Need schematic for SAMSON DB500a

[fredcapo]

Samson db500a powered speakers, bi amped. Anyone here worked on these?

I understand these are Class G amps...so linear?

I have not opened up yet but hoping they are not fully SMD...

Thanks

[mozwell]

I hope this helps

[Jazz P Bass]

The Class G mearly implies that there are at least two power rail levels.
On demand they are switched in & out.
It helps conserve power.

[fredcapo]

Thanks

Looks like bipolar TO packaged...I hope,I hope...

[Jazz P Bass]

Yeah, pretty standard stuff for Samson.
2SC5200 NPN & 2SA1943 PNP.
They are the flat packs.
TO-3P

[flyingdutchman]

No class G here anyway, just run-of-the-mill straight bipolar power amps. Although class G (or H) amps are quite common even in cheap amplified speakers, mostly for the LF amp only. The HF amp will usually be an IC (LM3886, TDA7293) running off the lower voltage rails.

[Jazz P Bass]

I don't know, Samson calls it Class G.
http://www.samsontech.com/site_media...ocs/DB500A.pdf
Page 4 of the schematic, Q30 & Q32 switch the high voltage rails (+ & -) in & out.

Both the Hi & the Lo freq amps are discrete.

[flyingdutchman]

I don't know, Samson calls it Class G.
Q30 & Q32 switch the high voltage rails (+ & -) in & out.

I stand corrected, I got fooled by the fact that those devices were not where I'd have expected them in the schematic

(If I'd been looking at the PCB instead, I'd have spotted them instantly - so much for the utility of schematics)

[Jazz P Bass]

Well, we got a chance to explain Class G.

[g1]

Thanks for the explanation! I got tripped up as I was looking at the schem. the same way as flyingdutchman.

[g1]

Looking at it again, I don't get it. The class G amps I'm used to have the extra rails and output devices connect to the main output devices. In this way the output can swing further when the second set of rails kick in.
This appears to be doing something else.
Am I looking at it wrong or is my definition of class G incorrect?
And where are the "high speed, high current MOSFET rail switches" they mentioned?

[Enzo]

The extra devices are there, they are just on the next page along with the power supply.

The woofer amp runs on rails V. Those are supplied by bridge D30 and rails LV through diodes D28 D29. Note there are also rails HV powered by bridge D32. They stack on top of LV. The output of the woofer amp is sampled by a pretty simple circuit there to turn on Q49 Q50 when need arises. Those FETs act as switches to pass the HV on into the V rails.

D28,D29 block HV from getting back into LV. Or put another way, when Q49, Q50 turn on the presence of HV on the rails V reverse biases the diodes D28,29.

And where are the "high speed, high current MOSFET rail switches" they mentioned?

Q49, Q50.

[Jazz P Bass]

Thanks Enzo, for the clarification.
And sorry G-One for the misconception.
I took a fast glance at the schematic & saw that Q30 & 32 branched off to the HV rails.
First mistake, the fast glance.
Second mistake, opening my mouth before I knew what I was talking about.

[g1]

Thanks guys, I wasn't looking at the supply drawing close enough as I didn't expect to see the switchers there. Have to remember to stop expecting things to be drawn certain ways as there does not seem to be any "right" or "wrong" way to draw a schematic. Not only that, but I haven't really looked at a rail switching schem. since back before the turn of the century .

[Enzo]

Look at it this way, the amp works the same either way, power rails to the corners. A lower power version could be made by substituting a regular single voltage supply.