Perhaps I should have mentioned that my reasoning for considering the use of the inductor (as opposed to simply a resistor of approximately the same value) is to get some ultrasonic filtering of line and rectifier switching hash and NOT for reducing 60 or 120 hz ripple. Recognizing of course that the transformer snubber may achieve the same benefit of reducing line and rectifier switching noise; but if the in-line resistor implementing the pi filter could also perform he separate task of reducing higher frequency noise, then it would be a good thing.
I agree that trying to implement a CLC for 60Hz line ripple reduction is probably not feasible in this application (and I would not want an outboard solution); it would be quite expensive to the point that it would not make sense.
Thank you everyone for your replies.
@HaflerDh500Fan
Ahhh... thanks. That helps. I was looking for post 1705 in the the Quasimodo thread (that I couldn't seem to find).
You would only need/want to install one PS-220 into the amp. It fits if you haven't used the "stock" space for something else... as I did originally.
The caps I choose to use are the "last" caps that'll go in, not the "first". Unless there's smoke and fireworks... which I don't expect. (One lives in hope, right)
I was interested in the Mundorf's not because they are "nice" but chiefly because the 4 pole idea was intriguing and promising. Any thoughts on that promise?
Ahhh... thanks. That helps. I was looking for post 1705 in the the Quasimodo thread (that I couldn't seem to find).
You would only need/want to install one PS-220 into the amp. It fits if you haven't used the "stock" space for something else... as I did originally.
The caps I choose to use are the "last" caps that'll go in, not the "first". Unless there's smoke and fireworks... which I don't expect. (One lives in hope, right)
I was interested in the Mundorf's not because they are "nice" but chiefly because the 4 pole idea was intriguing and promising. Any thoughts on that promise?
This is a good question for a SPICE simulation using representative values of ESR and ESL for the 10,000 uF capacitors. The 0.22-ohm resistors will definitely provide some attenuation at the higher frequencies, especially if at least the second ecap is bypassed by a film capacitor. There is another thing that the resistor does that is a good thing. In combination with the ecaps, it forms a low-impedance Zobel network that damps resonances in the ecaps.
I'm not sure how much a few microhenries would by you if used instead of the 0.22 ohm resistor.
Cheers,
Bob
I guess you could put a couple of ferrite beads on the leads of the pi R, for some extra RF rejection. A w/w R would have a bit of L as well. There is the R/C formed between the pi R and the 1uF film as Bob mentions. For best filtering best use a few C's that are a specific to the Freq range you want to filter, like 10m, 1u & 1n ... in parallel. Having overlapping large Cu area fills for supply and ground act as some HF filtering and come for free, since you want as much Cu as possible. Doing so also means you are not required to use 2oz Cu which is cost ++.
Tests could be performed, to see if any of this stuff makes a difference.
Tests could be performed, to see if any of this stuff makes a difference.
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Great to see the power supply discussion. I will certainly do what I can to help if Rick or others are interested in a PCB design to maximize space efficiency.
Quite frankly, I am surprised to hear folks say doubling the bulk capacitors makes any audible difference (absent of a topology change like two banks separated by a resistor). Was the improvement due to increased microfarads, or just the fact the caps are new? Is it better to choose caps with maximum ripple current rating (ie 105 degree caps) or maximize capacitance instead?
And to be utterly blasphemous, why not consider a front end switcher...providing a fully regulated front end supply, while likely freeing up massive space in the unit, and eliminating concerns like inrush current into gigantic capacitor banks?
——
I’ve changed by back order with mouser to get everything I am missing by end Jan, but need another order to get what I need for power supply, and to get a bunch of stuff for upgrade of my two used Adcom 535II’S (one untouched, other hacked considerably).
Haven’t got pcb’s yet...seems Canada post is stuck at “shipping label created” stage.
Quite frankly, I am surprised to hear folks say doubling the bulk capacitors makes any audible difference (absent of a topology change like two banks separated by a resistor). Was the improvement due to increased microfarads, or just the fact the caps are new? Is it better to choose caps with maximum ripple current rating (ie 105 degree caps) or maximize capacitance instead?
And to be utterly blasphemous, why not consider a front end switcher...providing a fully regulated front end supply, while likely freeing up massive space in the unit, and eliminating concerns like inrush current into gigantic capacitor banks?
——
I’ve changed by back order with mouser to get everything I am missing by end Jan, but need another order to get what I need for power supply, and to get a bunch of stuff for upgrade of my two used Adcom 535II’S (one untouched, other hacked considerably).
Haven’t got pcb’s yet...seems Canada post is stuck at “shipping label created” stage.
My 220 is a complete virgin. Virgins are ok, but I am looking for a more experienced design, as they perform better!
Admittedly I don't know the Haflers. I've just been stumbling over this thread because I have many Hitachi LATFET 2SJ50/SK135 pairs in my shelves. Anyway, some said that there isn't ample space within the chassis. And you'd need two LARGE inductors
.Best regards!
I would guess that the “size of capacitor necessary” question would be best answered by quantification of the power-supply-ripple-rejection figure for the driver boards and the output transistors.
Given the power transistors (except in the case where you are already at or near clipping) whole job is to isolate speaker out from bulk supply, I would expect that this figure is very high indeed.
That’s why, except in the case where you are running the amp very close to max output, I am surprised additional bulk microfarads makes any difference at all. I also note the 220c driver boards further isolate from bulk, so again I can’t see it causing troubles there.
If dramatically bigger bulk caps do make a difference, I can’t understand why. Seems important to understand that. I can see that new caps with dramatically lower esr could make a difference, particularly if driver boards don’t include their own bulk decoupling.
Seeking the truth of the matter.
Given the power transistors (except in the case where you are already at or near clipping) whole job is to isolate speaker out from bulk supply, I would expect that this figure is very high indeed.
That’s why, except in the case where you are running the amp very close to max output, I am surprised additional bulk microfarads makes any difference at all. I also note the 220c driver boards further isolate from bulk, so again I can’t see it causing troubles there.
If dramatically bigger bulk caps do make a difference, I can’t understand why. Seems important to understand that. I can see that new caps with dramatically lower esr could make a difference, particularly if driver boards don’t include their own bulk decoupling.
Seeking the truth of the matter.
Hi Peter,
The Xpresspost tracking number is in the system, available from either PayPal or eBay, since they are in-synch with each other. Canada Post shows, Expected delivery Today, 11 am to 3 pm.
Myself and Bob were discussing the PS options for the BC-1 PS design. DH-220C is not much different in PS requirements.
One simple option is to use the same transformer, but have a separate rectifier/filter for the front end only. It draws very little, so a small bridge, 1-2.2mF ecaps are all that is required. There are other options as well but they take up space and of course add $.
Rationalizing what is used as a means for improvement and the benefits of such, are highly debatable. With DIY, you holding the purse strings, you have the luxury of going way past what a mfg would usually do. A mfg has a cost target to adhere too, unless it a ridiculously expensive amp that is in the big $$ stratosphere.
Bob's recommendations, I find to be practical and with good engineering reasoning. For other's, well, to each their own They have to justify to themselves, firstly, if the $ spent is worth the investment!
We have heard feedback from the DH-220C beta testers. Many are reluctant to post because they want to avoid having to defend their choices. Apart from the instruments measurements we have to rely on listening experience which imo, is a can of worms. One beta tester said that his mono-block configuration was his best build using the DH-220C. It was evaluated driving his Electrostatic speakers which require a lot of energy. It was a new PS transformer and all.
Good luck
Rick
The Xpresspost tracking number is in the system, available from either PayPal or eBay, since they are in-synch with each other. Canada Post shows, Expected delivery Today, 11 am to 3 pm.
Myself and Bob were discussing the PS options for the BC-1 PS design. DH-220C is not much different in PS requirements.
One simple option is to use the same transformer, but have a separate rectifier/filter for the front end only. It draws very little, so a small bridge, 1-2.2mF ecaps are all that is required. There are other options as well but they take up space and of course add $.
Rationalizing what is used as a means for improvement and the benefits of such, are highly debatable. With DIY, you holding the purse strings, you have the luxury of going way past what a mfg would usually do. A mfg has a cost target to adhere too, unless it a ridiculously expensive amp that is in the big $$ stratosphere.
Bob's recommendations, I find to be practical and with good engineering reasoning. For other's, well, to each their own
They have to justify to themselves, firstly, if the $ spent is worth the investment!We have heard feedback from the DH-220C beta testers. Many are reluctant to post because they want to avoid having to defend their choices. Apart from the instruments measurements we have to rely on listening experience which imo, is a can of worms. One beta tester said that his mono-block configuration was his best build using the DH-220C. It was evaluated driving his Electrostatic speakers which require a lot of energy. It was a new PS transformer and all.
Good luck
Rick
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Many pro audio amps and some audiophile power amps, and most class-D amps successfully employ SMPS. However, designing SMPS into a power amplifier application can be tricky. SMPS are wonderful for somewhat constant loads without peak current demands that exceed by much the continuous current rating of the SMPS. In this regard, power amplifiers are different. The peak current demands can be very large, and last some amount of time for bass transients. This is where the big reservoir capacitors in a linear supply come in. They provide great energy storage.
Switching supplies are great at keeping ripple down with only modest filter capacitance. In audiophile amps, the large reservoir capacitors are not just there for ripple reduction.
Switching supplies can be made to meet the high transient current demands of an audio power amp, but they still need significant energy storage either in the up-front line rectification stage or on the rails. They would need to be quite over-sized to deliver the peak currents from the line without energy storage.
Depending on the SMPS design, their voltage-regulated nature can cause some to collapse once the current demands go beyond what they can supply in a regulated way. Many do not tend to sag in a graceful way like linear supplies do.
The DH-220C has been evaluated for burst power into a 2-ohm load (burst meaning about 5 seconds to avoid output transistor overheating). It does quite well into 2 ohms, and this may be related to the feedback we have received regarding its good bass performance.
Cheers,
Bob
Bob, I guess my thought here is that if I had a switching power supply transformer the size and weight of the 60 hz transformer in the 220, that switcher would be able to deliver multiple kilowatts rms to much smaller output capacitors, refreshed every several microseconds? Silly comment from me, but it highlights that theoretically, at least, switchers could be superior.
But this is not really viable, compared to existing classic solutions that already work I suppose. One gent in here has some switchers, maybe he will try it someday.
But this is not really viable, compared to existing classic solutions that already work I suppose. One gent in here has some switchers, maybe he will try it someday.
Peter, you can use Jan Didden's Silent switcher as an example of what can be done for clean low power SMPS. Big power SMPS make a lot of switching noise, that has to be dealt with by extra filtering, shielding, hidden costs. Reliability wise, a linear supply is exponentially more reliable than a SMPS.
If you just want to kill the SMPS discussion, fine.
I designed 100khz switchers at Mitel in the 80’s that were VASTLY quieter than the linears they replaced. We used saturable toroid secondary mag amps with orthogonal set/reset mode control, assuring every rectifier in the supply had a soft turnoff. Idle channel noise on the load line cards dropped universally across the entire cabinet by 15 decibels, even with codec sync disabled.
But I’m dropping this discussion now.
I designed 100khz switchers at Mitel in the 80’s that were VASTLY quieter than the linears they replaced. We used saturable toroid secondary mag amps with orthogonal set/reset mode control, assuring every rectifier in the supply had a soft turnoff. Idle channel noise on the load line cards dropped universally across the entire cabinet by 15 decibels, even with codec sync disabled.
But I’m dropping this discussion now.
I myself do not want to kill anything if it applies to a DH-200/220 mod. I am sure everyone would be interested in the SMPS design process and how the finished design compares to a stock DH-200/220 supply in cost, size, performance, reliability. Standard EE terms of product analysis.
Others following along might like to know the benefits and disadvantages of one PS technology vs the other. Also how it can be applied to an audio amplifier.
Class "D" is the new kid on the block for audio amplifiers and it is a Switch mode type of technology.
Others following along might like to know the benefits and disadvantages of one PS technology vs the other. Also how it can be applied to an audio amplifier.
Class "D" is the new kid on the block for audio amplifiers and it is a Switch mode type of technology.