eduardo Mata/Dallas Symphony
In my experience, a system that does well with orchestral music does well with all types of music. I went thru every track in each cd...with the "Star Wars-Main Theme" even getting repeated twice in one sitting!
With the cold temps I can play all day my Class A amps without the bonus of ear fatigue
Love's Been Rough On Me -Etta James
The Great American Songbook Vol. II -Rod Stewart
A Wonderful World -Tony Bennett and k.d. lang
Perpetual Motion -Bela Fleck
John Williams Conducts John Williams' Star Wars Trilogy -with The Skywalker Ranch Symphony
Appalachian Spring/Billy The Kid -Aaron Copland/Boston Symphony; Eugene Ormandy/Philadelphia Orchestra; Arthur Fiedler/Boston Pops Orchestra
Copland Symphony No. 3 -Eduardo Mata/Dallas Symphony
In my experience, a system that does well with orchestral music does well with all types of music. I went thru every track in each cd...with the "Star Wars-Main Theme" even getting repeated twice in one sitting!
With the cold temps I can play all day my Class A amps without the bonus of ear fatigue
John Williams and the musicians let their hair down on "The Cantina Band" track...with a dose of George Lucas sound effects...very nice!
Tympani was reasonably palpable(didn't think my 5 1/2" woofers would be convincing but it did very well including the shimmer) and the triangle was crystalline.
Going back the Bela Fleck album...it is expert banjo playing of classical standards from Bach, Beethoven, Brahms, Chopin, Debussy, Paganini, Scarlatti, and Tchaikovsky with a nice helping of Bluegrass. It is a finely crafted record...with violin, cello, bass, piano, guitars, mandolin, and marimba(!).
The voices of Etta James, Tony Bennett, kd lang were beautifully recorded. Surprisingly enjoyable also is the raspy Rod Stewart who came out smooth and mellow singing jazz standards.
Tympani was reasonably palpable(didn't think my 5 1/2" woofers would be convincing but it did very well including the shimmer) and the triangle was crystalline.
Going back the Bela Fleck album...it is expert banjo playing of classical standards from Bach, Beethoven, Brahms, Chopin, Debussy, Paganini, Scarlatti, and Tchaikovsky with a nice helping of Bluegrass. It is a finely crafted record...with violin, cello, bass, piano, guitars, mandolin, and marimba(!).
The voices of Etta James, Tony Bennett, kd lang were beautifully recorded. Surprisingly enjoyable also is the raspy Rod Stewart who came out smooth and mellow singing jazz standards.