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Post by cyteen on Jul 21, 2009 0:40:12 GMT
It was as much to to do with using left over LDRs from a Lightspeed attenuator. I liked the idea of the isolation but thought that maybe the LDRs would react too slowly.
Thanks for your input.
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Will
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Post by Will on Jul 27, 2009 19:22:52 GMT
After a little smoke letting incident  , I thought that I would clarify the layout of this board.  This is how the board is viewed from above. Pad 4 is -ve, Pad 1 is +ve, Pad 2 is signal in and Pad 3 is GND. If you swap the wiring on Pad 1 and 4, smoke comes out of the resistors, and everything!! Fortunately, The board still works after wiring it properly. |
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Post by Deleted on Jul 27, 2009 21:40:36 GMT
After a little smoke letting incident , I thought that I would clarify the layout of this board. This is how the board is viewed from above. Pad 4 is -ve, Pad 1 is +ve, Pad 2 is signal in and Pad 3 is GND. If you swap the wiring on Pad 1 and 4, smoke comes out of the resistors, and everything!! Fortunately, The board still works after wiring it properly. Will That didn't happen late at night, when you had just finished it, and wanted to try it before going to bed, did it ?  Alex |
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Will
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Post by Will on Jul 27, 2009 22:20:54 GMT
Yep, and after I'd done all the wiring nice and tidy  . Looks much more untidy now, so will have to re-do it before posting any pictures (got that Syd? ) Main reason for posting is that my circuit diagram show +ve at the top, which I took my cue from, rather than the physical layout. I wanted to get that and the buffalo up and running for my Dad, so he can have a good listen whilst I'm otherwise engaged. The Buffalo is shocking inside  I must admit to a very little listen (ear infection again  and It sounds very good, but know it'll be stunning with the JLH's. |
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Post by Deleted on Jul 27, 2009 22:32:33 GMT
Will
I can't say a thing about your wiring as I haven't even bought any yet. I'm highly impressed with the appearance of the shielding sleeving, I think that's what it is. At least you recovered from your +- reversal, I still haven't sussed what else I fried in my AK HA upgrade with +- reversal despite many new bits. I have a list of advice from Alex that I will work through when I work up some enthusiasm to let it out of the punishment box<G>
Syd
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Spirit
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Post by Spirit on Jul 28, 2009 1:47:26 GMT
Looking good there Will  |
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Post by Will on Jul 28, 2009 7:33:20 GMT
Thanks Guys! I sent Syd a few pictures of work so far, but as it's not quite finished, I'm holding back for now. Once the JLH's are in, and the wiring is as tidy as can be, I'll get some photies up! One completed part is the transformer housing, pictured below.  It houses two 15V 15VA transoformers, one per channel. Again, you don't need to do this as one 30VA transformer would do, it's just I'm going for overkill  The transformers are bolted to the case, which also help dissipate any heat (not much). Mains is wired as per the SCHA, except I've plonked a X2 cap across the mains main, and have ferrites on the mains wiring. The cables supply the AC to the main amp. In making this amp, I wanted to keep the mains away from the amp, and I have followed the same train of thought in the Buffalo and Shigaclone, with mains in a box to go at the bottom of the rack (yet to be made). Also, during layout, all power cables are on the extreme left or right of the case, and all signals (analogue or digital) are in the center. This includes the way they will be when on the rack. The box is your standard hammond die-cast aluminium mounted on a bit of mdf, and then painted OK, a little progress picture!  The rubbish black and red going everywhere wires are temporary, and will be tidied up and placed in expandable sleeving once the JLH are in, keeping the case neat and tidy. The audio wire to the board is not sleeved at the moment, as I plan to experiment with shunting the volco, and, in the future, the lightspeed attenuator. Audio to the headphone socket is sleeved. The power cable will come in from the back of the pcbs, to the power pins. The other thing I've done is make every audio cable exactly the same length, regardless of destination. This way, any losses are the same/Zen stuff. Anyway, It'll be a while until I do a substantial update, and It'd be nice to see what you other guys come up with! |
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Post by Deleted on Jul 28, 2009 7:54:06 GMT
Will
Interesting build.
Are you sure that the heatsinks on the voltage regulators are big enough ? ;D
Alex
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Will
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Post by Will on Jul 28, 2009 7:57:09 GMT
Will Interesting build. Are you sure that the heatsinks on the voltage regulators are big enough ? ;D Alex Hmm, I dont know? Sometimes it get to around 25C here |
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Post by Deleted on Aug 12, 2009 1:47:12 GMT
A new Class A HA for the PC. Many thanks to Will for organising the Group Buy of the dual transistors, which made things much easier this time, and also for his miniaturised Offset Corrector PCB design. I do intend to make another couple of Class A PCBs using Will's layout which avoids board modifications, and includes Test Points for adjustment of front end balance. Alex   All the better to hear those "imaginary " differences between "Bit Perfect" .wav files ! |
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Post by insomniac on Aug 12, 2009 2:21:20 GMT
A new Class A HA for the PC. Many thanks to Will for organising the Group Buy of the dual transistors, which made things much easier this time, and also for his miniaturised Offset Corrector PCB design. Alex All the better to hear those "imaginary " differences between "Bit Perfect" .wav files ! Tidy build there Alex  |
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FritzS
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Post by FritzS on Aug 12, 2009 16:19:49 GMT
A new Class A HA for the PC. Many thanks to Will for organising the Group Buy of the dual transistors, which made things much easier this time, and also for his miniaturised Offset Corrector PCB design. I do intend to make another couple of Class A PCBs using Will's layout which avoids board modifications, and includes Test Points for adjustment of front end balance. Alex new PCB mods - crossing legs of the dual BJT's are not needful? Or your mods included? |
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Post by Deleted on Aug 12, 2009 21:33:09 GMT
A new Class A HA for the PC. Many thanks to Will for organising the Group Buy of the dual transistors, which made things much easier this time, and also for his miniaturised Offset Corrector PCB design. I do intend to make another couple of Class A PCBs using Will's layout which avoids board modifications, and includes Test Points for adjustment of front end balance. Alex new PCB mods - crossing legs of the dual BJT's are not needful? Or your mods included? Friedrich Will's latest PCB design has provision for the front end balancing mods and a couple of test points to facilitate adjustment of the balance, so there are no further PCB modifications needed. Will found it would need quite a bit of work to change the transistor layout to accomodate the different pinout of the dual transistors. In any case, some people may prefer to use carefully matched single devices which fit straight in. There may even be a small advantage in doing this with the current mirror , where readily available BC550C and MPSA18 often have a much higher HFE than a typical LS313. Alex P.S. My HA is presently going through that damn electrolytic forming cycle, where SQ varies quite a bit for a couple of days. Hopefully, it should finish stabilising later today. In case anybody is wondering,the sound differences between this fully discrete version and the SC HA with JLH, but using a LM4562HA metal can device, are not night and day , rather, the discrete version sounds quite similar tonally, but builds on the performance of the other in virtually all areas, such as low end extension, transparency and dimensionality. This was quite noticeable with "Sara K's "Vincent", particularly where she thanks the live audience. Several members will have downloaded this track. P.P.S. It's now fully stabilised. |
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Post by FritzS on Aug 13, 2009 6:57:44 GMT
PS: My HA is presently going through that damn electrolytic forming cycle, where SQ varies quite a bit for a couple of days. Hopefully, it should finish stabilising later today. In case anybody is wondering,the sound differences between this fully discrete version and the SC HA with JLH, but using a LM4562HA metal can device, are not night and day , rather, the discrete version sounds quite similar tonally, but builds on the performance of the other in virtually all areas, such as low end extension, transparency and dimensionality. This was quite noticeable with "Sara K's "Vincent", particularly where she thanks the live audience. Several members will have downloaded this track. P.P.S. It's now fully stabilised. If I understand right the difference between the LMxxx metal can series and the discrete amp are very small I wait till autumn and the leaves are falling and the November mist track through the empty wood (I live on the other side of the globe than you) - and then I want to build this amp too. |
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Post by Deleted on Aug 13, 2009 7:19:48 GMT
Friedrich
I am not saying they are small. They are quite obvious, but rather build on the qualities of the SC HA with JLH and LM4562HA.
I am yet to properly adjust the front end balance, which was set initially when the channel modules were being tested, and set when cold, not at normal operating temperature.
I suggest you read reports by Leo and others regarding their impressions. I think Leo's quote (below) was before the metal can dual devices were installed .
Alex
"I've now got the metal can LM4562 in the SCHA which has improved the sound quality a fair bit.
In all honesty I still prefer the classA, the classA has serious depth which to me the SCHA cannot match when using the highly modified Buffalo dac.
It all just sounds more realistic to my so called golden ears
Leo"
"This thing still outclasses the SCHA by quite a lot imo when used as a HA
The input pair mods are really needed tbh to get the most out of it
Have you built yours yet Fritz?? come on man get your finger out "
"I've had a really good listen, and the amp is a wonder. I've jumped at some of the moments in the music, as the transients are stunning in speed. Music is presented in an authorative, liquid style which is very easy to listen too. I need to etch some JLH psrr's for this, but I'm a little scared about how good this amp will be after! (knowing how it transformed the SCHA)
Another thing. If you have AKG K701, you owe it to yourself to make this amp. It drives them beautifully, there seems to be a nice synergy going on.
Will"
See also, reply 105 on P.8 from Will. This was BEFORE the JLHs are installed,too.
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FritzS
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Post by FritzS on Aug 13, 2009 7:31:35 GMT
Friedrich I am not saying they are small. They are quite obvious, but rather build on the qualities of the SC HA with JLH and LM4562HA. I am yet to properly adjust the front end balance, which was set initially when the channel modules were being tested, and set when cold, not at normal operating temperature. I suggest you read reports by Leo and others regarding their impressions. I think Leo's quote (below) was before the metal can dual devices were installed . Alex "I've now got the metal can LM4562 in the SCHA which has improved the sound quality a fair bit. In all honesty I still prefer the classA, the classA has serious depth which to me the SCHA cannot match when using the highly modified Buffalo dac. It all just sounds more realistic to my so called golden ears Leo" "This thing still outclasses the SCHA by quite a lot imo when used as a HA The input pair mods are really needed tbh to get the most out of it Have you built yours yet Fritz?? come on man get your finger out " Alex, this make me more snoopy too ....... Have you a latest recommand part list of the Class A HA + JLH + PSU? |
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Post by Deleted on Aug 13, 2009 7:39:18 GMT
Friedrich
Reply 71 on P.5 from Will gives the Class A modules parts list.
The offset PCB parts are as shown in the schematics in reply 51 on p.4 , however the TL071 or other similar single FET input opamps should be O.K. instead of the AD744.
The JLH parts lists are in the SC HA Tweaks thread.
I am using the version with Current Limiting installed, and set at 600mA (1 ohm emitter resistor, and 1K8 base resistor.)
You will also need an externally cased 15-0-15 30VA toroidal transformer and a cable with suitable connectors and sockets etc.
Alex
See also additional SQ reports that I edited in while you were posting your reply.
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Post by Deleted on Aug 15, 2009 4:29:55 GMT
PSU Photos (as requested by Miguel) The case used was a "recycled " case, and the knob and rotary switch were a quick and easy way to cover up a hole from a previous project. Alex   |
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Post by FritzS on Aug 15, 2009 7:19:07 GMT
PSU Photos (as requested by Miguel) The case used was a "recycled " case, and the knob and rotary switch were a quick and easy way to cover up a hole from a previous project. Alex wherefrom did you get all this nice cases I want some but not expensive ....... |
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Post by Deleted on Aug 15, 2009 7:36:58 GMT
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Will
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Post by Will on Aug 20, 2009 11:34:53 GMT
Alex,
A really nice, tidy build there. You must have had some practice!
How about some of you other chaps? How are your builds going?
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Post by Deleted on Aug 24, 2009 3:30:02 GMT
OFFSET CORRECTOR.
I used AD744 because I had them at the time, and they have quite a low DC offset.
TL071 will work in this application, but they are likely to result in a higher DC offset from the preamp, unless trimmed with the typical 10K trimpot between pins 1 and 5, and the centre of the trimpot going to the -VE rail. The LF411 should be a better choice in this application, and is available from places like Futurlec for as low as US$1.30 each. (2 will be required.)
Alex
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Will
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Post by Will on Sept 6, 2009 9:45:00 GMT
A little update. JLH boards installed, wiring tidied up.    I've also installed an orange led for power on indication, which has just enough current flowing to light it up, giving a nice light without casting shadows 3 miles away! I've also backlit the volume knob with two leds of the same colour. Again, just enough to give a subtle orange outline. It doesn'y come out in photos, but I can assure you it's not garsih. It's sounding very good at the moment, but more impressions soon. |
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Post by Deleted on Sept 6, 2009 10:10:21 GMT
Will
Don't forget to redo the balance of the front end after the cover is placed on top and the unit reached normal operating temperature. There is unlikely to be a major difference in the reading, but the tighter setting is normally a little better sounding.
Alex
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Post by Spirit on Sept 6, 2009 10:15:31 GMT
Looking good Will! Is that one of the Galaxy cases? I like the idea of a backlit volume control... was going to do a similar thing on my scha build but couldn't think how to do it well. Would love a photo of the front, with 'illumination' activated ;D [even if you have to turn the [other] lights off  ] She can come out of the cupboard now... it's almost Monday here |
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, I thought that I would clarify the layout of this board.
. 
and It sounds very good, but know it'll be stunning with the JLH's.
The transformers are bolted to the case, which also help dissipate any heat (not much). Mains is wired as per the SCHA, except I've plonked a X2 cap across the mains main, and have ferrites on the mains wiring. The cables supply the AC to the main amp. 
]