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Post by PinkFloyd on Jun 17, 2006 17:58:34 GMT
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rickcr42
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Rest in peace my good friend.
Posts: 4,514
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Post by rickcr42 on Jun 17, 2006 18:13:59 GMT
in theory and on paper a lot of these bypassing schmes make some kind of twisted sense but you need to know there is a reason behind the action and there really is no universal "right way" for all active circuits with perhaps the need for the RF bypasses in the 0.1 uf range but even this is not an etched in stone value. all those parallel caps may be doing major SQ damage rather than offering anything positve if you actually think about the why of it. first off you can toss ripple and/or AC noise right out the window.Already taken care of at the power supply itself as is any need for storage of signal for large peak events. So why ANY need for caps right at the devices is what you need to wrap your brain around then think in terms of what is meant to decouple and what is meant to shunt unwanted frequencies to ground. Hint:ALL capacitors are a filter Hint #2-no RF bypass is doing shit if not right at the pins of the device.even a circuit board trace is enough to pick up then re-transmit the signals right to the power supply pins which ARE opamp inpput pins every bit as much as are the actual +/- inputs Bypassing caps are a simple shunt to ground of unwanted frequencies,decoupling needs some series resistance or series inductance/resistance (inductor coil) to complete the filter or you are doing no more than ending up with the sum of all caps as the final capacitor value figure
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Post by PinkFloyd on Jun 17, 2006 18:30:42 GMT
Hold on here Sir! If (and I say "if" as though I automatically assume it is the case) I have pretty complex ripple it's good to add several different values of bypass cap (in parallel) with each value targeting a different frequency? I also use a larger electrolytic cap in case the amplitude of the lower frequency is too great so I am looking at a "catchall" solution with one cap there to catch large voltage dips which are at relatively low frequencies, another cap to handle the midrange frequencies and one (or two) to handle the higher frequencies. Sounds good man!
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Post by PinkFloyd on Jun 17, 2006 18:33:17 GMT
From Analogue Devices: Power-Supply Bypassing Bypassing the power supply at the amplifier’s supply terminals to minimize noise is a critical aspect of the PCB design process—both for high-speed op amps and any other high-speed circuitry. There are two commonly used configurations for bypassing high-speed op amps. Rails to ground: This technique, which works best in most cases, uses multiple parallel capacitors connected from the op amp’s power-supply pins directly to ground. Typically, two parallel capacitors are sufficient—but some circuits may benefit from additional capacitors in parallel. Paralleling different capacitor values helps ensure that the power supply pins see a low ac impedance across a wide band of frequencies. This is especially important at frequencies where the op-amp power-supply rejection (PSR) is rolling off. The capacitors help compensate for the amplifier’s decreasing PSR. Maintaining a low impedance path to ground for many decades of frequency will help ensure that unwanted noise doesn’t find its way into the op amp. Figure 1 shows the benefits of multiple parallel capacitors. At lower frequencies the larger capacitors offer a low impedance path to ground. Once those capacitors reach self resonance, the capacitive quality diminishes and the capacitors become inductive. That is why it is important to use multiple capacitors: when one capacitor’s frequency response is rolling off, another is becoming significant, thereby maintaining a low ac impedance over many decades of frequency. Starting directly at the op amp’s power-supply pins; the capacitor with the lowest value and smallest physical size should be placed on the same side of the board as the op amp—and as close to the amplifier as possible. The ground side of the capacitor should be connected into the ground plane with minimal lead- or trace length. This ground connection should be as close as possible to the amplifier’s load to minimize disturbances between the rails and ground. Figure 2 illustrates this technique. Figure 2. Parallel-capacitor rails-to-ground bypassing. This process should be repeated for the next-higher-value capacitor. A good place to start is with 0.01 µF for the smallest value, and a 2.2-µF—or larger—electrolytic with low ESR for the next capacitor. The 0.01 µF in the 0508 case size offers low series inductance and excellent high-frequency performance. Rail to rail: An alternate configuration uses one or more bypass capacitors tied between the positive- and negative supply rails of the op amp. This method is typically used when it is difficult to get all four capacitors in the circuit. A drawback to this approach is that the capacitor case size can become larger, because the voltage across the capacitor is double that of the single-supply bypassing method. The higher voltage requires a higher breakdown rating, which translates into a larger case size. This option can, however, offer improvements to both PSR and distortion performance. Full blurb here: www.analog.com/library/analogDialogue/archives/39-09/layout.pdf
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rickcr42
Fully Modded
Rest in peace my good friend.
Posts: 4,514
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Post by rickcr42 on Jun 17, 2006 18:54:24 GMT
the working term you refernced is NOISE which is not ripple ripple is dealt with at the regulator,noise at every point where it can enter into the signal path be it mains line,power supply or signal line
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rickcr42
Fully Modded
Rest in peace my good friend.
Posts: 4,514
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Post by rickcr42 on Jun 17, 2006 19:01:59 GMT
the final "ripple" filter,the pin connected electros are low value low esr types.Since this is a current draw sensitive part The 2.2uf fine if only a low current opamp circuit but for buffers or discrete power stages and increase in size essential UNTIL you get carried away and start throwing capacitance at a problem that never existed.THAT is when the SQ goes down as the complexity + cost incurred goes up,not to mention the overly complex layout that comes with it-which invariably adds more "stray" compacitance and unseen resistance paths (hence setting up unintended filter networks). Not just about adding caps willy nilly (how's that for a word ? ) but adding them with a purpose to correct a KNOWN problem anything else is shooting randomly in the dark while your opponant sits 1/2 mile away with a night vision scope ready to take your ass out as soon as he stops laughing so he can steady his aim
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rickcr42
Fully Modded
Rest in peace my good friend.
Posts: 4,514
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Post by rickcr42 on Jun 17, 2006 19:06:35 GMT
BTW and TOTALLY OFF TOPIC I don't know if you folks in the U.K. have an equivelant to being a "Letterman" in your version of high school but if you do then here is a cool factoid. Usually it is the "jocks" that parade around showing off their varsity letter so they can tout their athletyic prowess without saying anything-all right there to see My son just got his two days ago but instead of for being a "jock" his is for perorming on the school rifle team Seems we have another crack shot in the family that when combined with his proclivity for making the honor rolls makes him doubly dangerous ! A thinking person who can aim true is a very dangerous combination,trust me on that one
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Post by PinkFloyd on Jun 17, 2006 20:01:14 GMT
Trust me Rick, what you see before you is "leading edge" hocus pocus carefully tuned to please my ears It sounds good, it keeps me occupied and it uses up old capacitors I've got kicking around. The best part is I can desolder the entire shebang and try something different another time. To my ears the multiple bypassing has "improved" the SQ in that the entire presentation now sounds more dynamic, clearer, spacier and generally more foot tapping and "musical". It certainly does not sound worse than it did or I would say so... so where does that leave us? Should I remove all my bypass caps because in theory they should be "degrading" the SQ or should I go with my convictions and leave them in place and enjoy the music? I think I'll leave them in place
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rickcr42
Fully Modded
Rest in peace my good friend.
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Post by rickcr42 on Jun 17, 2006 20:20:33 GMT
I would never doubt your ears Mikerama,your taste maybe but never your ears j/k
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Post by PinkFloyd on Jun 17, 2006 21:20:20 GMT
Proof of the pudding........... I've just desoldered them all: Listening now and I don't think it sounds quite as sharp as it did with them in place but obviously will let it warm up for an hour. Jesus Rick, this is enough to drive you mad! You know I spent ages today soldering all those caps on and was quite happy with the sound.... on the strength of your post it's taken me 10 minutes to desolder them all just to check my sanity and confirm that I wasn't imagining things.... this is pure madness!! I knew it was wrong to resurrect this amp from the "been there done that" pile, like going around in circles, deja vu.
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rickcr42
Fully Modded
Rest in peace my good friend.
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Post by rickcr42 on Jun 17, 2006 22:54:36 GMT
if by "less sharp" you mean the image is less focused then that is a bad thing.If by less sharp you mean the actual notes are not "etched in space" then you are hearing music and not electronics........as it should be................ Music is relaxed and should flow rather than have segments highlighted.I swear I never here a live peformance that sounds anything like what most consider to be musical electronics and live being my model have gone to great lengths NOT to produce great sound but to produce as little in the way as possible and if i must here electronics rather a diffuse field where notes come together as a whole peformance rather than "sharp" individual notes seemingly more solo performance than group simple because of the overly highlighted nature (something NEVER heard live until intended ).But that goes to taste and is mine alone (looks for tongue stuck out emoticon,finds none,uses the "kiss my ass" one in its place ) Example A : Presently my loudspeaker based system,the big rig,has a bottom end rolloff in the low-mid forties (hz) but is extremly tactile in both sound and at the "gut" level.Drums have a tight THWAK when meant to and if the heads tuned loose (listen to Robin Trowers Bridge of Sighs album for an example of "loose" tuning on the drum heads) sounds that way rather than the THWAK being superimosed on something never having it until changed by the electronics.More high toned thud than anything else with a bit more decay of the note. I like to use music having many instruments to evaluate a piece of gear and I listen for two things : Can I hear every instrument as an individual if i strain to focus on it yet not lose track of the ability to follow it when all the instruments mass which is a real strain on electronics and which requires a high amount of class-a operation to0 keep the low notes as musically articulate as the louder notes. Does the nature of an instrument or voice change as the volume increases.Not "volume control" type volume but peformance volume.If as it gets louder it becomes more crystalline,more etched,to some more articulate (but over time tiring and why sessions cut short) then you have upper octave emphasis.Volume should add bloom and increase level,not change the nature of Example B : Since my personal benchmark for music reproduction is LIFE and EMOTION over timbral accuracy (reasons in a sec.....) I tend to high efficiency headphones and speakers. When it takes little to get the mass of the actual transducer moving there is more likelyhood you will get ALL of the music and that at any listening level whereas low efficiency usually means there is a volume level sweat spot that must be reached or everything sounds limp,lifeless,dull.There is a lot of pro con on this and folks in both camps so again choice/preference. Sidebar : I was once "taken" by an audio dealer when I was young and green,setting out on a mission to purchase my first REAL loudspeakers. Having $500 as my budget,quite enough for entry level high end in the early seventies,I sat down and listened to all the featured loudspeakers and the salesperson kept switching back to one particular pair that i had to admit stood out from all the others which in the end i went home with......to my everlasting dismay ! No one likes to be a sucker and that is exactly what i was because I went home with a set of Cerwin Vega loudspeakers over many many better choices at the same price point in that room. Why ? Efficiency ! This "con artist" of a salesman must have been getting a hefty markup because he did not level match the loudspeaker systems which made the higher efficiency CV pair play LOUDER than the others for the same amount of input power.Anyone that knows what a Fletcher Munson Loudness Curve is knows that as volume levels decrease the bas and treble notes decrease more in prportion to the middle frequencies so as you lower the volume eventually all the life gets sucked out of the music unless restored with a compensation circuit.Same thing,different level here. The less efficient loudspeakers were playing at a lower level for the same amount of amplifier power than the competing systems with the effect that they had apparently less bass and treble than the CV system.In direct 1:1 comparison the Vegas stood out while ALL the other systems (Altecs,JBLs,AR.....especially the AR ) sounded dead ! Lifeless ! Inarticulate. So I got snookered into the Cerwin Vegas by deceptive selling practice (and have never ever stepped foot in that store again even though only one of two local audio salons).What sounded like Sparkle and Sharp with resounding bass in the store became headache material at home.Boom and tizz,monotonic music (everything highly colored by the speaker voicing,probably the D-horn) nothing like what Iexpected for half a K note that I worked hard to save I ended up HATING those speakers with a passion yet they whupped ass for parties (LOUD and DRAMATIC) so they stayed "in house" (actually on patio is closer to true) for years with a pair of Technics taking over inside for listening,later replaced by a set of DQ-10s that i truly miss even though imperfect speakers on many levels. Bottom line,I am not doubting you hear what you hear and in this case I may be 200% off base but sometimes you need to listen for a period of time to know if something is good or just exciting up front yet tiring or even headache material over time.I like to listen for the background over the main parts of the music to see if it is just background noise or part of the performance and if it is sit back and settle in for a long session to verfiy my initial thoughts. then again I am 50 so anytyhing over 15khz likely just as audible to me as a radio wave
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Post by gns on Jun 18, 2006 0:16:00 GMT
Hey Pinky! Did I see some capacitor impedance curves? See the inductance part of the curve? Unless you're using Tants it's a good idea to never repeat the same value or you'll get peaking at the frequency the cap deals with. I don't know if this is a new discovery "the Slee effect" or it's old hat but so far I've found nothing on the subject. But it shows up like crazy in - you guessed - RoHS!!!! I found it best to step the difference at twice or half the value, so if one op-amp has 10nf make the other 22nf. Give it a try, I'd be interested in your findings. Same with paralleling caps to make a wanted value or in bypassing. For bypassing do the 1 over 2piRC business to make sure all frequencies in a circuit are at least an octave apart, or you'll get audible ripple (ringing in your ears at that frequency ) just like with a steep slope multiple order filter. It's accepted that caps in parallel just combine to make a bigger cap. That's true but main and bypass also work independantly and the impedance curve graph actually tells you that . Like I said, I'd be interested in the findings of others. G
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Post by PinkFloyd on Jun 18, 2006 10:29:58 GMT
Hi Graham, I'm always bypassing caps as I believe multiple caps are better for audio. No point in just bypassing with one solitary cap when you can bypass with multiple values to cover all bases. There is much discussion on the advantages / disadvantages of multiple bypass caps and my ears tell me they are advantageous rather than a disadvantage. I always bypass PSU capacitors as I believe this method ensures a low source impedance to the power supply over a very wide bandwidth and I usually fit PSU bypass capacitors with the tiniest value being installed directly at the active device. They are a catchall solution and as AD say " That is why it is important to use multiple capacitors: when one capacitor’s frequency response is rolling off, another is becoming significant, thereby maintaining a low ac impedance over many decades of frequency." Certainly nothing "wrong" in bypassing electrolytics with several values of film / ceramic cap in parallel apart from maybe the "cost" factor and the time it takes experimenting until you find a combo that suits your ears. Classic scenario Rick and many people fall into this trap so you're not alone! Another great example is the all singing all dancing headphone amp that has 3% distortion and comes across as "dynamic", "full bodied", "exciting" etc. at a brief audition at a Head-Fi Meet. It's only when they get it home and have a prolonged listen that they find it torturous to listen to and have the urge to throw it out of their window. Things that sound head and shoulders "better" in a brief A-B comparo generally tend to be fatiguing and unlistenable in the long term. I made much the same error as you with regard to the sensitive speakers back in the day. I came out of the shop armed with a pair of huge "JBL" coffins (with glass tops) after thinking they sounded head and shoulders better than the other speakers that were run through the comparator.... more bass, more everything.... Got these things home after my friend and I struggled with them for 1 hour in a "bus" only to find they were the most vulgar, honky, boomy, bloated sounding speakers I'd ever heard. Great for parties or for annoying the neighbours but prolonged listening?? no way! We struggled back to the shop with these coffins a few days later and I exchanged them for a pair of Monitor Audio speakers which sounded thin in comparison but, boy, when I set them up at home I was over the moon with them.... pure quality! I lived with those for a couple of years. I have "always" recommended to people that they should listen to (and live with) an amp for a few weeks when auditioning and "not" to do a quick 5 minute comparo against another amp as the one which sounds more immediate and exciting will probably turn out to be a real dog long term. Some manufacturers feed off the initial "wow" factor in the audio demo room and they know that quite a few people will walk off with the piece of gear that sounds the "loudest" in a brief A-B through a comparator... it's a "classic" scenario and I know lots of people who have fallen into the trap only to find, long term, they've bought something more akin to a loud, honky pub karaoke machine than a quality "neutral" sounding piece of equipment. Head-time is the only way to audition gear and you need lots of it, I sometimes listen for 10 hour stretches (seriously) and there's no way I could do that with equipment that shouted at me, I'd have the urge to rip the 'phones off my head and chuck them in the bin so, yes, always audition your gear at home for prolonged periods and try not to walk out of the shop with something after only listening to a brief 10 minute "burst" of music... what you hear in the shop is not always what you get in the home, that exciting sounding "burst" of musak you heard in the shop may become a nightmare at home Mike.
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Post by PinkFloyd on Jun 18, 2006 14:06:01 GMT
And today has been spent going from this: To this: And now to this: As you may have guessed from the above picture it's back in with the AD-843 and 2.2uF caps have been fitted direct to pins 4 & 7 and then to ground. We already have 0.1uF (100nF) caps fitted to the board which go from pins 4 & 7 to ground so by adding the 2.2uF caps under the board we now have 0.1uF and 2.2uF in parallel going from pins 4 & 7 to ground in accordance with Analogue Devices grounding and bypassing recommendations. I didn't have any 2u2 tantalums so used 2u2 film caps (pulls from an MF X-10D) and of course the 100nF film caps that are already in place on the board. I much prefer the AD-843 to the AD-744 and will be sticking to it in this amp as it does most things well and nothing bad. It's nowhere as clinical as the LM6171 yet offers a similar insight into the music whilst maintaining the soul and musicality of the recording. 6171 was way too sterile and 744 was a bit on the light and airy side of neutral for my liking. 843 offers good insight into the recording whilst also adding a touch of organic warmth which suits my ears. I'm really not going further with this amp as the sound is now spot on and over egging the pudding or driving myself insane trying every opamp on the planet is not going to happen again! AD-843, no input / output caps = happy me! I believe Fritz also commented somewhere that he found the 843 a lot more "musical" than the 6171 and I tend to agree with that wholeheartedly. It gets your toes tapping and the music comes over as music and "not" as a load of seperate entities in their own space clinically presented on a plate to be analysed and studied through a magnifying glass. So, after probably 3 years of trying "many" opamps in WNA MKl, MKll and now MKlll I have finally settled on the AD-843 and have now totally discounted the LM6171, OPA627, AD-744, OPA-134, OPA-227, OPA-228, AD-8610, AD-797, AD-825, AD-8065, LM-6181 and others in favour of the AD-843 which I believe outperforms the aforementioned chips with "musicality" being its strongest attribute. Less electronics and more music comes through with this chip IMO and I'm sticking with it
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rickcr42
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Rest in peace my good friend.
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Post by rickcr42 on Jun 18, 2006 14:33:49 GMT
that is maybe the single biggest "deception" in all of audio and one newbies have no defense against.The DAMN THAT SOUNDS GOOD type of gear is an impulse buy because it stands out from the competition.What the unwitting purchaser did not realise at the time is the very fact that the one pice of gear stood out makes it the ONE to run away from not buy ! Standing out from the crowd unless that crowd is the worst crap known to humans usually means seriously colored to the point of imposing on music rather than reproducing it.Truth is most have no benchmark and having none go by what they know so usually end up with varying degrees of the same thing.It is so bad,the model for "good sound" that is,that I have been in homes where outrageous loot on glorified boom boxes ! All boom and tizz with the proud owner saying "what do you think rick ?". Heh,in order to keep the peace I do not say what I think but instead weasle out with something like "not exactly what my taste in audio gear is but if it suits you cool.It does look nice though".Most do not want the truth but instead someone to agree with their decision and if you are dumb enough to vocalise the truth your ass is in deep doo doo ! These folks really DO think they have hi res systems and when they hear one that has some actual musical reality mostly run away saying IT sounds like crap. Too forward,too little bass,not enough "etching" around the top octaves,the voices too forward,a mess and they then convince themselves that theirs sounds better and your opinion so much bull (or you are jealous so crapped on their choice) Yes they will admit MAYBE they hear things they never before heard on a CD they play all the time but that too is easily dismissed out of hand. You need to have something at some point in your life to compare to or you end up always choosing variants on what you know and if that is "mid fi" bells and whistles the search usually ends up more expensive,more glorified versions of the same touted as a "super system" and the manufacturers KNOW THIS so take advantage of it. Right now I am running loudspeakers that at best do from 45-50 hz to 18khz @ -6dB "in room".This on paper would send any true audiophile into fits of laughter because we ALL know a good system does 20-20K dead flat How do you fight against that ? How can you convince someone they are being conned when all the ad copy and all the equipemnt reviewers are telling them otherwise ? That even a system with a little tiny 6" woofer is flat from 30hz to 30khz and will take up so little space the wife will kiss your ass (or other things ) forever ? How can you talk sense to folks who truly beleive they are getting below 20hz in headphones !!!!!!!!!!!!!!!!! Something I can not get without a real monster of a subwoofer and then i need to "rattle proof" the entire room they are getting with 3" cones in a 3" chamber (if that ) strapped to their head ? or why so many headphone amps with a bass boost if accuracy is the goal and not "better than real" ? Or opamp based headphone amps that are actually oscillating in the mHz range called "articulate" or having "lots of high end detail" because the high notes are being reinforced by the osc ? again back to the boom box model.............all boom and tizz Side by side it is the exciting,the standout gear that will sell more often than not with only time+experience+tired of being conned allowing us to break out of the herd.I personally had to train myself to listen and it took music using instruments I could actually hear cose up and personal in real life as the "model" for comparing so acoustic guitar,piano (real bitch to get right,really),saxaphone,the human voice,even audience applause on a live album can be telling. The old saying of "fk me once shame on you,fk me twice shame on me" is even more pertinant in high end audio with most being fked so many times they don't even notice they have a two by four sticking out of their ass because it no longer hurts ;D
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rickcr42
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Rest in peace my good friend.
Posts: 4,514
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Post by rickcr42 on Jun 18, 2006 14:34:42 GMT
I probably should edit that last paragraph but not yet........not yet...............
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Post by PinkFloyd on Jun 18, 2006 14:47:30 GMT
I probably should edit that last paragraph but not yet........not yet............... Why edit fact? You could edit "two by four" to "four by eight" it's probably a more realistic dimension of "ass" accessory
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FritzS
Been here a while!
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Post by FritzS on Jun 20, 2006 11:22:46 GMT
But you use them in a wna mkIII PCB - we all have mkII, and I think if we test this we should change the one 5,6 mA current source to 3,5 mA or modify the output stage look as mkIII www.stockhammer.at/hifi/wna.php#Modification1
How are the difference in sound between 744 and 823?
Where I can get a mkIII (or a mkII) PCB now? I will use a second amp for test!
Mike please give me your right address per private mail - I will send you some test music ;DMike - my question to you "is going under" Yesterday I had a longer "session" - one of my CD's - "Pink Floyd" Final Cut - childrens laugh and talk, mens lumbering step's and other background noises are superb realistic with AD843 One of my favorite part, the air raid .... "WOOOM"
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FritzS
Been here a while!
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Post by FritzS on Jun 20, 2006 11:39:54 GMT
Nice caps - what manufacturer? Where to get? For a new PSU I am unsure what transformer I should use - EI core or Toroid core. RS Components 20 VA EI core 230V / 18V + 18V, 0,55A #805-085 € 6.49 30 VA Toroid core encased 230V / 18V + 18V, 0,83A #223-8550 € 17.00 or open #223-7844 €16.78 I will use the transformer for my cascode PSU ;D First step I will use them in series, sum 28V till 30V DC and use a trimpot inside. Today I get some AD744 and OP275 samples
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Post by PinkFloyd on Jun 21, 2006 9:05:31 GMT
Let me think........... ok I have had a think, the original class A mods to the WNA MKll consisted of changing I2 from a 3.5mA CRD to a 5.6mA CRD and also changing R6 from 120R to 75R.
So.................... to remove the class A biasing for the LM6171 you will have to remove the 5.6mA CRD from I2 and replace with a 3.5mA CRD and then you will have to remove the 75R resistor from R6 and replace with a 120ohm resistor, that's you back to the original MKll without class A biasing.
Mike.
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Post by PinkFloyd on Jun 21, 2006 9:12:32 GMT
Well, David White is not communicating with me as he's thrown a wobbly and gone into a hissy fit but he may well communicate with you and sell you one of his MKlll boards........... contact him at david.white38@ntlworld.com
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Post by PinkFloyd on Jun 21, 2006 14:15:30 GMT
Hi Fritz,
As said above, they are "pulls" from Musical Fidelity X-10D line buffers...... ie: they are caps I have removed from X-10D line buffers and replaced with polyprops so these "pulls" are not new caps.
I have no idea who the manufacturer is all they have on them is a big "L". I will send you four as soon as I "pull" some more out of X-10D.
Mike.
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rickcr42
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Rest in peace my good friend.
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Post by rickcr42 on Jun 22, 2006 0:45:55 GMT
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FritzS
Been here a while!
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Post by FritzS on Jun 24, 2006 17:44:16 GMT
this question is going under
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FritzS
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Post by FritzS on Jun 24, 2006 17:49:45 GMT
Today I heared some of my CD's ... Quincy Jones "Back on the Block" Marianne Faithful "Blazing Away" Horowitz "in concert" and some other all a very trueness, realistic sound with AD843 when I have more time I will wrote a report about my hearing test too
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