The DCB1 is sounding veyr nice at the moment. It certainly has smoothed out completely and just sounds great.
I'm going to give it another few days and then will go back to lower current on the shunt to see if that makes any difference.
Salas, I've seen you say the circuit works best with ~ 20k pot. Is there any reason why a 20k will still sound better than a 50k pot if you change the input resistors to 560k (from 220k)?
In other words should I try installing a 20k pot before trying the lightspeed?
Fran
I'm going to give it another few days and then will go back to lower current on the shunt to see if that makes any difference.
Salas, I've seen you say the circuit works best with ~ 20k pot. Is there any reason why a 20k will still sound better than a 50k pot if you change the input resistors to 560k (from 220k)?
In other words should I try installing a 20k pot before trying the lightspeed?
Fran
Nice to know it ultimately works nicely for you.
I have noticed that in my tests a year back, about the 20k doing better, but that was with sweeping normal pots, not switched with fixed resistors as you have. I think it must be more down to specifics of lower impedance pots than anything else. Of course it will be confirmed for impedance only or not if you change to a 20k switched and compare.
Ultimately the contact-less Lightspeed should prevail. But for builders to know steps and how they compare so they can decide on budget and construction effort, your contribution so far is invaluable.
Its good and relatively simple to be thorough when playing with the configuration of a so minimalistic circuit like DCB1S that allows near max transparency for things to get through.
I have noticed that in my tests a year back, about the 20k doing better, but that was with sweeping normal pots, not switched with fixed resistors as you have. I think it must be more down to specifics of lower impedance pots than anything else. Of course it will be confirmed for impedance only or not if you change to a 20k switched and compare.
Ultimately the contact-less Lightspeed should prevail. But for builders to know steps and how they compare so they can decide on budget and construction effort, your contribution so far is invaluable.
Its good and relatively simple to be thorough when playing with the configuration of a so minimalistic circuit like DCB1S that allows near max transparency for things to get through.
Hi Fran,
I have posted this listening impression and it may be different in your system, but when I had my Lightspeed set for 6k it sounded wonderful to me. I know thats in contradiction to what Salas has said and I have not measured the response (dont have the equipment to), but to my ears the lower impedance sounded better and it may be system specific. BTW that 6k was DC resistance, I have not actually measured impedance.
Uriah
I have posted this listening impression and it may be different in your system, but when I had my Lightspeed set for 6k it sounded wonderful to me. I know thats in contradiction to what Salas has said and I have not measured the response (dont have the equipment to), but to my ears the lower impedance sounded better and it may be system specific. BTW that 6k was DC resistance, I have not actually measured impedance.
Uriah
Thanks Salas,
well in the interests of giving something back, I have ordered 2 cheap 20k stepped pots from ebay and they are on their way to me. One is the vintage audio labs one - search for "24 step DACT" and you will find it, about €20. The second is from a seller "gigaworks", only costs about €13 and uses a cheaper switch but still the same smd resistors. That one is 21 steps. Both are 20k, are completely assembled and the quoted price includes postage.
I'll try both and then report more. In a few days I'll cut back the current and see if I can detect any change in SQ.
Fran
well in the interests of giving something back, I have ordered 2 cheap 20k stepped pots from ebay and they are on their way to me. One is the vintage audio labs one - search for "24 step DACT" and you will find it, about €20. The second is from a seller "gigaworks", only costs about €13 and uses a cheaper switch but still the same smd resistors. That one is 21 steps. Both are 20k, are completely assembled and the quoted price includes postage.
I'll try both and then report more. In a few days I'll cut back the current and see if I can detect any change in SQ.
Fran
Udailey:
Its not in contradiction if you think about it. The 20k pot did better than the 50k in my case. But I would not go lower due to output capacitors must be catered for many sources. Now if your sources could take it, why not the lower impedance theme would not continue doing better if there is water in it?
Its not in contradiction if you think about it. The 20k pot did better than the 50k in my case. But I would not go lower due to output capacitors must be catered for many sources. Now if your sources could take it, why not the lower impedance theme would not continue doing better if there is water in it?
B1 with Cmoy PS?
I don't read whole tread, maybe someone talk about this before:
How about this - B1 buffer schematic like in post 1, but instead bipolar PS use two resistors virtual ground or TLE2426 with simple PS/wallwart ?
Advantages - simplicity almost as in original Pass B1 and still without in/out caps.
With external PS it is possible to use simple 5.5/2.5mm DC connector, this make life more easy too.
Zigis.
I don't read whole tread, maybe someone talk about this before:
How about this - B1 buffer schematic like in post 1, but instead bipolar PS use two resistors virtual ground or TLE2426 with simple PS/wallwart ?
Advantages - simplicity almost as in original Pass B1 and still without in/out caps.
With external PS it is possible to use simple 5.5/2.5mm DC connector, this make life more easy too.
Zigis.
Virtual ground split doable of course. Never expect what people are getting with symmetric shunt Mosfet current sourced regs though.
Of course, Salas, with your regs this buffer is great step up.
I am thinking about rail splitter version like almost original B1 with all original simplicity, but still without caps.
I am thinking about rail splitter version like almost original B1 with all original simplicity, but still without caps.
If it is for casual use, OK a wallwart and an op amp split will save you the cost of possibly good film caps and gain in transparency on top of that. But if you want it for critical listening, its a pity no to go full with good regs. There are just a few and non exotic main components there. If your problem is spare 2SK170s for use in the regs, you can find 2SK117s on line too.
Ian,
I use this buffer with both an F5 and F3 for mid-highs.
Certainly different amps.
how about a new thread?
discuss alternative PSU options for the DC B1.
I suggest another option.
Wallwart to CCS to Shunt reg to active Rail splitter feeding a DC B1.
All except the wallwart are designed in one compact layout.
discuss alternative PSU options for the DC B1.
I suggest another option.
Wallwart to CCS to Shunt reg to active Rail splitter feeding a DC B1.
All except the wallwart are designed in one compact layout.
RE: current through the shunt...
I had a few buddies over last night to have a listen. After a while I got them to listen to a track, then snipped out the 10R (leaving 68//68 in parallel) and listened again.
Well before 10 seconds were up, they all said put it back the other way, put it back the other way.....
Sounded less full and a little harsher...
So it seems that maybe in my system at least, replacing the 68//68 with a single larger rated 10R (and suitable heatsink) yields significant improvement.
Fran
I had a few buddies over last night to have a listen. After a while I got them to listen to a track, then snipped out the 10R (leaving 68//68 in parallel) and listened again.
Well before 10 seconds were up, they all said put it back the other way, put it back the other way.....
Sounded less full and a little harsher...
So it seems that maybe in my system at least, replacing the 68//68 with a single larger rated 10R (and suitable heatsink) yields significant improvement.
Fran
Correct. We know from the shunt only threads that those IRFP devices pick up on their gfs curves around 200-250mA, and that subjectively it can be noticed. We knew it from the phono thread too, you confirm that the CCSed Jfet follower can benefit too. Next station is 3A, but it takes a power station too.🙂
Interesting. I haven't started the DCB1 building yet, still busy with the F2 and also waiting for those Jfets, I think I will start with 34R and then try the 10R. How big should be those heatsinks - or alternatively how big an aluminum case (3mm thickness) would suffice for power dissipation?
Think of 8-10W constant for the sinks for all Mosfets together at 10/-10 0.25A+0.25A depending on Vin-Vout due to trafo choice. Luckily we use low B+ here.
Thanks a lot. It seems that things are more straightforward with this DCB1 than with the F2 I'm currently struggling with. I'm on the brink of desperation due to contradictory information on appropriate heatsinking. My (emotional) novice diy-er progress steps seem to be: 
then 
and finally, hopelessly 
then and finally, hopelessly