jonclancy
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Post by jonclancy on Jan 24, 2008 17:43:47 GMT
Thanks Mate!! I'll go and have a root around in my "special" container! Cheers Jon
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jonclancy
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Post by jonclancy on Jan 24, 2008 18:07:35 GMT
...and all the info regarding the alternative servo *was* on the AMB page.... "Instead of the listed 10µF bipolar electrolytic capacitors, you may use 1µF 63V polyester film capacitors with 0.200" lead spacing instead. You will also have to increase R49, R51 to 100KΩ and R15, R39 to 3.01MΩ with this option." Doh - think I need glasses!!! Cheers Jon
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Post by Deleted on Jan 24, 2008 21:01:43 GMT
Leo and Allan I have emailed jonclancy the JLH info. Feel free to answer anything questions in that regard. Allan may even have built,and have in use, more of them than me by now ? Alex
jonclancy Re the 40V supply rail question : Allan is using upgraded dual polarity JLHs ( see revised schematic) to supply the front end of a 100W/Channel amplifier that uses + and - 55V supply rails with excellent results. Alex
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jonclancy
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Post by jonclancy on Jan 24, 2008 23:15:43 GMT
Hi Alex, Now that is great news to me, with only a 40VDC requirement. Current is next to nothing as well. Many thanks for the info sent through - I'll have a good look through it. I'm setting up the bias on the CK2III at this very moment (in the 15 min wait period), so soon, vey soon, I'll have tunes!! (Dunno why that smiley is labelled "sad" - hopefully I won't when I get those K701s plugged in!!) Cheers Jon
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jonclancy
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Post by jonclancy on Jan 25, 2008 0:34:20 GMT
OK folks - here's the first impression of the CK2III: A creamy or velvety delivery (I won't change my day job and become a reviewer!!) with a nice top end that is extended but not forward. Overall soundstaging is pretty good, and the detail is, quite frankly, excellent. I'm having a job setting the bias as it keeps rising and falling. I'm going to leave it on overnight and see if it settles. I have readjusted to 12.5mV to avoid a thermal runaway, but do have sinks on the output transistors and they are warm, but not hot to the touch. It's a lash-up at the moment, and I'll post a pic tomorrow, but overall I am absolutely delighted with it so far, and that's "out of the box" so to speak. A few weeks of running in on Classic FM should do the trick!! ;D I'd recommend this amp on the strength of what I've heard so far. Thanks very much to Leo for all his help along the way - what a fine fellow!! Cheers Jon
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jonclancy
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Post by jonclancy on Jan 25, 2008 10:10:53 GMT
Here are a couple of pics. It's a lash-up at the moment. Planning on casing it up using the stock Hammond case with the trafo in a separate box. Bias is very much dependant on temperature. With the heating off overnight the bias dropped back to 6.5mV - the only accurate way to set this will be when it's cased up and at "listening" temperature. I'll need to change the LED as well - the blue one has burned my retinas out!!! Cheers Jon
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Post by Deleted on Jan 25, 2008 10:33:14 GMT
Re JLH schematic It has been suggested that the upgraded version of the JLH schematic should be posted in case anybody else is interested. This version has been amended to work at considerably higher current and voltages than the original .( Double click on the image.) SandyK
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pagan
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Post by pagan on Jan 25, 2008 10:51:42 GMT
Re JLH schematic It has been suggested that the upgraded version of the JLH schematic should be posted in case anybody else is interested. This version has been amended to work at considerably higher current and voltages than the original .( Double click on the image.) SandyK Where have i seen that circuit before I can say it does does work very well
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jonclancy
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Post by jonclancy on Jan 25, 2008 16:21:12 GMT
Thanks very much for posting that schema!! Anybody else going to join in??? Cheers Jon
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Post by PinkFloyd on Jan 26, 2008 23:12:17 GMT
Anybody else going to join in??? For sure mate. As soon as my bollocks get the all clear and I've got time I'll be ordering one of these boards. Cheers leo, great thread mate
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Post by Deleted on Jan 27, 2008 0:49:51 GMT
Mike If you are referring to the JLH, it is an etch it yourself job. If you are referring to the Kumisa 3 , then you have lots of choices to make, like fet entirely, fet with bipolar O/P stage, all bipolar. It makes an O.K. sounding headphone amplifier.(and preamp?) Perhaps I am biased, but I just got the Voyager back, and I think I prefer it with headphones. ( Allan's version of Kumisa 3 was well tweaked too, although perhaps bias set a fraction too high ?) Alex
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Post by leo on Jan 27, 2008 3:20:01 GMT
The sound goes fat and a bit overly smooth imo if the bias is cranked up too high, mines now back to 15mV I've also lowered the gain as it was a bit high before I can tell these FM caps are starting to bed in as the sound has opened up which is typical with these caps Next stop is the JLH regs, pics to follow once fitted
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leo
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Post by leo on Jan 27, 2008 3:23:36 GMT
Anybody else going to join in??? Cheers leo, great thread mate It was a pleasure Mike, not a bad little amp and quite cheap to build, we'll see how it responds to some tweaks Theres not many diy amps about at the moment which is a shame so the choice of the next build was a bit limited
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FritzS
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Post by FritzS on Jan 27, 2008 8:51:40 GMT
I need glasses too - where you found this?
Have anyone compare Kumisa III with Greeen Solo?
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jonclancy
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Post by jonclancy on Jan 27, 2008 17:05:27 GMT
Hi Fritz, It was near the top of the parts page IIRC. A single paragraph that could easily be missed by the more visually challenged!! A quick update: I also reduced the gain on my unit to get a little more travel on the vol pot, but I've noticed some hiss (couldn't miss it actually!) now. I've reset the bias and played around with it, but the hiss is still there. I'll be returning the unit back to stock in the next couple of days, and might look at, say, a 100K pot - unless anybody has any pointers as to why this might be happening? Many thanks in advance for your thoughts!! Cheers Jon
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Post by leo on Jan 27, 2008 23:24:57 GMT
Soon as I can find a couple of heatsinks that will fit and I'll be trying the JLH with the Kumisa. Mine had some hiss too Jon after lowering the gain so may need to have a look at that too
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Post by Deleted on Jan 28, 2008 0:00:05 GMT
Allan may have some input on this area. He was already using a JLH though. Alex
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leo
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Post by leo on Jan 28, 2008 0:08:21 GMT
How hot do those transistors get when using this with the Kumisa Allan? I'm bloody struggling trying to find any heatsinks to fit
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Post by Deleted on Jan 28, 2008 1:02:45 GMT
If fairly heavy current draw on load,(>100mA) better not to use BC639 and BC640 in the current limiter. TO220 types like BD139 and BD140 (preferably with >100HFE) or 2SC5171/2SA1930 instead without Heatsink. After start up, provided the limiter transistors used have low VCE saturation. , there shouldn't be that much dissipation in them, and difference between IN/OUT should be <300mV ? (The current limiter transistors are near the voltage input to the module) Alex
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pagan
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Post by pagan on Jan 28, 2008 1:14:13 GMT
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Post by pagan on Jan 28, 2008 1:17:28 GMT
For the JLH. I removed the standard psu components. Separated psu (LM317/337 and variable), then to JLH, then feed to power rail holes. Used the holes from the removed 78/79's Centre earth on CK2 to star earth and centre earth from JLH to same star earth. [/quote] found it. I thought i did
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leo
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Post by leo on Jan 28, 2008 1:45:57 GMT
Thanks Allan, well I now have the JLH's fitted, separate regulated psu Theres no pussy footing about here, its clear to anybody with half an ear these JLH's have made a HUGE difference straight away!!! This is the test I wanted to do, compare them against standard regs and these things deliver BTW I don't have any hiss now!!!
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leo
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Post by leo on Jan 28, 2008 1:48:41 GMT
Oh and thanks AK
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Post by leo on Jan 28, 2008 1:50:22 GMT
Going by the difference they made with this headphone amp I can see they would have a large effect on any amplifiers VAS/input stage
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Post by leo on Jan 28, 2008 1:59:42 GMT
Excuse the wiring as it was quickly lashed up, the JLH ground is connected to the amps star ground
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