XTRProf
Fully Modded
Pssst ! Got any spare capacitors ?
Posts: 5,689
|
Post by XTRProf on Mar 30, 2011 10:44:01 GMT
Hi Chong, keep asking these pertinent questions I'm stacking up all the answers glad your going where I've not been yet Alan Ha, ha, it seems I will reach the finish line soon before fine tuning steps in ............ Whew!
|
|
Deleted
Deleted Member
Posts: 0
|
Post by Deleted on Mar 30, 2011 10:52:58 GMT
Chong Just remember to put at least 48 hours on the JLHs before you do any serious listening.At some times in that 48 hours, you may even get to think that something is seriously wrong ! The SQ will go up and down in cycles until that time.That is why I initially suggested that the JLHs should be built and run in, while the main PCBs were being built. Alex
|
|
Deleted
Deleted Member
Posts: 0
|
Post by Deleted on Mar 30, 2011 13:12:02 GMT
Hi Chong, keep asking these pertinent questions I'm stacking up all the answers glad your going where I've not been yet Alan Ha, ha, it seems I will reach the finish line soon before fine tuning steps in ............ Whew! Hi Chong way to go take care
|
|
XTRProf
Fully Modded
Pssst ! Got any spare capacitors ?
Posts: 5,689
|
Post by XTRProf on Mar 31, 2011 7:18:10 GMT
Chong Just remember to put at least 48 hours on the JLHs before you do any serious listening.At some times in that 48 hours, you may even get to think that something is seriously wrong ! The SQ will go up and down in cycles until that time.That is why I initially suggested that the JLHs should be built and run in, while the main PCBs were being built. Alex Noted! .........
|
|
XTRProf
Fully Modded
Pssst ! Got any spare capacitors ?
Posts: 5,689
|
Post by XTRProf on Mar 31, 2011 7:20:00 GMT
Ha, ha, it seems I will reach the finish line soon before fine tuning steps in ............ Whew! Hi Chong way to go take care Nope, naked and streaker don't need to .......... Heh, heh, heh ..........
|
|
Deleted
Deleted Member
Posts: 0
|
Post by Deleted on Mar 31, 2011 7:29:11 GMT
Chong Just remember to put at least 48 hours on the JLHs before you do any serious listening.At some times in that 48 hours, you may even get to think that something is seriously wrong ! The SQ will go up and down in cycles until that time.That is why I initially suggested that the JLHs should be built and run in, while the main PCBs were being built. Alex Noted! ......... Also, I would recommend that those that haven't populated the main PCBs yet, hold off on installing the 1N5819s and 82 ohm resistors for the moment. We MAY be able to do better.. Alex
|
|
jonclancy
Been here a while!
Mr. Ripple Eater
Amateur EAGLEist
Posts: 1,131
|
Post by jonclancy on Mar 31, 2011 16:12:42 GMT
Dang!!! Fire up the turbo-tweezers!!! Little update afer a small hiatus... Sinks installed today, as were some film caps I matched up. Plus the last 100uF elcos. The last transistors to match up and install and we're off!
|
|
Deleted
Deleted Member
Posts: 0
|
Post by Deleted on Mar 31, 2011 16:17:55 GMT
yeeeehaaaa Jon can you smell the finishing line yet almost home and hosed take care
|
|
jonclancy
Been here a while!
Mr. Ripple Eater
Amateur EAGLEist
Posts: 1,131
|
Post by jonclancy on Mar 31, 2011 21:03:24 GMT
It's near!!! Anyine doing a Farnell order in the near future. please?? Or, where can a get some SF12 without paying for a part order postage? Having just made an impulse speaker purchase, my DIY spending is under extreme scrutiny...
|
|
Deleted
Deleted Member
Posts: 0
|
Post by Deleted on Mar 31, 2011 21:16:23 GMT
It's near!!! Anyine doing a Farnell order in the near future. please?? Or, where can a get some SF12 without paying for a part order postage? Having just made an impulse speaker purchase, my DIY spending is under extreme scrutiny... Hi Jon Already done. If you nicely ask Will or Shaun....... Regards Alex
|
|
Deleted
Deleted Member
Posts: 0
|
Post by Deleted on Mar 31, 2011 22:09:25 GMT
It's near!!! Anyine doing a Farnell order in the near future. please?? Or, where can a get some SF12 without paying for a part order postage? Having just made an impulse speaker purchase, my DIY spending is under extreme scrutiny... Hi All Alex asked me to try out a mod he had been working on just to get another opinion on it. You’ve probably guessed from Jon’s exited post that it involved swapping out the IN5819 in the LTP balancing circuit with an SF12 and replacing R18 – 820r resistor with 120r. I’ll leave the more technical explanation to others. I used a hot solder sucker to remove the components which made the whole process much easier. After inserting the new components and very quickly re balancing the LTP I had a quick listen. The first thing I noticed was that the LTP test point voltages where much less prone to drift that before and seemed to be more stable. (Measured with the top off so I will do a full setup later) Ok sound Well I’m a bit shocked that a diode and resistor swap can bring about the level of change that I’m hearing. Before I go on I want to say that my comments on the sound now are in no way a criticism of the Class A as was. But a few things have changed quite noticeably IMHO. So I’ve just plonked on anything just to make sure things are working. 1) More fine detail. Things that I could just about hear before are MUCH more obvious now. 2) The sound has greater focus. I’ve listened to Limehouse blues and instrument placement is much more discernable than it was before. 3) Top end detail and extension is noticeably better. 4) OK with headphones I usually find scale and acoustic information can be hard to decipher but this sound is bigger and wider and clearer than before It sounds like it has a tad more gain but maybe that’s just the extra information getting through. So a very QUICK listen but I’m impressed. It still sounds like the Class A that I know and love but much better in the areas that I’ve mentioned. I think that Alex was right to halt anyone who has not put in their IN5819 in yet as the SF12 are an obvious improvement. Well worth the effort which was much less than I had feared with the super solder pump. Overall it’s squeezed another fat cherry onto a cake full of them Wife No 9 test to follow Well done Alex. It gets my vote. Hi Jon PM me your adress as i have some waiting for you. anyone else want some please PM me your address details. Take care
|
|
Deleted
Deleted Member
Posts: 0
|
Post by Deleted on Apr 1, 2011 1:29:01 GMT
A word of explanation.This front end balancing is based on a subjective finding that I first reported in 1987, and later confirmed in the DIYAudio "Current Mirror" thread of November 2008. The 1N5819 schottky diode and trimpot were used to help equalise the collector currents in both halves of the dual input transistors. The VAS transistor (2nd stage) has it's Voltage between base and emitter drop by 2mV/C with increasing temperature . Using a trimpot alone would not give temperature compensation, so as the required voltage drop was only several few hundred millivolts,a schottky diode was placed in series with the trimpot.The schottky diode has a temperature coefficient of 1.1mV/C, so although there was some tracking capability, the tracking was not perfect, and the adjustment was quite touchy.Changing the emitter resistor of the VAS transistor from 82 to 120 ohms permitted a low forward voltage silicon diode such as the SF11 or SF12, to be used in place of the schottky diode.The SF11/12 has a temperature coefficient of approx. 2mV/C, so the tracking with temperature became much better , thus permitting a much closer front end balance, in fact <1mV difference between the collectors of the input pair is quite achievable, and the drift with temperature was also markedly reduced. Please note that many EEs do not accept the notion that such extremely close balancing of an already well matched differential pair to better than 1% can result in any audible or readily measurable improvements. Alex Uploaded with ImageShack.us
|
|
Deleted
Deleted Member
Posts: 0
|
Post by Deleted on Apr 1, 2011 10:07:11 GMT
Hi Alex Thanks for the explanation it helps to explain the changes that i measured and heard. Hi All just a quick add on to my comments above. i just wanted to make it clear that when i was discussing the SF12 mod with Alex he did explain what was required for the mod component wise and even gave me a heads up on the hot sucker but was quite scrupulous about not telling me what to expect after the mod had been completed. so what i wrote above was based on my own observations and listening test. so with Alex's explanation I've learned something today that explains what I've measured and heard for myself. for me that's what DIY is all about. the hot solder sucker worked better than i was expecting. it was sooo much easier to use with just one tool to hold rather than the Olly the octopus effect of a cold sucker. it made working on Will's superb boards a real pleasure. ;D i used to find trying to squeeze the iron tip and sucker onto the same pad when removing components a pain ITB. the hot sucker fits over the component leads and flush with the pad for maximum suction. it seems to be a much more gentle process for the board too which can't be bad. the two 82R resistors just fell out of the board with a couple of sucks. the best £6.99 + P.P I've spent in a while. so remember''it don't bite but gives a nasty suck'' don't know how i got by without one
|
|
Deleted
Deleted Member
Posts: 0
|
Post by Deleted on Apr 1, 2011 13:42:55 GMT
?
As they say, "I think I missed that memo".
I'm no where near stuffing the main boards yet, so that's good.
|
|
Deleted
Deleted Member
Posts: 0
|
Post by Deleted on Apr 1, 2011 13:53:40 GMT
?As they say, "I think I missed that memo". I'm no where near stuffing the main boards yet, so that's good. Hi Chris good stuff. it should be a piece of cake (cherry of course) to work in the mod. take care
|
|
Deleted
Deleted Member
Posts: 0
|
Post by Deleted on Apr 1, 2011 14:21:56 GMT
|
|
Deleted
Deleted Member
Posts: 0
|
Post by Deleted on Apr 1, 2011 18:08:47 GMT
Thanks for the link Shaun. I could have used it a fair bit today!
Syd
|
|
Will
Been here a while!
Ribena abuser!
Member since 2008
Posts: 2,164
|
Post by Will on Apr 1, 2011 18:37:37 GMT
?As they say, "I think I missed that memo". I'm no where near stuffing the main boards yet, so that's good. Chris, I think Alex posted in this or the 'show your build' thread, so easy missed. Don't worry, you weren't being left out
|
|
Will
Been here a while!
Ribena abuser!
Member since 2008
Posts: 2,164
|
Post by Will on Apr 1, 2011 18:38:46 GMT
Nice link, Mr Shaun. I've summat similar on the way. What a bargain price as well!
|
|
Deleted
Deleted Member
Posts: 0
|
Post by Deleted on Apr 1, 2011 20:08:35 GMT
?As they say, "I think I missed that memo". I'm no where near stuffing the main boards yet, so that's good. Hi Chris Fit SF11 or SF12 diodes instead of the 1N5819 schottky diodes, and replace the 82 ohms resistors with 120 ohms. This makes the front end balance less touchy, and the tighter adjustment available results in a further small improvement in SQ, as also confirmed by Shaun. Regards Alex
|
|
Deleted
Deleted Member
Posts: 0
|
Post by Deleted on Apr 1, 2011 23:35:51 GMT
Hi All Any more for the great SF12 bonanza? i have one pair left and then it's over to Will. any one who wants them drop me a PM. take care
|
|
Deleted
Deleted Member
Posts: 0
|
Post by Deleted on Apr 2, 2011 0:06:26 GMT
Hi All Any more for the great SF12 bonanza? i have one pair left and then it's over to Will. any one who wants them drop me a PM. take care Shaun Perhaps you should have ordered a few more ? The SF12 is great in low voltage PSUs as not only does it have a lower forward voltage than most 1A rectifier diodes, it has a faster turn off than even the UF 400X series, of typically 30nS. This can mean a small audible improvement, as reported by several members. Alex
|
|
Deleted
Deleted Member
Posts: 0
|
Post by Deleted on Apr 2, 2011 0:20:33 GMT
Hi All Any more for the great SF12 bonanza? i have one pair left and then it's over to Will. any one who wants them drop me a PM. take care Shaun Perhaps you should have ordered a few more ? The SF12 is great in low voltage PSUs as not only does it have a lower forward voltage than most 1A rectifier diodes, it has a faster turn off than even the UF 400X series, of typically 30nS. This can mean a small audible improvement, as reported by several members. Alex Hi Alex yes i did look at the spec's for the SF12 and they do look very good. i have saved a few for trying in PSU duty so it will be interesting to try them out.(soon) but the last two are up for grabs. they look good and are cheap and easy to find @ farnell and RS so no worries. take care
|
|
Will
Been here a while!
Ribena abuser!
Member since 2008
Posts: 2,164
|
Post by Will on Apr 2, 2011 8:55:20 GMT
My SF12's arrived this morning, thanks Shaun! I have a carpet to lay, but as the wife is going shopping, I feel a slight re-scheduling coming on!
|
|
Deleted
Deleted Member
Posts: 0
|
Post by Deleted on Apr 2, 2011 9:21:36 GMT
My SF12's arrived this morning, thanks Shaun! I have a carpet to lay, but as the wife is going shopping, I feel a slight re-scheduling coming on! Hi Will Glad the SF12 arrived safely. carpet laying ooooh my back feels bad just thinking about it. take care
|
|