Stu's 1000 post Xers, Inspection, fix, test and ship.

[jbeckva]

Want some xers to fix??

Fix or mod?

Ok, so I had the 'blocks wide open. Not bad.. not bad! As the datasheet for the main amp IC sort of points at, they'd probably do better with 4 ohmers or less. I think the limiting factor is the PS voltage. It can only put out up to the voltage available.

Not knockin' em at all... they put out plenty of power to make the SPL's... definitely loud enough to get me in trouble with the honey..

Rather... I get the impression that the amps could put MORE power out with a higher supply voltage. Since it would take less voltage for 4 ohms to produce the same power output, conversely it takes more for 8 ohms.

Hmmmm... interesting thought just occurred. Anyone notice how there are a lot of those all in one HT receiver/DVD setups that come with 6 ohm speakers? I bet that change from traditional 8 ohmers is related!

BUT anyway... Overall I'm definitely stoked. Up to the clipping point, these guys seem to have unlimited capacity. No upper end compression noticeable. I'm going to try hooking the 2nd pair of speaks up in parallel. Shouldn't be an issue... datasheet says these guys can handle 2 ohm loads easily.

 

[laatsch55]

Ok, thats what Joe is thinking too, more PS voltage more power. I've got a power supply with a 2kva toroid, 88000 uf caps and a variac i can go from +, - 0 volts to 135 +,-., what'll ya suppose they can take??

 

[stuwee]

Hmmmm, that might explain why I really diggged the sound with the ML's and not so much with the easy to drive JBL's, they must like to be loaded down to get the tunes out. Kinda like my little SAE A202, magical with the Logans, kinda flat with the JBL's.

Dale has the JBL's hooked up to the Marantz 2270 and with that Grado Gold I got from you Jer,it's a wicked nice combo!

Any chance I could see the data sheet?

 

[speakerman1]

I'm scared very scared. LOL

Larry

 

[stuwee]

I'm scared very scared. LOL

Larry

Me too! But in a good way

 

[laatsch55]

I'm scared very scared. LOL

Larry

W ith a Laatsch having his finger on the button, BE SCARED, VERY SCARED!!!!!

 

[jbeckva]

Datasheet says +/- 30. Did you measure what the xamp's PS is putting out?

Another interesting spec on the datasheet. Says GENERAL;Vp = +/- 24V. I wonder if that's the absolute max?

[attachment=0:1gwcxszy]tda8924.pdf[/attachment:1gwcxszy]

 

[laatsch55]

Ok in bridged mode(which the monos are) we should be kickin 240 RMS!!

nevermind, thats 4 ohm load.

 

[laatsch55]

Jer!!!!!!!! the 350KHZ Sig is the PWM carrier freq!!!!!! We're golden MAN!!!!!!!!!!!!!

 

[jbeckva]

Jer!!!!!!!! the 350KHZ Sig is the PWM carrier freq!!!!!! We're golden MAN!!!!!!!!!!!!!

Awesome! So yeah.. if you want to send a few my way to mod, not a problem at all!

 

[laatsch55]

ANDDDDD, what i was seeing the other night WAS it switching in and out of protect mode, it tries every 100ms to restart after an over/under/ or short condition. whats the freq of a 100ms??

 

[jbeckva]

10 Hz?

 

[laatsch55]

60K.

 

[laatsch55]

So the traces i was getting the other night i thought were around 45k were the protect mode pulses??

 

[speakerman1]

Dumb question. Could we be getting the ground loop from the voltage regulators? I'm just looking at why pulling the grd stops it.

Larry

 

[jbeckva]

60K.

Ya sure? If there are 1000 milliseconds in a second, then how many 100 milliseconds can fit in the same second?

 

[laatsch55]

True, so a harmonic?? the input protects kick at 5.5volt , my ig gen can go to 15 volts so i probably was triggering input protect.

 

[laatsch55]

Dumb question. Could we be getting the ground loop from the voltage regulators? I'm just looking at why pulling the grd stops it.

Larry

Not dumb Larry, just a question I'm not qualified to answer, not that that has ever stopped me. I do a lot of thinking out loud so i'm gonna sound dumber than a box of rocks at times.............................

 

[jbeckva]

I was wondering about that too i.e. why the ground pin was pulled from the plugs.

I wonder tho... if you look at the schematic and how it says to do the bridging on the input side of the chip, it specifies the use of jumpers (J6 and J7) i.e. straight wires. But when I looked at what was installed on the amp board, it looked to me like there were two low-resistance resistors? Wouldn't/Couldn't that cause a difference of potential, hence a ground loop?

 

[laatsch55]

Maybe Jer, if the ground wasn't then terminated to HQG point?? perhaps that was severed while doing the rest of this??