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Old 26th March 2010, 04:48 PM   #1221
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Quote:
Originally Posted by Salas View Post
MKP10 has less dissipation factor, described as a ''pulse'' capacitor.
OK... so good or bad in this application?
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Old 26th March 2010, 05:15 PM   #1222
Salas is online now Salas  Greece
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Better than MKP4. Both adequate though.
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Old 26th March 2010, 05:50 PM   #1223
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Hi, I've got heatsinks for the dcb1 buffer. I removed them because I didn't have any insulators for the heatsinks.

Just wondering if they are necessary? If so, where can I get some mosfet insulators?
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Old 26th March 2010, 06:22 PM   #1224
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If you use the original low current setting 68R//68R and 12+12V mains transformer it can live without sinks as in many builds done so far like that. Individual small sinks that don't touch each other or any other metal part can be used even without insulation anyway. Its safer to use such if with a 15+15V transformer because it gets warmer, but still with the low current 68R//68R. No accidental short with wire, crock clips or probes must be done between them or grounded chassis if used so. For bigger ''hot rod'' currents you need a metal surface for L style Mosfets mounting, be it a thick panel or a chunky common sink. Insulation also is needed if on common metal between Mosfets as you know, like in Fran's example. TO-240 insulation pads you can find in any electronics store be it online or local.
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Old 26th March 2010, 06:57 PM   #1225
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Quote:
Originally Posted by DaveM View Post
I took mine over to a friend who is an all commercial hi-fi guy. He compared it to his $3500 Sonic Frontiers pre amp. He basically said that the differences were so minor that with a bit of reduction in humm in my B1 that they would be comparable. Pretty crazy how Nelson's simple designs well implemented are sonically comparable to pieces costing 3.5 times the cost.
Me neither have any hum, there must be a flaw in your implementation.
I'm glad we have a so valuable preamp for that ridicule cost. Less than 100 for me, including trafo and case.

Quote:
Originally Posted by merlin2069er View Post
Hi, I've got heatsinks for the dcb1 buffer. I removed them because I didn't have any insulators for the heatsinks.

Just wondering if they are necessary? If so, where can I get some mosfet insulators?
You don't need to insulate them, just be sure the heatsinks are not touching anything around them. I had little troubles specially with the ones closer to the CCS setting current resistors.

If you are not tweaking the CCS, just using the default resistors, you don't need heatsinks. The mosfets stay barely warm.
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Old 27th March 2010, 07:37 AM   #1226
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Quote:
Originally Posted by woodturner-fran View Post
A week or so back I said I put up some pics of my dcb1 build....

So I'm using:

shunt resistors: ~7R (68r//68r//10r)
variety of LEDs to get the voltage somewhat correct.
4 inputs and I ignored the other 2 positions
6pos 2 pole switch, using 1 set of pole for relay selection and the other pole to switch the LEDs for the front panel
$10 21 step attenuator from ebay. FWIW, I think this sounds better than the valab one.
Tried to get a lightspeed working but it sounded thin to me, most likely was my build rather than a problem as such with the LS
Using PRP for the audio resistors (thanks teabag) although very little difference noted.
Using wima 0.22uF in the cap positions behind the terminal blocks.
Whole thing housed in a case of a dead CDP, with damping added to the case. The circuit itself is mounted on a 3mm alu plate (which serves as heatsink for the fets).
Circuit ground separated from safety earth via 69er diodes paralleled with a 0.01uf cap and 10R 3W resistor.
Home-made knobs on the oak front panel.
All wiring to the board is navships silver in teflon, and I used some dip sockets with the wire just shoved into them - very handy for a board tweaked as often as this one.


Fran
Hi

why do you prefer wima mkp 10 0,22 uF to bennic mkp 4,7 uF
tight space or sound
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Old 27th March 2010, 12:10 PM   #1227
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Hi samoloko,

the experiments started about page 106 or so (I think) but for my specific comments about the wima vs the bennics (which have performed very well for me before) see here:

Building a symmetrical psu B1 buffer


Fran
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Old 27th March 2010, 04:45 PM   #1228
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thx for reply
glad you get improvement
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Old 28th March 2010, 09:32 AM   #1229
Ian444 is offline Ian444  Australia
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Just a data point to report, I tried WIMA MKP 10 0.1uF 400VDC for about 3 weeks, tonight I thought the sound to be not as good as it used to be, so I put the original 100uF electros back in, which are Suntan CD286 105C low ESR from a local supplier, Jaycar in Australia. The sparkle and liveness of the music has returned. Maybe the 400VDC rating doesn't help on the WIMA's I used, and my system is modest, but the 100uF electros win over the 0.1uF in my case. Maybe larger value film caps are the way to go but I have none on hand at the moment. My DC B1 is using all garden variety components, so that may have something to do with it too. It's always good to try new possibilities because sometimes the improvement is well worth it, and if something is not tried and tested then we never know. Seems like maybe a larger value film cap is worth testing, as some people have been doing. The trouble for me is, the DC B1 buffer sounds so good as it is, and it is easy to hear a forward improvement in sound, but more difficult for me to hear if it goes backwards a little bit. That's why it takes 3 weeks for me to "wake up". Not unusual for me
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Old 28th March 2010, 11:39 AM   #1230
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Guys, I've searched but found nothing...

Is it okay for me to use 2SK170GR's in the reg section of the DCB1, and to use 2SK170V's in the buffer section? I don't have any BL's you see, and they're getting scarce. Funny how ebay has loads of V's now and no BL's...
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