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Post by Deleted on Sept 15, 2011 19:18:43 GMT
Your guy has done a real neat job Dave. Have you any listening impressions yet? Syd Hi Syd, Frans and other readers, I told Frans at the time I ordered the bits that the main reason I was ordering it was because I was a big fan of his work and I didn't think he'd put anything out there that he wasn't happy with, and if he was happy I was fairly certain I was going to be ecstatic. I've never been so right!!! . Straight out of the box, powered up but with no input I had to turn the volume knob round to 3 o'clock before I picked up the slightest buzz. The full range of the volume knob is from 6-30 to 4-30 (both being pm of course ;D ;D ), so around 75% volume before any extraneous noise and even then only just audible. Normal listening for me (currently) is 9-00, to give you some idea. The phones I'm using are my current favourite ones, the Superlux 661s, so if Frans wants to extend his expertise to a numptie I'd appreciate his opinion on what to set the various jumprs at, or any other adjustments he thinks might improve anything. And why is it so good? I'm no audiophile but, as is probably apparent from the above, the noise floor is non existant at my normal listening levels, by which I mean its inky black and effectively not there, if you understand. Everything is crystal clear without being glassy or harsh - I've not noticed any harshness anywhere, smooth as silk is more the case. The first track that my random selector threw at me was a 1960s pop song that I'm very familiar with, the star male vocalist doing his stuff with a mixed chorus in the background. I must have heard this song thousands of times through the ages and this is the first time I can recall hearing and understanding the words the chorus were singing, well below the volume of the main vocals, but at the same time in the background. While I've been typing this a couple of tracks have played with a thumping bass line and it sounds quite taut as far down as it's gone. The upper end sounds fine to me but I don't think I've played anything to really test that end. Another thing I seem to be sensitive to is the reverberation of stringed instruments, hanging in the air as they decay away, and I can't fault the performance in that area either - probably the best I've heard on phones . I'm not backing away from anything I've written but do bear in mind this is based on the first 30 minutes listening straight out of the box. Just now listening to a track of heavy rock (heavy by my tastes at least ) and there are two lectronic guitars playing in tandem and I can clearly hear them separately. I can confirm that the 661s are fairly thoroughly run in, having been on virtually 24/7 since arrival some time ago, connected to the HP outlet on my Logitech Touch. Any questions, you know where I am. Dave.
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Post by Deleted on Sept 15, 2011 19:34:22 GMT
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Post by Deleted on Sept 15, 2011 21:11:00 GMT
That's a real neat setup Dave, very practical. I have no doubt that a lot people can hear differences with every change, others less so. I suspect if you never get to hear a twin traffo setup you'll be very happy. It'll be good to hear Frans thoughts as its his design. I just like to know I've done all I can to maximise performance, some things I hear quite a difference, other times not. I am convinced power supply is a major influence. Edit: Just noticed Frans says TWO in capital letters in the manual! Syd Hi Syd and Javier Frans has provided the ability to use dual transformers for the subjectivists among us. Alex
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Post by Deleted on Sept 15, 2011 21:31:04 GMT
You you ;D Syd
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Post by Deleted on Sept 15, 2011 21:52:14 GMT
I'll keep an eye on progress but don't know if I could live with one black case amongst my collection of silver equipment!
I'm sort of weakening to the idea of the Chinese case again. It might be possble to rub down and re-laquer the front if it does arrive damaged. My suppplier of the most recent was David Louis (made up I suspect) Other stuff I bought was fine, I think he changed his trading name since. I half suspect the two you have posted are one and the same party.
Syd
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Post by Deleted on Sept 16, 2011 8:50:26 GMT
I'll keep an eye on progress but don't know if I could live with one black case amongst my collection of silver equipment! I don't think ordering some black some silver should be any problem but until asked we won't know the answer. I half suspect the two you have posted are one and the same party. I don't know, one of them says he is Hong Kong based the other says he is based in mainland China. Pictures of the cases are obviously made on the same cloth, just different angle.
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Post by Deleted on Sept 17, 2011 13:55:51 GMT
Hi all,, Last night I added the couple of jumpers to match the impdance (at 65) to my 661s (at 68). It has improved the SQ but I would not say it was a night and day change. Has anyone else changed anything and noticed any difference? Dave.
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Post by Deleted on Sept 17, 2011 20:21:54 GMT
Hi Dave, if you read the first pages of the manual you'll see that the amp's output Z does not have to be matched to the HP's Z, thats a video thing not out audio. I've read that most lower Z cans sound best when driven from low out Z amps but I'm no expert. For the 661 you could try 10 or even lower, they sound quice nice driven by the big Neco. At the moment I'm so pleased with the CHAmp at: - 100 Ohm - lowest gain - DC coupled - BW-0 driving my 501 and 601 that I'm having a hard time to try other things. I've had brief sessions with all the headphones I have at this moment (661, 681B. HD250 Linear II, 501 and 601) but I end up changing quickly to either of the AKGs. Boy, this amp even without a case is bl*ody Fanstastic! Tomorrow if I find some free time I'll try to compare it to my modded X-Cans, the Frans/Mick modded Miri and the big and small Necos (which one's which? Mosfet/Bosfet ).
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Post by Deleted on Sept 17, 2011 21:40:58 GMT
Hi Dave, if you read the first pages of the manual you'll see that the amp's output Z does not have to be matched to the HP's Z, thats a video thing not out audio. Hi Javier (and whatever goes with "Buenos" to say 'Good Evening' in Spanish - sorry, but when I was 'selling' around Europe I could say Good Morning, Good Day and Good Evening in many of the main European languages but, having been retired 6 years, if you don't use it you lose it ) Anyway, yes you're right - my quick read led me to believe that the idea of a configurable amp was to enable you to match the impedance of the amp to that of the phones but (now you've pointed it out), I can clearly see that that is not the case, so I'll do some more jumper rolling. Thanks again. BTW it's nice to have friends to help you to get the best out of your kit without making you feel like a numptie ) Dave.
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Post by Deleted on Sept 17, 2011 22:17:41 GMT
Dave In general, increasing the value of the series output resistor will give the appearance of reducing the top end a little. Reducing the value of that resistor will in general, give the appearance of increased high treble. With the SC HA, (Jaycar) 68 ohms was a good general value.If the headphones meet the IEC specificastions, then 120 ohms is best. Alex
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Post by Deleted on Sept 17, 2011 22:39:51 GMT
Thanks Alex, I'll knock it up to 120 ohms tomorrow and see what I get and let you know. Meanwhile I'm listening (right now ) to it at 68 ohms through the 661 phones and I find it difficult to imagine it getting much better. Obviously my experience of such things is limited, which means I don't have much to compare it with . Dave.
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Post by Deleted on Sept 17, 2011 23:04:04 GMT
I'm still amazed of how much in the world of audio comes down to taste. In the world of video, my main hobby and 2nd job for the last 5 years, there are many well established standards that define how things should be done and how images should look like if you want an accurate picture. I'm amazed at the fact that it is impossible to listen to music as it was mixed and mastered beacuse there are no rules to comply to, just aproximations and personal liking.
Frans told me AKG designed at least some of their HPs according to IEC's 120 Ohm standard so thats what i use for the 501 and the 601. For the rest I guess one has to try and find what sounds best to one's ears though, as Alex says, impedance can be used to tweak the HP's sound even if they were not designed with a that value.
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XTRProf
Fully Modded
Pssst ! Got any spare capacitors ?
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Post by XTRProf on Sept 20, 2011 8:17:34 GMT
In the world of video, my main hobby and 2nd job for the last 5 years, there are many well established standards that define how things should be done and how images should look like if you want an accurate picture. So what do you have for your AV system at home. Care to share at my AV Network thread?
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Post by Deleted on Sept 20, 2011 9:08:49 GMT
Sure.
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Post by Deleted on Sept 24, 2011 21:18:02 GMT
Dave In general, increasing the value of the series output resistor will give the appearance of reducing the top end a little. Reducing the value of that resistor will in general, give the appearance of increased high treble. With the SC HA, (Jaycar) 68 ohms was a good general value.If the headphones meet the IEC specificastions, then 120 ohms is best. Alex Hi Alex, I have no idea whether the 661 phones meet the IEC specs (Frans ? ) but I upped the CH Amp's impedance to 100 ohms (seems to be the highest available?) and it has improved the SQ to my ears, so thanks for that. This combo is the best sound I've ever had from headphones - may not mean much but I'm very happy . Dave.
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Post by dicky on Nov 20, 2011 11:34:21 GMT
Hi Folks, I finally got my CHAmp in an enclosure so I thought I'd post some pictures: I'm very pleased with the finish and I'm looking forward to listening to it - I only spent a couple of hours listening to it in July! The case is a 230x230x80mm case from Modu (HiFi2000) - I needed this height to accommodate the attenuator. Thanks again to Frans for the PCB and fantastic instructions. Regards Dicky
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Post by Deleted on Nov 20, 2011 12:19:35 GMT
That's a real neat job Dicky. I'll really need to get a move on with mine, I've had a case sitting for weeks now.
You didn't fit an on/off switch?
Syd
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Post by dicky on Nov 20, 2011 12:51:33 GMT
Hi Syd, I wanted to keep the front panel simple - the on/off switch is built in to the fused IEC inlet:
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Post by Deleted on Nov 20, 2011 14:04:11 GMT
Very nice build. !
If the circuit is not grounded yet (perhaps it is via the outlet) you can use the grounding 'jumpers' (Hp5, JP6) on the PCB. Should 1 of those transformers ever give you trouble I have one spare lying around. 1 develloped a short so bought 2 others so I have 1 left.
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Post by dicky on Nov 20, 2011 14:15:59 GMT
Very nice build. ! If the circuit is not grounded yet (perhaps it is via the outlet) you can use the grounding 'jumpers' (Hp5, JP6) on the PCB. Should 1 of those transformers ever give you trouble I have one spare lying around. 1 develloped a short so bought 2 others so I have 1 left. Thanks, Frans. Does the circuit need to be grounded? The PCB stand-offs are connected to the mains earth. Are the pads therefore connected to earth? I don't hear any hum, hiss or any other anomalies - it is totally silent. What will happen if I don't connect JP5, JP6 to ground?
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Post by dicky on Nov 20, 2011 14:59:33 GMT
OK, so I found this in an earlier post relating to the grounding:
So, by connecting the 2 pads for JP5 and the 2 pads for JP6, this connects the PCB pads to the chassis via the stand-offs and no wires are needed to connect the PCB to ground?
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Post by Deleted on Nov 20, 2011 15:03:12 GMT
No it is not needed. Since you don't have any hum you can safely leave it this way.
To find out if grounding it is beneficial you can just short JP5 or JP6 with a small piece of wire or screwdriver. Also possible to place a 100k resistor on JP5 position. This way the audiocircuit is not hard grounded but leakage currents won't be able to build up a voltage inside.
use your ears to find out !
Not grounding the common?groundplane to the cabinet usually results in hum/strange noises when touching the cabinet or knobs but is not always the case. Perhaps it is already grounded via the outlet. Just measure Ohms resistance between the RCA shield and metal surface to find out.
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Post by dicky on Nov 20, 2011 15:21:54 GMT
Thanks, Frans. I've just checked the resistance from the RCA shield to ground and it is ~0.1 Ohm. The amplifier sounds good to me - absolutely no hiss or hum - and since I won't damage anything by not connecting the jumpers I will leave them un-connected. If any noise develops in the future I'll know what to do.
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Post by Deleted on Nov 20, 2011 16:28:04 GMT
I figured the circuit was already grounded (probably via the HP socket) as you stated it was silent. Leave it this way, connecting the ground via the jumpers is not needed as it appears to be grounded already !
Nice enclosure b.t.w.
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Post by dicky on Nov 20, 2011 16:48:05 GMT
Thanks Frans. I'm really very pleased with it.
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