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Post by Deleted on Feb 26, 2008 21:32:53 GMT
Sol Why don't you build a dual regulated power supply as per the original X-DAC thread,while you are waiting? You should hear an improvement in performance without even opening up the X-DAC V3, and you will be ready for the next stage. (or you can leave it at that) In the original PSU photo, I used a home brew PCB, but the transformer and dual regulated PCB Mike mentions (with photos) from Jaycar would be ideal. The Dual regulator kit comes with all components, as well as detailed instructions. You can even leave out the 5V regulator, and bridge it with (e.g.) a 4.7K etc. resistor, then use the 5V terminals to supply a LED for the front panel. If you don't have an electronics supplier nearby, you could also get the mains toggle switch and plugs and sockets etc. with the transformer and PSU kit. Alex rockgrotto.proboards39.com/index.cgi?board=m&action=display&thread=1203179182&page=2
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Post by PinkFloyd on Feb 26, 2008 22:40:57 GMT
Sol Why don't you build a dual regulated power supply as per the original X-DAC thread,while you are waiting? You should hear an improvement in performance without even opening up the X-DAC V3, and you will be ready for the next stage. (or you can leave it at that) In the original PSU photo, I used a home brew PCB, but the transformer and dual regulated PCB Mike mentions (with photos) from Jaycar would be ideal. The Dual regulator kit comes with all components, as well as detailed instructions. You can even leave out the 5V regulator, and bridge it with (e.g.) a 4.7K etc. resistor, then use the 5V terminals to supply a LED for the front panel. If you don't have an electronics supplier nearby, you could also get the mains toggle switch and plugs and sockets etc. with the transformer and PSU kit. Alex rockgrotto.proboards39.com/index.cgi?board=m&action=display&thread=1203179182&page=2I phoned these guys up Alex (Jaycar) at 3am GMT and the guy I was speaking with was as good as USELESS. He basically told me my order had not been shipped (from AUSTRALIA) but he didn't know "why" it hadn't been shipped. "It could be because we don't have certain parts in stock... I don't know" Fckin' useless! I have no time for crap service whether it be situated in the UK or the other side of the world. I'm sure the bits will turn up eventually but, in the meantime, it would be reassuring to get some input from these people. Not good at all.
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Sol
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Chief Technical Numpty
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Post by Sol on Feb 27, 2008 5:46:30 GMT
Mike/Alex .. .I totally understand ... I opened her up, dropped some bursons in there, and that had me shitting bricks! Messing with anything else in there is a definate don't go there for a hamfist like me. Your own worries have just re-affirmed it's best I leave it to someone with a bit of experience.
Mike - whenever you are ready dood - I'll have it packed and sent up before you know it ... full indemnity against a dead X-DAC when I do. If it goes tits up I'll just buy another of ebay, and swop the burson in again. Plus it would be good to get Mike's ears comparing the x-dac modded with Alex's ideas against his Mike's modded CD player.
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Post by Deleted on Feb 27, 2008 6:17:30 GMT
Mike Neither do I. That kind of service is not typical of Jaycar. I will be picking up the latest issue of Silicon Chip magazine from Jaycar's Hornsby store tomorrow, and pass your frustrations on to the manager. Alex
P.S. I have printed out an edited 2 pages from the 2 threads, including the photos you printed, the pleasant surprise at the pricing, as well as an unedited comment from you about the poor customer service via telephone. If the local manager shows a lack of interest, I will drop them in to their Silverwater (Sydney) HQ.
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Post by canjunkie on Feb 27, 2008 12:05:32 GMT
The 'Mk1's caps have been burning in continuously for about 72 hrs now. The changes - improvements - are not subtle. Pretty hard to be objective now as I'm way too busy listening to the music Mike's little mini-kit is an absolute nobrainer if you've got either of these little beauties. Quite fortunate for me really as my X-Cans is now starting to sound (and look on the inside) poorly . Still, with a bit of positive thinking this makes a 'Pink' upgrade kit a necessity
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Post by k2col on Mar 6, 2008 12:32:00 GMT
I've just picked up a MB-45 (was given it from a chap that I bought an old Meridian CD player from) and I'm currently enjoying it at the office with an old Pioneer CD610 as a source. Sounds great. My main complaints are that the volume control is noisy and requires only very minor adjustment to get up to listening level (maybe 8% is ok, 10% is loud, 12% hurts) and secondly that I hear a lot of interference from mobile phones in the office. Just now a crackle of interference was so harsh that I swore out loud and practically threw the phones off my head! My colleagues probably think I'm losing it I'm trying a different PSU since then and it seems to be better, but not cured.
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Post by PinkFloyd on Mar 6, 2008 14:48:39 GMT
I've just picked up a MB-45 (was given it from a chap that I bought an old Meridian CD player from) and I'm currently enjoying it at the office with an old Pioneer CD610 as a source. Sounds great. My main complaints are that the volume control is noisy and requires only very minor adjustment to get up to listening level (maybe 8% is ok, 10% is loud, 12% hurts) and secondly that I hear a lot of interference from mobile phones in the office. Just now a crackle of interference was so harsh that I swore out loud and practically threw the phones off my head! My colleagues probably think I'm losing it I'm trying a different PSU since then and it seems to be better, but not cured. My volume control was noisy, changed the capacitors and the amp is now silent
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Post by senj on Mar 6, 2008 16:18:08 GMT
Team QED MB45 is growing:)
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Post by k2col on Mar 6, 2008 16:40:10 GMT
Thanks Mike, I look forward to giving your new caps a try. Will post my thoughts and some before/after photos when I'm done. I'm currently running it with a 12v power brick that I found from an old Netgear wireless router. Would that limit the sound much? I don't fancy making my own (yet). If I was buying off the shelf, from say www.rapidonline.com/Electrical-Power/Power-Supplies/Plug-In-PSUs/Unregulated-plugtop-PSU/74993which of these would be best? AC/DC UNREG PTOP PSU 12V DC 200MA RC AC/DC UNREG PTOP PSU 12V DC 500MA RC AC/DC UNREG PTOP PSU 12V DC 1A RC Many Thanks, k2col
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Post by PinkFloyd on Mar 6, 2008 22:15:33 GMT
None of them. What you are looking for is a "regulated" PSU as these give much better sound quality over unregulated. www.maplin.co.uk you are looking for the 12V DC 400mA Supply Code: MG81C If you have a few amps (or are likely to) it may be worthwhile going for the Variable Mains Adaptor (1200mA) Code: VN10L this will give you a choice of voltages 1.5, 3, 4.5, 6, 7.5, 9 & 12Vdc Both PSUs come with a selection of plugs but make sure you connect them the right way round.... the bit that says "tip" mates up with the "+" I use the variable one with the MB-45 (VN10L) and it's a big improvement over the stock PSU. Hope this helps.
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Post by k2col on Mar 13, 2008 9:12:58 GMT
Fitted (most of) PinkFloyd's MB45 caps last night... found it a bit tricky at first as the last time I'd gone near a soldering iron was a long time ago at school. At first I felt like I needed three hands, but started to get the hang of it towards the end. And best of all it still works Too soon to comment on the sound as I took the amp home and this meant switching the source from a Phillips CD610 to a Meridian 206 player. I didn't do any 'before' listening on the Meridian as I was keen to get started. I have a question about burn in.... how long, best method? Does it matter if phone are connected or not? Turn it up loud or use normal listening levels? I haven't fitted the Rifa PME271, nor the optional film cap or 474J. I understand that the Rifa soaks up background noise, but what do you expect the other two optional caps will do to the sound?
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Post by canjunkie on Mar 13, 2008 10:41:32 GMT
For burn in Mike advised me about 200 hours with headphones plugged in to at least one channel and a signal being fed into it at normal listening levels. I think Mike posted some links to some burn in test tones on the Grotto website. The improvements over the burn in period were noticeable. The Rifa filters out any nasties coming from the PSU - especially unregulated wall warts. I went into anorak mode and tried three or four PSU's regulated, unregulated and switch mode and the Rifa made a positive difference no matter what I powered it with. Without it there was a definite harshness in the SQ that is so common in poor transistor designs. Everything took on a distinctly 'compressed' feel to it. It really is worth persevering with getting it in there! If you want to know how I shoe horned it in PM me. I had a hobby drill to hand to make a hole for one leg but you should be able to get away with soldering it directly to the back of the PSU socket. As for the source I had a go with the QED plugged into my MF CDPre as well as my 6000 KI and it rocked! I tried using the extra caps across the 2200uF & 470uF electrolytics but I didn't detect any noticeable improvement. As of now I would say My QED is 'good fun' too listen to. It doesn't have the finesse, detail & drive of my now fully functional X-Cans but it but bearing in mind the original cost of the thing - it was a bargain. Post mod it really is a completely different beast
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Post by PinkFloyd on Mar 13, 2008 10:54:00 GMT
If you want to know how I shoe horned it in PM me. I had a hobby drill to hand to make a hole for one leg but you should be able to get away with soldering it directly to the back of the PSU socket. Eh? Just solder it across the DC inlet +/- tracks...... no need to drill anything
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Post by canjunkie on Mar 13, 2008 11:45:50 GMT
If you want to know how I shoe horned it in PM me. I had a hobby drill to hand to make a hole for one leg but you should be able to get away with soldering it directly to the back of the PSU socket. Eh? Just solder it across the DC inlet +/- tracks...... no need to drill anything I know, but it was late and the Rifa kept fouling the lid. Also on the original 'mk1' the solder tracks are on the underside of the PCB - but looking back through the posts 'col's got a MB45 so just ignore me
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Post by PinkFloyd on Mar 13, 2008 13:47:55 GMT
Also on the original 'mk1' the solder tracks are on the underside of the PCB - but looking back through the posts 'col's got a MB45 so just ignore me Ah, of course, I forgot you had the original metal enclosure jobbie.... my apologies
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Post by k2col on Mar 13, 2008 19:09:43 GMT
Cheers guys, I'm convinced by the RIFA. Left it out deliberately as I wanted the full before/after experience. Still curious as to the purpose and effects of bypassing the diode with the 100nF WIMA film cap. And bypassing the 1000uF with the 474J. I am not questioning your choices, far from it I am a complete newbie to modding, but do have a curious mind and would like to understand what the intended cause and effect is with these two upgrades
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Post by PinkFloyd on Mar 13, 2008 20:14:50 GMT
Cheers guys, I'm convinced by the RIFA. Left it out deliberately as I wanted the full before/after experience. Yup.... always go with your ears, I also think the amp sounds better with the class X2 cap in circuit. A partial snubber, you could also add a suitably sized resistor in series and it would become an RCD snubber (resistor, capacitor diode).... do a google for "snubber diode" blah blah blah..... again.... sounds better with the cap across it than without (to my lugholes anyway) Paul Stamler explains: " The bypassed electrolytic has lower impedance at high frequencies than the electrolytic by itself. In power supply caps that translates to better filtering of high-frequency components, including RFI. When the electrolytic is a coupling cap, the impedance at the highest audio frequencies, even unbypassed, is low enough not to matter. The putative advantage of bypassing audio coupling caps is that the bypass cap, being film, suffers less from dielectric absorption, particularly at high frequencies. My own experience is that bypassing electrolytic coupling caps indeed reduces the amount of audible high-frequency "hash" on things like sibilants, but not as well as replacing the electrolytics with film caps. Of course, this often isn't possible due to space limitations. " Have fun!
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Post by k2col on Mar 14, 2008 15:17:41 GMT
many thanks Mike, I don't pretend to completely understand but I get the jist Brought my MB-45 into the office today after about 30hrs burn in and there is a definite improvement. The music is more clearly defined, the silences between notes are clearer and bass definitely sounds better. I will put the RIFA in tonight and carry on the burn in all weekend... can't wait!
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rickcr42
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Post by rickcr42 on Mar 14, 2008 17:08:09 GMT
The very first headphone amp I ever in my life built was a "chip amp" using the vernerable LM380 in the balanced bridge mode.The '380 is a kissing cousin to the LM1877 though a bit less "busy" in the architecture (most notibly there is no Darlington output stage) but that aside may be a worthy project for someone as a potentially better amp than the QED while providing both the same output level and the recent need for many to use a balanced headphone amp.The input will still be single ended but the output fully balanced. My original DIY amp was from a circa Mid 70's Popular electronics article (Yes I was a subscriber) but from memory is straight off the data sheet and it being the 70's there was not yet a such thing as "audiophile grade" boutique parts and/or much research in such a magazine on proper power supplies for audio work (came to PE in an article the early eighties ) so was really a nothing amps. Reading the data sheet now in the new millenium I can see not only where the original amp was lacking but where it can be improved on as well : I-The Chip Set Gain : Way too much gain there being a stated spec of +50dB as "typical",+40dB as a minimum and +60dB as the max so not only do you need a front end volume pot (50 or 100K ) but you must also use some series attentuation to lose say 30dB after it.This can be a good thing in that with the additional resistor already inline you can use it to make a nice RFI filter with the addition of a simple single capacitor shunt to ground creating a low pass filter at the input,WAY important in an amp with such high gain BTW-if you want to make this filter variable and maybe even have it slide all the way down in the treble range for use as a Noise Filter look at the Phono Amplifiers shema in the data sheet 2-The Heat Sinks : Next is the matter of heat sinking.The original article had you bend upwards pins 3,4,5 and 10,11,2 so you could connect them to a "top hat" style heat sink than in this case was a rectangular piece of unetched copper clad pcb material with holes drilled for the pins.Being part of the ground it needs also to be attached from the pcb heat sink TO the audio ground point on the main board (a thing I overlooked in my 1970's build and that was pissing me off until I caught it ).I don't recommend this because I went through a damn lot of amp chips trying to do the "bend the pins gently upward" because i kept snapping off the damn pins and when that happens the chip is junk (luckily Radio shack carried the chips back then ).I also notice many of the "kit" versions of this amp use the pcb bottom copper as the heat sink but I'm here to tell ya this is even more wonky than the Pins-Up version because heat RISES so just where the hell is all that heat going ? to the on board parts is where ;D Nope.this being 2008 a far better method would be to use a proper DIP Package Heat Sink and a thermal bonding agent to attach it to the chip top area. 3-Passive Parts : We (the we being hobbyists) knew nothing about pssive parts performance back then so we used whatever was on the shelf at Radio Shack and even went as far as having ceramic disc caps IN THE SINAL PATH not knowing any better.Now we have not only more knowledge but more options so the parts quality upgrade alone should make this a better amp than my earlier attempts at making the POS sound good 4-The Power Supply : You see that PSRR ? BRUTAL is the only word that can describe it and no wonder my amp sounded like crap when I used a simple zener shunt regulator to power this beast.You NEED a proper regulated power supply with my recommendation being an LM340T-15 fixed or better yet LM340T "user set" voltage @ 18VDC.Use a 3,300uF low impedance Electrolytic/10uF Film/0.1uF film cap preceeding and a 30uF (Solen)/0.1 uF film cap post V-Reg (smalles values right at the V-Reg pins ) as the way to go then another 0.01 right at the power pin of the chip.These last three caps need to be the absolute best you can get because they WILL be audible being the last stage of the power supply string This baby can swing both voltage and current so if done right I see no reason it can't kick some ass if done right with the above being some untried but possible ways to get there Rick Out www.national.com/mpf/LM/LM380.htmlwww.national.com/ds.cgi/LM/LM380.pdf
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Post by senj on Mar 15, 2008 9:54:06 GMT
Just got mine this morning. After a little confusion about which inputs to use, i tried a few Radiohead songs, and I'm getting a chunk more impact then what my cheapie Behringer gave me. Excellent so far, and really fun, I'm gonna leave it on for a couple of hours and see if it changes. There is SO much power available, I'm only using a quarter or so.
The volume control is quiet, and there is only a slight background hiss, so mine seems to be in pretty good nick. Recapping will commence on Monday or Tuesday once I've got some supplies. Right what do i need...
I've got loads of old solder which must be 6-years old at least, it's Tin/Lead 60/40 with flux in the core will this do?
Pinkfloyd you mentioned you washed the board with Isopropyl alcohol, how did you do this exactly? Just pour it on?! or use cotton buds or something? And I'd better get some BRASSO too, and some new solder tips, my cheap ones disintegrated before my eyes last time!
Will post pics soon of course!
Edit: Rick are there any modern designs using that LM380?
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Post by PinkFloyd on Mar 15, 2008 12:40:40 GMT
I've got loads of old solder which must be 6-years old at least, it's Tin/Lead 60/40 with flux in the core will this do? Perfect, 60/40 is ideal. Arm yourself with an old toothbrush. Dip said toothbrush in the isopropyl and scrub the PCB, repeat a couple of times. wipe with some kitchen roll.... you'll find the kitchen roll shreds when it goes over the joints, perfectly good, just go over the PCB with the dry toothbrush to remove all the shredded kitchen roll...... piece of cake man The more the merrier Look forward to seeing them senj Possibly.
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rickcr42
Fully Modded
Rest in peace my good friend.
Posts: 4,514
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Post by rickcr42 on Mar 15, 2008 14:40:23 GMT
seems there are loads of very inexpensive LM380 "Amplifier" kits out there but not one that I am aware of that uses the Balanced Bridge configuration so if you attempt to use four mono amp boards it could get a bit pricey plus the casing would have to be way huge not to mention likely having to re-do the input structure of the boards to make one half of the bridge an inverting amp. If I were to actually do one (and may if the parts turn up in my "stash" of electronica.Have a boatload of LM386's for guitar practice amps so a possible ) I would shoot to a G10 Fiberglass Universal PCB build to keep the footprint size down with CH-A amp pair at the top of the board,CH-B amp pair at the bottom,input from the left side,output from the right and use an off-board power supply using LM340/LM320 V-Regs running at +/- 18VDC (the BEST of the three pin V-Regs for audio BTW but only if you use 'em right ). What would it sound like in comparison to modern opamp or opamp/output buffer cascade amps using modern layout techniques and materials ? total unknown but looking at the schema of the LM380 suggests potential inside waiting to be let out of the box
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leo
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Post by leo on Mar 15, 2008 18:29:23 GMT
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Post by PinkFloyd on Mar 15, 2008 22:26:24 GMT
Holy torpedo can this thing drive the K-701!! No problems at all and it's definitely not a bad sounding amp is it guys? I had always assumed it would be pretty naff for the money but, nope, quite a good little performer It may not have the large soundstage some other amps possess but it's quite an intimate listen, more in head than out. The Doudou threw some of the sound clean out of the K-701 (a few feet it seemed like!) but the MB-45 keeps everything quite firmly in the head. It's also quite a warm listen with the K-701 which I like. Definitely a great little tool to drive inefficent 'phones with, that's for sure and for £40 or so on ebay can't be overlooked. Twin headouts too..... superb
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leo
Been here a while!
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Post by leo on Mar 15, 2008 22:40:46 GMT
Another potential project for later ;D we could draw out a nice little pcb for this chip, add in some kick arse regulation should prove quite interesting
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