2x250 IRS2092 amp build

[robertcottiers]

Re: 2x250 IRS2092 amp build

Lets continue the capacitor discussion with a modified scenario,lets say we have a large amount of 20,000 uf capacitors rated at 50 volts,The original specification called for a 20,000 uf capacitor at a 100 volt rating.

We have the required capacitance value but only half of the required voltage rating,we will need to wire 2 of our capacitors in series to double the voltage handling.We need to take the negative lead of 1 cap and solder to the positive lead of a second cap....nothing will be connected to this junction.This leaves us with two leads a plus and minus. Cover both series connected caps with an imaginary piece of shrink tubing :D. Now take a white marker and write our new value of 10,000 uf 100 volts.

Notice that our 20,000 uf rating is now cut in half,but we now have a 100 volt rating...We will need to make another series connected pair just like the first one...We now take the 2 pairs and connect them in parallel to obtain the final value of 20,000 uf at 100 volts. There are other potential issues with series connected caps but I won't cover them here.Connecting caps in series to obtain a higher working voltage is something you would do in a pinch ;).

I thought an "Over explanation" might help those who still a bit unsure...

Regards
Bob C.

[PWR RYD]

Re: 2x250 IRS2092 amp build

Part of me says "if it sounds good leave it alone". But the other part of me says you already have all the parts so it only takes a little DIY hobby time and some solder to rewire it for the maximum possible capacitance. Will it sound better? Maybe. Will it sound worse? Doubtful.

[PWR RYD]

Re: 2x250 IRS2092 amp build

Hi Hong,
What you said is correct. But that technique is rarely used, other than in DIY (because that's what I have to work with). Two 50V caps in series will most always cost more and take up more space than one 100V cap with the equivalent capacitance. Luckily for us DIY guys we can do what we want.

[neildavis]

Re: 2x250 IRS2092 amp build

So, What is the conclusion about my PSU?

Its sure sounds good!

I don't think that anyone can make a conclusion about the PSU until they know exactly how it is wired. Hong posted two different PDF files that are different from the "standard" center-tapped transformer with a single bridge rectifier. I'm not clear on how yours is wired, and how the grounds connect together. But I'm guessing that yours is equivalent to the second PDF schematic that Hong posted, which I believe is equivalent to the first one he posted, with 2 of the 4 rows of caps shorted out. The power supply will still work and the amp will sound great, but you aren't getting the full effect from all of those caps, since only half of them are in the circuit. See the attachment for more information. But again, I'm not certain that I understand how your PSU is wired, so I'm making some guesses...

PS.pdf

You can verify whether the caps are shorted out with an ohmmeter. If they aren't shorted out, then I'm with Pete--the first circuit that Hong posted is a head-scratcher . You can try following the flow through the diodes, but unless you have a clear idea what else "GD" is connected to, it's a waste of time. If GD isn't connected to ground, then measure the voltage at GD with respect to the ground--that will help us understand the circuit.

[hongrn]

Re: 2x250 IRS2092 amp build

Neil,

In this pdf, you wrote "It will work fine, but the middle rows of caps do nothing". I'm not really sure what you meant here, because there's no middle caps, since each rail has only one row of caps. Bottom line, the whole thing has to do with the 2 PSU requirement of the Sure board. I haven't tried it, but I'm tempted to use just one. You built one Sure amp a while back, did you use one or 2 PSUs in your build? Thanks.

I don't think that anyone can make a conclusion about the PSU until they know exactly how it is wired. Hong posted two different PDF files that are different from the "standard" center-tapped transformer with a single bridge rectifier. I'm not clear on how yours is wired, and how the grounds connect together. But I'm guessing that yours is equivalent to the second PDF schematic that Hong posted, which I believe is equivalent to the first one he posted, with 2 of the 4 rows of caps shorted out. The power supply will still work and the amp will sound great, but you aren't getting the full effect from all of those caps, since only half of them are in the circuit. See the attachment for more information. But again, I'm not certain that I understand how your PSU is wired, so I'm making some guesses...

[ATTACH=CONFIG]46993[/ATTACH]

You can verify whether the caps are shorted out with an ohmmeter. If they aren't shorted out, then I'm with Pete--the first circuit that Hong posted is a head-scratcher . You can try following the flow through the diodes, but unless you have a clear idea what else "GD" is connected to, it's a waste of time. If GD isn't connected to ground, then measure the voltage at GD with respect to the ground--that will help us understand the circuit.

[hongrn]

Re: 2x250 IRS2092 amp build

By the way, thanks for the warning Craig, but I'm slowly getting there. I'm dragging Lowell along with me as well.

Wait till you get bit by the vacuum tube bug and you run into lots of old text books that used the old school electron current flow instead of the modern "conventional" current flow. Everything is bass akwards. My electronics teacher in high school was a Vietnam vet radio man. He taught us the old military current (Electrons) flows from ground (negative) to the B+. Took me almost the whole first semester of college to get my brain turned around

[neildavis]

Re: 2x250 IRS2092 amp build

Neil,

In this pdf, you wrote "It will work fine, but the middle rows of caps do nothing". I'm not really sure what you meant here, because there's no middle caps, since each rail has only one row of caps. Bottom line, the whole thing has to do with the 2 PSU requirement of the Sure board. I haven't tried it, but I'm tempted to use just one. You built one Sure amp a while back, did you use one or 2 PSUs in your build? Thanks.

Sorry for the confusion. See the two rows of caps with red X's on them in the attachment. These caps might be shorted out, depending on how those "grounds" are connected.

That "2 PSU" requirement verbiage is misleading. The requirement is actually for 2 voltages: plus 65V and minus 65V. You can achieve that with two separate 65V supplies or with a single ±65 supply like the circuit that Pete included in his post. PE should get Sure to revise that data sheet--it is misleading.

PSx.pdf

[[email protected]]

Re: 2x250 IRS2092 amp build

Neil, GD goes to earth.

[[email protected]]

Re: 2x250 IRS2092 amp build

Your right Craig. I'm thinking Integrated tube amp in the future. Just waiting for you to design one.

[[email protected]]

Re: 2x250 IRS2092 amp build

Neil. Its like this but with more caps. And of course dual secondaries vs split like this.

[neildavis]

Re: 2x250 IRS2092 amp build

Neil, GD goes to earth.

OK, but does the ground for the input connect to earth? The Sure board uses a ground plane that connects the input ground, the output grounds (the speaker "-" connections) and the power ground (the connection labeled "Gnd" on the board). If any of these are connected to earth, then the capacitors that I marked are shorted out and not doing anything. You can verify whether there is a connection between GD and Gnd with an ohmmeter.

Given the symmetry of the PSU, there almost has to be zero volts on that GD line with respect to the Sure Gnd connection, which means there won't be any voltage across the marked capacitors. So even if there wasn't a short, those caps probably aren't doing anything.

[[email protected]]

Re: 2x250 IRS2092 amp build

OK, but does the ground for the input connect to earth?

no.
The gnd on the amp is a sum of the minus from one and plus of the other rail.

[hongrn]

Re: 2x250 IRS2092 amp build

[Pete Schumacher]

Re: 2x250 IRS2092 amp build

Neil. Its like this but with more caps. And of course dual secondaries vs split like this.

The grounding scheme can be dispensed with completely. These voltages are floating with respect to one another, but there is no need to have the caps meet and connect to ground unless it is to keep the voltages from going too high. The two series caps can be replaced by a single.

Also, this schematic shows the secondary wired as a center tap, not individual windings being full wave rectified. Doing that allows you to get rid of the second rectifier bridge further simplifying the circuit.

I can see why hong is pulling his hair out right now . . . :D

[[email protected]]

Re: 2x250 IRS2092 amp build

When I finish my Polk redo, I will re-wire to have 8 parallel caps per rail and loose the ground.
Like this one.
Except I'll wire the rectifiers right unlike this one.