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Post by Deleted on Apr 7, 2009 11:55:16 GMT
With the mains turned off (serious answer? haha)
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robertkd
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Post by robertkd on Apr 7, 2009 12:58:39 GMT
With the mains turned off (serious answer? haha) no sense of adventure
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Spirit
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Post by Spirit on Apr 7, 2009 13:32:28 GMT
helping to avoid scratching furniture Yeah... when the hardware store has some 3mm (instead of 1/8th...) countersunk screws back in stock... then I'll replace all the external screws... As it stands currently (ho ho), they protrude *just* further than the feet With the mains turned off (serious answer? haha)
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Spirit
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Post by Spirit on Apr 8, 2009 11:54:45 GMT
It's done Mostly... ;D Needs a rewire with some longer wires for some stuff so I can open the case up again easily... and will touch up the Robert-style flower heatsink for the 4562HA so the petals flare out more... UV led looks great (It goes without saying it sounds *%$#ing amazing ;D)
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Post by Deleted on Apr 8, 2009 12:06:38 GMT
It's done Mostly... ;D Needs a rewire with some longer wires for some stuff so I can open the case up again easily... and will touch up the Robert-style flower heatsink for the 4562HA so the petals flare out more... UV led looks great (It goes without saying it sounds *%$#ing amazing ;D) Phil Just wait until the LM4562HA,( kindly sourced for members by Robert,and with a few still available) settles in over the next 24-48 hours ! Hey, you might even be able to hear the difference between those files, identical checksums notwithstanding. Alex P.S. Nice work, and no major dramas either. ;D
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Spirit
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Post by Spirit on Apr 8, 2009 12:26:31 GMT
P.S. Nice work, and no major dramas either. ;D This is because there were many photos... and "monkey see, monkey do" ;D
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robertkd
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Post by robertkd on Apr 8, 2009 12:26:53 GMT
well done Spirit,.. I guess it's in the next few days you will likely get to the point of "I didn't realise that was in the recording" As for the wiring I try to cable to a PCB in such a way as to allow it to flip over easily which allows you to work on it easily for repairs if needed or easy mods ;D Robert
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Will
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Post by Will on Apr 8, 2009 19:25:52 GMT
Phil,
Sounds like you've been having great fun.
But we really do need to see pictures, it'll be nice to see another addition to the RG SCHA family!
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Spirit
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Post by Spirit on Apr 8, 2009 21:16:49 GMT
But we really do need to see pictures, it'll be nice to see another addition to the RG SCHA family! All in good time Will, all in good time... Ie when it's ready to be photographed... ;D
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Post by johnmclean on Jun 10, 2009 4:14:19 GMT
Quick question, sorry to butt in, how does this amp perform with low impedance headphones. Can someone give me examples?
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Post by Deleted on Jun 10, 2009 4:29:21 GMT
John
How low an impedance are you talking about, and which version ? The original Jaycar kit was suitable for even 8 ohm headphones, but with different diodes installed to limit hearing damage due to excess power.My version is quite happy with 30 ohm headphones and upwards. I haven't tried lower than that . Alex
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Post by johnmclean on Jun 10, 2009 5:31:22 GMT
Hey sandyk how are you going? Are you coming along to the meet at Nicks place on the 5th July? Look forward to seeing you there if your coming I’m in the process of selling this amp the headphones the buyer has are the ATH-AD any ideas in regards to the impedance, will there be a problem? About 32 ohms I believe.
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Post by Deleted on Jun 10, 2009 5:37:49 GMT
John Provide that the grandchildren don't lay me low with another lousy schoolground winter virus, I hope to be there. 32 ohms will be no problem,as my Sony headphones are from memory, 32 ohms. In any case, to get a little extra drive, alll you need to do is replace the 68 ohm output resistors with a lower value such as 56, or even 47 ohms. Alex
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Post by johnmclean on Jun 10, 2009 5:59:07 GMT
Cheers, thanks for your help.
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Post by elliot42 on Jun 10, 2009 7:39:15 GMT
John, just reinforcing what sandyk has said. I use my amp (with all of your mods, sandyk) with both AD900 and MS2i, no problems with either and it really sounds great.
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robertkd
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Post by robertkd on Jun 10, 2009 9:02:20 GMT
whilst I have retained the low output impedance and slightly different mods,
however I have for testing purposes I have run the amplifier with 11R per channel (parallel 22R's) with no difference in distortion measurements* or other problems at all.
*with either 2SC5171/2SA1930 OR 2SB649/2SD669 output transistors @ ~45ma bias
Robert
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Post by johnmclean on Jun 13, 2009 7:51:32 GMT
John, just reinforcing what sandyk has said. I use my amp (with all of your mods, sandyk) with both AD900 and MS2i, no problems with either and it really sounds great. Thanks Elliott, glad your enjoying your build - haven’t seen pics yet Sandyk, I’m about to build another amp, Penrith Jaycar still only have the older yellow pcbs. Were’s the best place to source for the newer nice looking green pcbs?
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Post by Deleted on Jun 13, 2009 8:21:50 GMT
John, just reinforcing what sandyk has said. I use my amp (with all of your mods, sandyk) with both AD900 and MS2i, no problems with either and it really sounds great. Thanks Elliott, glad your enjoying your build - haven’t seen pics yet Sandyk, I’m about to build another amp, Penrith Jaycar still only have the older yellow pcbs. Were’s the best place to source for the newer nice looking green pcbs? John Altronics, or you will need to search for Jaycar stores that have new stock. Alex
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Post by Deleted on Jun 13, 2009 15:41:02 GMT
I've spent a bit of time adding the balance of main modifications to my SCHA (Alex version). Removal of resistance selector, instalation of permenant 68Rs on the board. Increased the gain resitors, just a little from 1k to 1k5, this gave the little extra volume for low level recordings I wanted. Cap across the +/- input of PSU = audible improvement, a tad more clarity HFE matched BC560C/550C on JLH = errr, no, I couldn't hear any difference at all, but maybe it helps comulatively. Big muvva caps on signal input of amp board = Definite improvement, more clarity again plus a touch of smothness. Shorting links on the above caps = Wasn't sure to start with, I had to undo/redo several times before leaving them on by preference. I think the difference is quieter silences. Stepped attenuator (SMD vsn.) = An opening-up of the music in general, makes for better/easier flow. I then re-tried the different opamps I had available, from the 2134 used in testing. 4562 = more of everything! TL072 = Yuk, really nasty in comparison, dead sounding. SunV2 = Beautiful thing! Openess, detail, smoothness, speed and well balanced, nothing out of place. 4562HA = A surprise here, before the obove mods I prefered the Sun on balance. However, post mods the HA seems to build on everything the Sun does, it can still be a bit cruel to poor recordings but what the hell! Plus that lovely bass is irresistable. Collectively, all the above are a resounding success, so thanks to all involved for the work and sharing of info. Piccy of SCHA in mad professor mode.
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Post by Deleted on Jun 13, 2009 21:36:47 GMT
Chris Did you also add the 2K7 collector resistor, which is part of that modification ?
I presume that you mean the 470pf 100V capacitor across the outer terminals of the AC input from the transformer's secondary windings ?
Alex
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Post by Deleted on Jun 13, 2009 22:02:31 GMT
Chris Did you also add the 2K7 collector resistor, which is part of that modification ? I presume that you mean the 470pf 100V capacitor across the outer terminals of the AC input from the transformer's secondary windings ? Alex The 2k7, yes, I had already popped those in the previous time I had the box open. The cap, yes, that one
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Post by loupy31 on Aug 5, 2009 12:41:24 GMT
Hi Everyone I am new on this forum and new to modding audio kits, Ok, I have purchased this jaycar kit and its power supply kit, As money is tight, I am only able to do a few mods at a time, As I get paid monthly, So that being said, what would be the best few mods to start with. Regards Peter
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robertkd
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Electronics Engineer from sunny Queensland
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Post by robertkd on Aug 5, 2009 13:09:54 GMT
Hi Everyone I am new on this forum and new to modding audio kits, Ok, I have purchased this jaycar kit and its power supply kit, As money is tight, I am only able to do a few mods at a time, As I get paid monthly, So that being said, what would be the best few mods to start with. Regards Peter Hi Peter, interesting question, depends what your looking for, there are many mods as you may have discovered on this very thread ;D the best bang for buck depends how adventuress you are, for me decoupling the opamp and providing good decoupling on the output transistors is important, as is tidying up the input and feedback arrangement as well. this applies to pretty much any design,... decoupling opamp upgrade replacement of input coupling capacitors input and feedback arrangement output transistor upgrade for starters Robert
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Post by PinkFloyd on Aug 5, 2009 21:10:14 GMT
Hi Everyone I am new on this forum and new to modding audio kits, Ok, I have purchased this jaycar kit and its power supply kit, As money is tight, I am only able to do a few mods at a time, As I get paid monthly, So that being said, what would be the best few mods to start with. Regards Peter Numero uno "mod" would be the opamp, simply a case of plugging in an opamp of your choice. The stock 2134 is actually pretty good but you will get better results with the likes of LM4562, OPA2107 etc. The JLH is a worthwhile addition. A class X2 suppression cap fitted across L/N and a 275V MOV varistor across L/N is another thing you can do, you can also fit a class Y2 cap from L to earth and from L to earth. The 10uF output caps...... either lose them altogether or fit quality non polars (Black gate / Nichicon MUSE etc.) here.... you can also fit film caps here but 10uF film caps are BIG and, IMO, not worth the effort / cost. There is PLENTY of tweaking info here mate, you'll just have to search for it. Mike.
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Post by Deleted on Aug 5, 2009 21:17:13 GMT
Peter My suggestion would be to build it in it's original form as published by Silicon Chip magazine, and live with it for at least a couple of weeks before considering the next step. If you have a DMM/multimeter, you could initially check that the equipment that will be supplying the signal has no more than a couple of millivolts DC at it's output. If that is the case , you can then short out the input capacitor with a blob of solder between the capacitor's input pads under the PCB,as the pads are quite close together. You are able to do this because the I.C. specified is a JFET type, and not a bipolar type. Alex P.S. The Silicon Chip Headphone Amp Tweaks thread is a good place to start. I would suggest that first off you remove the Power Supply PCB components as shown with yellow dots in the included drawing, as they were only needed for use with the main SC Studio Series Preamplifier project. The PCB will run cooler without them, and have a little more power in reserve. rockgrotto.proboards.com/index.cgi?board=chitchat&action=display&thread=3622&page=1Whereabouts Downunder are you located ?
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