neutrik A1
I bought neutrik A1, it would like if possible you use him/it in the windows 98 connector rs232.
fred@machine-audimax.com.br
I bought neutrik A1, it would like if possible you use him/it in the windows 98 connector rs232.
fred@machine-audimax.com.br
maybe a question, which shows, I have no clue about class H:
How big the actual CE voltage of the output Bipolar transistors can be in a class H circuit? (worst case, real word data)
Could it be somehow limited to only one voltage step voltage? (40-50V)
is there any way to apply voltages to the - rail of the amp even some positive voltages? (when the +rail =150V-->then the -Rail gets for example +100V)
that would mean, that you track the needed output voltage within say 40-50V, which is still not as good as with a class TD, but not bad at all...
Thanks,
Tamas
How big the actual CE voltage of the output Bipolar transistors can be in a class H circuit? (worst case, real word data)
Could it be somehow limited to only one voltage step voltage? (40-50V)
is there any way to apply voltages to the - rail of the amp even some positive voltages? (when the +rail =150V-->then the -Rail gets for example +100V)
that would mean, that you track the needed output voltage within say 40-50V, which is still not as good as with a class TD, but not bad at all...
Thanks,
Tamas
It could be limited like that but there isn't much point really. The transistors used can take the voltage and the phase angle of current for a loudspeaker load isn't really big enough to warrant it.
A 50-100-150 stepping amplifier would see max ~200V over an output device. (for example, output at -150V and positive rail at 50V)
You could add in 0V as a step and then the max voltage would be 150V and have a little less heat with highly reactive loads. If you start to add opposite polarity steps too then maybe the class TD or D amplifier is starting to look like a cheaper and simpler solution.
There is no amp I know of that does this. It is possible of course, but are there any real benefeits?
They seem pretty small to me. There isn't that much recoverable energy after crossing the 50V rail in the other direction.
A 50-100-150 stepping amplifier would see max ~200V over an output device. (for example, output at -150V and positive rail at 50V)
You could add in 0V as a step and then the max voltage would be 150V and have a little less heat with highly reactive loads. If you start to add opposite polarity steps too then maybe the class TD or D amplifier is starting to look like a cheaper and simpler solution.
There is no amp I know of that does this. It is possible of course, but are there any real benefeits? They seem pretty small to me. There isn't that much recoverable energy after crossing the 50V rail in the other direction.
thanks,
the advantages are just the Uce requirements for the output devices.
but this advantage could be not minor in some case (high output voltage - high supply voltages)
what do you think the issues could be, when switching even +100V to the - rail of the output section while the +rail is at +150V?
this way, when you chose more steps like 4 to 6 steps, even higher output powers are easier to reach with the common 230-250V Bipolars.
Just considering 40 V steps x 6= +/-240V max rail voltage while the max Uce could be less than 100V....
is it a bad idea?
I did tests with 3 step Class H amps ala QSC and with Crown's BCA class D, but the class D seemed to have even lover efficiency with sinus input and resisitve load....
thanks,
Tamas
the advantages are just the Uce requirements for the output devices.
but this advantage could be not minor in some case (high output voltage - high supply voltages)
what do you think the issues could be, when switching even +100V to the - rail of the output section while the +rail is at +150V?
this way, when you chose more steps like 4 to 6 steps, even higher output powers are easier to reach with the common 230-250V Bipolars.
Just considering 40 V steps x 6= +/-240V max rail voltage while the max Uce could be less than 100V....
is it a bad idea?
I did tests with 3 step Class H amps ala QSC and with Crown's BCA class D, but the class D seemed to have even lover efficiency with sinus input and resisitve load....
thanks,
Tamas
I think the extra complexity would be a real pain in the rear. Especially because of the way reactive loads behave. When the signal voltage swings negative, there can be positive current flowing - which is why the NPN side can have a high VCE with significant current. In order to switch the negative rail with positive current - the switch needs to turn both on and off bi-directionally. The body diode of the hexfet will complicate that.
If a 3-step class H and the BCA give similar efficiency with sinewave or real world signal, then you're at the point of diminishing returns dissipation-wise anyway.
BTW - the biggest amps out there only use +/-195v. You could do a 4-step class H with MJ21193/4 on that no problem. No one said the rails all had to be the same increment - the low one could be 25V with the balance between two or three more steps. Mine tend to be the same, but that's because I cheat and stack identical lower voltage trafos in series.
If a 3-step class H and the BCA give similar efficiency with sinewave or real world signal, then you're at the point of diminishing returns dissipation-wise anyway.
BTW - the biggest amps out there only use +/-195v. You could do a 4-step class H with MJ21193/4 on that no problem. No one said the rails all had to be the same increment - the low one could be 25V with the balance between two or three more steps. Mine tend to be the same, but that's because I cheat and stack identical lower voltage trafos in series.
There isn't more complication than usual, see attached picture.
But you are right in that it's probably not worth it. Letting it drop to 0V might be worth the extra FET and diode but I seriously doubt that any more is worth doing. The more FETs used the more series resistance...
It's possible to rearrange them a bit to get around this penalty but then you would need higher voltage FETs which have higher resistance...
But you are right in that it's probably not worth it.
Letting it drop to 0V might be worth the extra FET and diode but I seriously doubt that any more is worth doing. The more FETs used the more series resistance...It's possible to rearrange them a bit to get around this penalty but then you would need higher voltage FETs which have higher resistance...
Attachments
Question, Mega. Do you think a 2.5 rail with 56V steps would work about as well a a 3-rail with 28-28-56? Especially with reactive loads (horn subs). The reason is I'm thinking ahead to the next project so I may be getting ahead of myself. I found some reasonably small 68kuf/75V caps, and I'm pretty sure I can fit four in the chassis with a pair of Signal 80-25's (can't fit six or eight at all) along with the PCB assemblies from the "RMX5050 killer" project in progress. It would be heavy as all heck, but the trafos are plenty big enough to bridge into 2 ohms and I can fit the extra transistors on the heat sinks. Because of the chassis fit issues, I had abandoned the idea for a while, but it may become practical with the new caps.
My post #16 on page one should have Pol HSU changed to Poh Ser Hsu.
"The theoretical class B efficiency is 78.8%, a three rail design like the M1.0 is 87% (after Pol HSU). When you consider bias in a class AB design, 60% is more in line. Pol HSU found that the rail switcher showed even higher efficiency driving reactive loads vs resistive."
It should be noted that the B&O Icepower 1000A module is specified to be 87% efficient at 500W/4R (fig.7), improving into higher impedance loads at full power to about 93% (fig.6)
"The theoretical class B efficiency is 78.8%, a three rail design like the M1.0 is 87% (after Pol HSU). When you consider bias in a class AB design, 60% is more in line. Pol HSU found that the rail switcher showed even higher efficiency driving reactive loads vs resistive."
It should be noted that the B&O Icepower 1000A module is specified to be 87% efficient at 500W/4R (fig.7), improving into higher impedance loads at full power to about 93% (fig.6)
wg_ski said:
2 ohms bridged...
Sounds fun! Good thing you like using triple EF output stages...I just modified my calculator-thingy for triple rails. Not 100% accurate as it's pretty simplified. Rail voltages are totally stiff and it clips 5V below highest rail. Rail switches activate 6V below their corresponding rail. I believe relative values should be relatively close as all rails drop by the same number of percent under load.
For a pretty heavily compressed piece of full range music (resistive load, average power is 27% of full power sine) the 28-56-112 driven output stage had 63% efficiency instead of 60% for the 56-112 two step. 56-84-112 gives 67% and decreased peak power for the output devices compared to the other ones.
The last one doesn't make much more sense than 56-112 for reactive loads though. 28-56-112 still has good efficiency if level is decreased or the peak-to-average ratio is higher. But how much do you need that? It won't help your power draw or dissipation much with 1/3 average power signals at clipping.
So I guess the 0-56-112 is almost as good as 28-56-112, especially if average output level is relatively high and the load is highly reactive.
At one time I had a behavioral model for the rail switcher, but like otehr things on this machine, has disappered. With the rails sagging to 75% or so of no-load, that will put it around 1kW of dissipation and 3kW (4-5kVA) draw at "full blast" clipping heavily. Tolerable, as these trafos can be strapped for 220.
And it looks like it all fits - in a 6U case, anyway. Each one would "replace" four RMX2450's (which I would only want to run at only one driver per amp).
And it looks like it all fits - in a 6U case, anyway. Each one would "replace" four RMX2450's (which I would only want to run at only one driver per amp).
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Crest audio Pro 9200 amp 2-Tier Class-H with lower rail at 60VDC and upper rail at 165VDC, what surprises me most is the uneven Tier voltage with almost double the difference, not symmetrical, anybody knows its advantages, plz present your views.
acc to my opinion, it helps in reactive load driving capability more than a symmetric rails and way to go with 230V toshibas. what about the efficiency then?
acc to my opinion, it helps in reactive load driving capability more than a symmetric rails and way to go with 230V toshibas. what about the efficiency then?
The efficiency will be higher for lower power outputs than an even split. But higher when driven hard where it's running off the upper tier a lot more often. I guess they figure with that much power you're using the amp for 'headroom' only, and with as much heat sink is it does have you can run for quite a while at high power before shutdown.
The Crest amps use separate transitor banks for the upper and lower tiers, as opposed to a rail switch. The total power dissipation is the same as a switched rail, but it effectively hands it off from one bank to the other when the rails commutate. The high dissipation in the upper bank (with 100V across it) happens for shorter than a full half cycle so I guess they figure it can take the peaks.
The Crest amps use separate transitor banks for the upper and lower tiers, as opposed to a rail switch. The total power dissipation is the same as a switched rail, but it effectively hands it off from one bank to the other when the rails commutate. The high dissipation in the upper bank (with 100V across it) happens for shorter than a full half cycle so I guess they figure it can take the peaks.
wg_ski said:
Well said WG,
this kind of uneven split is beneficial for headroom usage more, rather than continuous hard drive application as in the case with QSC PLX2 series with lower Tier at 80V and upper at 130V.
The amp which i previously mentioned pro200 series 9200 is a switched rail having an IGBT HGTG30N60A4D as a switch and parallel bank of 8X MJ21195/6 bipolars at output. The heatsink is average not much, but still the amp manages to do 2 ohms load happily at 3200W per channel.
I am currently checking my prototype with both cases 75V and 175V in upper and lower rails in vice -versa. Rail switch gives a nasty spike while switching, whereas Linear switiching is clean as in older crest amps the ones you mentioned[CA series] which have bipolars for each tier.
Is there any considerable difference between efficiences of 2-step vs 3-step class H provided upper most Tier rail voltage is same.?
I guess the biggest difference is that the more tiers (up to diminishing returns) gives high efficiency over a wider range of operating conditions. I have yet to see a 2-step have a 2-ohm FTC rating. The 3 and 4 step will if they don't 'cheap out' too badly. RMX5050 does, MX3000 did not.
For something with a 175V upper rail, I'd be very cautious with only 2 step. That's a lot of heat and some pretty high Vce's - even for 21196's - and a lot of AC draw. I'd want to go 3-step just to keep a 20A mains breaker at the panel from nuisance tripping. I'm still thinking about going to 4-step with the 80-25 project. The only way I can fit the required 8 caps in the box is if I redesign the PCB assembly, but it's not out of the question. Ideally, I'd want more than 9 outputs per bank anyway. On the 5050-killer 3-tier project I'm still assembling the 8 main PCBs. Only getting an hour or two at a time to work on it it took a week just to put in all the resistors! When I get 'em running (some time around Memorial Day, I suspect) we'll see how long they take being blasted at 2 ohms.
I have a small batch (6) of 40-0-40 650VA trafos that I could use to make two 3-tier 170-volt rail units. Probably monoblocks that can do 2 ohms. But I'll probably make some 'big boys' with the 80-25's first because it will help with the 'natural progression' of upgrading my main sound system. I always seem to have more amp work than I can possibly do.
For something with a 175V upper rail, I'd be very cautious with only 2 step. That's a lot of heat and some pretty high Vce's - even for 21196's - and a lot of AC draw. I'd want to go 3-step just to keep a 20A mains breaker at the panel from nuisance tripping. I'm still thinking about going to 4-step with the 80-25 project. The only way I can fit the required 8 caps in the box is if I redesign the PCB assembly, but it's not out of the question. Ideally, I'd want more than 9 outputs per bank anyway. On the 5050-killer 3-tier project I'm still assembling the 8 main PCBs. Only getting an hour or two at a time to work on it it took a week just to put in all the resistors! When I get 'em running (some time around Memorial Day, I suspect) we'll see how long they take being blasted at 2 ohms.
I have a small batch (6) of 40-0-40 650VA trafos that I could use to make two 3-tier 170-volt rail units. Probably monoblocks that can do 2 ohms. But I'll probably make some 'big boys' with the 80-25's first because it will help with the 'natural progression' of upgrading my main sound system. I always seem to have more amp work than I can possibly do.
I am extremely skeptical of how long 6 pairs of C5200/A1943 will last in that situation. Having done the math and reluctantly deciding that nine MJL21193/4 pairs will have to do. On +/-140.
Maybe those trafos in the 5050 are smaller than I originally thought. The core size is that of the 625/750 VA depending on manufacture. You only need +/-100V dc under load to get 2000 w/ch unclipped (FTC rating, not EIA which is in light clipping). That's an awful lot of drop from +/-165. +/-100 is what you should get under heavy overload starting with +/-140.
Maybe those trafos in the 5050 are smaller than I originally thought. The core size is that of the 625/750 VA depending on manufacture. You only need +/-100V dc under load to get 2000 w/ch unclipped (FTC rating, not EIA which is in light clipping). That's an awful lot of drop from +/-165. +/-100 is what you should get under heavy overload starting with +/-140.
Hi! My name is Andres, someone have the service manual for QSC MX1500 with PCBs.
Thanks!
My E-Mail is: ramon12300@gmail.com
Thanks!
My E-Mail is: ramon12300@gmail.com