Sounds like Christmas arrived on the last day of November . . .
Absolutely! Just a quick question, whats the jack socket on the back of the oled display for?
It's for programming the PIC that controls the OLED display. I installed it 'just in case' but the software works perfectly and I have found no reason to use it so it will not be included on OLED boards after this first run.
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Cool, if your stuff ever reaches unreachable prices, mine will be worth all the more for been different, not that I will ever sell it.
Cool, if your stuff ever reaches unreachable prices, mine will be worth all the more for been different, not that I will ever sell it.
No matter what, there will always be a non-stratospheric version of my design. My philosophy is 'biggest bang for the buck' -- thus the simple circuitry that does a great job of controlling the LDRs, and once you've heard them, the LDRs just sell themselves. I want to keep the basic LDR control board small and affordable and spread the gospel of the LDR sound while offering options to expand into a complete system with every bell and whistle that adds real value.
I now have enough feedback to be confident that this system is going to be pretty straightforward to install and will make a big difference in what you hear from your other components. And I believe that you will hear a difference even when the rest of the system is high end.
I am almost ready to build my amp but I have a question about my layout, I have active Low Frequency drivers which can take either line level or speaker level signals, its been suggested on DIY that its ok to split the output of a volume pot and run it to sub amps via RCA's at the same time as the input of the 3875 chip amps. Do you think this would compromise the performance of your design? Is it a bad idea in general? The RCA cables will be approximately 1.5 meters long, would this be enough to bring down the sound quality or is connecting it up this way a bad idea full stop? I am thinking, if nothing else its going to take longer for the music to hit my LF but even if I go speaker level from the chip amp output it then has to go through another amp at my speaker so this could be a case of which is the best of a bad way to connect up my system.
If you drive both the chipamp and the line level input of the sub amp from the volume control pot, you are in effect paralleling the inputs of the two amplifiers (chipamp and plateamp). The question becomes -- what is the effective resistive load of the two paralleled amps, and how well will that paralleled input impedance play with the output impedance of the volume control pot? I think this is a matter of personal opinion, and you'll find a wide variety of opinions.
The LDR pot is a 10K pot and the output impedance of the pot is as you see it in the graph at post #29. Maximum output impedance peaks at a high volume level at about 2.5K ohms. I think ideally, you would want a load impedance of about 25K for optimal performance at that position of the volume control.
I think in the real world that the 25K could be a lot lower before you hear the difference so it probably would work OK. However, since you're only driving a subwoofer with the plate amp perhaps it also wouldn't matter much if you took the subwoofer signal from the output of the chipamp while it would slightly improve the sound of the main speakers if you don't load the LDRs with paralleled amps.
The input impedance of the chipamp is probably 22K to 25K, and I don't know the input impedance of the plate amp but perhaps about the same. That would give you an effective parallel load of about 11K, and that's a low value to drive directly from the LDR control.
My vote would be to use the chipamp output to drive the plate amp. That's the way the plate amp is designed to work, and the chipamp and main speakers are the components that will decide how musical your overall system sounds and they should be given every opportunity to sound their best.
That's just my opinion, I think it would be safe to try it both ways if you want, but verify the load values of the two amplifiers -- remove all power and use an ohm meter to measure the DC resistance between input and ground for both the chipamp and the plate amp, and do the math for parallel resistors. I think you'll be at 10K~15K which is, again, lower than I'd want for best sound. And that doesn't take into account any effect your line-level wiring capacitance will have on the sound.
The LDR pot is a 10K pot and the output impedance of the pot is as you see it in the graph at post #29. Maximum output impedance peaks at a high volume level at about 2.5K ohms. I think ideally, you would want a load impedance of about 25K for optimal performance at that position of the volume control.
I think in the real world that the 25K could be a lot lower before you hear the difference so it probably would work OK. However, since you're only driving a subwoofer with the plate amp perhaps it also wouldn't matter much if you took the subwoofer signal from the output of the chipamp while it would slightly improve the sound of the main speakers if you don't load the LDRs with paralleled amps.
The input impedance of the chipamp is probably 22K to 25K, and I don't know the input impedance of the plate amp but perhaps about the same. That would give you an effective parallel load of about 11K, and that's a low value to drive directly from the LDR control.
My vote would be to use the chipamp output to drive the plate amp. That's the way the plate amp is designed to work, and the chipamp and main speakers are the components that will decide how musical your overall system sounds and they should be given every opportunity to sound their best.
That's just my opinion, I think it would be safe to try it both ways if you want, but verify the load values of the two amplifiers -- remove all power and use an ohm meter to measure the DC resistance between input and ground for both the chipamp and the plate amp, and do the math for parallel resistors. I think you'll be at 10K~15K which is, again, lower than I'd want for best sound. And that doesn't take into account any effect your line-level wiring capacitance will have on the sound.
Thanks for the prompt reply Karl, looks like im not quite there then. The input of the chip amp is 22k, Peter Daniel says the best connection is going to be using 2x 3875's dedicated for the plate amps, (i have 2 spare) this puts 4 on the pot so however I go its the same result, a low input impedance.
Ok, I should probably post this in the chip amp thread but what about changing the shunt resister on the chip amps? Im sure theres a reason for it been 22k but maybe theres some play in the value. Alternatively would changing the LDR value help? im guessing not as you would of probably suggested it. Apologies for the stupid questions, Im just getting my head around the science. Peter has told another member that connecting a sub to the speaker terminal of a stereo config is fine but he doesnt mention if this would affect the performance. I guess my other option is using the DCB1 buffer sat in my parts box, Im not sure of the specs but im guessing this would be the best compromise even though I wanted to build a no compromise amp. at least it will have no problem driving the interconnects and the chip amp together, it may be better than compromising your LDR?
Ok, I should probably post this in the chip amp thread but what about changing the shunt resister on the chip amps? Im sure theres a reason for it been 22k but maybe theres some play in the value. Alternatively would changing the LDR value help? im guessing not as you would of probably suggested it. Apologies for the stupid questions, Im just getting my head around the science. Peter has told another member that connecting a sub to the speaker terminal of a stereo config is fine but he doesnt mention if this would affect the performance. I guess my other option is using the DCB1 buffer sat in my parts box, Im not sure of the specs but im guessing this would be the best compromise even though I wanted to build a no compromise amp. at least it will have no problem driving the interconnects and the chip amp together, it may be better than compromising your LDR?
It does sound like you need a buffer for all those chipamps.
I think I've heard about increasing the input impedance of chipamps, but there's a limit to how far you can go with that before you start affecting frequency response and noise levels.
James Hill mentioned a buffer called "Kuartlotron" that he found to be the most transparent of them all, you might search for that in diyaudio -- I think there was/is a group buy of boards for it. He mentions it at post #647 on the precision LDR thread.
In my system I use the LDR control without buffer driving a single chipamp per channel and I love it; however, I'll bet that the superb sound of the LDR control won't be seriously compromised if you insert a really transparent buffer of some kind, and if the load impedance is going to be as low as yours sounds like, I think you're better off getting the best buffer possible rather than trying to make-do without one and having the sound suffer through impedance mismatch.
I think I've heard about increasing the input impedance of chipamps, but there's a limit to how far you can go with that before you start affecting frequency response and noise levels.
James Hill mentioned a buffer called "Kuartlotron" that he found to be the most transparent of them all, you might search for that in diyaudio -- I think there was/is a group buy of boards for it. He mentions it at post #647 on the precision LDR thread.
In my system I use the LDR control without buffer driving a single chipamp per channel and I love it; however, I'll bet that the superb sound of the LDR control won't be seriously compromised if you insert a really transparent buffer of some kind, and if the load impedance is going to be as low as yours sounds like, I think you're better off getting the best buffer possible rather than trying to make-do without one and having the sound suffer through impedance mismatch.
I thought there must be a point where the value of the shunt was too much, I will have to investigate further. I've read that post that mentions James Hill, not sure if he has tried every guise of the buffers, there's a few variations on the dcb1, I'm already invested in one of the salas types, cost me about $130 for the kit so I will run with that if that's the best way to go. I need to make some decisions quick though, mail order is going to be cutting it close for a Christmas holiday build, thanks again for the input, I am at least wiser to issues on hand.
Hi Dawg,
I've tried a few types of buffers over the years (including the dcB1, etc) and found them to be incredibly useful, but I can't be considered an expert, sorry. They each do tend to have their own 'sound', particularly the valve buffers
The dcB1 (Salas Hypnotize or BIB?) is a pretty good buffer, IMO, and I think it will be a good combination with the 'chipamps'.
It's really amazingly simple - the vol control is, essentially, 2 variable resistors on the signal path and the buffer will add only 2 jfets and a few more resistors - and it works so well.
I shifted house a couple months ago and I'm still struggling to get the workshop setup - no idea where the soldering station disappeared to!
I've tried a few types of buffers over the years (including the dcB1, etc) and found them to be incredibly useful, but I can't be considered an expert, sorry. They each do tend to have their own 'sound', particularly the valve buffers
The dcB1 (Salas Hypnotize or BIB?) is a pretty good buffer, IMO, and I think it will be a good combination with the 'chipamps'.
It's really amazingly simple - the vol control is, essentially, 2 variable resistors on the signal path and the buffer will add only 2 jfets and a few more resistors - and it works so well.
I shifted house a couple months ago and I'm still struggling to get the workshop setup - no idea where the soldering station disappeared to!
Lol, Hi James, thanks for the vote of confidence on the buffer, it's looking more and more like I need to finish building it, I'm stuck on the led's but that's another story. I've always found less to be more, certainly in my younger days anyway, I cut a 1mtr interconnect in half, blew me away...... I removed the crossover from a pair of townsend Glastonbury speakers and it was life changing, ok I've had a beer but I can't compare any hifi event to that in nearly 30 years. Now 50 I probably won't be able to hear the difference of adding a buffer! Here's the thing, I stopped listening to music like that more than 10 years ago, Im hoping to get my ears back and hoping my choice of parts puts that smile back on my face. Hope you find that solder station and your other half didn't use the house move as an opportunity to bin your stuff, I know mine is going crazy with all the crap I've dug out of the cellar!
Alan
I think you'll be pleasantly surprised when you add the buffer - it's not just the impedance solutions and all that tech stuff, but it seems to soften off some of the rough edges without losing any details or transients - hence the good match to the 'chipamp'
Had to search a bit for the Towsend Glastonbury speakers - had me wondering if this was one of those "Who' products! If so, no wonder you're having hearing problems!
Yes, damn soldering iron's driving me nuts, and I still haven't finished Karl's full kit of bits and the valve amp's power caps are starting to bulge on the tops! (I'm in trouble here without my 'hotrod'!)
Had to search a bit for the Towsend Glastonbury speakers - had me wondering if this was one of those "Who' products! If so, no wonder you're having hearing problems!
Yes, damn soldering iron's driving me nuts, and I still haven't finished Karl's full kit of bits and the valve amp's power caps are starting to bulge on the tops! (I'm in trouble here without my 'hotrod'!)
You must have a lot of bits if you haven't finished it, do you have more bits than me? Lol. Just do what I do, buy another, you know it will turn up and it can be a spare. Yeah good old Max Townsend, a legend. Nothing compared to when I bolted 4 of Ted Jordans jx52s to the side of them though, they looked like the son of frankenstien but I've heard multi thousand pound systems and none come close to the detail and information given by a linear array thats designed to have no crossover, not perfect but not beaten for open ness, if that's a word, I have built Hawthorn Audio silver Iris Duets as a replacement, open baffle amazing bass but even at this level I really mis the detail retrieval of Teds array, probably why they have been sat in the kitchen with max's cabinates for nearly 2 years, (dug them out of a 8 year sitting in my cellar) My other half just put a throw over them, God she is tolerant!
Sounds like you've got a good one if she'll put up with big ugly speaker boxes like that. I'm single but still cringe at times with some of the 'concoctions' that seem to find their way into my 'cave' - I even contemplated a set of Lowthers for the 'better dynamics' but thankfully, saw the error of my ways.
I'm currently playing with a pair of the 8" Audio Nirvana's from 150Hz upwards and it's here that the ldr volume control seems to excel, even with the 845 valve amp, with it's ailing power caps
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All the best ...
I'm currently playing with a pair of the 8" Audio Nirvana's from 150Hz upwards and it's here that the ldr volume control seems to excel, even with the 845 valve amp, with it's ailing power caps
\
All the best ...
Hi!
I`m thinking to use your LDR with my hotrodded DCB1, but my circuit is a balanced design. I understand that, for this case, I need two LDR modules, correct?. I only use volume control and not balance control.
I suppose that is possible to use only one encoder module with the two LDR modules.
Thanks, and merry Christmas for all!
Ignacio
I`m thinking to use your LDR with my hotrodded DCB1, but my circuit is a balanced design. I understand that, for this case, I need two LDR modules, correct?. I only use volume control and not balance control.
I suppose that is possible to use only one encoder module with the two LDR modules.
Thanks, and merry Christmas for all!
Ignacio
Hi, Ignacio.
Yes, you would need two LDR modules to control balanced line stereo. I am not an expert in this, so you need to be sure of the requirements for balanced because I can't assure you.
At this point one encoder module will not control two LDR modules because the digital communication protocol between the boards is not set up to do that. However, I believe that it would not be difficult to enable this in in the encoder module software provided the LDR board software is also slightly modified so that the encoder module would know which LDR module it was sending control instructions to and could send to both. So, technically, it is quite possible and probably not difficult to implement.
It is possible right now to operate two LDR modules with a single 10K linear potentiometer. So, if you wish, you could use the potentiometer control option to operate a balanced line volume control if that fits in with your design goal.
See attached image of proof-of-concept prototype, in progress. I envision two versions -- one a no-holds-barred, all-LDR with no contacts in the signal path, and perhaps a second version with a relay in the signal path and no LDRs to make it more compact.
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