Guys its Leukemia. Making me extremely tired. I basically can do one job a day. Mow the front patch of lawn or take my daughter swimming and I'm done. When I get a good day and over do it I am out for two more. Hoping to get it under control, the tiredness, soon. Hemoglobin is real low cuz of the meds so not a lot of oxygen getting retrieved from my lungs, at least thats my take on it.
Javier Galvan and I talked today and he is going to take over kitting for me. Hes a real good friend and knows LDRs very well as he has been helping me for about 3 years now. Outstanding orders of just kits are about 2 weeks out, my guess. Built units even further. I can refund if you need me to and its no problem.
Love you guys and hope you dont have to put your family through this. Go get a complete blood screen. I found out in a routine cholesterol scan but it has to be a complete blood count. Its easy and so is a colonoscopy so do that to. Seriously a piece of cake. They slightly drugged me and I thought I was watching TV.
Next thing you'll see from me will likely be an integrated amp. Year end probably. Also will likely be just a board. Oh and I will be redoing the Lighter Note into something much simpler to assemble using only the necessities from the LN design. Right now its to big, to complicated and to expensive so I know I can knock it down and keep the sound quality.
Heading for bed. Take it easy.
Javier Galvan and I talked today and he is going to take over kitting for me. Hes a real good friend and knows LDRs very well as he has been helping me for about 3 years now. Outstanding orders of just kits are about 2 weeks out, my guess. Built units even further. I can refund if you need me to and its no problem.
Love you guys and hope you dont have to put your family through this. Go get a complete blood screen. I found out in a routine cholesterol scan but it has to be a complete blood count. Its easy and so is a colonoscopy so do that to. Seriously a piece of cake. They slightly drugged me and I thought I was watching TV.
Next thing you'll see from me will likely be an integrated amp. Year end probably. Also will likely be just a board. Oh and I will be redoing the Lighter Note into something much simpler to assemble using only the necessities from the LN design. Right now its to big, to complicated and to expensive so I know I can knock it down and keep the sound quality.
Heading for bed. Take it easy.
Hello guys!
Uriah and I have been talking on and off again about lots of subjects, but mainly his health, as he has to make adjustments in his life.
For now, I've offered to help him out. I'm a busy guy with a regular job as a test engineer, and a family of my own, but I spent many years working in kitting operations for a major computer manufacturer and a small company here in Austin. So we plan on getting our ducks in a row as soon as possible, getting things boxed up, and shipped.
As Uriah has said, he has loved doing this and helping all of you out with builds or questions. He thoroughly enjoys hearing about your positive experiences with the various LDR products out there. But as he said, his reservoir caps are a little low right now. Feel free to shoot me a PM. Uriah and I will prioritize things and get you an answer.
Uriah and I have been talking on and off again about lots of subjects, but mainly his health, as he has to make adjustments in his life.
For now, I've offered to help him out. I'm a busy guy with a regular job as a test engineer, and a family of my own, but I spent many years working in kitting operations for a major computer manufacturer and a small company here in Austin. So we plan on getting our ducks in a row as soon as possible, getting things boxed up, and shipped.
As Uriah has said, he has loved doing this and helping all of you out with builds or questions. He thoroughly enjoys hearing about your positive experiences with the various LDR products out there. But as he said, his reservoir caps are a little low right now. Feel free to shoot me a PM. Uriah and I will prioritize things and get you an answer.
Hello,
I have a very silly newbee question for you, but first of all I'd like to wish to all of you and in particular to uriah a happy, successfull and healty 2013.
I'm very interested in this mod and in general about LM1875 and LM3886 mods.
But one doubt I still have specifically about using this LDR in place of R1 resistance that is in the signal path: why do not simply leave out the R1? I mean what could the sonic difference be between a line of wire, an 1k resistance or some 220ohm military grade resistance, and this LDR?
Thanks in advance for explaining,
tent:wq
First lets not assume military grade means anything more that more robust and more accurate over an operating range. That said though, Dale military resistors are pretty good. Thats what I upgraded from in my chip amp.
I have a customer that is using ldrs for attenuation. He can also adjust volume digitally. He says ldrs add a subtle softness to the sound. I agree. Whats different with ldrs is that there is a softer and sweeter sound, more musical than without ldrs. We get this with no loss of transparency. No addition of a veil. My feeling is its due to resistive material, like when using tantalum resistors. Straight wire will nit be as sweet but will be hyper transparent.
I have a customer that is using ldrs for attenuation. He can also adjust volume digitally. He says ldrs add a subtle softness to the sound. I agree. Whats different with ldrs is that there is a softer and sweeter sound, more musical than without ldrs. We get this with no loss of transparency. No addition of a veil. My feeling is its due to resistive material, like when using tantalum resistors. Straight wire will nit be as sweet but will be hyper transparent.
Im working on a LM3886 amp using LDRs in Ri and Rb resistor positions. I think I will use Mr. Evil's new power supply to power it. Trying to make it work on single sided copper. Will share so you can all etch and build if you like. Might take me a few months. It all takes a few months, at least! Also working on an F4 and Bob is sending me some fremen editions to listen to. Hoping to be able to compare.
Hope everyone is well.
Hope everyone is well.
I'm very glad you are back and doing things. Let's hope you get better and better.
What Mr. Evil's supply is that? Can you specify or URL?
Almost all projects can be designed on single-side pcb, even more an LDR. Designed a few for myself.
I recently experimented with making a variable gain amp and to do that I put a little blue multi-turn cermet pot instead of the feedback-shunt resistor (not the feedback resistor).
That was great! Easily and quickly, it fine tuned up nicely.
So, I went to replace this with a fixed resistor of the same value.
FAIL!!!
There was no fixed resistor, even of the same value that sounded as nice as the little blue pot. Well, perhaps if I had found a cermet composition resistor, but only then.
Previously, I thought that resistors didn't sound much different from each other; however, I found out that they really can, if put into a high gain area, such as one leg of the feedback divider.
Result:
I ended up leaving the little blue pot in circuit since I didn't have a resistor that performed as well.
Anyone tried cermet?
That was great! Easily and quickly, it fine tuned up nicely.
So, I went to replace this with a fixed resistor of the same value.
FAIL!!!
There was no fixed resistor, even of the same value that sounded as nice as the little blue pot. Well, perhaps if I had found a cermet composition resistor, but only then.
Previously, I thought that resistors didn't sound much different from each other; however, I found out that they really can, if put into a high gain area, such as one leg of the feedback divider.
Result:
I ended up leaving the little blue pot in circuit since I didn't have a resistor that performed as well.
Anyone tried cermet?
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So Rf is a conventional resistor. Highest quality you can afford/find. I would love to stick an LDR there of all places however they are not very stable at 20k and most importantly they will add distortion, a lot of it, when that kind of voltage passes over the resistive side. Maybe a low voltage headphone amp with an ouput transformer to step it up a little but not this amp. Should be a 1/4w resistor and it fits across pins 3 and 9. You solder it direct to the pins.
Zm, Rm and Cm are all part of a slow start or more of a delayed start. See, they force the amp to mute until the supply comes up to the zener voltage. You can use any zener you want here as long as its not close to your supply voltage. Maybe a 12V would be fine. What happens is that the major burst of power entering the supply will normally create a turn on thump. We've all heard it. This will help to lessen that thump as the supply will already be halfway full before the amp kicks in. I got this from one of Apex' amp and he got the idea from some amps Yorkville uses for guitar and PA work. I havent tried it yet. In fact I havent tried this amp at all. So far I have only replaced Rb with an LDR. Other folks have replaced Ri. I havent.
Rz and Cz are the Zobel of course and we can use a few values there. Common are .22uF and 4.7R.
See the Link? Its that white trace at the bottom. It is for powering the LDR circuits. You MUST MUST MUST never power up the amp before having calibrated/dialed in the LDRs to their correct values. So what do you do? Dont hook up anything but ground of your supply to the board. Then with no LINK inserted yet you can give positive supply voltage to the LINK side of R1. This will then power up the LDR power supply. (Z1 should be around 5V6 but could be slightly higher and .5W minimum. This zener could be as low as 3V3. The lower the output of the zener the more you must worry about its heat dissipation)
You will use a multimeter to measure the resistance of the LDRs. As you turn the trimpots P1 and P2 they will vary the current supplied to the LDRs by CS1 and CS2 which are LM334 current sources. P1 controls CS1 which controls LDR1. You know how LDR2 is controlled now. You will dial these LDRs to the correct resistance. LDR1 should be around 680R when the biploar Cf is around 47uf. You should always set LDR2 to around 1k. C3-C6 will help to further smooth supply voltage to the LDRs. I know you dont think LEDs should need this foo foo treatment but they like it and they sound better when you add caps here. The ceramic smt caps are around .1uf to .22uf and the electrolytics can be 10uf to 100uf. I have heard a difference adding caps to LDRs which did NOT have caps but I have not heard a difference between cap quality or value on the LDRs.
The white lines going out from the LDRs just indicate the wires from the resistive side of the LDRs should follow these lines to their corresponding through holes. Rb is made by LDR2 and Ri is LDR1.
TB1 is a 3 position terminal block with 5.08mm pitch. Its for power to the amp. You will use V-, Gnd and V+.
TB2 is a 2 position 5.08mm terminal block and so is TB3.
TB2 is for output to the speaker. It will allow Out+ and Out- which is actually ground.
TB3 is the signal input and uses In+ and In- which is tied to ground on the board.
You can see there is a star ground.
C1 and C2 are 100uf to 1000uf and I plan to solder .1uf Wima caps to the bottom of mine.
There are some small filled in zones on the board that do not connect to anything. These are so that your board will etch faster and lose less copper into your solution. You will want to test your board after etching to make sure that no zone touches (use your multimeter on the resistance setting) another zone. If you find tiny shorts you will want to scratch them out with something like an awl. I usually use an awl to scratch between all zones anyway.
Zm, Rm and Cm are all part of a slow start or more of a delayed start. See, they force the amp to mute until the supply comes up to the zener voltage. You can use any zener you want here as long as its not close to your supply voltage. Maybe a 12V would be fine. What happens is that the major burst of power entering the supply will normally create a turn on thump. We've all heard it. This will help to lessen that thump as the supply will already be halfway full before the amp kicks in. I got this from one of Apex' amp and he got the idea from some amps Yorkville uses for guitar and PA work. I havent tried it yet. In fact I havent tried this amp at all. So far I have only replaced Rb with an LDR. Other folks have replaced Ri. I havent.
Rz and Cz are the Zobel of course and we can use a few values there. Common are .22uF and 4.7R.
See the Link? Its that white trace at the bottom. It is for powering the LDR circuits. You MUST MUST MUST never power up the amp before having calibrated/dialed in the LDRs to their correct values. So what do you do? Dont hook up anything but ground of your supply to the board. Then with no LINK inserted yet you can give positive supply voltage to the LINK side of R1. This will then power up the LDR power supply. (Z1 should be around 5V6 but could be slightly higher and .5W minimum. This zener could be as low as 3V3. The lower the output of the zener the more you must worry about its heat dissipation)
You will use a multimeter to measure the resistance of the LDRs. As you turn the trimpots P1 and P2 they will vary the current supplied to the LDRs by CS1 and CS2 which are LM334 current sources. P1 controls CS1 which controls LDR1. You know how LDR2 is controlled now. You will dial these LDRs to the correct resistance. LDR1 should be around 680R when the biploar Cf is around 47uf. You should always set LDR2 to around 1k. C3-C6 will help to further smooth supply voltage to the LDRs. I know you dont think LEDs should need this foo foo treatment but they like it and they sound better when you add caps here. The ceramic smt caps are around .1uf to .22uf and the electrolytics can be 10uf to 100uf. I have heard a difference adding caps to LDRs which did NOT have caps but I have not heard a difference between cap quality or value on the LDRs.
The white lines going out from the LDRs just indicate the wires from the resistive side of the LDRs should follow these lines to their corresponding through holes. Rb is made by LDR2 and Ri is LDR1.
TB1 is a 3 position terminal block with 5.08mm pitch. Its for power to the amp. You will use V-, Gnd and V+.
TB2 is a 2 position 5.08mm terminal block and so is TB3.
TB2 is for output to the speaker. It will allow Out+ and Out- which is actually ground.
TB3 is the signal input and uses In+ and In- which is tied to ground on the board.
You can see there is a star ground.
C1 and C2 are 100uf to 1000uf and I plan to solder .1uf Wima caps to the bottom of mine.
There are some small filled in zones on the board that do not connect to anything. These are so that your board will etch faster and lose less copper into your solution. You will want to test your board after etching to make sure that no zone touches (use your multimeter on the resistance setting) another zone. If you find tiny shorts you will want to scratch them out with something like an awl. I usually use an awl to scratch between all zones anyway.
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Thats a fun experiment! Glad you found a good solution and it must be great to be able to vary gain while you are listening so you can see what suits you best.
I think the best solution to your experiment and mine would be to have a 3 resistor Rf. Two resistors would be in series and one would be in parallel with one of the series resistors. Of the paralleled resistors there would be one that is variable and the other would be a regular resistor as would the other series. This way you can never adjust to much or to little gain but you can change the value inside this window of resistance.
Interesting conversation this. When I suggested fitting expensive resistors to my Brian GT LM3886 boards a couple of months or so back, some members told me to save my cash because it would be a waste of time and money.
Anyway, I hope to have a couple of mono block My Ref FE's completed in the near future so that's where my limited funds are going. That and a DCB1 to go with them.
I will probably find another use for the Brian GT kit at some point though, it's good to know it can be improved further as it's pretty decent already.
I also believe it's a good idea to build in variable gain for power amp's but i was quite effectively dismissed by a certain Mr T when I suggested it
Anyway, I hope to have a couple of mono block My Ref FE's completed in the near future so that's where my limited funds are going. That and a DCB1 to go with them.
I will probably find another use for the Brian GT kit at some point though, it's good to know it can be improved further as it's pretty decent already.
I also believe it's a good idea to build in variable gain for power amp's but i was quite effectively dismissed by a certain Mr T when I suggested it
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