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Old 15th January 2006, 02:59 AM   #1
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Default Beyond the Force?

Just picked up a used set of NuForce Ref 8 mono loafs. Can't really bring myself to call these things "Blocks". These amps were factory updated in August. The price was right and they do sound very good. Went just about blind the other night reading threads here.
My question is what would the folks in the know here recommend as a project to outperform the NuForce. It would seem that the UCD 180 or 400 with upgraded parts would do the trick. Seems that most of what I read was mostly cap upgrade. What about output inductor upgrade? Are ther any circuit changes worth including? Do any of you have project sites for Hypex amplifiers? Are there switching supplies available for the Hypex and if so are they the way to go? If you have references to useful threads that would help out with the eye strain. Thanks for any assistance. PS: I have an old Hafler 220 with a transformer with 240 windings so if I used that (with 120 volt input) I would have about the optimum voltage to run to run a UcD 180. Best regards Moray James.
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Old 15th January 2006, 03:25 AM   #2
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Be careful about swapping out filter coils. Almost all of the radiation will come from it.

SMPS can be a blessing and a curse. I have heard of instances where the SMPS sounded better, as it let less crud from the AC mains through.

OTOH, it makes more of its own.

Helps to have an RF spectrum analyzer.

(Yeah, they cost $$$$. Yet another reason commercially produced gear is expensive.)

Jocko
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Old 16th January 2006, 11:17 PM   #3
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Default Thanks more Q's

Joco: thanks for the advice. Assuming that the position/orientation of the output coil is kept the same would not a higher rated coil of better quality not get into saturation as soon as a smaller lower rated coill? Or are these things usually designed with enough margin to make coil swapping a waste of time?
Is there any sonic advantage to going for a ucd 400 over the ucd 180 putting aside the issue of power?
Regarding the issue of switch mode power supplies Vs analog supplies. I have been listening to the Nuforce Ref 8's for several days now (getting better all the time) and I would have to say that the SMPS in these amps sound very good. Given the cost and size efficiency of such designs and the fact that most of these designs are being done by large competant companies what would be the advantages of using standard analog supply?
Thanks for the answers to such basic questions. Best regards Moray James.
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Old 17th January 2006, 12:53 AM   #4
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Ah.........you are assuming that they are all competent. I have heard things, behind the scenes so to say, that are not verifiable, and even if they were, aren't cool to repeat.

But some brands do have a reputation as being EMI generators. I have reason to believe that those issues have been adddresed. But as I have not looked at any of the iterations, it is all a guess. So, I won't.

Well, I do have inside knowledge of a buddy's amps w/SMPS. They had trouble passing the CE thing, and I gave them advice that was applicable. Whether they listened or not, I don't know. So, any brand, by anyone, can have that problem.

A SMPS can introduce crud into the low-level circuitry. May. So that is one reason some don't use them. That is one of those engineering compromises that you have to contend with.

Market expectations are another, as to some, if it ain't heavy, it can't sound good. Just look at places like Audiogon if you don't believe me.

Now.........I bet you want to know how they sound, as I may have built amps with both types of supplies. Right?

Tell the truth........the greedy capitalist that I am..........I have not spent a lot of time comparing them. I have others do that for me. None of them can agree on diddly-squat, so as long as they measure ok, and sound ok, I have no problems using either. I'll build whatever for whomever wants it. In whatever flavour they want.

Come to think of it.........I had another buddy that was using SMPS in conventional amps. Expensive ones. He had lots of failures. But another story for another thread.

I am not going to speculate on Hypex's flux margin. I can only go by what is on the coil, and I am too lazy to do independent test to verify it. Other factors may include the DCR of the coil. You may improve your sound because of that, and not the saturation. (See Dan Frasier's post in the 250ASP thread.) Their coils radiate a bit less than some other amps, so I would stick to something in the same genre.

Jocko
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Old 17th January 2006, 02:13 AM   #5
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Quote:
Originally posted by Jocko Homo
Be careful about swapping out filter coils. Almost all of the radiation will come from it.

SMPS can be a blessing and a curse. I have heard of instances where the SMPS sounded better, as it let less crud from the AC mains through.

OTOH, it makes more of its own.

Helps to have an RF spectrum analyzer.

(Yeah, they cost $$$$. Yet another reason commercially produced gear is expensive.)

Jocko

Or get a PC-based scope, they usually have spectrum analyzer like software included. I use a scope from www.tiepie.com, the HS3, has 8-bit resolution at 100Mhz (sampling frequency), 12 bit below 50Mhz and modes to use oversampling to get 14 and 16bits resolution. Very nice tool and good software. Also has built in arbitrary waveform generator (use if for capacitor testing for example). I use the scope and spectrum analyzer to analyze the HF noise that is coming from the SMPS, you can nicely see the effect of the inductance of an additional piece of cable and caps etc. So a tool like that is needed to optimize the SMPS and the additional filtering after the SMPS. It is also nice to see the riple that the UcD modules themselves impose on the DC rail (few mV if I remember correctly, 400kHz + harmonics), by changing the 470uF caps in the UcD modules and the main power supply caps, that maybe changed? Have not checked yet.

Best regards

Gertjan
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Old 17th January 2006, 05:16 AM   #6
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Most of the Class D modules that I have seen emit most of their crud in the 60-80 MHz range. That gizmo should suffice, assuming the noise floor is low enough.....probably is.

As for the SMPS, that will vary depending on which one it is. The ones that I have seen have strong emissions from 20 MHz and up, with most 20-40 range. NuForce is reputed to have lots of emissions above 100 MHz. Have not seen one, so no way to confirm. But you may want to keep that in mind.

When all else fails......a TV tuned to the low VHF stations will work. But with modern TVs that go blue screen with no RF present, you may not see anything. We have CH.2, 4, and 5 here, and that is prime area for Class D amps.

Jocko
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Old 17th January 2006, 04:12 PM   #7
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Quote:
Originally posted by Jocko Homo
A SMPS can introduce crud into the low-level circuitry.
Hey Jocko, would the crud come from EMI radiated down the rails? I'm also interested in your comment that SMPSs let less line garbage through. Appreciate any further elabortion if you have a minute.
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Old 17th January 2006, 05:06 PM   #8
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Ever use a toroid for a power transformer? I have stories about those, but not here..........

Well, if the SMPS is separate.....yeah.

But the only ones I have worked with are all on one PCB. You then see it on the AC mains.

As for how it affects the low-level circuitry......I have not had time to look into that closely. I would rather have my own input stage(s) to begin with, so we are already at a disadvantage when using modules produced by someone who knows more about this stuff than I do. So, I concentrate on how to do that, and convince the folks who occassionally throw money my way to do silly things like that. At that point, I suppose I will have to get serious about switcher noise.

Jocko
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Old 18th January 2006, 04:25 AM   #9
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Default yes and no?

So it sounds as if the answer is yes and no with respect to SMPS with the heavy weight being on the no side due to lack of knowledge regarding the manufacturer. Sill I was under the impression that a SMPS was far more cost effective not to mention size effective Vs an analog supply(not to mention benefits such as power factor correction). If that is the case then the question then becomes one of finding SMPS's that are propperly designed by a reputable company that knows what it is doing and buiilds suitable ones for this kinf of application at a better cost than that of a analog supply. I take it from your response Jocko that is easier said than done. Would you say that by the time all the necessary concerns are met that a conventional analog supply is just the safer more cost effective way to go to eliminate surprises of the negative kind?
Giver the design expertise at a company like Hypex I am still curious why if they can design such a fine switching amplifier module(s) why they have not designed a SMPS of ther own or if that is project is restricted due to financial constraints (at the present)? Why then not recommend an available one that meets the requirements. The obvious answer (though not perhaps the correct one) is that short of a custom unit (expensive in small runs) they (available units) are not cost effective while suitable supplies to get people up running and happy fast abound in any used amplifier or in parts at any local supply shop.
Perhaps Bruno would be willing to jump in and discuss this. I do not have any experience in the area but I must say I do find this situation to be strange given the incredible proliferation of products in the marker place with SMPS that would seem to meet specs regarding emissions etc. especially in Europe wher they are ahead of NA in this area. There must be a thousand companies designing and building such products. Regards Moray James.
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Old 19th January 2006, 08:39 PM   #10
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So with all that wind we've learnt....? I could give a few answers but it wouldn't be conducive to proper texiquette.

Your option is really a standard supply. As a bonus you can tweak it to no extent to get just the right sound, something you can't really do with a SMPS of anothers design, and it will be far more reliable.

The UCD400 is likely to have the edge, having a foil coil, more sophisticated drivers, better mosfets, properly taken advantage of you'd no doubt notice the difference.

I really wouldn't think you can "upgrade" the coil, you're likely to only degrade performance by changing it.

Start with the basics and go from there, no need to be worrying about such things at this stage.

As stated in another recent thread Hypex is releasing a SMPS but for OEM products only... possibly due to certification reasons.

Look at that... substance.
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