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Post by Deleted on May 6, 2011 23:36:14 GMT
Lark Most attenuators like the Valab are broadly based on the DACT CT2. Like Miguel, I don't normally listen at high levels, and I used mine with a gain of 2 which is adequate for most sources like CD, DVD etc. With a 50K attenuator, the setting would normally only be around 2Kohms from "wiper"to earth for my typical listeniing level. My ears prefer proper dynamics that don't overload the ears with a continuous high compressed level, and the peaks are REAL peaks where the producer intended them to be real peaks. A proper uncompressed dynamic range is not normally fatigueing with long listening sessions. Alex www.dact.com/html/ac_calculator.html
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Post by lark on May 7, 2011 0:42:27 GMT
Alex, I only have a lay understanding of electronics so I'm not exactly sure what you mean. Are you saying that these attenuators will provide enough control at low volumes? If so, that's good enough for me I'm also having trouble finding any images of the JHL ripple eater PCB layout - there may have been one in your SCHA tweaks page, but it seems that image shack has removed it. Is there a thread around with the images and schematic using the parts you suggest? (I'm going to try and get the components today and think I will need some PCB layout images to assemble it..)... Cheers, Lark
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Post by lark on May 7, 2011 0:46:07 GMT
I have the 50k log valab in my scha. Obviously I can only speak from my own personal experience but I find the first half of the rotation pretty useless, I like it loud! Ah, ok, that sounds good to me, seems like it will have enough control a low volumes..
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Post by Deleted on May 7, 2011 2:55:59 GMT
Lark Have a look at Greg Erskine's website. users.tpg.com.au/gerskine/greg/default.htmClick on Power Supplies, then click on JLH at the top of the choices. As the SC HA isn't using the Current Limiter on this occasion, I would recommend using 4 x 4,700uF 10V Low ESR electros from Jaycar. Just remember that they will need a minimum of 48 hours on them before the SQ stabilises. At one point in the electro forming cycle, it may even sound like something is very wrong. . Alex P.S. Putting a JLH in line with the PSU will give an apparent increase in dynamic range, as well as better low level detail and a more powerful and clean sounding low end.
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Post by lark on May 7, 2011 11:02:05 GMT
Alex,
I picked up the parts for the JLH today but grabbed "green cap" polyesters for the 4 x 1.5uF 63V caps.. Are these appropriate or should I get something better?
This is to replace the 4 x 2,200uF caps on the JLH?
Lark.
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Post by Deleted on May 7, 2011 12:19:26 GMT
Alex, I picked up the parts for the JLH today but grabbed "green cap" polyesters for the 4 x 1.5yF 63V caps.. Are these appropriate or should I get something better? This is to replace the 4 x 2,200uF caps on the JLH? Lark. Lark The caps will be O.K. as long as they aren't physically too large. IIRC, the hole spacing is 5mm and 7.5mm (?) I am told that the 2 x4,700uF per supply rail improve the bottom end a little more again. I can't prise the original HA off my son to try it ! Alrx
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Post by jeffc on May 9, 2011 11:10:56 GMT
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Post by lark on May 9, 2011 13:47:48 GMT
Thanks jeffc,
I did already get one of the Valab ones, but I need to replace one in another HA so I'll grab one of these and compare them..
Cheers.
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Post by ninkasi on Nov 24, 2011 12:31:24 GMT
Sorry to pull up an old thread, but just wanted to know if anyone happens to have a spare kit (or 2) that they haven't started and can part with. Just getting started in this and wanted to learn on this kit, but alas, Jaycar no longer sells them. So this is a long shot, but can do cash locally, bsb transfer, or paypal.
Cheers, Ryan
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Post by ninkasi on Nov 26, 2011 15:03:11 GMT
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Post by punkjr on Feb 5, 2013 10:13:58 GMT
Hi
Keeping this old thread moving right along.....
I've just bought a set of Audeze LCD-2's. they are 60ohm cans with a sensitivity of 90db/1mW. I'm now concerned that the SCHA won't be able to drive these cans. According to their website, they say the following:
"Lets us say you listen to symphony-orchestra. This type of music can have dynamic range of 60 dB. i.e if silence (room noise) is at 60 dB (LCD-2 is pen type headphone design with almost no attenuation of ambient noise) and the maximum occasional peak needs to be 120 dB. I am just giving an example here, but depending upon the type of music and the recording this varies. 120 dB is very loud - almost Rock Concert level close to the speaker.
For the LCD-2, if you put 1 mw of power, you get about 90dB output. For this example, let us assume 90dB is the level you listen normally. To reproduce the occasional 120 dB peak without clipping on the LCD-2, the amplifier would have to output 1000 times more power than 1mw, i.e 1 W.
So, an amplifier that can output 1w is the bare minimum. Amplifiers will have distortion metrics at different wattage levels. If an amp can output maximum 1w it would be barely sufficient and might have a lot of distortion at full output."
I checked the specs on the SCHA according to Silicon Chip article, and the output seems to be much lower. Has anyone tried this combo?
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Post by Deleted on Feb 5, 2013 11:21:43 GMT
Hi You don't need levels anywhere near as high as quoted when the sound is directly coupled to your ears. Listen at levels like that for more than a couple of minutes a day and you will first get tinnitus ( ringing in the ears) followed by permanent hearing loss. The strappable diodes in this anmplifier are actually there to help prevent the risk of hearing damage when using 8 ohm headphones. If you lived in the E.U. your headphone amplifiers are reduced in power by legislation for the same reasons. Ir's designed to protect people from their own stupidity. Alex
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Post by punkjr on Feb 6, 2013 3:14:19 GMT
Thanks Alex. I received the LCD's today and plugged them in(I've read there is a long burn in with these, as well as the Schiit Bifrost that also came today). With the HD600's, the volume was just right. I'm using digital volume control in JRiver, and for nearly all of my albums, I play at 100% volume, or attenuate by about 5-10dB. I immediately noticed with the LCD's that the music that I was attenuating is now just load enough, maybe not quite, and the other tracks aren't nearly loud enough. Can I mod my amp to get more volume?
I know it won't make a difference to the volume, but I am also running the 20Va tranny in this rig. There has been a lot of discussion in this thread on the 20Va vs the 30Va. Is there any conclusion that has been reached as to whether the 30Va will give anything extra re. dynamics....?
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Post by Deleted on Feb 6, 2013 4:14:41 GMT
Try changing R1 and R4 from 1Kohm to 2.2K or even 3.3Kohms. When using a JLH, it shouldn't make any difference when using a 20VA transformer, as it is only used for the headphone amplifier section, whereas the original 30VA was also supplying the rest of the preamplifier, including a substantial load on a +5V supply for a motorised potentiometer and relays. Regards Alex
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Post by punkjr on Feb 7, 2013 1:23:15 GMT
Hey thanks Alex. So I have a pack of 2K2 % mini 0.5w, and I have the same in a 2K7. Are either of these suitable?
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Post by Deleted on Feb 7, 2013 2:21:17 GMT
Hey thanks Alex. So I have a pack of 2K2 % mini 0.5w, and I have the same in a 2K7. Are either of these suitable? Yes, either will be suitable. They will only give a small lift though. Going higher will further lift the gain, but will also give a small decrease in SQ. Regards Alex
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Post by punkjr on Feb 7, 2013 2:24:54 GMT
what about the 47 ohm resistors that you say to "adjust to suit headphones"? Is it worth changing these? My Senny's were 300ohm, these are 60ohm cans.
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Post by Deleted on Feb 7, 2013 2:58:33 GMT
what about the 47 ohm resistors that you say to "adjust to suit headphones"? Is it worth changing these? My Senny's were 300ohm, these are 60ohm cans. Decreasing that value further will give a smidgin more volume, but is likely to increase perceived HF detail and perhaps make them sound fatigueing to listen to. Conversely, if the treble is a little too hot and tiring , increasing that value will help tame that a little while giving the appearance of an improved low end. Regards Alex
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Post by punkjr on Feb 7, 2013 3:57:17 GMT
Okay, thanks AK, I'll try your suggested mods initially.
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Post by punkjr on Feb 7, 2013 12:33:16 GMT
I put the 2k7 resistors in and it has made the difference in sound usable now. Much obliged.
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Post by bluerob on Mar 6, 2013 20:09:38 GMT
Hellow Chaps! I know I´m late for this train, very very late LOL! I just could not resist to buy a new and unassembled Jaycar kit that I found on Ebay (amp kit+KC5418) It was so dirty inexpensive that I jumped right in, then found this thread while googleing and men! now I´m exited...well..after reading the 92 pages(well not all but most of it) of the thread my eyes and brain hurt plus I think one of my kidneys is falling but I´m exited! PMSL. I started taking some notes of the "must do" mods but TBH now I am confused an quite lost, It seems there are several and each with different options plus I see that the project took several different roads at some point or at least is what I recall from the extensive read. I was hopping someone around could provide me with a summarized version of the actions to take....my kit is on its way so I have a few days to plan, gather the necessary goods and heat up the soldering iron BTW I haven't searched for a compassion between this amp and the O2 and/or Panda (which I saw a thread around here)... someone around has done a comparison yet? Thanks! Rob.
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Post by Deleted on Mar 6, 2013 20:43:54 GMT
Hi Rob The bulk of the information is shown in pages 1 and 2 of this thread rockgrotto.proboards.com/thread/3622/silicon-chip-headphone-amp-tweaks?page=1#page=1Robert's version was quite different, and unique , as it used even higher voltage for the output stage. This modified HA was among the best available at the time with around 160 constructed, and should still be good value for money. For best results you will also need the JLH PCB as mentioned in the JLH Group Buy thread. If you are lucky, one of those who ordered some may not reply and a few will become available again. I suggest you keep an eye on the thread, or send Jon Clancy a PM. Regards Alex
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Post by bluerob on Mar 7, 2013 0:22:26 GMT
Hi Rob The bulk of the information is shown in pages 1 and 2 of this thread rockgrotto.proboards.com/thread/3622/silicon-chip-headphone-amp-tweaks?page=1#page=1Robert's version was quite different, and unique , as it used even higher voltage for the output stage. This modified HA was among the best available at the time with around 160 constructed, and should still be good value for money. For best results you will also need the JLH PCB as mentioned in the JLH Group Buy thread. If you are lucky, one of those who ordered some may not reply and a few will become available again. I suggest you keep an eye on the thread, or send Jon Clancy a PM. Regards Alex Thanks Alex! I went through the tweak´s first pages, what I got is that there are...lets call it 3 "main" approaches for the amp, one yours which the las rev. is from 2008-10-20, most images uploaded by yourself are still active and gives me a clear idea of the complete process. On the other hand a second approach to the amp is that one from "robertkd" which at some point uploaded some pdf´s that seem to be offline. The third main design mod is the one from David Gilmour, no no sorry Roger Waters no no sorry Pink Floyd! which seems rather complex and scattered all over the 92 pages of the "original" thread...I dont recall a summary of some sort from him ?¿ I saw the JLH ripple eater added to most of builds, excuse my ignorance but that is what is called a "shunt regulator" by any chance or are two different things? BTW can you point out the JLH pcb group buy thread, please I dont seem to find it around here... :/ By any chance do you have a copy of robertkd´s PDF....I was going to send him a PM but I noticed he has not been active for several months. Cheers! Rob.
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jonclancy
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Post by jonclancy on Aug 26, 2013 11:46:15 GMT
Just to bump and old thread, I'm going through my "room", er bombsite, and found my old Jaycar amp. Unboxed, but built up and sporting a metal can LM4562. You know what, I might get all the old amps fired up when I get my room finished - just for old time's sake. All of them were no slouch, but I do recall that the modded SCHA had the edge over the CK2III.
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