Nigel
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Post by Nigel on Aug 9, 2007 16:37:25 GMT
Yes, they sound fantastic.
I will refrain from being too enthusiastic at this stage though.
Reasons being, when I first got the amp from you it had an AD823 fitted. I changed to a LM4562, initially thinking it sounded better - it didn't. Back to the AD823 then, DY2000 ceramic same thoughts back to the AD823. Then the DY2000 metal, same back to the AD823. With hindsight, I'm not convinced the metal version out performs the ceramic in the Heed.
I could live with any of the opamps though, none of them have sounded anything other than wonderful.
I can't write anything about opamps inside the CanAmp without a heads up to dc. He led the way, I'm simply following in his footsteps.
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Nigel
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Post by Nigel on Aug 9, 2007 16:38:25 GMT
Head fi takes ages to load or what.
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Post by PinkFloyd on Aug 9, 2007 16:49:16 GMT
I think I led the way with the AD823 ;D dc went one further and added a 20 onto it making 843 AD823AN is a good audio chip Nigel, I used to rave about it and sent Graham one over..... the Solo has been running AD823 ever since
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Post by PinkFloyd on Aug 9, 2007 16:50:39 GMT
Head fi takes ages to load or what. It's because there are thousands of people online all at the same time arguing about opamps and transformers
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Nigel
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Post by Nigel on Aug 9, 2007 16:52:47 GMT
Well dc did 'discover' the DY2000.
Hey, when I checked the AD843 on the RS link you sent, I'm sure there are two versions very similarly priced.
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Post by PinkFloyd on Aug 9, 2007 16:58:51 GMT
Well dc did 'discover' the DY2000. Hey, when I checked the AD843 on the RS link you sent, I'm sure there are two versions very similarly priced. There are a few versions will all sound exactly the same.
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leo
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Post by leo on Aug 9, 2007 17:00:41 GMT
AD843's have only been running a couple of hours, a quick listen and first impression is they have lots of midrange! seem very easy to listen to, no nasties yet Lets see how it goes after a good run in
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leo
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Post by leo on Aug 9, 2007 17:44:44 GMT
These buggers get warm! I measured the outputs and noticed some DC offset which is probably caused by a bit of oscillation using these in my Heed Clone so I moved the decoupling caps closer to the supply pins and also fitted that 100nf cap going to pin4 and 8 directly onto the pins, it seems to be behaving now
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Post by PinkFloyd on Aug 9, 2007 18:00:43 GMT
What about 2u2 and 0.1uF in parallel from both +Vs & -Vs to ground ?
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leo
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Post by leo on Aug 9, 2007 18:05:53 GMT
I'll give it a go Mike, she seems ok now, I first built it the same as the original Heed , I have some 5mm 3.3uf I can stick in there
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Post by PinkFloyd on Aug 9, 2007 18:06:36 GMT
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leo
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Post by leo on Aug 9, 2007 18:21:06 GMT
Thanks Mike, well it runs fine now so must have been oscillation, crank the pot to zero and DC shot up to 300mV! luckily I test stuff before plugging the phones in Going fullrange with the pot and everything is ok now
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Post by PinkFloyd on Aug 9, 2007 19:27:51 GMT
Your 'phones would withstand 300mV no problems Was it 300mV on both channels? +/- ?
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leo
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Post by leo on Aug 9, 2007 20:16:56 GMT
Your 'phones would withstand 300mV no problems Was it 300mV on both channels? +/- ? Yes, it was both channels Mike, around 0.6mV right and 0.4mV left now, it varys a little.
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Post by PinkFloyd on Aug 9, 2007 21:02:03 GMT
Your 'phones would withstand 300mV no problems Was it 300mV on both channels? +/- ? Yes, it was both channels Mike, around 0.6mV right and 0.4mV left now, it varys a little. It will vary with the thermal drift, leave the amp powered up for 30 minutes and take the reading then it should have stabilised. 0.6mV is fine, you'll either find that increases to about 0.9mV or decreases closer to 0.0mV as the chip stabilises.
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Post by PinkFloyd on Aug 9, 2007 21:06:18 GMT
So Leo, not having the Heed to hand do you reckon the offset (when using the 843) will be quite high at zero volco on the stock Heed? We better get Nigel and dc to check it ;D As far as I can remember they were pretty close to zero when I tried them "naked" in the Heed.
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leo
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Post by leo on Aug 9, 2007 21:46:04 GMT
So Leo, not having the Heed to hand do you reckon the offset (when using the 843) will be quite high at zero volco on the stock Heed? We better get Nigel and dc to check it ;D As far as I can remember they were pretty close to zero when I tried them "naked" in the Heed. I already mailed him Mike just as a precaution really, maybe fine with a proper Heed, remember mines a clone built on the old Chiarra pcb Problem is apart from that 100nf film cap the original decoupling caps are much too far away from the op-amp pins, the Chiarra was the same so you had to be careful, I had to do lots of bodging in mine
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leo
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Post by leo on Aug 9, 2007 21:48:05 GMT
its why in another thread I complimented Grahams layouts on his PCB's, his look very nicely done
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Post by PinkFloyd on Aug 9, 2007 21:50:40 GMT
Totally off topic.... is that your cat Leo and what is it's name?
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leo
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Post by leo on Aug 9, 2007 22:08:24 GMT
Yes, that’s my ginger furball, his name is Busoms
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leo
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Post by leo on Aug 10, 2007 11:13:44 GMT
Just edited this picture, should allow simple measurement of DC offset for Sennheiser owners?
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Post by PinkFloyd on Aug 10, 2007 15:44:49 GMT
Just edited this picture, should allow simple measurement of DC offset for Sennheiser owners? And / or www.rock-grotto.co.uk/dcoffset.htm probably best to start at the 2 volt range and then check at the 200mV range.
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leo
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Post by leo on Aug 10, 2007 17:10:06 GMT
I didn't see that one, good write up Mike! Main problem with amps like the Heed etc, you've got no protection, folks moan about coupling caps but at least it helps saves your phones incase of a problem
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Post by PinkFloyd on Aug 10, 2007 18:22:25 GMT
I didn't see that one, good write up Mike! Main problem with amps like the Heed etc, you've got no protection, folks moan about coupling caps but at least it helps saves your phones incase of a problem Yep, nothing like the belt and braces approach.... better than "KABOOM!!!" into your lugholes, resulting in you having a heart attack and your favourite headphones up in smoke
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Post by PinkFloyd on Aug 10, 2007 18:23:30 GMT
Lovely cat Leo, more of a dog man myself but I do appreciate a well turned out animal.
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