This is another example of my extreme lack of electronics knowledge. I'm trying to learn but any help will be greatly appreciated?
I think I may know how to check DC offset but just so nothing goes up in smoke please let me know if I understand the procedure.
1. Have NO XLR input cables or speaker cables are connected to the amp
2. Plug in amp and turn it on
3. Let the Amp warm up for 10 minuets
4. Set the multi meter to 2VDC or lower
5. Place red probe on right channel Mod86 J1 out and black probe on J1 GND
6. Repeat for left channel Mod86
Thanks,
henry
I think I may know how to check DC offset but just so nothing goes up in smoke please let me know if I understand the procedure.
1. Have NO XLR input cables or speaker cables are connected to the amp
2. Plug in amp and turn it on
3. Let the Amp warm up for 10 minuets
4. Set the multi meter to 2VDC or lower
5. Place red probe on right channel Mod86 J1 out and black probe on J1 GND
6. Repeat for left channel Mod86
Thanks,
henry
The best way to measure the DC offset is actually to measure it with the input of the amplifier shorted.
If you are using balanced input (XLR) connect pin 1, 2, and 3 together.
If you're using unbalanced input (RCA) connect the centre pin to the shell of the connector.
If your multimeter does not auto-range, check with a >35 V range first. If that reads 0 V offset, change the range to the most sensitive range (usually 200 or 300 mV). Measure the DC offset.
Correct.
If the DC offset is less than 1 mV, you can test the amp. I suggest using a test tone as you can perform this test using a multimeter. Create a 5 second test tone: sine wave, 400 Hz, -3 dBFS at wavtones.com. I recommend 400 Hz rather than the more commonly used 1-2 kHz as many multimeters have 440 Hz bandwidth.
If the amp checks out this far, I'd rig a speaker, crack open a microbrew, and enjoy the music.
Tom
PS: I do know that RMS and AC may be perceived as redundant, but if I only specify RMS, I usually get asked, "by 'RMS' do you mean AC?", so I figured I'd nib the question in the bud.
If you are using balanced input (XLR) connect pin 1, 2, and 3 together.
If you're using unbalanced input (RCA) connect the centre pin to the shell of the connector.
- Turn the amp on.
- Allow the DC servo to stabilize (takes about 10 seconds)
- Measure the DC voltage on the output of the amp. Should be less than 1 mV (usually way less). Mine measure 45 µV.
If your multimeter does not auto-range, check with a >35 V range first. If that reads 0 V offset, change the range to the most sensitive range (usually 200 or 300 mV). Measure the DC offset.
Correct.
If the DC offset is less than 1 mV, you can test the amp. I suggest using a test tone as you can perform this test using a multimeter. Create a 5 second test tone: sine wave, 400 Hz, -3 dBFS at wavtones.com. I recommend 400 Hz rather than the more commonly used 1-2 kHz as many multimeters have 440 Hz bandwidth.
- Play the test tone on repeat.
- Adjust the volume control on the player until you measure 1.0 V RMS (AC) from J2, pin 2 to J2, pin 3 (IN+ to IN-) on the MOD86. If you can't quite get to 1.0 V, adjust for, say, 500 mV instead. The value is not critical.
- You should have 10.0 V RMS (AC) on the output of the MOD86 (J1) for 1.0 V RMS (AC) in. You can also measure this across the speaker connector/binding posts. If the input voltage you used is lower than 1.0 V, you can compute the output voltage as Vout = Vin*10.
If the amp checks out this far, I'd rig a speaker, crack open a microbrew, and enjoy the music.
Tom
PS: I do know that RMS and AC may be perceived as redundant, but if I only specify RMS, I usually get asked, "by 'RMS' do you mean AC?", so I figured I'd nib the question in the bud.
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Do diyers dig great beers? Belgian ales are my favorites. I brewed beer for about 15 years, focusing on the Belgian style. My last batch measured 14%abv and it was great.
I bottled about seven gallons and didn't open the first bottle for six months. It had the classic yeast residue stuck to the bottom of the bottle. The rest were opened over the next two years.
I swear they got better and some small amount of bottle fermentation continued for many many months. Luckily no bottles blew up but a few corks did pop out.
I bottled about seven gallons and didn't open the first bottle for six months. It had the classic yeast residue stuck to the bottom of the bottle. The rest were opened over the next two years.
I swear they got better and some small amount of bottle fermentation continued for many many months. Luckily no bottles blew up but a few corks did pop out.
Wouldn't the XLR plug need the solder cups connected to each other to achieve your recommendation below?
"If you are using balanced input (XLR) connect pin 1, 2, and 3 together".
I've already bent a length of 24awg wire that can easily connect the three XLR pin receptacles.
I don't understand why I would use a plug connected to nothing. I think I'm miss-understanding something.
"If you are using balanced input (XLR) connect pin 1, 2, and 3 together".
I've already bent a length of 24awg wire that can easily connect the three XLR pin receptacles.
I don't understand why I would use a plug connected to nothing. I think I'm miss-understanding something.
Henry, You may have missed Tom's "shorting" in his plug recommendation. The XLR plug would have the three pins shorted together with short wire(s).
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This is my interpretation of the last two posts. Connecting the chassis mounted xlr female connections with wire will work but they might be damaged. Using an xlr male plug with its three solder cups wired together would be less likely to cause damage to the chassis mounted xlrs. Am I finally understanding what should be done?
I am making the general recommendation to use a shorting plug, i.e. an XLR plug with the three pins tied together. I do this for two reasons:
1: It ensures a good connection between the three pins.
2: It prevents damage to the female input XLR connector.
I am trying to minimize the amount of support work that I have to do so that I can focus on new product development and the continued operation of my business.
Tom
1: It ensures a good connection between the three pins.
2: It prevents damage to the female input XLR connector.
I am trying to minimize the amount of support work that I have to do so that I can focus on new product development and the continued operation of my business.
Tom
henryjr...you have stated several times that your knowledge of electronics is minimal. You have built an amp with boards stuffed by Tom. After doing the cursory checks he recommends during startup you would be wise to improve your knowledge of electronics BEFORE attempting to take additional measurements like DC offset. Assuming the amp works just hook it up and listen to some music while reading The Art of Electronics.
+1
Everything Henry has said so far indicates that the amp works as it should. This is exactly as expected as I built and tested the amplifier and supply modules before shipping them to Henry and Henry did a fine job at completing the build from there. Henry, just plug it in and enjoy it.
Tom
Tom,
Started listening to the Mod86 about an hour ago. It's fantastic. Far better than my Aragon 8000bb and better the my Mccormack deluxe edition DNA0.5. And this is just using an Aragon 18K MKII. I expect better with my Audible Illusions MA3...but another night.
Piano, cymbals,everything is better. Great job. I thank you for putting up with my most basic questions. It was well worth it to me.
Started listening to the Mod86 about an hour ago. It's fantastic. Far better than my Aragon 8000bb and better the my Mccormack deluxe edition DNA0.5. And this is just using an Aragon 18K MKII. I expect better with my Audible Illusions MA3...but another night.
Piano, cymbals,everything is better. Great job. I thank you for putting up with my most basic questions. It was well worth it to me.
I'm glad you enjoy the amp and found it to be worthwhile. No worries on the questions. While I will admit that I found myself near the boundaries of my patience at times, it was well worth it to me to have your build experience be a success story.
Tom,
I think this will be my last question. I read many posts on wiring an LED and, as usual, found a wide variety of techniques. Some folks said use a variac (don't have one) to checks things. Some said connect to the AC with resistors and diodes. Some said only connect to DC. Others said, depending on where its connected, noise could be introduced.
I read your post where you used an HLMP-D101 and found lots of sites with data sheets listing, among other things, it should be powered with 1.8Vf and 20mA.
Since your design is dead quiet I'm sure you carefully selected where to connect it. Would you provide info on how and where you connected it?
Thanks for all the help.
henry
I think this will be my last question. I read many posts on wiring an LED and, as usual, found a wide variety of techniques. Some folks said use a variac (don't have one) to checks things. Some said connect to the AC with resistors and diodes. Some said only connect to DC. Others said, depending on where its connected, noise could be introduced.
I read your post where you used an HLMP-D101 and found lots of sites with data sheets listing, among other things, it should be powered with 1.8Vf and 20mA.
Since your design is dead quiet I'm sure you carefully selected where to connect it. Would you provide info on how and where you connected it?
Thanks for all the help.
henry
I'm guessing you want a power-on indicator. The best place to connect it is on the NEGATIVE rail, so from GND to V-. The reason is that the LM3886 will create a thump on the output if its positive rail collapses before the negative as the MUTE function is dependent on the negative rail voltage. By putting the LED on the negative rail, you ensure that the negative rail collapses first and there will be no thump.
With the roughly ±30 V that you have available, I suggest using a 5.6 kΩ, 1 W series resistor with the LED. Connect the anode of the LED to GND at the Power-86, the cathode to the resistor, and the other end of the resistor to V- on the Power-86. 5.6 kΩ will give you a bit over 5 mA which is plenty to power the LED.
Keep the lead length short to avoid short circuits. I also suggest covering the connections in heat shrink tubing so you don't create an accidental short circuit.
Expect the resistor to get a bit hot (~80 ºC would be my guess) during operation, so make sure it isn't leaning against any wiring or other plastics.
If you don't like the idea of hot components within the chassis, I suggest using a chassis-mounted resistor.
Tom
With the roughly ±30 V that you have available, I suggest using a 5.6 kΩ, 1 W series resistor with the LED. Connect the anode of the LED to GND at the Power-86, the cathode to the resistor, and the other end of the resistor to V- on the Power-86. 5.6 kΩ will give you a bit over 5 mA which is plenty to power the LED.
Keep the lead length short to avoid short circuits. I also suggest covering the connections in heat shrink tubing so you don't create an accidental short circuit.
Expect the resistor to get a bit hot (~80 ºC would be my guess) during operation, so make sure it isn't leaning against any wiring or other plastics.
If you don't like the idea of hot components within the chassis, I suggest using a chassis-mounted resistor.
Tom
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