The Av800, how good is it?

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#81
So you think its not a good idea to put it all in one casing?

My original idea was something like this:

the two torodials in serie
+48+48=+96V AC
-48-48 = -96V AC

+/- 96V AC -> +/- ...?? DC for the 1KW sub amp (2x av800) or (2x 2800)

4 amplifiers of about 200W/250W that can operate on the same voltage rails as the sub. Should be possible, its just a matter of decreasing output devices to get 200/250 W

This way the power consumed is equally divided over the two torodials. They are 1.6KW each, so 3.2KW should be just about enough for 1KW + 4x 250W.

But, 96V AC will become, uhmmm, a lot more DC, and im wondering if the AV800 can handle it. Or maybe thyrlander's 2800. Or is a 250W amp very inefficient on such high voltage rails?

Regards
 
#82
Well the first thing is AC is not designated as negative and positive as you have indicated, although I suspect you know that and are referring to a configuration.

The AV800 uses +/- 85VDC rails from a 60VAX dual secondary source. A 90VAC dual secondary source would almost certainly be too much for a stock AV800. BTW 90VAC Dual Secondaries would yield +/- 120VDC or more!!

Anthony
 
#83
Yeah you are right in every way.

I didnt mean +/- AC, just the configuration.

The 1KW sub is a must. So I gues there is not much choice. 65VDC rails wil not be enough to get 1KW.

Time to check and or modify the circuits so they can handle 120VDC rails.

Kind of funny actually +/-120VDC is about 240Vdc. Almost enough to do it without tranny, just make DC out of the net and centertap that somehow 😛 😛

Seccond problem that shows up, 120V 40mF capacitors :cannotbe: :cannotbe:

I feel this is gonna be one big amp 😀 😀

Regards,

Jacques
 
#84
Just a quick update.

I plugged one of the monster torodials in. autofuse of 10amps blew a few times 😛 😛

I first tried a 5 winding 230cable just to check if it worked and to be sure i didnt blew anything important. It made some nice sparcs @ 3volt 😀 😀

I was surprised about one thing though. The idle AC voltage was 39 volt, although it clearly stated 48volt on the label. it was 39volt AC both secundary windings on both torodials :S. After making it DC and putting a cap over it it was 51 volt idle. Is it possible that they stated the peak voltage, or the voltage after rectifying on the label??

I don't mind so much, because this gives me the +/- 100volt for the 1KW amp from aussieamplifiers. I do find it very strange though. What are your experiences on torodial voltages and labels 😛 please let me know.

I hope the irf's can take 100volt, and if im not mistaking is the 200wat version on aussiamplifiers about the same schematic, so it should also take 100volt.

Regards,

Jacques
 
#85
Since you have the transformers already your choices
narrow.

Idea #1;

Build two independent power supplies.

One transformer for the 4 channel amplifiers.

One transformer for the subwoofer 1 channel amplifier.

Your toriods are 48VAC which is about +/- 67VDC rails.
This should be good enough to have a good amplifier.

Build four standard AV800's, one for each channel and operate
these off one transformer, the 1.6KVA rating should be ok
considering that music is not 100% duty cycle. Realistically
it would work.

Build two standard AV800's and bridged them to form a single
channel of greater power and operate these off the other
transformer, 1.6KVA. I searched the archives here and
Holton claimed that the AV800 can be bridged but he recommended that you reduce the rail voltage no higher than
75V rails.

67V x 2 = 134V ... This should give you the power you need
for the subwoofer.

**************************************************
Idea #2;

If the transformers are indentical in output voltage you
can parallel the bridge rectifier outputs and make one
large power supply that drivers all those six AV800's mentioned
above. Some people prefer not to do this because they don't
want the subwoofer to load down the rail voltage - the same
rails that feed the other non-subwoofer channels.

**************************************************
 
#86
DiMenSioN said:
Just a quick update.

I plugged one of the monster torodials in. autofuse of 10amps blew a few times 😛 😛

I first tried a 5 winding 230cable just to check if it worked and to be sure i didnt blew anything important. It made some nice sparcs @ 3volt 😀 😀

I was surprised about one thing though. The idle AC voltage was 39 volt, although it clearly stated 48volt on the label. it was 39volt AC both secundary windings on both torodials :S. After making it DC and putting a cap over it it was 51 volt idle. Is it possible that they stated the peak voltage, or the voltage after rectifying on the label??

I don't mind so much, because this gives me the +/- 100volt for the 1KW amp from aussieamplifiers. I do find it very strange though. What are your experiences on torodial voltages and labels 😛 please let me know.

I hope the irf's can take 100volt, and if im not mistaking is the 200wat version on aussiamplifiers about the same schematic, so it should also take 100volt.

Regards,

Jacques
Click to expand...

Since you tested the amplifer at 51VDC (rails) you can now
examine the transformer series connection you proposed. In the archives
Holton said his +110VDC 1KW amplifier was actually +96VDC
when loaded.

Perhaps you can build a dual rectifier power supply to get
some extra voltage drop to keep your rails just under 100v ?
Plus, as soon as you play some music you will get rail sag,
the rail voltage drops as it's being loaded down. /hehe

You might want to build one of those transformer 'soft start'
circuits, aka resistor, relay, delay or equivalent to limit the inrush
current at power-on.

Perhaps build one <100V rail power supply and build one
channel of AV800 and test this. If ok, then build the remaining
AV800's.......
 
#87
thanks

I will build that softpower with a resitor and a relais, it's a must, because my brother doens like it if his computer goes out everytime i wan't to play with the torodial 😉 😉
I think i even have to build some kind of polarity checker and corrector for the primairy windings, so i can feed the transformers from different groups, 3.2KW is a bit to much for a non dedicated power outlet 😀

There is not much left of the two options, as regarding option 1, i could build a 4x av800 circuit with 1 transformer. But that would leave me only 1 transformer of 51VDC idle voltage rails, which is not enough for the 1KW sub.

So there is no other choice then to go for option 2, build one big supply with all secundairy's in serie to obtain +/- 100volt idle rails. I was planning on using at least 40mF for stabilisation so i don't think the sub will draw to much power.

As for the Sub, my plan was to build the 20 o/p device version of av800, I believe this about how the 1KW amp on aussieamplifiers is build. It's stated to deliver 1KW to 4ohm.

But how is it going with your 2800 project thyrlander, sounds that it's even beter then the original av800. The schematic pdf link some posts back doesnt work, or is that just me? And how are those PCB's coming?

Regards,

Jacques
 
#88
DiMenSioN said:
But that would leave me only 1 transformer of 51VDC idle voltage rails, which is not enough for the 1KW sub.

Jacques
Click to expand...

1 transformer and two AV800 bridged should give you close
to 1kw.... /guessing

I haven't worked on my amplifier project in a long time, I stopped
after pcb layout to work on the speaker project.
 
#90
DiMenSioN said:


Could i have a look at the schematic? It sounds very interesting. If it looks as good as it sounds, I sure would want to try to build one.

Regards,

Jacques
Click to expand...


Download the doc here;
http://home.pacbell.net/lordpk/amplifier/amplifier.html

I created this document to combine all the resources to make
it easier for me. It has the Holton document, redrawn schematics
in OrCad, the Rob Elliot clipping detector document, the Pass Labs
transistor matching doc, in Microsoft Word format.

All I did was take the AV800, 1KW version and do some pcb layout
that also included some extra stuff. 28 transistors vs. 20, more
on-board rail capacitance, 4 layer pcb with power planes, molex
connectors, speaker relay w/protection circuits, etc.

The pcb layout is done but I need to build a prototype to see
if the AV800 can drive 28 transistors. It's untested. The protection
circuits were tested independently.

You can build the base AV800-1KW version (20 transistors)
and add the protection circuits on another pcb if you want it.
Circuit-wise, it's really the same schematic.

20 output transistors per channel is a beefy design and should
accomodate your plans. Many commercial 'mid - range' costing amplifers may only use 1/3 to 1/2 of that.
 
#91
Thanks m8.

There is some realy nice stuff in there.

I am a bit confused about the Thd values tho. i thought the amp had a Thd of 0.005% instead of 0.01% in your document. Ofcourse for the sub its not that important, but for the 4x modules to drive the full range speakers i would like A class amplifiers.

Regards

Jacques
 
#92
DiMenSioN said:
Thanks m8.

There is some realy nice stuff in there.

I am a bit confused about the Thd values tho. i thought the amp had a Thd of 0.005% instead of 0.01% in your document. Ofcourse for the sub its not that important, but for the 4x modules to drive the full range speakers i would like A class amplifiers.

Regards

Jacques
Click to expand...

The AV800 document I have says the power ratings achieved
were based on 0.01% THD. Sure if you lower the test, the THD
may drop.

I wouldn't worry about THD too much. People say that it's
difficult to hear 1% - 3% THD.

If 1% THD was bad, then that would indicate that the Pass Labs
amplifers are no good - because they are rated for 1% THD
at max power and 0.01% at 10W .....
(XA200 amp) <-- class A ............ /hehe
 
#93
thylantyr said:


The AV800 document I have says the power ratings achieved
were based on 0.01% THD. Sure if you lower the test, the THD
may drop.

I wouldn't worry about THD too much. People say that it's
difficult to hear 1% - 3% THD.

If 1% THD was bad, then that would indicate that the Pass Labs
amplifers are no good - because they are rated for 1% THD
at max power and 0.01% at 10W .....
(XA200 amp) <-- class A ............ /hehe
Click to expand...


Science would say that it is nearly impossible for the Human ear to hear less than 3% distortion.
🙂

Anthony
 
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