FritzS
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Sound of Blue Danube
Sound of Blue Danube
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Post by FritzS on Feb 16, 2008 16:26:22 GMT
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FritzS
Been here a while!
Sound of Blue Danube
Sound of Blue Danube
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Post by FritzS on Feb 16, 2008 20:18:37 GMT
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Deleted
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Post by Deleted on Feb 16, 2008 21:04:08 GMT
Fritz Silicon Chip regularly contributes articles now to EPE. This is the HA amplifier that I have modded, and use a JLH supply with. Now sounds fabulous with my Sony headphones. As Graham said, it works better without a zobel network too. Alex
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rickcr42
Fully Modded
Rest in peace my good friend.
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Post by rickcr42 on Feb 17, 2008 21:51:18 GMT
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Post by Deleted on Feb 17, 2008 22:27:56 GMT
Rick There has already been some discussion re this HA. Graham was NOT impressed with the Zobel presence. I have revamped the circuit to use a LM4562 and 2SA1930/2SC5171 as well as fitting a 47 ohm resistor in series with the output to replace the Zobel. There are other changes too, as well as feeding via a JLH parallel regulator. It sounds much better than the original, and the 47 ohm resistor can easily be changed to better match other headphones.
BTW, I hope these other guys realise that they are in breach of copyright by publishing the ORIGINAL SC schematic? Particularly, seeing it is still available as a kit from SC advertisers. Alex
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leo
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Post by leo on Feb 17, 2008 22:37:47 GMT
I thought the amp in that pic looked familiar , maybe a good one for Krisno ;D
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rickcr42
Fully Modded
Rest in peace my good friend.
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Post by rickcr42 on Feb 17, 2008 22:38:40 GMT
why I was a bit hesitant to post the link.... BUT The basic topology is nothing new but rather just another example of the basic "assisted Op-Amp" headphone amp/line driver of which there are bazillions of examples of both DIY and commercially (most of the amps discussed here at the grotto in fact ) so just another "example of" rather than anything ground breaking. The Zoebel-what many confuse is home hi-fi ultimate SQ with prosound studio monitoring which is what this amp is designed for.In the pro arena YES you want accurate sound but more importantly you CAN NOT have blips/blurbs/equipment failure or anything that detracts from the job at hand which bottom line is "time is money' and in the studio a LOT of money so the zoebel is there more for feedback loop RFI protection than it is for any "SQ" merit and in the pro arena a required part if you want a clean feed to your cans
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rickcr42
Fully Modded
Rest in peace my good friend.
Posts: 4,514
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Post by rickcr42 on Feb 17, 2008 22:54:00 GMT
another example sound.westhost.com/project113.htmplus a boatload more over at the Headwize Project Library pretty standard stuff actually with the devil in the details NOT the topology ;D
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Deleted
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Post by Deleted on Feb 17, 2008 22:57:41 GMT
Rick That's not why the Zobel was there. He showed some graphs which claimed a flatter frequncy response with some of the cans tested. He also took issue with the IEC recommended 120 ohm source impedance. BTW, it sounded terrible with that 1N2 in the FB network. All in all, a very mediocre design. SandyK
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rickcr42
Fully Modded
Rest in peace my good friend.
Posts: 4,514
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Post by rickcr42 on Feb 17, 2008 23:27:05 GMT
Hmm.Maybe shoulda read the article / that suggest the circuit is not stable into all loads OR he misunderstood what he saw on the plots and assumed the natural cans impedance /amp output impedance interaction (and why amp/cans combos SOUND different) was something to be addresssed instead of it being part of the natural order.Pretty much a "the cure is worse than the disease" type thing and one we see way too often Anyway.My earlier point on RFI protection : I use both input and if the amp uses overall feedback,output RFI protection in every solid state amp I make plus go to great lengths to make the psu as imperturbable as I am capable of because SS don't like any "hickups" at ANY input and the feedback loop even though at the output jack connection is STILL an input because that is where it will end up and because the signal came in "backwards" will not be cancelled out by the normal differential input of the input circuit (signal to +,feedback to -) enough by me,back to the race
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rickcr42
Fully Modded
Rest in peace my good friend.
Posts: 4,514
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Post by rickcr42 on Feb 18, 2008 0:17:34 GMT
never been too good at juggling 1-doing email 2-reading and posting here 3-watching the Daytona 500 and posting here during wrecks 4-downloading some electronics files 5-looking for service info for a buddies PA amp 6-playing fkn PHONE TAG with my employer on tomorrows gig which is turning into a freakin' PROJECT rather than a simple "go there and fkn do it" type thing And NOW it looks like it will be a GD sleepover so i have to pack up just in case and this being unforseen entirely is pissing me off (I like to have a GD plan then follow it to the letter.....) so not even sure if any of the above posts make sense so will read it later tonight or maybe if i have to tomoorow or the FKN NEXT DAY if i get caught out and see what the fk is what ;D
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Deleted
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Post by Deleted on Feb 18, 2008 0:39:55 GMT
Modified Silicon Chip Headphone Amplifier.
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Post by headtestament on Feb 18, 2008 3:20:38 GMT
Very good Measured Performance,very interesting project. But I don't know why it uses diodes before the output transistors? Is it better than diamond buffer?
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Deleted
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Post by Deleted on Feb 18, 2008 3:42:23 GMT
headtestament The diodes are mainly there to reduce excessive level into different impedance headphones, so as to help prevent hearing damage. The number of diodes strapped in/out depends on the impedance of the headphones used. There shouldn't be a need for anything like a diamond buffer provided the opamp used has a good output drive capability. e.g. Low distortion into a 600ohm load , as specified in some I.C.s data sheets. SandyK
SandyK
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Post by PinkFloyd on Feb 18, 2008 6:07:42 GMT
Graham was NOT impressed with the Zobel presence. So what? Graham is god now is he? As Rick says (and David White) the zobel network is there for a very good reason..... belt and braces. I, personally, found the zobel to have pretty much zero insertion loss when implimented into the WNA amp.... I will quote David White here: "The WNA headamp is very fast ( power bandwidth is several hundred kHz ) and has no compensation capacitors; deliberately so. The resistor, or wire ended lamp, on the output serves two purposes; short circuit protection and isolating the headamp from the load. The amp doesn't mind reasonable duration short circuits like those caused by hot plugging or unplugging the headphones so the resistor/bulb isn't really needed here. The resistor/bulb increases the output impedance of the amp, which is bad, particularly for good bass response where high current is needed, but in the absence of any other measures is needed for stability. This is where the zobel network comes in, it will keep the amp stable in the absence of an output resistor. It works by presenting the amp with a low impedance load at very high frequencies, and this tends to kill any tendency towards oscillation. Interestingly enough you rarely see power amplifiers without zobel networks but the converse seems to be true with headphone amplifiers."Full article here: www.rock-grotto.co.uk/wna-MKll-tweaks.htmWord on the street is David White may be appearing here soon (yes, posting here at the Grotto) but he needs coaxing out of retirement I'll start the chant........ We want WHITE.... we want WHITE.... we want Doctor WHITE!
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Deleted
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Post by Deleted on Feb 18, 2008 6:37:10 GMT
Mike How many headphone amplifiers have you reviewed using Zobel networks, percentage wise ? Name a few off the top of your head On this occasion I happened to agree with Graham, as I built the amplifier to the original specifications and it sounded shite. I removed the zobel network and it sounded much better. For Christ's sake, we are talking about a headphone amplifier, not a frigging power amplifier ! Very few new high quality headphones these days are 8 ohms, and the majority of new ones now comply with the EU specification of being driven by a 120 ohm impedance,so where is the necessity for a Zobel network (AKA "Boucherot Cell") ? Sorry if I offended you by mentioning Graham's name !! FTR, I do not always agree with everything this person , who's name I won't mention again in this forum, says. BTW, who is David White ? SandyK O.K. So he designed the WNA. Wow, now I am really impressed !
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Post by PinkFloyd on Feb 18, 2008 6:43:12 GMT
BTW, who is David White ? Who is David White? good question Alex. If I said he was Doctor White would that ring any bells? You know I am professor Pink right? Sorry man I am wrecked (litre of scotch) erm.... what was the question again? Oh yes, "who is David White?"..... erm...... This guy www.wnaudio.com/index.html
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Post by PinkFloyd on Feb 18, 2008 6:54:02 GMT
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Deleted
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Post by Deleted on Feb 18, 2008 6:54:58 GMT
Mike Let's put this all into context. You have reviewed MANY headphone amplifiers, so off the top of your head, which would be the ones that impressed you most ? My apologies for snapping back. I realise that you are in one helluva state at the moment, and it isn't alcohol related either. The torment should soon be over, my friend. Alex
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Post by PinkFloyd on Feb 18, 2008 7:00:35 GMT
The WNA MKlll "who is David White?" erm.......................................
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Deleted
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Post by Deleted on Feb 18, 2008 7:10:56 GMT
The Silicon Chip amplifier used an L + CR network. Many amplifiers have simple Zobel networks as described previously , for stability. My main issue is with the use of the series inductor in this particular application.
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pagan
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Post by pagan on Feb 18, 2008 8:12:15 GMT
the wma
Are they large output caps? electrolytics too?
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Deleted
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Post by Deleted on Feb 18, 2008 9:44:06 GMT
Allan The attached , is it what you were referring to ? Alex.
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leo
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Post by leo on Feb 18, 2008 9:58:46 GMT
Be nice to have a big shoot out with all these diy headamps , out of the few DIY available ones I've heard
Chiarra Millet Hybrid various simple op-amp only based WAD HD3 Kumisa with a few mods
I'd probably say I like the modified Kumisa best out of those, I may try the Silicon chip one next
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FritzS
Been here a while!
Sound of Blue Danube
Sound of Blue Danube
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Post by FritzS on Feb 18, 2008 11:02:20 GMT
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