Battery PS
I think the B1 _may_ operate properly with one 12V transistor-type battery (.02 amp load and relatively big capacitors to store the input DC) but you may want to use two, wired in series so you get closer to 24 V DC as an input.
My first one (transistor battery PS at first) usually stopped operating properly after the batteries had drained a little over half, so it's probably best to test the circuit with two known-as-full- charged12 V batteries wired in series.
Did you post any pictures or diagrams of your B1? That may help. The folks on this forum are wizards with this stuff but often like photos and diagrams and measurements. Good luck!
Jonathan
I think the B1 _may_ operate properly with one 12V transistor-type battery (.02 amp load and relatively big capacitors to store the input DC) but you may want to use two, wired in series so you get closer to 24 V DC as an input.
My first one (transistor battery PS at first) usually stopped operating properly after the batteries had drained a little over half, so it's probably best to test the circuit with two known-as-full- charged12 V batteries wired in series.
Did you post any pictures or diagrams of your B1? That may help. The folks on this forum are wizards with this stuff but often like photos and diagrams and measurements. Good luck!
Jonathan
What watt and ohm and Tolerance pot would handle the load,
Also could someone suggest a toggle switch for the B1?
I never tried 10v. I tried 9v, 12v, 15v and 18v with 18v being far and away the best sounding to myself and my local panel of human guinea pig listeners. 12V and 15v were awful by comparison to 9v and 18v, and batteries were better than wall warts by a lot.
9v did have something ethereal going on in the mids and treble, but the bass and soundstage focus was just out of control...so maybe that's why some like 10v.
best,
chris
PPC now that we have talked a bit I think for you the best bet would be to use that little power supply you just got and change the voltage output on it between 9 and 18 til you find something you like. I believe its adjustable and if not all you need to do is replace Rset with a pot of around 5k in value and any size will work for that. You dial the pot and the voltage changes for you.
Chris, interesting about your 9v comment. I cant stand out of focus soundstage and that would turn me off for sure.
Uriah
Chris, interesting about your 9v comment. I cant stand out of focus soundstage and that would turn me off for sure.
Uriah
Hey, thanks everyone for your help. OK, so I was about to give up on the Dell power supply (the second one that quit in the same way the first one did; hence by concern for something to do with the B1), but first, taking lae2's advice, I wanted to measure DC voltage at D2--which has never worked (lit) before I changed power supplies. It was 1.24 volts, which seems low to me. So, as I am waiting for the power supply to switch off like it had done many times before, it stayed on. So my B1 is working fine again, even though I didn't 'fix' anything. Wierd. What is typical for D2 voltage? I don't really care if the LED lights up or not, just curious what others are seeing here. As for pictures, I will see if I can figure that out (a re-purposed wine box for a case). This is my first project building something using a PCB--fun project, and I would encourage anyone scared of trying this to go for it. It is much better than my tube-based preamp, and I spent much less on putting one of these together than I did just on tubes. You will have fun with the build, and the sound is much more that I could have hoped for, with my hack skills...Thank you Nelson Pass for sharing your gift of engineering skills with us!
limits
p.s. Sorry my attempt at uploading 2 jpegs failed; I selected the pictures (they are on my computer) and hit the upload radio button. It looked like they were uploading (got the progress bar), but then it said upload failed. Anyone have suggestions on correct procedure?
limits
p.s. Sorry my attempt at uploading 2 jpegs failed; I selected the pictures (they are on my computer) and hit the upload radio button. It looked like they were uploading (got the progress bar), but then it said upload failed. Anyone have suggestions on correct procedure?
Is D2 lit now? I believe that NP chose the value of R4 to provide for a dimly lit LED. You may have to reduce the resistance for your particular LED. Based on your DC measurement it appears that the LED is installed with the correct polarity.
You may find that this "problem" will return after the B1 has been turned off long enough for the caps to discharge. If so, the indication may be that the Dell PSU senses a transient current draw that it does not like. Cycling power may possibly be pumping the caps up to the point where the initial current draw is in agreement with the PSU. I am not familiar with the Dell PSUs so I don't know whether they have a protection circuit that could account for the problem you have seen. Could simply be a faulty PSU. Loren
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Hi Loren:
On my board, D2 has never lit--It is Digikey part # 365-1006-nd; Manufacturer PN: op265wps. I did get polarity correct (pretty sure, anyway)--long leg is positive, right? It does read +1.24 volts on DMM when observing correct polarity.
Good points about this particular power supply. It is somewhat of an odd duck, as it has an outer shield of fine bare wire, which is negative, an inner fine bare wire, battery positive, and a small insulated wire in the center, that (going on memory when I first constructed my buffer) is a lower voltage battery positive (something like 12 volts IIRC). I have left the inner wire unconnected. I didn't put a power switch on my buffer, although the center position of my DPDT switch serves this function. I have never turned power off before, so you may be right in that I may have issues getting the power supply and the buffer to play nice with each other if I cut power again. I guess I will just have to do what I did before--break out some wire, soldering gun, and two 9 volt batteries--then things will start working again...Still no clue on posting pictures; I think they aren't too big (3072x2304) looking at the FAQ, but I can't think of why else I can't upload these.
On my board, D2 has never lit--It is Digikey part # 365-1006-nd; Manufacturer PN: op265wps. I did get polarity correct (pretty sure, anyway)--long leg is positive, right? It does read +1.24 volts on DMM when observing correct polarity.
Good points about this particular power supply. It is somewhat of an odd duck, as it has an outer shield of fine bare wire, which is negative, an inner fine bare wire, battery positive, and a small insulated wire in the center, that (going on memory when I first constructed my buffer) is a lower voltage battery positive (something like 12 volts IIRC). I have left the inner wire unconnected. I didn't put a power switch on my buffer, although the center position of my DPDT switch serves this function. I have never turned power off before, so you may be right in that I may have issues getting the power supply and the buffer to play nice with each other if I cut power again. I guess I will just have to do what I did before--break out some wire, soldering gun, and two 9 volt batteries--then things will start working again...Still no clue on posting pictures; I think they aren't too big (3072x2304) looking at the FAQ, but I can't think of why else I can't upload these.
http://www.optekinc.com/datasheets/OP265WPS.PDF
Yes, the short lead, the cathode, (near the flat case mark) should be at ground in accord with the B1 schematic. The max forward voltage is 1.8V according the datasheet. It appears that you have it installed correctly. Notice that the typical forward current is .020 A. With an 18V supply you are dropping approximately 17 VDC across R4. I=E/R = 17/15000 = .0011 A. That might be quite dim.
To be academic. Suppose you wanted .010 A bias. Then R=E/I = 17/.010 = 1700 ohms.
Have you looked at the LED in a dark room? You might want to temporarily bridge bridge R4 with a 5K resister and see if the LED lights. Loren
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Hi,
selected Idss is good for the B1.
Better than 2% is good, better than 1% is very easy to obtain and worth measuring for.
The B1 is a source follower biased to operate @ Idss.
I am reporting back on the left channel louder issue with my B1. I got the Gigawork Stereo Pot, changed it, and there might be a short moment that I feel it's balanced. Now the left is again louder but not as loud as the Alps Stereo pot. So the image is shifted to the left on the Gigawork but not as left as the Alps.
I switched back to my HK 635 as the preamp and the image is again centered.
1. Using one stereo pot.
What should I do? If there is something wrong with the preamp, how can I locate that? Could that be a bad resistor or cap? The volume pot doesn't seem to be an issue here. I am trying to work on a solution without involving two pots.
2. Using two pots - Could I use Gigawork pot and Alps pot for each channel? They are different designs so it might not be ideal but for a test, it might work. Gigawork pot has 21 steps. If I use two of them, would I be able to adjust them precisely using steps? Or is it better to get two PEC Log pots?
My final question is: if I can achieve a center image with HK 635 using a single pot, why not Pass B1 using a single pot?
Thanks a lot - it sounds really good so I want to make it work.
I switched back to my HK 635 as the preamp and the image is again centered.
1. Using one stereo pot.
What should I do? If there is something wrong with the preamp, how can I locate that? Could that be a bad resistor or cap? The volume pot doesn't seem to be an issue here. I am trying to work on a solution without involving two pots.
2. Using two pots - Could I use Gigawork pot and Alps pot for each channel? They are different designs so it might not be ideal but for a test, it might work. Gigawork pot has 21 steps. If I use two of them, would I be able to adjust them precisely using steps? Or is it better to get two PEC Log pots?
My final question is: if I can achieve a center image with HK 635 using a single pot, why not Pass B1 using a single pot?
Thanks a lot - it sounds really good so I want to make it work.
Do I need to check cap value as well? I don't have a tool to check. I went to Sears and found these:
http://www.sears.com/shc/s/search_10153_12605?keyword=digital+multimeter&x=0&y=0&vName=
Which one would work or none?
none of those 4 Sear's DMM are any good for our use.
You need 600Vdc to 200.0mVdc and 300Vac to 200.0mVac as maximum scale on a 2000count meter.
A wide range of resistance 20M00 down to 200r0 is usually good enough.
Any extra ranges are simply nice to have but not essential.
Expect to pay <$10 or <£7 for a basic DMM that reads to those scales and guarantees <0.5% +-1LSB on it's most accurate DCV scale.
You need 600Vdc to 200.0mVdc and 300Vac to 200.0mVac as maximum scale on a 2000count meter.
A wide range of resistance 20M00 down to 200r0 is usually good enough.
Any extra ranges are simply nice to have but not essential.
Expect to pay <$10 or <£7 for a basic DMM that reads to those scales and guarantees <0.5% +-1LSB on it's most accurate DCV scale.