No, wirewound potentiometers are for power applications and not for volume control.
Anyone knows MUR 860 has 3 legs? I buy these diode and it has 3 legs, fake one? Searched everywhere but still not finding any info about it.
An externally hosted image should be here but it was not working when we last tested it.
http://www.fairchildsemi.com/ds/RU/RURP860.pdf
I guess the middle leg is the fake one, but this is easily measured with a multimeter.
I guess the middle leg is the fake one, but this is easily measured with a multimeter.
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After having the valab 20k stepped pot in for a while, I subbed in my lightspeed 2 nights back. The set up is AC shared with 1 of the DCB1 supplies, after rectification into a teddyreg (gyrator based reg) and then 500k dual pot. My batch of LDRs needed 500K to get them to work...
So initial impressions are that this change is all about the soundstage and clarity. The LS does have more clarity than the stepped pot, but also seems a little dryer, if that makes sense to anyone. In my earlier B1 build I had a lightspeed but in the early stages the LS impedance was too low and I ended up with the bass being cut. It is possible that some of that is going on here too and I would need to go to a 1meg pot rather than 500k. But its not like I'm loosing any bass, just that its not full or warm as before (sounds like a contradicition, I know).
However, the soundstage is quite remarkable. Front to back depth is really very very good and vocals etc are frighteningly real. It scores a lot of points on that score - It would seem that the DCB1 and LSmkII is a pretty unbeatable combination. Now I don't have any fancy stepped pots to try, only the ebay ones, but the LSmkII beats them, and even they sounded good.
Very positive result I would say, and I would encourage anyone thinking of going this route but is undecided to not delay and fire ahead!
BTW, just so no misunderstanding - that issue with the 500K/1meg pot is peculiar to my lot of LDRs, and if you have bought other ones, and especially matched sets from Uriah, you won't see this. Also, I have kept my output caps in the source equipment fairly small, maybe too small so this may also be in play.
Fran
So initial impressions are that this change is all about the soundstage and clarity. The LS does have more clarity than the stepped pot, but also seems a little dryer, if that makes sense to anyone. In my earlier B1 build I had a lightspeed but in the early stages the LS impedance was too low and I ended up with the bass being cut. It is possible that some of that is going on here too and I would need to go to a 1meg pot rather than 500k. But its not like I'm loosing any bass, just that its not full or warm as before (sounds like a contradicition, I know).
However, the soundstage is quite remarkable. Front to back depth is really very very good and vocals etc are frighteningly real. It scores a lot of points on that score - It would seem that the DCB1 and LSmkII is a pretty unbeatable combination. Now I don't have any fancy stepped pots to try, only the ebay ones, but the LSmkII beats them, and even they sounded good.
Very positive result I would say, and I would encourage anyone thinking of going this route but is undecided to not delay and fire ahead!
BTW, just so no misunderstanding - that issue with the 500K/1meg pot is peculiar to my lot of LDRs, and if you have bought other ones, and especially matched sets from Uriah, you won't see this. Also, I have kept my output caps in the source equipment fairly small, maybe too small so this may also be in play.
Fran
Fran,
You like to tinker so try this.
Use a 100k pot or any other value. Put a 100R multiturn trimmer in series from power source positive to the 100k control pot. Now, with DMM attached to Series LDR and pot turned down all the way, turn on power to LDRs and turn the 100R from 0R up slowly and watch DMM. I think you will find a value that suits you. Then you can get rid of that 500k pot which is quite a hassle to many people. I wish I had known more about the interactions of the 500k pot when those LDRs were matched to provide a better suggestion. When I tested my own pair with the 500k it worked fine and I didnt test further. Seems a lot of people had trouble with 500k and I think this little work around will be fine.
Another option would be to use LM317 and adjust the voltage to LDRs down. Do the same thing... Put in LM317 and turn down voltage while watching value of the series LDR when its turned all the way down. Its going to be really touchy most likely but you will be able to find a resistance you like and will get away with using 100k. If you have 100R in series with LDRs like in George' schematic these values might change your low volume point if you use lower voltage, or they might not. Another experiment.
Uriah
You like to tinker so try this.
Use a 100k pot or any other value. Put a 100R multiturn trimmer in series from power source positive to the 100k control pot. Now, with DMM attached to Series LDR and pot turned down all the way, turn on power to LDRs and turn the 100R from 0R up slowly and watch DMM. I think you will find a value that suits you. Then you can get rid of that 500k pot which is quite a hassle to many people. I wish I had known more about the interactions of the 500k pot when those LDRs were matched to provide a better suggestion. When I tested my own pair with the 500k it worked fine and I didnt test further. Seems a lot of people had trouble with 500k and I think this little work around will be fine.
Another option would be to use LM317 and adjust the voltage to LDRs down. Do the same thing... Put in LM317 and turn down voltage while watching value of the series LDR when its turned all the way down. Its going to be really touchy most likely but you will be able to find a resistance you like and will get away with using 100k. If you have 100R in series with LDRs like in George' schematic these values might change your low volume point if you use lower voltage, or they might not. Another experiment.
Uriah
Just a weird batch of LDRs that were way more efficient than any others I ever tested. So with much less current they would show low resistance than normal. This might be nice as they will get quieter with less current than what the average LDR will. So, with 100k they only got down to about 2k. With 500k they got more desirable resistance. A better value would have been 400k but who sells a 400k dual audio pot? No one I know of.
I agree that the DCB1 helps the bass with the LDRs a lot. Love it for this reason.
Uriah
I agree that the DCB1 helps the bass with the LDRs a lot. Love it for this reason.
Uriah
It's working...
Done. (Almost...)
Today I finished my B1. The wire, attenuator and sinks still need attention but it is good enough to be put in production.
It sounds very good (no break-in time yet) in he sense that the music was still very detailed. If it changed anything I will never know as I removed the selector switch and attenuator from my tube-amp and I do not plan to put it back. I just needed a pre for my coming F5 and Tubelab SE.
Thank you very much for the circuit, pcb and support!!
Jeroen
Done. (Almost...)
Today I finished my B1. The wire, attenuator and sinks still need attention but it is good enough to be put in production.
It sounds very good (no break-in time yet) in he sense that the music was still very detailed. If it changed anything I will never know as I removed the selector switch and attenuator from my tube-amp and I do not plan to put it back. I just needed a pre for my coming F5 and Tubelab SE.
Thank you very much for the circuit, pcb and support!!
Jeroen
Attachments
Omron 12V relays
I've just ordered what I believe to be Omron G6H2 12V relays. I must receive them first to confirm this. I expect them to arrive in 10-14 days.
If they prove to be as expected, more are available and I'd be glad to source them for those who are interested. The expected cost each is ~$1.70 + shipping and depends upon the amount of interest. I would like to return something to the forum from the proceeds.
PM me to express interest with the number you want. We'll see where this goes.
I've just ordered what I believe to be Omron G6H2 12V relays. I must receive them first to confirm this. I expect them to arrive in 10-14 days.
If they prove to be as expected, more are available and I'd be glad to source them for those who are interested. The expected cost each is ~$1.70 + shipping and depends upon the amount of interest. I would like to return something to the forum from the proceeds.
PM me to express interest with the number you want. We'll see where this goes.
Thanks. Yes, they are Metal Takman. My other board is exactly the same but then with the Carbon Takman. Curious if I can hear the difference. Probably not....
Thanks. The green wires need to be replaced by something bettter though. And... if I hold my hand between the transformer and board I can see the "noise" going down. Or better, I measure less mV AC on the output (very quick and dirty measurement without any input shorted etc).
Jeroen
I recently got a batch of these as well for anther project. I like the SQ but they can be a bugger to solder, the pads seem to be very low quality plating. I ended up tacking on to the last resistor for a secure jint.
Let us know if your batch is better...
Got mine working, no case yet. Relays are different because could not find the Omrons close, but they work fine.
The DC offsets are -2.1mV and 0mV when the relay goes on, and they drift to 0.7mV and -0.7mV slowly, takes few minutes. Maybe need to do some changes to get them lower.
The DC offsets are -2.1mV and 0mV when the relay goes on, and they drift to 0.7mV and -0.7mV slowly, takes few minutes. Maybe need to do some changes to get them lower.
