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Post by Deleted on Nov 24, 2012 12:51:40 GMT
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Post by Deleted on Nov 30, 2012 11:37:23 GMT
Hi Will just a quick post to let you know that my Class A boards and LS devices arrived safely in the post this morning. WOW SUPER QUALITY but then your work always is and these boards are no exception. top notch and of the sort of quality that I've only ever seen in ultra expensive kit. i feel really spoiled rotten to have them. unfortunately I'm not going to be in a position time wise to start my build until after Xmas but look forward to seeing some other builds progress. just to say that after nearly a year of using Alex's pre/PA I've never failed to be impressed by it's calm, clear, lucid and musical sound. it really is top notch you guys are in for a real treat take care
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Post by Deleted on Nov 30, 2012 14:34:52 GMT
+ 10 from me to all the above^. Mine arrived today also - great stuff. I only wish that I knew what to do with them ;D but hopefully that minor detail is taken care of . Thanks a bunch Will for being kind and understanding enough to welcome a total 'know nowt' into this project . Got your e-mail too, Will. Cheers, Dave.
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Post by Deleted on Dec 1, 2012 12:07:01 GMT
@ Will, Have I got everything now that your GB is providing? I ask so that I know when I can dump everything on my builder and tell him to get on with it ;D . TIA, Dave.
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Post by Deleted on Dec 2, 2012 5:47:01 GMT
Further Improvements to the Class A HA/Preamp and 15W Class A.
In the attachment, it can be seen that the Offset Corrector for the Class A HA/preamp and 15W Class A amplifier is a further development of an original David Tillbrook design. We have however been using the AD744 for it's higher precision instead of the original TL071 which can also be relatively noisy. The 100nF capacitor at the junction of the 10K and 75K resistors was added to reduce the noise output of the I.C. a little further, in conjunction with the ratio of the 10K + 75K to the 4.7K base resistor in the HA, or the 1.2K resistor in the 15W Class A. Recent tests that I have made,and that have been verified by Shaun, indicate that replacing the AD744 with an OPA134 results in a further noticeable improvement in low level detail. Additional testing, again verified by Shaun, has shown that fitting an inexpensive capacitor of either 2.2nF or 4.7nF in parallel with the 1 meg ohm resistor results in a further small but worthwhile improvement. This capacitor can be fitted across the 1M resistor underneath the PCB.This results in a further reduction of low level wide band noise from the opamp by around 10 times at 1kHz and even more at higher frequencies. This additional capacitor will also result in an improvement if you decide to keep using the AD744. For those using both the Class A preamp and 15W Class A amplifier together, the results are further improved. Alex
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Post by Deleted on Dec 2, 2012 11:17:55 GMT
Hi All just to confirm Alex's findings i found that using the OPA134 in conjunction with the 2n2 cap (i used 4n7 because that's what i had to hand) in Alex's HA/pre gave a sweeter more detailed and natural sound. i have another two 134's to try in the PA and just need the time to plug them in. well worth the small amount of effort involved. if i could be controversial (well slightly) if any one is set on using the AD744 or TL071 in that position then use a DIL socket. I'm sure glad that i did in Alex's PRE/HA/PA as it makes swapping op amps easy. just to add Alex's amps are well worth the small extra expense involved in using the OPA134. super high end sound at a very modest price. the down side is that I'm now stuck with fiddling with the front end and cables (but more on that later). these amps are so good i can't see myself wanting to replace them any time soon if at all. still you guys are going to be finding that out pretty soon can't wait take care
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Post by Deleted on Dec 2, 2012 15:06:51 GMT
X2
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Post by Deleted on Dec 2, 2012 20:31:15 GMT
Hi Shaun Don't forget to fit the 2n2 there as well when you get some caps to replace the temporary MKPs in the preamp. Yesterday was cooler here, and I had a chance for a more relaxed listen after fitting them there the previous stinking hot afternoon. The difference, even with DTV, was obvious to me, and no stupid DBTs needed ! Kind Regards Alex
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Post by Deleted on Dec 4, 2012 19:20:46 GMT
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Post by Deleted on Dec 4, 2012 21:45:39 GMT
A photo of the original S.C. 15W Class A amplifier which should give some idea of the type of case or construction needed. Someone adept at metalworking could take the appropiate heatsinks and cut aluminium top,bottom, and front and rear panels to size and carefully tap the heatsinks to accept the panels. Alex P.S. The heatsinks used in the original should be similar (or higher) in heatsinking capacity to to those shown at the Altronics link. www.altronics.com.au/index.asp?area=item&id=H0545
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Post by Deleted on Dec 7, 2012 6:47:06 GMT
I received Will's PCBs this afternoon, and as usual from Will, they are most impressive. Regards Alex
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Post by Deleted on Dec 7, 2012 21:55:41 GMT
Hi Alex, yes Will's boards are "the Bee's knees". Here are the specs for the 15 Watt case à la drymdrum. pics to follow. 15 Watt Power Amplifier CaseMade from readily available materials in the UK minimal cutting required and the CCL board is nice to work with. Aluminium Angle 15mm X 15mm X 1.5mm X 2 . 5 meters B&Q £19 Aluminium Angle 40 X 10 X 1.5mm B&Q £08 One pack FR4 PCB Copper Clad Laminate 5x 160 x 100mm 1.6mm 1/0 £3.42 plus postage One pack FR4 PCB Copper Clad Laminate 5x 300 x 200mm 1.6mm 1/0 £10.68 plus postage Pop Rivets..............Self Tapping Screws Find it here on Ebay.............. stores.ebay.co.uk/PCB-Consumable-SuppliesLamar Group Ltd, Olympic Complex, Drybridge Road, Dundonald, Ayrshire, KA2 9BE Finished case.............. Internal 100mm X 405mm X 300mm External 105mm X 485mm X 310mm.....( 367mm) ( add heatsink at back for power supply plus 67mm ) All inside surfaces electrically bonded You will use 4 sheets 200 X 300mm FR4 CCL two for the base and two for the top lid and five of the 100mm X 160mm for the sides back and front the case size is based around the FR4 sheet size and 300 x 100 heatsinks I used 4 x 200 x 300mm for top and base and 5 x 100 x 160mm for the sides back and front plus the heatsinks for the sides a case without heatsinks would require two packs of the 100mm x 160mm and extra 2 meters of the 15mm x 15mm for the sides. What did it cost...............case Approx.................................................................................£43.00 Heatsinks two for the sides one for each of Will's 15 watt modules..................................£67.00 Heatsinks for the two PSU modules two ..............................................................................£13.00 Total.......................................................................................................................................£123.00 Heatsinks from www.wattbits.com/catalogsearch/advanced/result/?manufacturer=Birmingham+Aluminium&search_category_id=483and www.ebay.co.uk/itm/size-120-x-65-depth-varies-36-42mm-/290419460060?pt=UK_Computing_Other_Computing_Networking&hash=item439e5947dc
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Post by Deleted on Dec 7, 2012 22:03:32 GMT
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Post by Deleted on Dec 7, 2012 22:26:12 GMT
Hi Alan It looks great! I envy your metal working skills. Don't forget to add a 2.2nF or a little higher, across each of the 1M resistors for the opamps under the PCBs. Kind Regards Alex
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Post by Deleted on Dec 7, 2012 22:44:38 GMT
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Post by Deleted on Dec 7, 2012 22:45:59 GMT
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Post by Deleted on Dec 7, 2012 22:46:42 GMT
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Post by Deleted on Dec 7, 2012 23:03:45 GMT
Hi Alex, I'm pleased to see this one made up, it did knacker me a bit just popping the rivets never mind the weight of the bloody thing, plus our lovely weather of course meant I could only suffer an hour or so in the workshop. That said though, I do get a kick out of my projects when they turn out well, the pics don't do it justice.
Yes I've noted your latest mods in that department, I've still a lot to do and haven't pushed juice through any of the modules yet, so there could be tears to come. However I'm pleased with where I've got to on this one. Syd......who knows the power amp might come down the lum yet. ;D
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Post by Deleted on Dec 7, 2012 23:26:37 GMT
Hi Alan It will be much easier to fit those 2 caps now than when all put together. Kind Regards Alex
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Post by Deleted on Dec 8, 2012 1:15:14 GMT
Thanks Alex, modules are all built both for the 15 Watt and the HA/Pre with just minor bits and a good eyeball and clean before wiring in. Still got the LS devices to put in and hard wiring points on Will's boards so the caps will be added then. Here's a pic of what I intend for the hard wire points, it gives the best of both worlds for hooking up..........connecting blocks and Alan's pins.
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Post by Deleted on Dec 8, 2012 10:46:20 GMT
Hi Alan
super high quality work as usual and a lovely case.
well done
take care
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Post by jeffc on Dec 9, 2012 21:48:42 GMT
x2 awesome Alan And its given me a question to ask........... For obtaining the amps super-low distortion figures, do only the 2 x 20-0-20 transformers need to be kept away from the amplifier circuitry. That is, like Alan is doing, can the PSU PCBs live in the same case? Are longer runs of low-voltage AC between cases less ideal than low-voltage DC? cheers.. jeffc
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Post by Deleted on Dec 9, 2012 22:15:27 GMT
x2 awesome Alan And its given me a question to ask........... For obtaining the amps super-low distortion figures, do only the 2 x 20-0-20 transformers need to be kept away from the amplifier circuitry. That is, like Alan is doing, can the PSU PCBs live in the same case? Are longer runs of low-voltage AC between cases less ideal than low-voltage DC? cheers.. jeffc Jeff The main thing is to keep the transformers separate. I have the PSU PCBs in a separate case along with the 2 toroidals for the preamp, because there isn't enough room in the amp case I am using for the PSU PCBs as well.Besides which, that is what S.C. did, and they may have had good reasons for doing so. They need to make their projects repeatable in results. Regards Alex P.S. Don't forget that with the preamp I am feeding in AC, not D.C. to onboard PSU PCBs.
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Post by Deleted on Dec 9, 2012 22:20:12 GMT
....and another vote from me, very slick and an interesting method.
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Post by Deleted on Dec 9, 2012 23:52:04 GMT
Hi Jeff, my first build of the AKSCMODS15W has been regaling me with top notch audio now since June past and as Shaun has posted here already, with no audio and the volume control turned way up black hole silence with your ear hard up to each speaker makes you wonder if the bloody thing is switched on. Since I have no way of measuring for the above figures the black hole ear test is good enough for me. There is .....no HUM.......no HISS..........just beautiful clear detailed HQS. With regard to this build I took a lesson from the first one and have given the power output trannys the full 300mm length of heatsink per side, they obviously need that, with separate heatsinks on the back wall for the PSUs. Hanging both PSU and Output devices on the one sink per side and running at full bias gets pretty hot so the bias is throttled back a bit. Hopefully #2 build will sort that and I'll be able to say that it equals or surpasses #1.............nah! don't see how it could be better. So from my experience with build #1............. traffos in steel boxes 240mm above the power amp case and PSU boards in main amp case with the AKMODSSCHA/preamp sitting a further 100mm below works for me. With a bit of luck build #2 will confirm that the PSU boards can live in the same case as the main amp boards. Regards, Alan
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