matt7941
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Post by matt7941 on Oct 10, 2008 23:26:40 GMT
Good evening ladies and gentleman.
I'm hoping someone can help me. I've got a lovely old MF A3 integrated amp which has served me well for several years. I didn't want to (and couldn't really afford to!) part with it so decided to upgrade her. I've already replaced most of the ceramic caps with polyprops, the nasty Jamicons for Panasonic FC/FMs in the audio side and Oscons on the power supply side, the main 6800uf have been changed for Panasonic TSHAs. The CD input RCAs have been changed for CMC silver plated and the outputs for CMC silver plated 4mm sockets too (nice). The wire from the CMC RCAs is Mundorf Silver/Gold teflon insulated. The 1Nxxxx diodes have been replaced with UFxxxx series.
This has already been a major improvement. However, having chanced upon a previous thread re a MF X-150 the basic circuit seems similar to mine, indeed it has at its heart a Motorola MC33079P opamp which I'd like to replace. The thread mentions OPA4134 and LME49740 as good options, I could do with opinions which would be better and where to source them in the UK. I can get the LME49740 from Farnell's, but for the OPA 4134 they want to charge me the cost of the OPA4134 plus £16.00 as it is "US" stock. RS, Rapid and CPC seem to be of no help.
Also, I have replace the internal wiring from the circuit board to the speaker outputs with QED Silver Anniversary but can anyone suggest a better (preferably solid silver) wire to use. Would 1mm diameter solid silver wire be good or would I need specific speaker type wire.
I hope someone can help, as you'd be helping out a poor starving stressed out (!) mature student to relax.
Thanks
Matt
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Post by Deleted on Oct 11, 2008 0:04:38 GMT
matt7941 The OPA4134 would have been my choice, but not at those prices. I found that even Digikey stocks only the surface mount version.The LME49740 would appear to be your only real option, but you would have to make sure that it was stable in this particular layout. Instability usually manifests itself as a graininess to the sound, or the I.C. getting quite warm. There are quite a few members who could offer advice if it becomes necessary to "tame" this device. I won't go there with most of the other stuff. (except for UFxxx diodes which are a good choice) IMHO, Good design doesn't need assistance from exotic (expensive!) wire etc. However, having used silver plated teflon covered wire in HUGE quantities in my time in Telecommunications, I would use it in a passive preamp if I was ever to construct one again. SandyK
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Post by canjunkie on Oct 11, 2008 6:36:38 GMT
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matt7941
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Post by matt7941 on Oct 11, 2008 8:49:01 GMT
Thanks guys, I've ordered the LME49740 as per Canjunkie's link. I never thought of eBay for some reason.
With regards possible distortion and oscillation from the LME49740 I was thinking of bypassing the power supplies in any case as per my experience, and Alex's previous advice, with the LM4562. Should be a bit easier on this board with a touch more space to work with than in the X-24K.
Thanks again for the help, most appreciated.
One thing, apparently this is for two pieces and I only require one. Should anyone want the other just PM me, you can have it for free in the UK just so long as I manage not to fry the first one (!). I've also got a few Oscons and Panasonic FC/FMs left over from other tweaks if I can help people out. They are generally odd ones or twos but PM me if you need one or two, I might have them (no guarantess) and they'll cost you nothing.
Cheers
Matt
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Post by Deleted on Oct 11, 2008 10:58:37 GMT
Matt Just curious, what do you not like about the A3 as standard? What do you hope to achieve with these mods? I have an A3 and quite like the sound though with the current speakers, Castle Richmond 3is, it can sound a little too 'plummy' but mostly fine (its a second system). I have seen some people calling it bright, I always found the opposite!
Alex When you say you won't go there with the other mods, do you mean you would leave them as is or use alternatives? juke
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Post by Deleted on Oct 11, 2008 11:37:16 GMT
Juke Originally, I didn't want to go there ,for fear of offending Matt, but you DID have to ask ! I mean that they are getting into the area of "snake oil" and "fiddling around the edges", and invariably expensive. Almost everything you do in an amplifier can make minor audible changes,though not necessarily for the better. Things like solid silver wire are usually put in to try make an otherwise dull sounding amplifier sound brighter. Well designed amplifiers don't need this kind of modifying. I defy anyone to reliably pick the difference between 2 otherwise identical amplifiers , but one using CMC silver plated sockets in a "double blind" listening test, provided that the one not using them has sockets that are clean, and not worn. They might look attractive though. ;D Other changes used by people trying to make a dull amplifier sound brighter, include copious numbers of big brand name, low ESR electrolytic capacitors, A.K.A. "Audio Grade" , and smaller value capacitors across input and output capacitors, and every other electrolytic in sight,even the low ESR types ! Some people even put even smaller capacitors across the smaller value parallel capacitors ! A better way to go with dull sounding amplifiers might be to use something that Rick recommends - Tone Controls. BTW, The SC HA with JLH only uses standard , commonly available components. There is nothing special in the circuitry, not even a big expensive polypropylene , or other fancy input capacitor. The only concession made was to replace a cruddy bipolar electrolytic with a cheap, commonly available Wima film type.
SandyK
P.S. As far as wiring to the speaker terminals goes, just use something like the wire out of a 10 amp mains cable. If you think about it, you can't really expect "magical" results from replacing what is in effect ,the first 10CM ,or so, of the speaker cable with exotic wire,when the other 2 metres uses ordinary multi core speaker cable, even jumbo types where the end of the cable has all the individual wire ends soldered together.( HINT!) Most speaker cables eventually oxidise and go higher resistance at that place.
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matt7941
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Post by matt7941 on Oct 11, 2008 14:15:49 GMT
Good afternoon gentlemen.
In response to Juke's question, I agree with the "stock" sound of the A3, it is definitely a little too relaxed and a little shy in the treble. Where people have got the idea that it is bright I have no idea. What I have found it lacks is a touch of dynamics and it does possess a softening of the bass with an accompanying "thud".
What I hope to achieve, and must say I have (at least to my ears) to some extent, is to open up the top end a touch, add a touch of dynamics and most importantly underpin the bass. The caps and diodes have cost next to nothing and I've enjoyed tinkering. I would recommend replacing the 6800uf originals in there with the Panasonic TSHAs as this really makes a difference. The sockets weren't cheap, neither were they anywhere near as expensive as using Audio Note Gold audiophile caps. However, I feel they are of much better quality and have added a touch more detail and openness. I must also admit to having put the sockets on the outputs of my modded X-24K dac and the interconnect is solid silver with silver Eichmann Bullets which made a huge improvement. Thus with my silver plated speaker wire I have a complete silver signal path.
At this point I must admit to being slightly anal in this department, I probably wouldn't have slept at night knowing the RCAs were cheap gold plated and not silver!
What I cannot argue with is that the stock sound of the A3 is perfectly palatable. When I purchased it several years ago it was auditioned against a Sugden A21 (too soft and relaxed for me) and an Arcam A85 (slightly brutish and unsubtle). The A3 was a middle ground, not the lush detail of the Sugden admittedly but more dynamic and lively but not to the extent of the (in my opinion) raucous A85. I merely wished to retain the overall sonic character but to try and iron out what I saw as perceived flaws. I feel that I have gone someway to achieving this for modest outlay without spending the earth. My current student income does not approach my previous means and thus I have to cut my cloth to suit. Plus, I quite like tinkering with the soldering iron in hand, it feels somehow cathartic.
Alex, don't worry you have not offended me in the slightest. What we each get out of this is subjective and if it makes us happy then so be it. Besides, after all the advice (once again much appreciated) you've offered me of late it would be rather churlish of me to get upset by any criticism.
For the record apart from the X-24K dac the A3 is feeding a pair of Epos M15.2 and a REL Quake sub just to fill in the very bottom end. Most of my music is soul so most of the modern and 80s stuff relies on basslines.
Cheers, take care
Matt.
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Post by Deleted on Oct 11, 2008 21:12:21 GMT
Matt What lets down most gear is the power supply. Most of the problems that you mention can usually be sorted out by making a big improvement to the power supply. This is the reason for the rationale behind the JLH module mentioned in other threads. A very good power supply will not only reveal extra HF detail, but it will lower the noise level, AND improve dynamics. Perhaps you can see if there is any further improvement that you can readily make in that area ? Alex
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Post by Deleted on Oct 11, 2008 21:36:33 GMT
Thanks to Alex and Matt for the answers. I would have a go at the power supplies if I ever had a to b to c instructions! Meantime I'll think about changing the speakers.
Could the opamp be replaced alone, or does it always require other mods? Maybe too big a question for a general query. juke
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Post by Deleted on Oct 11, 2008 22:19:00 GMT
Juke If you can obtain a DIP OPA4134, it is likely to slot in without any problems.None that shouldn't be readily corrected, anyway. The LM4562 and it's brothers and sisters, are more picky with their power supply arrangements. BTW, does anybody have a schematic of this unit ? That would enable more specific advice from the usual suspects. Alex
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Post by Deleted on Oct 11, 2008 23:01:54 GMT
Alex Just searched the Net and no sign of a schematic. I'll try to get the OPA4134 soon and see what it does to the sound. Thanks, juke
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matt7941
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Post by matt7941 on Oct 12, 2008 9:42:01 GMT
Echo Alex's request, if anyone has a schematic that would be fantastic. I've scoured the web and manufacturer sites and found nothing.
Juke, I believe that the OPA4134 is now only available in SOIC configuration so an adaptor board would be necessary. Please let me know if you can find any in DIP configuration for less than a king's ransom, they seem to be in very short supply. I quite like the sound of the opa2134 and it's cousin the opa2604 so probably would be excellent for the A3. I've just fitted a 14-DIL socket so opamps can be plugged in and unplugged readily.
I've also ordered a pair of LME49740 opamps. I couldn't find them singly and should only require one. I see you're just across the water so to speak in Northern Ireland, if you'd like the other it's yours for nothing if you PM me with your address. Might be a short while before it arrives as it coming from overseas. I'm hoping it will make as much difference to the sound as changing the original NE5532 opamp in my DAC to the dual version of the LME49740, the LM4562. Even if it only approaches the gains of the aforementioned LM4562 it will be worth it. It's probably a good idea to remove and save the MC33079P that is in yours and solder in a 14-DIL socket so if you don't like the sound or the LME49740 does distort you can remove it easily.
Alex, the power supply is well fed by dual toroidals (I'll try and find out the VA etc) but has the usual 1Nxxxx diodes as discussed and a pair of BR104 bridge rectifiers. I suppose replacing these also with UFxxxx series diodes of the correct type would be a worthwhile and inexpensive tweak. By the way I was wrong in stating that the caps were mainly Jamicon, they are actually mainly Teapo and when removed several of mine were bulging badly. I have come across a few threads on the internet where these have failed badly, especially in computer equipment, although this of course could be down to bad circuit design. However, they don't seem to be well liked.
Juke, let me know your thoughts,
Cheers,
Matt.
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Post by Deleted on Oct 12, 2008 10:22:41 GMT
Matt7941 By now you would have quite a few members wondering what the exterior and interior of this amplifier looks like. Any chance of posting a few photos ? Alex
P.S. I like this bit : "You can always trust politicians. You can trust them to lie, cheat and be consistently hypocritical!"
Now for a leading question, do you think that the Governor of Alaska has hurt her election chances with the U.S. female voters, by standing up for her sister in that messy divorce action, and getting her brother inlaw sacked ? I suspect that many women would have a lot of sympathy for her actions in this case ?
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matt7941
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Post by matt7941 on Oct 12, 2008 10:45:34 GMT
I'll dig the digital camera out and take some photos. Can't guarantee they'll be of truly publishable quality but I'll attempt over the next couple of days when I get a moment or two. Just tell me how to upload them to this site and you can see the now legendary beast! I'll also post some pictures of the inside of of what was Dave's (Canjunkie) X-24K DAC and how it's changed compared to the original photos elsewhere in the forum.
I think Sarah Palin is busy trying to sabotage McCain's last hopes in this election. But, the campaign team only have themselves to blame by wheeling in someone as politically inexperienced and particularly naive as her just to try to siphon off some of the female vote that might otherwise ally themselves to Hilary Clinton and the Democrats. Personally I wish to see Obama and the Democrats triumph as 4 more years of Neo-cons would truly send the global situation spiralling to disaster. Without trying to be too political it's the legacy of the right wing Neo-liberals of Reagan and Thatcher fame that sowed the seeds for both political and economic instability we see today. Having said all that, you've got to feel sorry for McCain. Not only is he having to try and follow the now despised Bush Jr. but he's now got all that to contend with, what chance does he stand?
Sorry for the politics everyone I know it's a little off-thread, it won't happen again. I'm a politics student, what else can I do when asked a question!
Cheers
Matt.
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Post by Deleted on Oct 12, 2008 11:14:27 GMT
Matt There are places like Photo Bucket and Image Shack where you can register for free, and upload images within certain limits, before you need to pay. I use ImageShack for mine, and after uploading an image you can then click on it and be given the option of posting the full size image or a thumbnail. You are presented with forum options etc, and all you have to do is "copy" (Control +C) the Forum posting information, then in your actual forum post, you "paste" this information (Control + V) Alex imageshack.us/
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matt7941
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Post by matt7941 on Oct 12, 2008 11:35:47 GMT
Cheers Alex.
I'll post some pictures as soon as I can as long as you promise not to laugh or criticise my soldering too much. We can't all wield a soldering iron like Mike.
The amp is partially disassembled at the moment so I'll post how she looks now, people can always check the MF website if they want to see the showroom views. I'm just considering the options re the internal wire to the speaker outputs, still think I'm plumping for the silver wire though. I just can't help myself!
Matt.
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Post by canjunkie on Oct 12, 2008 13:30:41 GMT
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Post by Deleted on Oct 12, 2008 23:03:06 GMT
Matt, Canjunkie I've ordered the 4134s from Canjunkie's link. As there are 4 I can sort you. Adapters already ordered also. juke
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matt7941
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Post by matt7941 on Oct 13, 2008 18:59:12 GMT
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matt7941
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Post by matt7941 on Oct 13, 2008 19:06:40 GMT
By the way, apologies for the less than brilliant quality. My camera and my photographic skills are less than ideal. There are other images of the amp on the site so feel free to scroll through. Cheers, Matt
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Post by Deleted on Oct 13, 2008 20:50:13 GMT
Matt Try pasting the whole of the FORUM line. If you change to THUMBNAIL MODE "No" , the full image will be posted. Alex P.S. I can see why you love those silver sockets ! The dual supplies for the preamp, in the photo of yours that I took the liberty of inserting in your post, seem an interesting area to experiment in. Especially things like those small bridge rectifiers etc. Alex P.P.S. I have sent you an email with schematic of power section of MF A2 in case there is any resemblance.
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matt7941
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Post by matt7941 on Oct 14, 2008 14:32:00 GMT
Alex, you're right about the sockets. I just couldn't believe the sheer physical weight of them, they really are solid pieces.
You can see I've replaced the Teapos with Oscons and FCs and the ceramics with Evox polpropylenes in the power supply stage, which I think was worthwhile.
Unfortunately, it would seem that the A2 and A3 are completely different beasts. I have tried to transpose the schematic you sent to the actual board and, although I would say I am not the world's best at it, it would appear to be quite different from start to finish.
The bridge rectifiers and possibly the voltage regulators seem to be a possible area for upgrade, the bridge rectifiers especially from what I have read although never undertaken myself. The larger two are BR104 (10A 400V?) and the smaller one is marked W04M (1.5A 400V?). For the latter would an arrangement of UF4007 or UF4004 be suitable and what would you recommend to replace the BR104? I was also thinking that upping the main supply caps from 6800uf to 10000uf can only be beneficial, even if it would require some surgery to the case to fit them in as the headroom is rather shallow. Could the voltage regulators be addressed with JLHs?
I trust that I am not offending you by asking for a bit of your expertise, my knowledge is rather basic and I truly am grateful for any help.
Take care
Cheers,
Matt.
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Post by Deleted on Oct 14, 2008 20:34:27 GMT
Matt You could replace the W04M with 4 x UF diodes on a bit of perf/veroboard. I am not sure replacing the big bridges would be worth the trouble . 10,000uF caps could be worthwhile if they can fit, particularly if the unit is fairly old.It could be a bit tricky implementing a JLH or 2 without some knowledge of the circuit, as both sides at the front aren't mirror images. Alex P.S. I hope you are recovering well from that major surgery?
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matt7941
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Post by matt7941 on Oct 14, 2008 21:02:16 GMT
I'll try the W04M replacement, I can pick up some UF4007s tomorrow and have a stab at it. I presume they should be fine, it's just the W04M is allegedly rated at 1.5A which is slightly higher than the UF4007s. I'll leave the larger rectifiers where they are, 10A ultrafasts seem to be a little thin on the ground at least at the 400V rating.
Thanks again.
Cheers
Matt.
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Post by Deleted on Oct 14, 2008 21:38:12 GMT
Matt Go for the UF4004,they are faster than the UF4007, and the same voltage ratings as the W04M. Alex
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