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Post by Dickybottle on Jul 23, 2010 19:21:13 GMT
Hi Will, I ordered mine on the 21st too, but they aint arrived yet - Maybe tomorrow...
Are your measurements made with the big caps on their side? And what length of spacer have you used between the two boards?
Also, have you used the JLH current limiter with your SCHA, or is it OK without?
Cheers - Ken
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Post by Deleted on Jul 23, 2010 21:05:18 GMT
Ken With the SC HA, use the JLH without the CL in circuit. The initial current limiting is then done by the LM317 and LM337 in the PSU PCB. Alex
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Post by Dickybottle on Jul 23, 2010 21:39:02 GMT
Thanks Alex.
Ken
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Will
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Post by Will on Jul 24, 2010 8:02:56 GMT
Hi Ken,
I measured the pcb's with the caps on the side. Measuring from the bottom of the pcb to the top of the highest components (the tosh trannys) it's approx. 18mm, so 20mm standoffs should give clearance. I'm awaiting a delivery of some 20mm from ebay, and will let you know if my eye and rule are accurate when they arrive! I also don't use the CL in my SCHA.
Will
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Post by Dickybottle on Jul 24, 2010 8:35:19 GMT
Many thanks for that Will - And to Alex for the CL advice.
Even with a bit of mucking about with washers, I think 20mm spacers will be fine - Which as you say will still give me some leeway on height.
I have decided to stick with 2200uF caps for C4 so I can mount them vertically.
Just a quick question - Will there be any negative effects by replacing the 2.2uF film caps with 1.0uF film? Also, could I use 10uF tant's in place of the 10uF Elect's?
Cheers - Ken
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Post by Will on Jul 24, 2010 9:12:16 GMT
No problem using 1uF instead of 2u2, if thats what you have, I used the same value in my first JLH. I did read the 'technical' difference it should make, but I can't remember it now. I don't know about the tantalum, but you could pick up a 10uF from maplins or similar. You can also lie the 2200uF down as well, unless you just don't want to. The C4 caps do work hard, so they may appreciate the rest
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Post by Dickybottle on Jul 24, 2010 11:12:36 GMT
Will, They may very well enjoy a rest, but I can't stand an idle capacitor - Stand up and be counted I say! Postman has just been - Still no JLH boards - Looks like I was not in the first batch... Ken
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Post by Deleted on Jul 24, 2010 11:52:26 GMT
Postman has just been - Still no JLH boards - Looks like I was not in the first batch... Ken You has the itch, an' you has it baaaad! I'll have to wait yonks for the Spanish postal system to bring mine, we almost celebrate when something takes less than 2 weeks to arrive
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Post by Dickybottle on Jul 24, 2010 13:00:19 GMT
Postman has just been - Still no JLH boards - Looks like I was not in the first batch... Ken You has the itch, an' you has it baaaad! Indeed I have - It comes to something when you make a cardboard copy of the PCB - I have it bad... Here's another thing - Why do Jaycar include non-metric spacers with their kits? I suppose sending M3 spacers and screws was out of the question Ken
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Post by Deleted on Jul 24, 2010 22:10:26 GMT
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Post by Dickybottle on Jul 25, 2010 7:20:23 GMT
Alex, It could of course be me ... It's just that a couple of my screws I tried would not thread into the spacers - Perhaps I picked up non-metric ones. Ken
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Post by jonclancy on Jul 28, 2010 19:39:46 GMT
Will, They may very well enjoy a rest, but I can't stand an idle capacitor - Stand up and be counted I say! Postman has just been - Still no JLH boards - Looks like I was not in the first batch... Ken Just to let everyone know, I'm off to Brazil with Ken's boards.... Nah, we're onto it. Sorry they haven't arrived yet, Ken. We'll sort it out. Cheers Jon
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Post by Dickybottle on Jul 29, 2010 8:07:22 GMT
Will, They may very well enjoy a rest, but I can't stand an idle capacitor - Stand up and be counted I say! Postman has just been - Still no JLH boards - Looks like I was not in the first batch... Ken Just to let everyone know, I'm off to Brazil with Ken's boards.... Nah, we're onto it. Sorry they haven't arrived yet, Ken. We'll sort it out. Cheers Jon No worries Jon - I'll call off the dogs Just as an update - I have the amp, regulator and transformer mounted in the Hammond case. I (hopefully) have enough space reserved for the stacked JLH's and am also awaiting the attenuator from Taiwan. Front and rear panels are done except for the volume pot hole. I'll post a few pictures when I have the amp completed. Can I just ask a quick question? - Are you guys setting the default gain at something different from the standard 2? My short listening tests seem to suggest that it may be on the low side, particularly with K701's. Ken
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Post by Deleted on Jul 29, 2010 8:22:06 GMT
Ken The gain needed is mainly dependent on the source. Are you able to get maximum USEABLE volume just before full potentiometer rotation ? If you are , that will give best performance. Changing R1 and R4 to 2.2K or 3.3K will give a modest increase in gain without a noticeable decline in performance. i.e. increasing gain from 2 x , to 3.2 or 4.3 Alex
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Post by Dickybottle on Jul 29, 2010 11:48:07 GMT
Ken The gain needed is mainly dependent on the source. Are you able to get maximum USEABLE volume just before full potentiometer rotation ? If you are , that will give best performance. Changing R1 and R4 to 2.2K or 3.3K will give a modest increase in gain without a noticeable decline in performance. i.e. increasing gain from 2 x , to 3.2 or 4.3 Alex Hard to say as it stands Alex, as I have no potentiometer - I am controlling the volume via the Squeezebox control. The K701's are the problem - During quieter music passages, the control needs to up around the 90%+ mark, which, to me seems high with little scope for a good head banging session I think I will go for a modest increase with a 2K2 resistor in R1, that should cover it I think. Many thanks - Ken
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Post by Deleted on Jul 29, 2010 15:47:46 GMT
Ken The gain needed is mainly dependent on the source. Are you able to get maximum USEABLE volume just before full potentiometer rotation ? If you are , that will give best performance. Changing R1 and R4 to 2.2K or 3.3K will give a modest increase in gain without a noticeable decline in performance. i.e. increasing gain from 2 x , to 3.2 or 4.3 Alex Ken, Alex helped me on this too. I only needed a very small increase in gain, call it a "number 11" on the volume. I just needed a snadge more volume on low level sources with low level recodings (using AKG701) e.g. portable Mini Disc player with a low level recording. If that is the kind of increase you need then I found 1.5k resistors were just enough, I tried these first as I was a bit paranoid of loosing SQ after all the efforts to get there in the first place. As I say, for me it was just enough. If you think you need more than the slightest tweak to the volume then go straight for the values Alex stated.
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Post by Dickybottle on Jul 29, 2010 18:15:13 GMT
Ken The gain needed is mainly dependent on the source. Are you able to get maximum USEABLE volume just before full potentiometer rotation ? If you are , that will give best performance. Changing R1 and R4 to 2.2K or 3.3K will give a modest increase in gain without a noticeable decline in performance. i.e. increasing gain from 2 x , to 3.2 or 4.3 Alex Ken, Alex helped me on this too. I only needed a very small increase in gain, call it a "number 11" on the volume. I just needed a snadge more volume on low level sources with low level recodings (using AKG701) e.g. portable Mini Disc player with a low level recording. If that is the kind of increase you need then I found 1.5k resistors were just enough, I tried these first as I was a bit paranoid of loosing SQ after all the efforts to get there in the first place. As I say, for me it was just enough. If you think you need more than the slightest tweak to the volume then go straight for the values Alex stated. I decided to take Alex's advice and keep on the low side - I was the same as yourself and didn't want to lose any SQ. Looking through my parts bin I found some 2k37 1/4W resistors which I thought were worth trying - Result: Spot on! I've had the 'scope on the amp, and the signal has lost nothing up to 100KHz and I can't tell any difference in the quality - Except there is now that little bit extra poke Thanks for your help guys - Munch appreciated. Ken
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Post by Deleted on Jul 29, 2010 22:02:19 GMT
Ken Good to hear that you only needed the modest increase. It will sound better than with the original value suggested in the magazine for extra gain. Alex
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Post by Dickybottle on Aug 4, 2010 16:57:55 GMT
OK, as promised - Here are a few pictures of my completed SCHA. The height issue I expected with the stacked JLH's worked out OK - Not a lot of clearance between the top of the TO220's but enough (2mm). The case is a Hammond 1455T2201. The JLH boards really are superb quality and as you can see they can be stacked easily. Never a problem, the cover fits easily - phew!! Here's a shot from the rear - The Valab stepped attenuator works very well - a little "clicky" and a bit tricky to wire, but otherwise no problems. The cooler for the Opamp came from Farnell. Many thanks to all involved with the SCHA project - I really enjoyed building this amp - In fact I have become quite attached to it ... I'm hopeless at describing the sound quality - I'll just say that I am more than happy with the sounds this SCHA make - I can see it becoming my amp of choice. Ken
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Post by Will on Aug 4, 2010 19:36:47 GMT
Ken,
That looks brill, mate! You even have a mm or so clearance on the toshies, you could get a bus through that gap! Seriously though, a nice compact build.
Have you got the part number for that heatsink on the lme49720?
Will
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Post by jonclancy on Aug 4, 2010 22:33:35 GMT
Beautiful work, Ken!! Congrats! Jon
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Post by jonclancy on Aug 4, 2010 22:43:28 GMT
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Post by Deleted on Aug 4, 2010 23:13:27 GMT
Jon You have to be joking ! Almost US$5 for a single heatsink is highway robbery.They wouldn't even cost cents to make. These are more than likely TO5 heatsinks anyway. I notice that as TO5 heatsinks are no longer manufactured , that even Farnell wants similar prices.I have now used my remaining TO5 heatsink stocks, which originally cost a fraction of current asking prices. Alex P.S. I second your comments about Ken's beautiful work.
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Post by Deleted on Aug 5, 2010 5:29:22 GMT
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Post by mrarroyo on Aug 5, 2010 10:52:43 GMT
Alex, is this stackable version of the JLH an improvement over the single board version? Thanks.
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