XTRProf
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Post by XTRProf on Mar 27, 2009 2:39:49 GMT
He's my fellow countryman. Nice guy, btw.
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Post by jeffc on Mar 27, 2009 4:16:46 GMT
yer, totally agree that Yeo seems to be a guy who just loves really good music and simply wants to share his somewhat 'left field' means of obtaining this with his Monica DACs at almost zero return to him financially. From all the gar-gar happening at the DIYparadise forum over the past 6 mths or so, Monica now seems to have been tweaked to a point, with an i/v stage incorporating a Nelson Pass 2sk170 jfet-based buffer, where it can match oversampling DACs in dynamics, pace and frequency extremes but still leaves them for dead in terms of midrange magic and musical enjoyment. Must get back to upgrading mine. cheers.. jeffc
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XTRProf
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Pssst ! Got any spare capacitors ?
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Post by XTRProf on Mar 27, 2009 13:06:48 GMT
yer, totally agree that Yeo seems to be a guy who just loves really good music and simply wants to share his somewhat 'left field' means of obtaining this with his Monica DACs at almost zero return to him financially. From all the gar-gar happening at the DIYparadise forum over the past 6 mths or so, Monica now seems to have been tweaked to a point, with an i/v stage incorporating a Nelson Pass 2sk170 jfet-based buffer, where it can match oversampling DACs in dynamics, pace and frequency extremes but still leaves them for dead in terms of midrange magic and musical enjoyment. Must get back to upgrading mine. cheers.. jeffc Yeah, Yeo is pretty good with those stuffs. So what are you moding next for your dac? A Monica too I believe.
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Will
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Post by Will on Mar 27, 2009 20:53:48 GMT
Will, One more thing, the SQ of this DAC, and my guess any DAC with low power needs, is likely to be improved startlingly when placed downstream of a balanced isolation transformer to negate the nasties of common ground mode noise. Hooking up mine was one of those OMG what have I been missing moments. Not just me on this one, guys at DIYparadise found that beyond the use of medium to massive 12V batteries, the use of a balanced isolation transformer delivered profound improvements in SQ to the Monica NOS TDA1545A DAC that I've also been toying with. I made one using 2 x 12-0-12 30VA encapsulated transformers I had at hand that seems to work quite OK but DIYparadise sells one specifically designed for the job. Not too expensive either. No affiliation with Yeo except that I think he's a very decent guy and has quite a bit of my hard earned. diyparadise.com/shop/index.php?main_page=index&cPath=9diyparadise.com/web/index.php?option=com_content&task=view&id=77&Itemid=26cheers.. jeffc Jeff, What an intriguing idea! As you say, not to expensive to implement, and if you build it into a box with a socket, it could be tested on other equipment as well. One thing I would like to clarify is that this is the principal, for myself, and any others (who are confident and competent with main voltage). You take two transformers (perhaps Rapid PN:88-2618 or 88-0305). you connect the secondary of the first as 12-0-12 and then connect the secondary of the second transformer (also 12-0-12) to the first transformers secondary. You connect the 0V (CT) of the first transformer to earth. What effectively happens now is you would measure 230VAC out the output of the second transformer, if you fed 230VAC into the first, minus mains born rubbish. A question though, what do you do with the 0V (CT) of the second transformer? Do you leave this floating or is it also connected to earth? I would also guess that if you have good mains in your local area, this mod would have limited benefit.
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Post by jeffc on Mar 27, 2009 22:35:28 GMT
Hi Will, Correct, centre tap of the second transformer is left floating. Losses in the transformers might drop output voltage by a fraction, but really a non-issue. Words of caution I got excited by results with the DAC and balanced power from the twin resin-encapsulated transformer unit. These have separated windings from what I can gather. Anyways mates got excited too and we built a couple more using large toroidals 9-0-9 300VA. These were tested on various CDPs, amps with some real benefits in noise floor drop and accompanying gains in resolution of low level nuances in the music. However, there was also some downsides in terms of constricted bass oomph and lessened involvement, something just not quite right. Got into researching balanced isolated transformers and it appears that torodials are not constructed in away lent to this application 'for audio at least' and are a 'big no no'. Something to do with core saturation and other problems. Might invite the resident tech-sperts Alex, Leo and Robert for input here and on issues of gear safety re fusing and 120V output on the A and N to give 240V. Anyway, if you wanted to try this, recommendation would be to avoid toroidals and either get the DIYparadise unit, endorsement is its 'sold out' at the moment, or try the Rapid 50VA EI transformers with either 6-0-6 or 9-0-9 secondaries. a few links on commercial units www.transcendentsound.com/power_supply.htmwww.equitech.com/and check here as well, some words on safety www.audiocircle.com/circles/index.php?topic=34605.msg307911cheers.. jeffc
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Post by jeffc on Mar 27, 2009 22:44:46 GMT
Hi XTRProf, The pace of mods being recommended for my USB Monica NOS DAC over at DIYparadise got way too much for me, been sitting on the sidelines, but new i/v board kits are available now which accommodate most mods. Beyond this its all been about capacitors and regulated power supply quality being fed to the various DAC sections, where unfortunately $s can be spent until the cows come home. cheers.. jeffc
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robertkd
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Post by robertkd on Mar 27, 2009 23:12:15 GMT
Ok this is a common trick, to get rid of common mode noise and other krap found on the mains.
Do be aware that the mains is not balanced! (Australia)
you have a supply "Active" and a return "Neutral" the Neutral and Earth are connected in the meter Box and ONLY at that point, MEN system.
Fuse the Active into the input transformer.
What are you doing with the earth?
The efficiency cops a couple of blows especially with low secondary voltages, hence getting into core saturation under even moderate loads.
Be aware the isolation given here may defeat any RCD device protection!
Robert
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Post by Deleted on Mar 27, 2009 23:29:28 GMT
Robert has made a very good point. There are other methods of achieving similar results without the risks. Some of these already feature in some of Mike's projects. However, be aware that many mains filters will degrade sound quality with power amplifiers. Better results may often be obtained by making your own, using heavy gauge enamelled wire on ferrite rods. You also need to be careful about the use of capacitors from Active to earth, as this may cause RCD devices to intermittently trip at the most inconvenient times. Alex
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leo
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Post by leo on Mar 27, 2009 23:41:47 GMT
I've been listening to a Monica 3 dac here
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Post by jeffc on Mar 27, 2009 23:41:59 GMT
Thanks Robert, Learn something new every day. So does this mean that Neutral being tied to Earth in the meter box does give a measure of earth leakage protection for gear like CDPs, TVs, boom boxes or whatever with no earth wire connection? Secondly, on the balanced power idea, do higher secondary voltages help then with current load levels at which transformer core saturation will occur? Thirdly, any idea of transformer VA ratings needed so that current load would be a non-issue with a dinky DAC like this, either for digital and analog sections or digital section only which would be very low? Permission to say go figure this yourself. cheers.. jeffc PS Alec and Leo, sorry didn't see your posts before posting this. And I do have ferrite rods for that kind of noise reduction schema for power amps that I intent to try out, sometime.
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robertkd
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Post by robertkd on Mar 27, 2009 23:52:29 GMT
Thanks Robert, Learn something new every day. So does this mean that Neutral being tied to Earth in the meter box does give a measure of earth leakage protection for gear like CDPs, TVs, boom boxes or whatever with no earth wire connection? that is not what it is intended for. to a degree, larger cores are better but come at a cost of lower efficiency. higher voltage secondaries mean lower current for a given VA yes these a low VA circuits I would probably just double your load e.g. you need 20VA so 40VA or better, it's not like your running a kilowatt amp ;D
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Post by jeffc on Mar 28, 2009 0:14:45 GMT
OK, cheers Robert, will go climb back into my cave Leo, I take the is because you're disappointed in the SQ of Monica 3. Worth a thread maybe to supply your impressions, good value mods etc. I gather you're using it with the revised i/v-buffer stage etc. And on this cheapo CS4397 DAC, you haven't by chance tried it with a LM4562HA, I thought it a fantastic improvement over the plastic case opamp. cheers.. jeffc
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leo
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Post by leo on Mar 28, 2009 0:28:32 GMT
Apart from it lit up like a Christmas tree I think its a nice sounding little dac tbh, as it is I prefer my modded Buffalo and AYA but the M3 is good performer Obviously some scope for modding too It uses the 2sk170's tagged on the bottom of the board for buffer duties I need more time getting to know its circuit
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leo
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Post by leo on Mar 28, 2009 0:32:00 GMT
TBH I've not used the Elcheapo CS4397 dac for a while but I'll be sure to stick the metal can LM4562 in and see how it goes
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Post by mwofsi on Mar 28, 2009 9:21:33 GMT
Do be aware that the mains is not balanced! (Australia) you have a supply "Active" and a return "Neutral" the Neutral and Earth are connected in the meter Box and ONLY at that point, MEN system. Robert Hello and sorry to butt in but I've been confused about this for along time. If you've got an AC supply what's the difference between Active (Live) and Neutral? Aren't they just part of the same circuit, current flows one way and then the other? Not sure about the Earth being tied to Neutral, doesn't that make Earth part of the live circuit? Is the UK different? I thought that the Earth was completely separate, a safety feature? Regards, Mike W.
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Post by Deleted on Mar 28, 2009 9:56:33 GMT
Mike In the U.K. the Neutral leg of the mains supply is only earthed at the local distribution transformer,and not at the premises as in countries like Australia. This means that the Neutral wire has only a small voltage on it. The Active wire has the full mains voltage across it. there is a reasonable explanation at the attached link. Just remember that the earth wire at your place, and the earth wire/Neutral connection at the local transformer are in essence, connected together via the relatively low resistance of the earth between them. Just how low the actual resistance between them is, will depend on the nature of the land itself. e.g. whether it is predominantly sandstone , or other features such as moisture content of the earth itself etc. At one of the Telephone Exchanges that I worked at in Sydney, we had a degree of difficulty in getting a satisfactory earth, due to the local terrain. This caused some of the telephony circuits to have a little higher than desireable noise level due to this exchange's earth resistance, being markedly higher than other nearby Telephone Exchanges earths. www.bbc.co.uk/schools/gcsebitesize/science/add_aqa/electricity/mainselectrev_print.shtml
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Will
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Post by Will on Mar 28, 2009 10:07:43 GMT
Couple of things on the mains voltage.
On the point of some volts being lost, as long as you have 220VAC coming out, you will be fine. This is the standardised voltage we should be getting at the main socket anyway (europe). The fact we get 235-245VAC in the UK harks back to our recent industrial past, which placed load on the supply.
In my line of work, we have been able to make great savings using voltage optimisation equipment, which reduces incoming voltage to 220VAC, and massively reduces capactive and inductive power losses. Savings of 8-10% of total electrical consumption are common. Coming soon to the domestic market..
As for what earth connection we use, I'll have to check my 16th elec regs books, but I think that local (as in distribution, not consumer) N to PE is used when the area is supplied by a TN-C system. That is what I have in my home, but 10 minutes up the road, PE in my father in laws house is provide by local earth stake. All different ways, but in general - be careful, your RCB/RCBO will not be your guardian angel - hence the confident/competent remark.
Thanks for the confirmation of my thoughts on using EI as well. Helpd that they are cheaper too..
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robertkd
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Post by robertkd on Mar 28, 2009 10:42:52 GMT
Do be aware that the mains is not balanced! (Australia) you have a supply "Active" and a return "Neutral" the Neutral and Earth are connected in the meter Box and ONLY at that point, MEN system. Robert Hello and sorry to butt in but I've been confused about this for along time. If you've got an AC supply what's the difference between Active (Live) and Neutral? Aren't they just part of the same circuit, current flows one way and then the other? Not sure about the Earth being tied to Neutral, doesn't that make Earth part of the live circuit? Is the UK different? I thought that the Earth was completely separate, a safety feature? Regards, Mike W. Mike do butt in, not sure where to start, your correct with the current flowing in alternate directions, and they are part of the same circuit.. the neutral is the return path back to the supply. Think of the supply that comes in to your home as coming from a transformer secondary (actually that's because it does) the neutral is derived from one side of the transformer winding that is referenced to ground or zero volts, the other end of the transformer winding is your active. The voltage at the active wire alternates from Ov to +234V to 0 to -234V then to 0 and repeats this at a rate of 50 times a second hence 50Hz supply frequency. Ok the safety earth, well the idea is that this is at zero volts and whilst this is connected to the neutral at the meter box, remember the neutral is also at zero (well this is theory isn't it) the earth is also is at zero potential difference. In normal circumstances the earth caries no current! it's there should a fault occur say a wire breaks, say the active wire breaks and makes contact with the earthed metal enclosure, well lots of current flows and the fuse blows and no one got electrocuted. you will also notice on mains plugs that the earth pin is longer then the active and neutral this is to ensure that this is the first connection made when plugging something in and the last when unplugging something. HTH
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Post by mwofsi on Mar 28, 2009 10:44:56 GMT
Thank you Alex, and Robert of course,
I think I've got it, and you've addressed doubts I had about the Ground part as well.
When one makes a circuit it's alternating current that flows, but it's mostly the changing potential in the Active/Live wire that makes it happen.
I'll probably still get confused, just the way I'm built.
Regards, Mike W
Edit, missed a couple of posts from Will an Robert while typing, will keep reading.
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XTRProf
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Post by XTRProf on Mar 29, 2009 0:21:48 GMT
Hi XTRProf, The pace of mods being recommended for my USB Monica NOS DAC over at DIYparadise got way too much for me, been sitting on the sidelines, but new i/v board kits are available now which accommodate most mods. Beyond this its all been about capacitors and regulated power supply quality being fed to the various DAC sections, where unfortunately $s can be spent until the cows come home. cheers.. jeffc I know what you mean as I had been thru that as well when sheer lunacy kicks in until "bankrupt". Ha, ha, we need to learn how to control ourselves and be a good "boy" at home sometimes.
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XTRProf
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Post by XTRProf on Mar 29, 2009 0:56:32 GMT
Actually, this balanced isolation transformer thingy, I'm not too impressed, at least for first impression. My peer invited me to hear the "improvement" after seeing all the positive vibes about them and built one using a 2KVA trans to "kill" all doubts about load being a limiting factor. It was used driving his SET (300B I think as that was sometime ago of about 1.5 years) amp. I still remembered him jive talking about all the good things about the sound but according to my ears were all about shitty sound, being undynamic, shrill and the muzak was just not involving and moving anymore. The eye opener came when someone in the crowd asked to see how the trans looked like after being brainwashed impressively. So my peer builder took out the trans to show the crowd and had his SET amp plugged back directly into the wall and switch the amp on to continue entertaining the crowd while those interested have a look at the trans. Boy, oh, boy, what a revelation as the sound opened up with drive, dynamic and moving music, far away from what we were getting from the trans. I even remember my friend moving to one corner in embarassment and the crowd all of a sudden shows no more interest in the tran and everyone were talking about the tranformation whisperingly to avoid embarassing the host. The moral in this is we better try it in your application before saying all the "good" about it. It can be good and it can be bad although technically good. If it works for you, congratulation ............ but if it doesn't, don't fret as well.
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Post by jphoward on Mar 29, 2009 4:10:01 GMT
In normal circumstances the earth caries no current! it's there should a fault occur say a wire breaks, say the active wire breaks and makes contact with the earthed metal enclosure, well lots of current flows and the fuse blows and no one got electrocuted. I still find this neutral/earth stuff a bit confusing - sorry I know I'm a bit slow... Here's a question I've been struggling with: my new SC 135W amp kit has a wiring diagram in which they suggest attaching the earth directly to the 0W PSU input, along with the two wires from the transformer. I haven't seen this suggested for other kits (i.e. the SCHA). When/why should earth be connected to 0V? In a related question: what's the earth pin on the SCHA amp for? The SC article says to connect earth there, but folks here say not to unless in a metal case. I'm find this all most befuddling!
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Post by Deleted on Mar 29, 2009 4:25:57 GMT
Jeremy Don't forget that this HA was only part of a larger project, which included a preamplifier,motorised volume control , and remote control volume and source selection. I haven't constructed the SC ULD2, so I will have to re-read the original articles to see what they are referring to. Alex
P.S. The earthing arrangement described is pretty standard for many amplifiers.
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robertkd
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Post by robertkd on Mar 29, 2009 4:34:32 GMT
I still find this neutral/earth stuff a bit confusing - sorry I know I'm a bit slow... Here's a question I've been struggling with: my new SC 135W amp kit has a wiring diagram in which they suggest attaching the earth directly to the 0W PSU input, along with the two wires from the transformer. I haven't seen this suggested for other kits (i.e. the SCHA). When/why should earth be connected to 0V? ordinarily here is where I would put you through a whole world of hurt, in a good way Ok look at the diagram, I'm guessing there is a split power supply maybe +/- 50V for the amplifier, well the 0V point on the PSU is where they suggest you connect the mains earth to that point where the 2 secondaries are connected, i would also imagine from that point to the chassis as well. As a generalisation one school of thought promotes that you have one point which is common and wire(s) is/are taken from that point to whichever circuits also need to be connected to 0V, you also never make multiple connections to other circuits. there is a lot involved but that's the gist of it. As for the SC HA, well my earth connection goes to the chassis, then to is at the 0V point on my PSU isn't yours all inputs are isolated from the chassis and there are no other connections to the chassis. and as for the "earth point as marked on the PCB don't connect it, IMO the last thing you want are "ground loops" i.e. 2 or more return paths.
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Post by jphoward on Mar 29, 2009 10:24:09 GMT
As for the SC HA, well my earth connection goes to the chassis, then to is at the 0V point on my PSU isn't yours My earth does indeed go to the chassis (or at least, the alum baseplate, since I have a plastic case). What do you mean by 'then to is at the 0V point on my PSU'? Do you mean that I should connect my PSU's 0V to the chassis too? Is that a safety thing, or a SQ thing?
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