The final BLUE edition board has the direct provisions for the two popular mods (film Vref caps, high CCS current ease) plus more and bigger filter caps, TO-220 diodes. But its not a big deal to do it with black boards too since you stashed away. Nice that you like it. Happy listening.
Thanks Salas, I will be getting the new board. My biggest grip about the black board hypno is the size of the holes. I bought a whole set of resistors that didn't fit or had to be forced through because the leads were too big (granted they were 1/2 watt, not 1/4 but the Dale 1/2w fit just fine). So I'm looking forward to some breathing space with the new board.
The only mod I may pop on this current board are the film caps, as I have a good amount between .1 and 1uf, including Jantzen Superiors, Dayton film/foil, ClarityCaps, and some PPS caps as well...
Yes. Dropping the 68//68R down to about a 10R 5W resistor. That will need sinking the Mosfets, an easy way is to mount them down to the metal floor using insulation pads. There are posts and even reviews of before/after by members. I guess I will have to do a concise recap at a point soon along a BLUE BOM.
Great, thank you. I found some before/after reviews, just not a straight this-is-how-you-do-it. Recaps are always nice
It seems to be hard to find unmatched 2sk170bl's here in the US. The only source I found was Amplab's 20pcs for $26. I would go for that if I knew I could get the 4 matched Idss as well. It would cost just as much to get Blues' matched fets and unmatched fets from that guy in HK (or Ebay). Not to mention I'd have extras for any additional builds.
Is there a good chance I would get 4 close enough Idss out of 20pcs?
Is there a good chance I would get 4 close enough Idss out of 20pcs?
Yes there is. You will need a total of 10x 2SK170BL. I bought 20 too, and had a VERY close matching. I have my matching paper here, my 2 closest ones were:
IDSS:
-8.365mA and 8.362mA
-6.872mA and 6.884mA
Far closer than what we need here. Keep the unmatched for the shunt part of the circuit.
The bigger ones you could fit/afford. I wouldn't go bigger than a CPU heatsink for each mosfet.
Regards,
Regi
Hrm, so i take it something like this wouldn't be good enough...
An externally hosted image should be here but it was not working when we last tested it.
Not at the moment, it's in an ABS, but I've ordered a Par-metal anodized enclosure, so that should do the trick!
Finished my B1 this weekend. Today I added heatsinks, raised the current and changed the caps parallel to the 5 LEDs to MKP18371 100nF (which makes more sense then a huge cap in my opinion).
Some remarks on the build:
Next steps:
My power-amp is a Hypex. First impressions with the DCB1 this WE were a smoother sound and basses were a bit tighter, although not louder. I keep you informed after shortening wires and listening some more.
In any case the DCB1 is a very nice design. Without coupling caps is really great. The PCB is nice and easy. I'll build a 2nd one for fun, and to use as a universal buffer. I'll make some pictures, and show statistics of leds and fets later.
Some remarks on the build:
- All of a batch of 36 LEDs were from 1,691 to 1,718V (AVAGO HLMP-K101). By lowering current resistor to 12,59Ohm, I have currents -111 and +102mA. Output voltages are -8,68V and +8,97V at the moment. With lower current (34Ohm resistor) I had -9,25 and +9.58V.
- IDSS are less then 0,01mA different for each pair, easy to sort out of 40 pcs. Output offset voltages are around 1mV now. At higher voltage they were about 5 times smaller. I definitely need to raise voltage again. I guess I will add another LED or a regular diode to the chain.
- I bypassed the delay relais as I don't want this contact in the loop. I use the relais to ground the signal. This is a very easy change on the PCB. Just connect the 2 unused pins of the relais-switches to the ground, and link the middle and output pins of the switches together (by channel off-course).
- I saw that temperature has a big influence on offset voltage. I reduced this by linking the 2 fets of each pair together. That lowers a lot the thermal drift. At the moment I have just a metal clamp by pair, but I will put some aluminium to improve. I don't like the DC drifting, even if it is slow. It can cause woofer movements on a DC-coupled poweramp.
Next steps:
- I will avoid the long PCB-track to the left input. I will connect the inputs next to the 220R-resistors and cut the PCB-traces. Yes, I agree, it's of no importance but I like complete symmetry in audio.
- I'll put the DCB1 in my preamp instead of tubes (now a DIY CleoV-amp from Triode Dick). I stopped the tube-amp some weeks ago and work passive now. The quality of the amp went down after some years. I don't want to start changing tubes regularly.
My power-amp is a Hypex. First impressions with the DCB1 this WE were a smoother sound and basses were a bit tighter, although not louder. I keep you informed after shortening wires and listening some more.
In any case the DCB1 is a very nice design. Without coupling caps is really great. The PCB is nice and easy. I'll build a 2nd one for fun, and to use as a universal buffer. I'll make some pictures, and show statistics of leds and fets later.