SOS--Help with Amp/Head unit troubleshooting!
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From: Chippewa Falls, WI
SOS--Help with Amp/Head unit troubleshooting!
So I have an issue. Going through being all **** retentive and seeing if my Sony 7k distorts with different inputs at different levels. Prior to adjusting my gains
Take the AC volts from HU with a grain of salt...but that's where/when I noticed the issue
.
Everything is set flat. 1200.4 EVOX 4 ohm Amp on full pass, crossovers all the way down, gain for both channels all the way down, and DD1 and DMM in use. Speaker wires diconnected.
I was looking for distortion levels as above. After I find the max distortion level I took a few DMM readings to see if what the HU output was since the amp should essentially be off. This is what the DMM manual suggest to do as well.
Turns out that when I switch inputs, something triggers the amp to come on and start boosing the volatge.
Ex. I start in carplay playing the (1KHz)dB test tone at lets say the safe level 39 I established. I get readings of about 3.6v. Seems normal. Then I change to USB2 or disconnet the cord and switch to bluetooth. Keep my volume the same, not touching it. Play the same track (which is lossless .wav from the DD1 disc...forgot to say that) and all of a sudden my amp output voltages are 20-21.x...well WTF. I pulled off the RCAs one by one and checked the voltage just before the amp and they were all about 1.9v.
It doesn't matter which order I switch input devices in. The first one will be unamplifed and the next ones will be boosted...
Any idea? I'm thinking its something with the amp but then again....what is triggering it to start being more sensitive?
I'll paypal someone enough for a pack of beer via paypal if they can figure it out. POS HU or Amp is not sufficeint
Thanks everyone
I called sony-take it back to the installer to figure out (doh)
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From: Chippewa Falls, WI
Obviousy, I didn't complete the above chart but I will once I figure this out and post it incase it helps someone else.
Also it seems to kick in the amp if it switches from 1k0dB to 40hz0db. USB drive has been excluded. Tried on usb2 first. Then 1. Same issue.
got rid of it and was playing with connected iPhone. All seemed stable for a bit so I set my gains with dd1 and checked voltage with dmm. 30.1v for 1k0dB. Track switched to 40hz0dB and voltage instantly read 40.1v and the other channel was at 11.2 with the gain all the way down yet.
thought it may be improperly named cd track from SMD. Trying function generator app on iPhone now to rule out it actually being a - XXdB track. . Theres definitely a gremlin here and I dont think its the tracks
grr
Also it seems to kick in the amp if it switches from 1k0dB to 40hz0db. USB drive has been excluded. Tried on usb2 first. Then 1. Same issue.
got rid of it and was playing with connected iPhone. All seemed stable for a bit so I set my gains with dd1 and checked voltage with dmm. 30.1v for 1k0dB. Track switched to 40hz0dB and voltage instantly read 40.1v and the other channel was at 11.2 with the gain all the way down yet.
thought it may be improperly named cd track from SMD. Trying function generator app on iPhone now to rule out it actually being a - XXdB track. . Theres definitely a gremlin here and I dont think its the tracks
grr
Last edited by Usmc0861; May 19, 2021 at 05:35 PM.
Thread Starter
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Novice
Joined: Jun 2020
Posts: 16
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From: Chippewa Falls, WI
So...I ran out and tried this just with the battery, not running, to see if it makes a difference.
I tried via the RCAs
40Hz distorts wired and by bluetooth at 49, max clean 48.
1K detects signal but not never1k signal, or distortion...even working my way up to a -15dB track.
Tried with probes---futile
Tried on the back side of the amp by speaker outputs for ***** and giggles. Signal detected, 1k detected, distorts at 43, max clean 42.
Amazon says my OScope should be here today but form what I have already seen with the DD1 and DMM I don''t know that looking at the waveform is going to change anything.
I know I'm becoming a pain in the ***...sorry about that.
Thanks!
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Joined: Jan 2013
Posts: 10,637
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From: Lake, Ms
Use a 1k -5db test tone across the board on the HU and determine your max clean volume. It's not uncommon for the different sources to have different max volumes. Write each one down so that you remember them. Once your max volume for each source is known, then hook to amp and set gains using the lowest max volume from your source inputs. Then hook the DD1 to the amp and check for distortion using the same test tone as above.
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