leo
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Post by leo on Jan 18, 2008 19:04:05 GMT
Ok, First I'd like to say a big thank you to a mate for ordering me the pcb and a few other bits and pieces, he knows who is The PCB arrived this morning, I'll add more pictures during the build process incase anybody is interested. Being a bit busy at the moment I'll do bits when I get the time, normally I'd have this up and running in a day but have a lot on at the moment. I still have to try the classA amp too, infact hopefully try this Kumisa as a pre-amp with the classA too I'm going to knock it up as stock first, make sure everything is ok, have a good listen to it and then add a few upgrades.
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vixr
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Post by vixr on Jan 18, 2008 19:29:12 GMT
I built mine totally from the BOM, and it sounds perfect...I did cheat and score the matched "Qs" from amb labs, though.
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leo
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Post by leo on Jan 18, 2008 20:16:23 GMT
I'll be doing the same to start with, then its time to do some fiddling ;D
I have matched J-fets for the input and will also try transistors
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Deleted
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Post by Deleted on Jan 18, 2008 22:04:47 GMT
They are not that well matched, but you can't complain about the price. The most important thing is that their power devices seem genuine, not fakes , which are so common these days. SandyK
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leo
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Post by leo on Jan 19, 2008 1:10:56 GMT
Soldered in the resistors, BC550/560C transistors and a few other bits. Transistors was from AMB, resistors from Maplins, caps from Farnells
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Post by sometrolls2 on Jan 19, 2008 8:07:18 GMT
Leo, please keep updating this thread; I was thinking of getting one of these as my first ever build as it has a lot going for it: cheap, not too hard, works as a preamp, forum support, component kit available.
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Deleted
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Post by Deleted on Jan 19, 2008 8:32:30 GMT
Leo Seeing that you had 3 of each type of input transistors for the front end (per channel), I presume you took the opportunity to select the closest pair in HFE for the input stage ? Alex
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Post by dc on Jan 19, 2008 11:26:44 GMT
I was thinking about building this kit too... but casework scares me
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Post by sometrolls2 on Jan 19, 2008 11:57:16 GMT
DC, you can always get the version of the Hammond case that has plastic end pieces, so the only metal work would be for the hole for the transformer's mounting bolt. Or simply use a cheaper plastic case and follow the different grounding instructions.
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Post by dc on Jan 19, 2008 13:06:10 GMT
DC, you can always get the version of the Hammond case that has plastic end pieces, so the only metal work would be for the hole for the transformer's mounting bolt. Or simply use a cheaper plastic case and follow the different grounding instructions. I need to drill a hole for the tranny?! I was just going to mount it on a funky angle... Damn, since most of the connectors are board mounted, I was hoping I could get away with just keeping the end plates off and using it as a good ventilation technique...
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leo
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Post by leo on Jan 19, 2008 14:45:10 GMT
Sometrolls2 Sure, I'll keep updating, building one of these is straightforward, if you do decide to build one and get any problems just post on here and we'll help you out I'm going to build it as standard first and then will try different regulation etc SandyK I always match input and output transistors, the J-fets was brought matched as these are more expensive to buy over here and the other transistors was brought from the same place. I source the input transistors and match them myself as these are cheap You should also notice the little transistor sockets, once I decide what I like best they will be soldered to the pcb DC, Casing is one of the things that causes a lot of diyers problems including me. I leave the case until last once I'm sure what other bits and pieces I want to use like regulation etc
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leo
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Post by leo on Jan 19, 2008 16:48:29 GMT
Just needs to be wired up and tested now Excuse the over sized output resistors, they are all I had in 0.47R
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Post by Deleted on Jan 19, 2008 20:39:59 GMT
Leo I knew that ! Now the other guys also know that best results are obtained from doing that ! SandyK
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pagan
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Post by pagan on Jan 19, 2008 22:22:51 GMT
Sometrolls2 I'm going to build it as standard first and then will try different regulation etc Even the output trannies??
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leo
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Post by leo on Jan 19, 2008 23:06:24 GMT
Leo I knew that ! Now the other guys also know that best results are obtained from doing that ! SandyK Alex, Thats a good idea and I'm glad you mentioned it, as much info on here for others wanting to build one of these should help Leo
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leo
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Post by leo on Jan 19, 2008 23:10:34 GMT
Sometrolls2 I'm going to build it as standard first and then will try different regulation etc Even the output trannies?? No, those will be an exception, I was going to first try 2sB649/2SD669 but because of those largish output resistors it caused a problem with heatsinks so I just fitted some Toshiba 2SC4382/2SA1668, because these are reversed it allowed the heatsinks to fit
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leo
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Post by leo on Jan 19, 2008 23:16:11 GMT
Well guys its up and running, everything measured spot on, the servo is fine giving less than 1mV on the output and bias was set, its currently at 15mV across the output resistors. The sound is actually very nice to say its only been running a few hours, I'll let those caps have a good run in before having a proper listen but so far sounds promising. BTW rectifier diodes are MUR860, they are what I had spare so fitted those
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pagan
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Post by pagan on Jan 19, 2008 23:17:57 GMT
Excuse the over sized output resistors, they are all I had in 0.47R Or 2 * 1ohm 0.5Watt resistors in parallel. Made it easier/adjust to check bias
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leo
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Post by leo on Jan 19, 2008 23:29:08 GMT
I didn't have any of those either I'll get some though and swap out these chunky things What sort of difference did you hear Pagan after fitting the JLH's? I think that will be the first mod to try after a couple of days once its run and I've heard it as standard
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pagan
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Post by pagan on Jan 19, 2008 23:53:23 GMT
"What sort of difference did you hear Pagan after fitting the JLH's" More details, better separation on intruments. similar to fitting Tent clock on dac. Side bonus with JLH is, no turn on thump. ps those heatsinks are a bit overkill I'm using normal "U" shaped heatsinks on the headphone amp and a small strip of aluminium connecting all 4 on the preamp.
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pagan
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Post by pagan on Jan 20, 2008 0:07:46 GMT
Leo Something else. I always wondered if you converted the standard psu to a CRC or CLC before the 78/79's would make much audible difference?
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Post by Deleted on Jan 20, 2008 0:30:36 GMT
Allan We forgot to mention that nice little attribute previously, didn't we ? Hopefully, should do the same for the Class A, as well as many other bits and pieces. Who is going to be first to try to make a small JLH with a 7805 integrated , instead of a current limiter. Should only need a diode across IN and OUT of 7805 for added protection ? BC639 and BC640 will then be O.K. for all except the diff. pair. If it can be shrunk enough, it should be a very cheap alternative to all the other fancy regulators ? Alex
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leo
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Post by leo on Jan 20, 2008 0:31:47 GMT
"What sort of difference did you hear Pagan after fitting the JLH's" More details, better separation on intruments. similar to fitting Tent clock on dac. Side bonus with JLH is, no turn on thump. ps those heatsinks are a bit overkill I'm using normal "U" shaped heatsinks on the headphone amp and a small strip of aluminium connecting all 4 on the preamp. That sounds very promising, I can see me fitting it sooner rather than later Most of those bits you see are what I had as spares so I fitted anything that was useful so I could get it up and running
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leo
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Post by leo on Jan 20, 2008 0:39:03 GMT
Leo Something else. I always wondered if you converted the standard psu to a CRC or CLC before the 78/79's would make much audible difference? I'd imagine it would help, I've tried this before with a digital section for a dac in a cdp, it helped clean things up, I have same arrangement for the Avondale NCC200 main PSU too (cap6) It uses 6800uf + inductor+6800uf+inductor +6800uf on each rail I'm thinking of tthe best way to fit the JLH to the Kumisa, was actually tempted to cut the tracks on the onboard 78/79 regs and add the JLH on the output there rather than adding another rectifier LM317/337 separate
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leo
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Post by leo on Jan 20, 2008 0:40:38 GMT
Allan We forgot to mention that nice little attribute previously, didn't we ? Hopefully, should do the same for the Class A, as well as many other bits and pieces. Who is going to be first to try to make a small JLH with a 7805 integrated , instead of a current limiter. Should only need a diode across IN and OUT of 7805 for added protection ? BC639 and BC640 will then be O.K. for all except the diff. pair. If it can be shrunk enough, it should be a very cheap alternative to all the other fancy regulators ? Alex I'm sure we can do this Alex, if we post some idea's and pics of a rough layout, once finished it can be converted to pdf
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