Hence my comment about the chromium adhesion layer used in some semiconductor manufacturing processes and BrianL's comment about the nickel layer used on circuit boards.
The issue is not that gold is soft. The issue is that it is inert and won't easily bond to anything. It's hard to form covalent bonds if you aren't willing to share your electrons.
Tom
The issue is not that gold is soft. The issue is that it is inert and won't easily bond to anything. It's hard to form covalent bonds if you aren't willing to share your electrons.
Tom
Well, I can look at memory card and some amp cards from various kits, it is obvious the memory card fingers have more gold content. Possibly better for slide in contact quality softer material also allows for better pressured contact quality. So the issue is the kind of contact is going to dominate the plating type.
The main reason for nickel or chromium between gold and copper is that when gold is directly laid over copper it will eventually diffuse into the copper and vice versa. Given the relatively thin layer of gold, eventually there will be copper, and hence copper oxide, on the surface. This, obviously, negates the benefit of gold.
The other key benefit of the nickel or chromium barrier layer is that in connector/contact applications the harder metal improves the wear properties where the contacts mate.
The other key benefit of the nickel or chromium barrier layer is that in connector/contact applications the harder metal improves the wear properties where the contacts mate.
Tom -
Question on using SMPS's to power this or any of your other Modulus boards. In Douglas Self's "Audio Power Amplifier Design", he discussed pros and cons of different power supplies. For SMPS's, he lists one of the disadvantages as "The response to transient current demands is likely to be relatively slow" (from page 261). Is this applicable to your designs?
I saw that you indicated the rails of a linear unregulated supply will sag near full output reducing peak power when compared to a regulated supply. If peak output is not a primary concern, does this give an material advantage to a linear unregulated supply? Other than reduced cost and/or complexity.
Question on using SMPS's to power this or any of your other Modulus boards. In Douglas Self's "Audio Power Amplifier Design", he discussed pros and cons of different power supplies. For SMPS's, he lists one of the disadvantages as "The response to transient current demands is likely to be relatively slow" (from page 261). Is this applicable to your designs?
I saw that you indicated the rails of a linear unregulated supply will sag near full output reducing peak power when compared to a regulated supply. If peak output is not a primary concern, does this give an material advantage to a linear unregulated supply? Other than reduced cost and/or complexity.
Is it applicable to my designs? Yes. Is Douglas Self's claim valid? Well. It depends. Specifically, it depends on the regulation bandwidth of the SMPS. I don't know precisely what that is for the Mean Well units I've talked about, but I would expect it to be a few kHz at least. So up until that frequency, the SMPS will respond just fine. Past that frequency, you're relying on the on-board caps to provide the energy.
Contrast that with a linear unregulated supply that cannot respond at all. A transient demand on a linear unregulated supply will cause the rail voltage to sag instantaneously and remain sagged until the next mains cycle comes in.
I did state that the difference in max output power between the linear supply and the SMPS is caused by the sagging rails of the linear supply. However, this should be taken in its proper context. The sag always happens. At least unless you have infinite supply capacitance or draw zero load current. The sag is the highest at the highest load current and lowest at the lowest load current.
Thus, if you compare the rail perturbations on a linear supply versus those on an SMPS, you will always find the SMPS to have lower wiggle than the linear supply - at least within the regulation bandwidth of the SMPS.
The question is what happens beyond the regulation bandwidth of the SMPS. If the regulation bandwidth is high enough, i.e. beyond the frequency where the on-board caps are delivering most of the energy, the performance will be determined entirely by the Modulus-686 and not by the supply.
If, on the other hand, the regulation bandwidth is low, i.e. below the frequency where the on-board caps can supply all the energy needed, it basically becomes a question of "who has the most energy storage". The linear supply wins here, but given that the Mean Well RPS-400-36, for example, is specified for a hold time of 16 ms I find it doubtful that you will ever have a case where the linear supply wins. Maybe in the case where someone unplugs the power cord for longer than 16 ms and plugs it back in...? This doesn't seem like a common use case.
The linear supply does win on complexity but unless you're designing your own SMPS, you are outsourcing that complexity. The linear supply certainly wins on "feel" as the amp will be heavier (thus, by males perceived as "better quality"). If you go without a soft start you'll get that impressive HUMMM!!! and lights dimming on startup, which will impress your friends. Even with a soft start, you will get cool clicking noises of relays, which is always awesome.
The SMPS wins hands down on all the technical aspects as long as it has decent regulation bandwidth. All my measurements indicate that the Mean Well units fit the bill.
What I do like about the linear supplies that I have recommended (Power-86 with 2x24 or 2x25 VAC transformer) is that the rail sag makes it a little easier on the thermal system. Not by much, but by some. Also, the linear supply gives you the option of using 2x22 VAC, which would result in 125-150 W (8 Ω) out. That's a nice option for those wanting a more conservative build ... unless you can find the RPS-400-27 (27 V version) in stock somewhere.
Are you sure you're looking at the exact same version? I'm showing $101 (CAD) for the RPS-400-36 at Mouser and $107 (CAD) at Digikey. The various versions of that supply (with cage, fan, side fan) have started to show at Mouser, which may lead to some confusion. The caged version is nice but requires a lower ambient temperature than the cage-free version.
Tom
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Google tells me that there are several distributors, at least in the US, that specialize in power, who also distribute MeanWell. At least one has prices slightly below Digi-Key and Mouser (USA pricing), though you'd need to evaluate the whole cost including shipping.
There should be distribution in the EU and UK that might make the total cost for EU/UK users less than importing from the USA.
There should be distribution in the EU and UK that might make the total cost for EU/UK users less than importing from the USA.
You can find their list of distributors here: Distributor Network-MEAN WELL Switching Power Supply Manufacturer
I've dealt with TRC Electronics in the US. They're a pretty solid outfit. It's easier for me to get the supplies through Mouser/Digikey/et al. but having TRC on speed dial is nice when the others are out of stock.
It looks like there are a couple of distributors in the UK and quite a few more in Germany, so Europeans should have quite a few options to choose from for ordering within Schengen/EU.
Tom
I've dealt with TRC Electronics in the US. They're a pretty solid outfit. It's easier for me to get the supplies through Mouser/Digikey/et al. but having TRC on speed dial is nice when the others are out of stock.
It looks like there are a couple of distributors in the UK and quite a few more in Germany, so Europeans should have quite a few options to choose from for ordering within Schengen/EU.
Tom
Everybody have been pushing the switching frequency UP as that allows for smaller magnetics at the expense of higher switching losses. The latter seems to have been addressed by FETs with lower gate capacitance and other clever tricks.
The Mean Well switchers seem to hover around 60-70 kHz. Many of the smaller DC/DC converters now switch at upwards of 1 MHz.
In the old days, the switching frequencies were barely above audio frequencies.
Tom
The Mean Well switchers seem to hover around 60-70 kHz. Many of the smaller DC/DC converters now switch at upwards of 1 MHz.
In the old days, the switching frequencies were barely above audio frequencies.
Tom
Modulus-686: 380W (4Ω); 220W (8Ω) Balanced Composite Power Amp with extremely low THD
60~70KHz seems to be the range right where the EMI is out of the critical certification areas. So it might be possible to pass without shielding, and have a broad enough application to support a common design architecture. Probably powering computers would need higher switching frequency.
Higher switching frequency probably also allows for smaller transformers.
60~70KHz seems to be the range right where the EMI is out of the critical certification areas. So it might be possible to pass without shielding, and have a broad enough application to support a common design architecture. Probably powering computers would need higher switching frequency.
Higher switching frequency probably also allows for smaller transformers.
The little module I am using originally was at 110KHz. Seems like when the supplier looked at the data I sent them, they reduced the frequency. But I think it possibly may also depend on the quality of oscillation and the harmonics it generates. It is the harmonics that get into the EMI critical test range if I recall correctly. I can check the data.
Nice!
The SE-600 is 68 kHz. Many of the smaller switching bricks are around there too. I do like the higher switching frequency of the RPS-400 (and EPP-400) as that would allow for a wider regulation bandwidth (if I remember the SMPS theory correctly).
Tom
Though I wonder if there is a chance for intermodulation of the two frequencies, either in the switcher itself or via radiation to the audio circuitry that would create a 10kHz 'birdie'?
Also, I wonder how much HF radiation, in general, one can anticipate between the SMTS and amp circuits in the close quarters of an amp chassis? (I.E., should the SMTSs be shielded from the audio circuitry?
Also, I wonder how much HF radiation, in general, one can anticipate between the SMTS and amp circuits in the close quarters of an amp chassis? (I.E., should the SMTSs be shielded from the audio circuitry?
I was just going to ask this. Should we consider shielding the power supply if a SMPS is used and located in the same chassis?