Ideas for parts in insanely powerful amp?

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Hi.

Djk...what do you expect?Can you make a stereo 1300W amp for a few bucks...I don't think so!
About the Crown VZ5000.I haven't seen the schematic,but here are some basic calculations:

55 x 2=110 x 1,41= 155,1/2=77,55 (+-77,5V)

This supply voltage is suitable for an 500W amp.To get 1000W you will have to bridge two amps of 500W.For a stereo 1000W amplifier you will have to build 4 amps of 500W!Does this make the amplifier cheaper?And this still isn't those 2600W the RMX4050 can deliver.

About 1 pair of 10,000uF.Hmm... lets see:

Icmax.= 2000/4= 500 sqrt = 22,3 x 1,41 = approx. 32

The amps will draw 32A peak to peak from the power supply!Can 1 pair of 10,000uF be enough?I don't think so!

What about 230V transistors can't deliver 1000/4R?Did you see the schematic?This is a multi-tier supply based amp ,so we don't have to confuse people around here.
Regards friend.:)
 
HighTec:

I'm sorry you don't understand my posts.

Power supply capacitance is determined by the % of voltage regulation you need and the ripple frequency of the supply. Energy stored goes up with the square of the voltage, as does power to the load, so a large amp does not need any larger filter cap in µf than a smaller one, just higher voltage.

A Crown MA10000 uses a single 10,000µF filter cap to deliver 10KW at 0.5 ohm, 7KW at 1.0 ohm, etc.

I said:

"Unless you do a multi-tiered supply, bridge amp, or a fully regulated supply, there is no way to get 1000W/4R from a 200V transistor. "

What part of that didn't you understand?

You said:

"What about 230V transistors can't deliver 1000/4R?Did you see the schematic?This is a multi-tier supply based amp ,so we don't have to confuse people around here.
Regards friend."

You would seem to not have read or comprehended my statement.

You said:

"About the Crown VZ5000.I haven't seen the schematic,but here are some basic calculations:
55 x 2=110 x 1,41= 155,1/2=77,55 (+-77,5V)
This supply voltage is suitable for an 500W amp."

I said:

"It is a bridge design, as most Crown amps are, "

I'm afraid I must repeat:

"You would seem to not have read or comprehended my statement."

You said:

"Djk...what do you expect?Can you make a stereo 1300W amp for a few bucks...I don't think so!"

My reply is:

I can do it, the question is can you do it?

As a point in fact: I have been the chief designer on projects with amplifiers, mixers, electronic crossovers, etc.

Most of it was low-priced stuff, it is much easier to design high-priced stuff.

I am currently paid for doing PA work on high power L-band (1.2Ghz) RTs, and two of the current units use my FET modulator amp design.

If you get a permit from NATO, I can sell you the one that goes into an F15E fighter plane for about $31K. For $31K you get the PAI, P_ower amp, I_nverter, A_ntenna interface. The exciter and reciever are extra.

I did audio for almost 30 years, RF pays better.
 
"Cool, that Crown design is very much like what I was planning on doing. My transformer is exactly 55-0-55 VAC and I have the recifiers for it, and caps. How much power do you figure I'd get running one channel (not bridged) with the 55-0-55 tranny and 5 pairs of MJ21193/21194??"

Depends on the VA rating of the transformer and the design of the amp.

Adcom only gets 325W/4 from the GFA555 on that voltage, but they have a small transformer (700VA) for both channels and their circuit can't get very close to the rail.

If you have a 55-0-55V at 1KVA per channel, and use a high voltage tier for the voltage gain stages(or a rail-to-rail CFP output stage)you can get the 500W/4R you are looking for.

But to get the 2KW/4R bridged you will need a much bigger transformer VA rating, and many more pairs of outputs and heatsinking.

The Crown has a two 80V supplies in parallel. At low power the amp runs off this 80V, at high power a SPST switch (in practice an FET) re-wires the parallel supplies to series, or 160V.

This improves the efficency of the amplifier and reduces the amount of outputs and heatsinking required.

While you can bridge a stereo amp, if you intend to run it that way all the time it is best to design it as a bridge amp.
 
"Do you check every single device before it goes into the circuit ?
Do you test each device before it goes into the stock ?
What happens if parts are out of 'your spec' ?"

On MJ series outputs from ON Semiconductor I have found it to be a waste of time to check the PNP devices, they all have the same gain(in a given date code).

NPN devices are worthwhile to screen for gain if you are using very low value emitter resistors. I mark the gain on the case with a felt-tip. Eventually you can match them all up.
 
Do you think a 5kva transformer is going to be enough to be outputting 2kw/ch in class B?

Realistically, playing ordinary music
you should be ok. Some prefer
a 2 to 1 rule (give or take), if
you want 1kw out, use a 2kva tranny.

If you plan to play "tones" and not
music, then more stress is placed
on the amplifer and you may miss
target output power.

You said this is for casual listening,
so .. you don't think 5kva tranny will
work for you ? hehehe

You are going to run two different circuit
breakers off 110 VAC or run 240 VAC ?

I'm also nutz, I was thinking that
I may need a dedicated 10kva line
for my system - when I finish my
amps.. I'm looking to power 22 drivers.... (two stereo cabinets)..
subwoofers not included yet.....

/ fun stuff /
 
"How many tiers do you think I need in my amp?? I was thinking of using just one. Would it be better to use more?

Duo djk: Yes I think my PSU will suffice. I have a single 5kva transformer that I intend to use as a common supply.

Do you think this is enough power to run the amp to nearly 2kwa channel? "

5KVA is close, you might be 1dB less than the 2KW/ch you are expecting.

The problem is that to copy the Crown you would need a transformer winding of 55-0-55 for each channel(the Crown uses two 55V without a center tap).

Ideally I would specify a dual 58V 3KVA transformer for each channel. This is figuring 80% efficency for the amp and a .83 power factor on the supply.

You could buy a 30-0-30 1.25KVA transformer for the lower tier and make it work similar to the Crown.

For 50hz I would recommend 16,500µF at 50V for each channel, for 60hz 13,500 at 50V would be enough. The main supply caps need to be the same size in µf but 100V rated.

Run a set of rectifiers and filters for each channel, a total of four bridges, four 50V caps, and four 100V caps. Use 35A 400V bridges. If you go much bigger on the caps you will need to build a bridge out of individual diodes.

You will also need a small supply of ±85V at 100mA or so for the voltage gain stages of the amplifier. And a Baker clamp to both the ±40V tier and the ±80V tier.
 
Hi.

Well....it seems that here are some misunderstandings.It wasn't my intend to offend you or put in question your knowledge!
And I don't....really...need anntenas,F16 and that kind of stuff.Djk...no heart feelings.
If you really want to help Duo,send him the schematics,construction notes,specifications etc.We are confusing him!

Duo...sorry about the fuss I've caused!I didn't ask you the purpose of yours projects.It's out
of question building RMX4050 with that transformer you have.
Regards guys.:)
 
Well, like I said, my transformer is 55-0-55. I can't really put it on two seperate breakers because it only has two 55V primary coils and they have to be in series to have a 55-0-55V output.

I'll just have to find a way to get 45A fuses on a 110V circuit... I could maybe put three 15A circuit breakers in parallel... Then if one blows, you can be sure the rest will blow, or maybe I'll just tie them together with a rod so that only all three can be on at once...
 
"Well....it seems that here are some misunderstandings.It wasn't my intend to offend you or put in question your knowledge!"

Hey, no problem. Unfortunately I have no tact.

"The owners manual says 5kw @ 4 ohm bridged."

Maybe a resistor, it will not drive two 8 ohm speakers in parallel (in a dance club situation).

"I'll just have to find a way to get 45A fuses on a 110V circuit... I could maybe put three 15A circuit breakers in parallel... Then if one blows, you can be sure the rest will blow, or maybe I'll just tie them together with a rod so that only all three can be on at once..."

Just use a 25A slow-blow fuse. You can't get more than 20A out of a 120V plug anyway. On music that's enough power.

The power switch presents a problem.

I would use a soft-start circuit with a 40A triac. After a time delay you will want to have a 20A relay short out both the soft-start and the triac. On power down you want the relay to open and then the triac.

The triac can handle the start current, but not the run current. The relay can handle the run current, but not the start current.

Or you can use inverse parallel connected 70A SCRs and the relay. This avoids the complex power down sequence.
 
Well, I didn't intend to use a typical house outlet for the amps. I am going to run 8AWG wire from the fuse box directly to my transformer. That's what I did before in saskatchewan, I wired the transformer in directly. The PSU would stay on all the time and I would just connect the amps to it when I wanted them on. Then I don't ever have such a large inrush current to deal with. Therefore I don't have to worry about switches
 
Yesterday i completed my monster amp, it has 10 pairs of motorola´s mj15024/25 in output stage. I used two transformes with each is 2x 74V / 2kW and i paralleled them after bridge rectifiers. I used 30000µF filter caps per rail. The rails now are 2x98V (even at completely unloaded psu with no amps or anything connected to it) psu but i dont understand why, they should be around 104V (74 x sqr root 2 = 104).
Any ideas here?

I tested amp at various frequencies at full power for whole night in it survived vithout problems.

Testing (i tested at various frequencies and power is about the same at all of them..) one channel at time i get 400W RMS to 8ohm and power supply voltage drops to 85V, at 4ohm load i get 750W RMS psu voltage drops to 80V and at 2 ohms i get 1200W and psu voltage falls to 75V - this is almost at 74V RMS that trafos are putting out.. Transformers have enough power, so its the filter caps fault or maybe my bridge rectifiers are somehow bad and theres voltage fall on them rising with power - i didnt measured that yet because i cant get to them, theyre at the bottom of the amp, but ill do this too..

Is it possible that rails fall so much because the psu caps i used are old (my guess is 10yrs - but i got them 4 free so i used them:))?
 
Yeah, one of my concerns is the PSU caps. I can't afford anything fancy so I'm either going to use four 10000uF caps from a mainframe comptuer PSU, or I'll use a bank of about 20pairs of those 10000uF caps you see in the Technics classA amps that always blow up. I've gotten so many of these amps from people who won't pay to fix them. lol, they are complete garbage... But anyway, the caps seem nice.

i think maybe it'll be best to use the 20pairs of 10000uF caps from the amps. That way the caps are less than ten years old and they've barely been used. I just hope they are the right voltage. My PSU will put out +/-75V under a load up to about 40A continuous.
 
I have a question about heatsinks... Will a flat slab of half inch thick aluminum which is about 13" by 20" suffice for each channel?

I have two such slabs in excellent condition that I could easily drill holes into and make into heatsinks... These would look very nice in the amp and make it feel quite solid...

Please say they will work.. If not, could I simply add a bunch of thin pieces of sheet metal that are perpendicular to the surface of the main plate to dissipate the heat?
 
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