OO1 Posted July 22, 2020 Share Posted July 22, 2020 44 minutes ago, babadono said: All righty then, wiring is completed. how much power -? Quote Link to comment Share on other sites More sharing options...
codewritinfool Posted July 22, 2020 Share Posted July 22, 2020 1 hour ago, babadono said: All righty then, wiring is completed. Amp works on bench but only if an extra wire is added from the input buffer board to the Ground on the EVM3255 board. This wire connects the 2 grounds together but they are already connected without it. Really does not make much sense to me yet. Without the added wire I get a fault (fault red LED) on and it shuts down the C and D outputs. This is my first Class D amp, so let me ask this. I see about 2 volts peak to peak signal @450 kHZ with no signal being output. This is the residual switching frequency that makes the amp work? Or is my amp really screwed up? And oh yea still waiting on some LED meters from Ebay/China/Taiwan/Hong Kong. What's the voltage potential between the two grounds without the wire? 2V P-P doesn't sound right. Is that loaded or unloaded? Quote Link to comment Share on other sites More sharing options...
Edgar Posted July 22, 2020 Share Posted July 22, 2020 50 minutes ago, codewritinfool said: 2V P-P doesn't sound right. Is that loaded or unloaded? That's an important question. Class-D amplifiers use the speaker as part of a passive lowpass filter in the output stage, to reject the switching waveform. If there is no load connected, then the filter is missing an important component and filtering may be incomplete. 1 Quote Link to comment Share on other sites More sharing options...
babadono Posted July 22, 2020 Author Share Posted July 22, 2020 14 hours ago, RandyH000 said: how much power -? It is supposedly 315W per channel into 4 ohms, about 150 into 8. Quote Link to comment Share on other sites More sharing options...
babadono Posted July 22, 2020 Author Share Posted July 22, 2020 13 hours ago, codewritinfool said: What's the voltage potential between the two grounds without the wire? 2V P-P doesn't sound right. Is that loaded or unloaded? voltage between grounds with no wire is 0.1 millivolt DC about 0.3 millivolt AC. I am currently running it into a 4 ohm dummy load. They are big power resistors we use here at work. I have no idea what their inductance might be. I am going to use this amp to run the bass cabinets on my Jubilees(hopefully). This will be post Xilica crossover and just the 2 12" drivers in the cabinets, no other reactive components. 12 hours ago, Edgar said: That's an important question. Class-D amplifiers use the speaker as part of a passive lowpass filter in the output stage, to reject the switching waveform. If there is no load connected, then the filter is missing an important component and filtering may be incomplete. Hope above answers your questions or at least explains my intention for this amp. Quote Link to comment Share on other sites More sharing options...
Edgar Posted July 22, 2020 Share Posted July 22, 2020 4 minutes ago, babadono said: I am going to use this amp to run the bass cabinets on my Jubilees(hopefully). Excellent choice. My TPA3255 amps sound superb in the bass. Quote Hope above answers your questions or at least explains my intention for this amp. That 2Vpp at idle with load seems a little high, even at 450kHz, but then I've never actually measured it on mine. 1 Quote Link to comment Share on other sites More sharing options...
babadono Posted July 22, 2020 Author Share Posted July 22, 2020 9 minutes ago, Edgar said: That 2Vpp at idle with load seems a little high, even at 450kHz, but then I've never actually measured it on mine. I'm going to check into it further, go over the datasheet more throughly etc. If I still don't understand I will reach out to T.I. directly. Quote Link to comment Share on other sites More sharing options...
OO1 Posted July 22, 2020 Share Posted July 22, 2020 26 minutes ago, babadono said: It is supposedly 315W per channel into 4 ohms, about 150 into 8. not bad --------almost equivalent to a Crown XLI 800 Quote Link to comment Share on other sites More sharing options...
Edgar Posted July 22, 2020 Share Posted July 22, 2020 29 minutes ago, babadono said: It is supposedly 315W per channel into 4 ohms, about 150 into 8. Be careful -- some vendors quote power at 10% distortion, which is well into clipping. Even at 1% it's being driven too hard. 1 Quote Link to comment Share on other sites More sharing options...
babadono Posted July 22, 2020 Author Share Posted July 22, 2020 19 minutes ago, Edgar said: Be careful -- some vendors quote power at 10% distortion, which is well into clipping. Even at 1% it's being driven too hard. Roger. Those are the 10% ratings. I had it doing 150 watts per channel RMS into the 4 ohm loads and it gave an over temp warning after 10 or 15 seconds( don't quote me on the time there was a lot going on). Fortunately the Jubes would blow me out of the basement at those wattages, outdoors may be a different story. 2 Quote Link to comment Share on other sites More sharing options...
babadono Posted July 23, 2020 Author Share Posted July 23, 2020 Ok all the specs in the datasheet keep talking about a AES17 +AUX-0025 measurement filters being used while taking measurements. Anyone? Ima thinnin' that takes out the 450kHZ Ima seein' Anybody? Quote Link to comment Share on other sites More sharing options...
Edgar Posted July 23, 2020 Share Posted July 23, 2020 6 minutes ago, babadono said: Ok all the specs in the datasheet keep talking about a AES17 +AUX-0025 measurement filters being used while taking measurements. https://www.ap.com/analyzers-accessories/accessories/aes17-filters/ https://www.ap.com/analyzers-accessories/accessories/aux-family-switching-amplifier-measurement-filters/ Quote Link to comment Share on other sites More sharing options...
babadono Posted July 23, 2020 Author Share Posted July 23, 2020 14 hours ago, Edgar said: https://www.ap.com/analyzers-accessories/accessories/aes17-filters/ https://www.ap.com/analyzers-accessories/accessories/aux-family-switching-amplifier-measurement-filters/ OK so these are add ons to Audio Precision analyzers. I just want to look at signal output with an Oscope. I added a capacitor across the outputs so effectively across the load and it made it worse. ??? Quote Link to comment Share on other sites More sharing options...
Edgar Posted July 23, 2020 Share Posted July 23, 2020 8 minutes ago, babadono said: OK so these are add ons to Audio Precision analyzers. I just want to look at signal output with an Oscope. I added a capacitor across the outputs so effectively across the load and it made it worse. ??? Well my intent was only to offer info about the frequency responses of the filter; High-Frequency Rejection Typically > 50 dB, 250 kHz to 20 MHz (AUX-0025 & AUX-0100) With that filter in place there is really no way to know the raw output at 450 kHz. So what you measure on your device without the filter cannot be compared to what the manufacturer claims with the filter. Quote Link to comment Share on other sites More sharing options...
babadono Posted July 23, 2020 Author Share Posted July 23, 2020 @Edgar thanks. I get it. I just did not expect a cap across the output/load to make it worse. I got my extra wire needed mystery figured out. I just connected the shield of the twisted pair between the input buffer boards and the EVM3255 board to the DC RTN on both ends and it now comes up no problem. I don't know why I thought the common connection back at the power terminal block would be sufficient. Since i don't have anything other than a voltmeter and oscope (no Audio Precision distortion analyzer etc) I guess it is time to hook this up to my system and give it a spin. Quote Link to comment Share on other sites More sharing options...
babadono Posted July 23, 2020 Author Share Posted July 23, 2020 Pix of the finished amp, just need to button it up. 1 Quote Link to comment Share on other sites More sharing options...
babadono Posted July 24, 2020 Author Share Posted July 24, 2020 Made a interesting find on this amp. The +(red) output from this Eval board is 180 degrees out of phase with the input. So if using it full range into a passively crossed over speaker it should not matter. But if like I am using it just to drive a portion of an actively crossed over bi amped system this phase reversal must be kept in mind. Quote Link to comment Share on other sites More sharing options...
mboxler Posted July 24, 2020 Share Posted July 24, 2020 15 minutes ago, babadono said: Made a interesting find on this amp. The +(red) output from this Eval board is 180 degrees out of phase with the input. So if using it full range into a passively crossed over speaker it should not matter. But if like I am using it just to drive a portion of an actively crossed over bi amped system this phase reversal must be kept in mind. I believe the TPA3255 chip is an inverting amplifier. With the inverting op amps in front, the output phase would have been the same as the input. Can't tell how you connected the input signal to the EVM. Is it underneath...bypassing the op amps? Mike Quote Link to comment Share on other sites More sharing options...
babadono Posted July 24, 2020 Author Share Posted July 24, 2020 Yes Mike. I went directly to the input coupling caps from my input buffer board outputs. I put a link to the boards and the I.C. s in an earlier post. So if one uses the T.I. inputs they took care of the phase inversion, makes sense, I see it now in their schematic. Thanks for pointing it out. I did a brute force fix by just taking the red output from the board to my final black output post on the back of my chassis. And vice versa for the black output from the board to my red post. Should be OK since neither out is ground but a bridge tied load (BTL). Right? Quote Link to comment Share on other sites More sharing options...
mboxler Posted July 24, 2020 Share Posted July 24, 2020 Swapping the red/black outputs is the solution. Just so you know, this is the solution even if one of the outputs is grounded. When I built Nelson Pass's ACA, the outputs had to be swapped because the single-ended output is inverted. Sorry about missing the picture links. Mike Quote Link to comment Share on other sites More sharing options...
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