Kilowatt, a nice 500W schematic for you!

Hi,

I just found a schematic that I received about a year ago.
I've never build it, because I didn't have the right PSU and I couldn't buy the outputdevices by my local dealer.
Does somebody know equivalent types of the transistors in the very nice schematic you can find at:

link

PS: If someone would like to build it please let me know

best regards,

Hugobross....
 
I've been studying this amp for a while and I remarked this:

The current limiter (Q24, Q25, D3, D4, 2 X 270 ohm and 2 x 300 ohm) is calculated to allow a current of +/- 2,7A through each output transistor or to allow about 16A in total.
The amplifier is said to handle 500W, can anybody explain me why the fuses are rated 5A for a 8ohm load and 7.5A for a 4ohm load.
(P=I² * R), so the maximum power (not RMS) for a 8 ohm load with this fuses is only 200W.
Why are such fuses used when the current limiter allows 16A ???

Am I right or did I missed something?

Greetings,

Hugobross.
 

blmn

Member
2001-02-01 2:43 am
.
HugoBross,

The protection circuit is designed to allow the peak of the current plus some margin to impedance dips and the fuse is designed to RMS values sometimes plus some margin too, considering the response of the device to the current peaks (slow-blow, fast etc). I didn´t do any calculation about the protection, but the value of the fuse seems right to me for normal units. If you consider an class B circuit the total continuous power allowed by the fuses it seems to me correct (80V*5A*2)=800W, and despite the nominal value of the fuse, I prefer to put more margin in the power supply (more than 5A available at the power supply. As Subwo1 said, these fuses allow more than the nominal value for long periods of time.

Regards
 

blmn

Member
2001-02-01 2:43 am
.
HugoBross,

Another thing I notice now is the total voltage (160V) can't allow 500W continuous (near 180V), so, this amp might be a 500W unit at 4 ohms. If you consider 140V max on the load it would reach near 600W at 4 ohms. the peak current will be near 17A or, considering 500W/4ohms, 15.8A, wich agrees with your math.

Regards
 
Sounds like a job for the MJ21193/4, or MJ21195/6, which are
slightly more rugged than the former and both of which have
more dissipation/SOA than the MJL plastic case parts.

I like the Leach configuration better, but I'll have to come up
with a modification that'll stand 90 volt rails. Or scale back my
enthusiasm. (This is all YOUR fault, Kilowatt!)

Initial testing will have to be done at much lower voltages.
 

blmn

Member
2001-02-01 2:43 am
.
Damon,

I Built many years ago, based on the RCA application notes for audio an amp using the IC CA3100 at the front end and capable of 350W continuous at 8 ohms. It worked fine and I think it can be modified to 4 ohms use easily or even to more power at 8 ohms and for today´s components use. I think I have the schematics somewhere if you, Killowatt or someone else were interested.

regards
 

djk

R.I.P
2001-02-04 4:23 am
USA
"I like the Leach configuration better, but I'll have to come up
with a modification that'll stand 90 volt rails. Or scale back my
enthusiasm. (This is all YOUR fault, Kilowatt!) " The QSC USA1310 runs on +/- 93V with eight paralleled pair of MJ15022/15023 per channel.Considering that the safe area at 100V on the MJ21193/21194 is twice that of the MJ15022/15023 I think you could get away with five pair of MJ21193/21194 on your tunnel."I Built many years ago, based on the RCA application notes for audio an amp using the IC CA3100 at the front end and capable of 350W continuous at 8 ohms. It worked fine and I think it can be modified to 4 ohms use easily or even to more power at 8 ohms and for today´s components use. I think I have the schematics somewhere if you, Killowatt or someone else were interested. " That was a nice front end, virtually the same as the Crown M600 and the Carver M1.5, the output stage was quasi-complimentary.Not one of those transistor numbers are still available.I could see doing up a board for the front end and driving a full complementary output stage with it.
 
Thanks for replying!!

Indeed Blmn, with a PSU of 80V you can't achieve 500W RMS into a 8ohm load. It can be maximum 400W RMS.

I also understand now that fuses (used in amps) will blow at about twice (or more) the current indicated on the fuses. Probably because we work with (half) sinus waves instead of constant currents.

I'm always interested in other schematics, please mail them to:

[email protected]e

HB.
 

blmn

Member
2001-02-01 2:43 am
.
HugoBross,

Yes, I agree with you. As I said above:



Another thing I notice now is the total voltage (160V) can't allow 500W continuous (near 180V), so, this amp might be a 500W unit at 4 ohms. If you consider 140V max on the load it would reach near 600W at 4 ohms. the peak current will be near 17A or, considering 500W/4ohms, 15.8A, wich agrees with your math.

I will scan the schematics to put it in this thread.

Regards
 

blmn

Member
2001-02-01 2:43 am
.
schematic

This is the amp. I reached 360W continuos with less than .1% distortion at 8 ohms. The outputs are bd550b (Vceo=250V, Pt25oC=150W, Ic 7A, hFE between 15 and 75 and fT=5MHz), that you can use for RCA1B05 and 1B09 replacement.
 

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Amp PCB design

Who designed that pcb?

Whoever did it did exactly what I do, and I think should be done to draw pcbs. That is filling in as much copper as possible, particularly in high current places.

Is there anything against designing pcbs like this?

I ask because it seems obvious to me, and also uses less acid to corrode copper, because there's less copper to corrode. Only twice did I see such a design in commercial products: on a Rotel power amp and on a Yamaha power amp.



Carlos
 
I don't know who designed the pcb, but the guy who send it to me said it was a traxmaker format and that the software freely can be downloaded at: www.circuitmaker.com
It's included in a nice circuit-simulator, I've just downloaded it too, and it seems that this program works better than other simulation programs I've tried in the past.
I think the pcb can also be opened with protel.

Indeed the pcb is nice designed, I think there's nothing wrong with using as much copper for LF amplifier pcb's, for HF schematics you must remember that the space between copper tracks must be large enough to avoid that they will act like capacitors.


best regards,

HB.