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Post by Deleted on May 12, 2011 8:42:34 GMT
Hi Shaun, nice to have you back just a quick reply........weekly shopping at Morrison's looms.......... Spdif is the easy part I see...........now have to suss out a cheap DAC..........thought Will's Saber project might suit me. Back later for more. Alan
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Post by Deleted on May 12, 2011 9:32:50 GMT
Hi Alan just out of interest what kind of volume control are you using? OK not wanting to stray to far into controversial waters but i found that with my metal bodied DACT i did get a slight metallic buzz with the case UN-grounded (i thought''i know that sound'' it's the vol pot). so i grounded my case back through the PSU box directly to it's case ground and the buzz disappeared. i know that it's not supposed to be necessary but i think that it may come down in some small part to the IP sensitivity of the following power amp. I've been playing with my (class of amp that Dare not speak it's name) and with it's IP sensitivity (1.5v) for full OP. (same as your new Quad) the Vol control did need to be grounded. so that's how things panned out in my set up and it may be something else in yours. we'll have a nice chat about DACs (and phono stages)when you have time. so a five min job give it a go and let me know what you find. i may be wrong so I'd be interested in your input. take care
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Post by Deleted on May 12, 2011 15:49:13 GMT
[Hi Chris Presently, because it isn't in a case, you have the input and output leads in close proximity, which could possibly cause a little instability. 1 I presume that when it is cased up, that the headphone socket will be on the front panel, along with the volume control. The input sockets will of course then be on the rear panel. 2 If there are still niggly problems then, we will sort that out with you. 3 Do you now have 120 ohm output resistors, instead of the 2 series resistors with a higher total resistance ? 4 One transformer or 2 ? Alex, Yes, I assumed from previous posts here that the case would be part of the final answer. 1 = affirmative! 2 = understood 3 = no, I'm accumulating a general order at the mo. 4 = just the one and on that subject; should I stick to buying a new pair of toroidals (same make and spec) or, is there any advantage/disadvantage to going for something like these R-core jobbies? I remember Technics used to swear by them in their better gear. I think Chong has a different version of these on his build. I stayed up way too late last night just listening, even tugged my CDP out of its hidey hole to play more stuff
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Post by Deleted on May 12, 2011 20:44:37 GMT
Hi Chris I do not believe there will be anything gained by changing to R-core with this HA. Why not just replace the damaged toroidal, as the other one appears to be O.K.? I gather that it isn't running excessively hot, and remember that it will only need to work half as hard when 2 are used, so it will run less hot than presently. If you are concerned that the working one may have been stressed too much, then for your own peace of mind replace both. Regards Alex
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Post by Deleted on May 12, 2011 21:23:03 GMT
Hi Shaun, so far my VC is not yet installed in the great sounding AK....I was just about to throw a question at RG regarding which one to use given that I have limited funds when Jeff came up with the answer. DACT Type 21 Stepped Attenuator / Volume 20K for PreAmp on Ebay....purchased one and it's sitting in front of me waiting......I've said before....I'm slow.......even writing this my attention is more on the great sounding Jazz coming down the broadband from the BBC....don't know what SQ they pump out on Radio 3 but I like it..... base is solid and clean with great sounding cymbals, highs that are high and clear, the track playing now has very detailed percussion.....probably as much to do with how the AK handles it. Yes I'd ground the AK case back to the supply case if I had a case OH! how slow am I. Case wise I'm getting there after binning the first attempt I was sitting in the Lochside on the great island of Islay enjoying a Bowmore 12 year old with my mate Gavin when I had a flash of inspiration......to digress a second or two we are now in New York at the Opera.....just love the BBC......okay the inspiration centered around some chrome tube holding up a small shelf on the bar gantry........now you'll have to wait and see what transpires....case wise......it'll be a concoction of salvaged chromed copper tube polished aluminium sheet and mahogany type wood a pull from my local window installer's skip. The Quad is superb now that I've managed to refurb it.....I'm quite pleased with myself on this one. The IP sensitivity is now down by a factor of 3 much more controllable and the noise level is lower than my hearing can discern....I might yet up the power supply capacity to 15000uF and a few other bits to add some time. I'm sure my probs with noise are all related to the venerable PC sitting at my side but I'm quite attached to it. AK to Quad is totally quiet but I am only able to push my CD player output through it, at the moment I'm working on a RIAA phono circuit of Alex's so that I can play my VINYL into AK then Quad I'm looking forward to that so when that's up and running I'll report back. By the way HP listening is first class out of the PC into the AK....no noise very clean and quiet...except for the music of course. Yes to your help with Dacs I haven't a clue. Regards Alan
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Post by Deleted on May 17, 2011 22:32:57 GMT
Hi Alex, with regard to your phono circuit can I use BC560 as replacement for BC559? I've two boards made and just started stuffing them but my eyes are needing a rest so I'm heading for pyjama land soon. Had a job locating the LM394H at a reasonable price....Cricklewood had them at £18 I said no....just hope what I've ordered are genuine. Alan
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Post by Deleted on May 17, 2011 23:03:40 GMT
Hi Alan You can use the BC560 in place of the BC559 here. You could also have used LS313 in place of the LM394H if you had any left. Also, closely matched high HFE (800 ot so) BC550C would do too, if thermally bonded.I tried getting some pairs matched with MPSA18 that have an HFE of >1,000. You take great care, think you have several good matches, then re-test them 30 minutes later and they aren't as closely matched as you had thought ! It should be used internally with minimum cable capacitance at it's output. The 1.5uF will need increasing in value for lower impedance input stages. Regards Alex P.S. Frans will undoubtedly pick this one to pieces, but it works well, better than the SC I.C. based designs from the Semi makers data sheets, and it has simplicity. A JLH replacing the PSU input series resistor does further improve it, according to a friend who is still using my old preamp with a high quality TT and high output MC cartridge.. Attachments:
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Post by Deleted on May 18, 2011 8:44:00 GMT
I see no reason to..
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Post by Deleted on May 20, 2011 9:00:26 GMT
Hi Alex, thanks for that info, when you say " used internally do you mean at the TT or inside the AKHA my preferred location would be inside the AKHA. Is it OK to power the Phono from the AKHA at the outputs of the JLH and would this require me to drop the voltage to 15v or will it run at 20v? The LM394H arrived yesterday they measure out at 572 for both sides so should be OK. I have one board completed and one almost there.
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Post by Deleted on May 20, 2011 9:43:05 GMT
Hi Alan I would recommend inside the Class A HA/preamp's case. I was also lucky enough to fluke some LM394H with HFE of 1,300 or thereabouts.Shouldn't make much difference though, as it is the close matching that is more important. +-20V is too high for the LM394. In this case it may be easier to fit a 15V 1N4744 1 Watt Zener Diode across each of the 1,000uF capacitors. You would need to increase the 47 ohm supply resistors to around 200 ohms. Alex
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Post by Deleted on May 20, 2011 12:11:53 GMT
Hi Alex, that sounds an easy fix if I had the Zeners. I was thinking along the lines of 78/79L15 reg as I have them to hand. Alan
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Post by Deleted on May 20, 2011 12:18:37 GMT
Hi Alex, that sounds an easy fix if I had the Zeners. I was thinking along the lines of 78/79L15 reg as I have them to hand. Alan Hi Alan That would be even better, but I would then reduce the value of the 1,000uF to 100uF, and fit a 10uF or less between the VREG input and earth.Don't forget their different pin out. Alex
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Post by Deleted on May 20, 2011 13:13:53 GMT
Hi Alex, thats fine then, looks like you have just added phono stage to my rendition of your amp. I'm looking at how I can fit regs on boards pity I didn't think to ask before cutting the copper. Next up Will's switching boards for inputs. Many thanks , Alan
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Post by Deleted on May 22, 2011 22:13:15 GMT
Hi Alex, phono's ready..... power is now running at 15v on both boards tomorrow when I'm fresher I'll adjust for less than 1mv on the SSM2220 however before that I think I should add the volume control to the preamp only I'm not sure where or how, can you advise please. Thanks Alan
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Post by Deleted on May 22, 2011 22:13:33 GMT
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Post by Deleted on May 22, 2011 22:23:12 GMT
Hi Alex, phono's ready..... power is now running at 15v on both boards tomorrow when I'm fresher I'll adjust for less than 1mv on the SSM2220 however before that I think I should add the volume control to the preamp only I'm not sure where or how, can you advise please. Thanks Alan Hi Alan The output of the Phono preamp will only be something like 300mV, so you can use your normal volume control, but you MAY meed to increase the gain of the HA a little if maximum level is still too low when using Phono.Don't forget that adjustments should be made with the cartridge connected.It may be wise to initially connect a resistor at the input which is fairly similar in value to the DC resistance of the cartridge, while you check all voltages, especially across the input to make sure that most DC due to the input transistors bias current has been cancelled by the 20Megohm resistors. Alex
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Post by Deleted on May 31, 2011 15:39:58 GMT
Hi All Alan thats just lovely work and i hope that it sounds as good as it looks anyone else used the Class A as a pre? I'm using mine to drive the class T at the moment (i know it's not ideal but it's all i have SS wise). it just sounds superb. (yes i know it should not but it really does work well) I've bypassed the pot on the T and the difference in sound is quite phenomenal. just huge sound stage and total clarity. i think that the extra MA driving the class T has improved things no end.the sound has grip and subtlety and is smooth without masking detail. so just Mr Chong so far who's not happy ;D pm me your address I'll send you some cotton buds. ;D ;D I'm still totally impressed with the Class A. it's got the lot as far as I'm concerned. anyone left to finish? take care
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jonclancy
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Post by jonclancy on May 31, 2011 20:08:38 GMT
Yup - still yet to put some notes trough mine. initial power up was fine...
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Post by Deleted on May 31, 2011 20:20:11 GMT
Hi Shaun, nice to have you around, Alex's phono looks like it'll give me a few thrills again with my "Direct to Disc" black stuff......some of it's white of course..... pumped through the "GREAT AKHA/PRE". I know Alex is a bit hung up on the PC sound stage......and why not...... it's certainly the way ahead..... and vinyl is not rated in his SQ armory but I've a fair whack of my life bound up in the hole'y platters and am reluctant to just discard so much music. So getting the phono up and running is first in line for my time. Then the "ubiquitous" DAC has to be next to get me a little further into the digital SQ concert hall. The AKHA/PRE ticks all the boxes for me, right now I'm listening to BBC Radio 2 via the HPs the Quality is very good and more so since I ironed out the noise on PC to AK to Quad. Your tip on the VC grounding reduced the level a little and then just by moving the traffos box I had the bugger by the tail and a little more faffing around with cable placement gave me the lowest noise stage I've ever had. So my old PC is really not the culprit in fact it's proving to be quite a sweet old music player and all the nonsense I had with W7 is put on hold now I'm back with XP. Oh the other thing I did was to follow Alex's advice and add the ground lift 10R resistors. The Pre through the revitalised OLD Quad is way beyond what I had hoped for... "The SANDY K IN CLASS "A"......rules the day.....certainly gets my vote. Alan
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Post by Deleted on Jun 1, 2011 9:31:37 GMT
Hi Alan yes I'm pretty much in the same boat with the black round stuff (must be an age thing) but I'm finding that i listen to most of my music with Wills music PC and to be honest the SQ is very good. I've found that the gain of my phono stage is a little low when used with the class A as a HA. so i may end up tweaking that up at some point in the future. the SQ is so good from the PC that i don't feel the need to rush with that. the quad tune up sounds like it's gone well and just shows what a capable design it was to begin with. well done on that and your phono build. take care take care
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Post by Deleted on Jun 1, 2011 16:10:39 GMT
Hi Shaun and Alex, too soon....too soon, Alan's stuffed up on the phono build so it's time for an in depth look at what I've done....I've had a few senior moments with this one......Shaun wont know that one Alex but I'm sure you get the drift. So I'm going to recheck my layout pull out all the transistors and replace with fresh only I'll use disposable ones and save the new matched dadioes for when it checks out ok.....but don't hold your breath......i'm slow..slow...slow. I had some issues with the PC but must say again that my PC music is a whole lot better now that I've resolved the noise floor which had more to do with traffo box placement and cable runs. Alex's Hi-res PC files really stand out now, yes PC music is good.....that's the "Sandy K Way" Have you tried the BBC output? they are pumping out good sounding HD stuff. Alan
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Post by Deleted on Jun 1, 2011 17:30:50 GMT
Hi Shaun and Alex, too soon....too soon, Alan's stuffed up on the phono build so it's time for an in depth look at what I've done....I've had a few senior moments with this one......Shaun wont know that one Alex but I'm sure you get the drift. So I'm going to recheck my layout pull out all the transistors and replace with fresh only I'll use disposable ones and save the new matched dadioes for when it checks out ok.....but don't hold your breath......i'm slow..slow...slow. I had some issues with the PC but must say again that my PC music is a whole lot better now that I've resolved the noise floor which had more to do with traffo box placement and cable runs. Alex's Hi-res PC files really stand out now, yes PC music is good.....that's the "Sandy K Way" Have you tried the BBC output? they are pumping out good sounding HD stuff. Alan hi Alan well thats just all part of the fun BBC sounds interesting i must get the TV box hooked up and have a listen. good luck with the phono I'm sure it will come good. take care
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Post by Deleted on Jun 1, 2011 22:26:46 GMT
Hi Shaun just google BBC Radio take your pick it's all there, stream it into your music PC or general workhorse PC. Alan
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Post by Deleted on Jun 2, 2011 22:35:25 GMT
Tail end Charlie here I've at least started, must place an order and get a move on.... Syd
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Post by Deleted on Jun 2, 2011 23:02:48 GMT
Tail end Charlie here I've at least started, must place an order and get a move on.... Syd I think Friedrich has yet to commence his ?
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