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Post by asclepius on Jan 30, 2016 17:14:57 GMT
Sorry, drip feed of info - I appreciate that this may be unhelpful. Some sources are fine, some esp a USB DAC create the problem. All OK into other amps. Ring any bells? Thanks Mark
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Deleted
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Post by Deleted on Jan 30, 2016 20:45:12 GMT
Which I.C. did they supply with the kit ?
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Post by asclepius on Jan 30, 2016 21:01:38 GMT
Thanks. Standard 353. I've got a couple of 627BPs on order and an adaptor. I don't know whether my ears are up to telling the difference, but maybe I'll convince myself! Might that affect this specific issue as well as overall sound quality? Regards, Mark
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Post by PinkFloyd on Jan 30, 2016 21:57:23 GMT
Thanks. Standard 353. I've got a couple of 627BPs on order and an adaptor. I don't know whether my ears are up to telling the difference, but maybe I'll convince myself! Might that affect this specific issue as well as overall sound quality? Regards, Mark Your ears will soon tell us if you noticed an improvement in SQ........ we await your findings..... Mike.
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Deleted
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Post by Deleted on Jan 30, 2016 22:11:41 GMT
The old LF353 is FAR from the quietest opamp available these days.
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Post by PinkFloyd on Jan 30, 2016 22:18:54 GMT
A good starting point is the OPA 2134..... take it from there
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Post by PinkFloyd on Jan 30, 2016 22:35:51 GMT
Man..... that was a nice amp
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Post by asclepius on Jan 31, 2016 9:04:11 GMT
Thanks everyone, I'll certainly report back. But any ideas on the specific question of some sources causing crackling when (a) others don't and (b) those noisy sources aren't noisy into other amps? And noisy on both channels irrespective of which channel the source is connected to! Cheers, Mark
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Post by freddypipsqueek on Feb 2, 2016 19:13:32 GMT
Open the top - take a photo - and post it here.
The last time i had something like that it was an Op amp failure but there can be various other reasons.
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Post by asclepius on Feb 3, 2016 18:53:00 GMT
Here it is - looks to me exactly like all the pictures of how it's meant to look like. Update - I've now upgraded to two 627BPs on a Lucid Technologies adaptor. It IS better sound quality - but no change to the noise. The offenders, now that I've done more testing, are two DAC, or rather a USB DAC and an on board sound card, fed from my silent fanless VIA PC running Daphile. I would just blame that, except that both the native audio and the DAC (Arcam rDAC) are silent into other amps. But the rDAC is fine with the Chiara when fed from my laptop! I can detect no DC offset on any input to the Chiara. 1.1mV only at the output when fed by one of the "silent" sources, 30mV when fed by noisy source. A mystery.
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Post by asclepius on Feb 3, 2016 18:54:48 GMT
Sorry to be thick - how do I upload a photograph? I assumed it was the IMG button
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jc
Fully Modded
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Post by jc on Feb 3, 2016 19:17:13 GMT
You need to use a an online hosting site, such as photobucket, flickr etc. Upload your photos there and grab an "image" code (choice of the full image, thumbnail, social media etc) for any particular piccy, then paste that directly here or use the image function (depending on host).
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Deleted
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Post by Deleted on Feb 3, 2016 20:58:26 GMT
Those measurements suggest that the source has either a high output impedance, or more likely from an output coupling capacitor in the source. You could try something like a 10K resistor across each of it's RCA output sockets to see if it helps.
Alex
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Post by asclepius on Feb 3, 2016 21:17:40 GMT
I'll try it - thanks - but three different sources, a DAB tuner, a sound card, and a USB DAC all exactly the same, and all absolutely fine into other amps? Bit odd? Could there be any other characteristic of the source signal that could be perturbing it? 44.1 kHz interference? It's only from digital sources...
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Deleted
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Post by Deleted on Feb 4, 2016 0:22:13 GMT
I'll try it - thanks - but three different sources, a DAB tuner, a sound card, and a USB DAC all exactly the same, and all absolutely fine into other amps? Bit odd? Could there be any other characteristic of the source signal that could be perturbing it? 44.1 kHz interference? It's only from digital sources... I am more concerned about the much higher DC out with some sources. Can you post a copy of the schematic, as the original design used input coupling capacitors ,which would prevent this from happening. A lower input impedance may help to get rid of the problem, and may even be able to be implemented in the amplifier itself.
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Post by asclepius on Feb 6, 2016 9:19:58 GMT
Thanks everyone for suggestions. I've got a bit of a work deadline problem and am not going to be able to do much this weekend, but will get back to you ASAP. The delay is not ingratitude! Mark
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Post by JamesFeline on Feb 8, 2016 14:47:43 GMT
Hello .. just noticed some of my old picture links are not working, I will try and sort this out
regards
Nick
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Post by asclepius on Feb 8, 2016 14:55:53 GMT
How kind - thanks. Mark
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Post by asclepius on Feb 21, 2016 19:50:31 GMT
Another question - has anyone got any information about the Audiophile power supply? Can I use one of the other outputs to power a low power PC? What is the rated output? Will it cause a problem to use +15v only, rather than -15 and +15? Thanks Mark
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Deleted
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Post by Deleted on Feb 21, 2016 21:06:30 GMT
The Chiara shouldn't need more than a 30VA transformer. A PSU of this rating is far too low in current capabilities to power even the most modest of low power PCs. Most low power PC PSUs need to have at least a 100 Watts rated PSU when using a Linear PSU. That means that if you only need say a single high current +15V supply rail , with the motherboard creating the other needed voltages with it's onboard voltage regulators, you would more than likely need a PSU with > 5A capability. Even though the voltage regulators on the Andante PSU use voltage regulators rated at 1A ,(7815 ? ) the amount of heatsinking used means that any continuous current draw of more than 0.5A would cause them to get way too hot, and probably fail.
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Post by asclepius on Feb 21, 2016 21:13:36 GMT
Thank you. I'll forget that idea, then!
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Post by garyh on May 12, 2016 13:15:20 GMT
Hold on to your hats guys, Mike's amazing sounding (and looking) JLH - Chiara headphone amp from this thread is now up for sale !!!Used as part of a desktop system (with a Cyrus CD7Q) at my work. Sadly my new Dev manager doesn't approve of hi-fi kit on our desks so it has to find a new home. My loss is your gain £400 + insured P&P
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Post by garyh on Sept 25, 2016 20:45:50 GMT
No interest guys?
Too much?
Ok, £300
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Post by freddypipsqueek on Nov 11, 2019 23:32:49 GMT
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pingu
Been here a while!
Reallising what has been taken on with the GB
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Post by pingu on Nov 12, 2019 1:48:38 GMT
Ha ha I have one of these Freddy. Built the kit years ago. Taken out the balance pot, improved the caps and used various op amps in it. In fact it was either you or Mike that sent me a sun or moon long ago and still works well.
Yes anyone wants a very good quality HA well worth a punt and an iconic bit of British audio history to boot
Nice one Freddy All the best Martin
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