Go Back   Home > Forums > >
Home Forums Rules Articles diyAudio Store Blogs Gallery Wiki Register Donations FAQ Calendar Search Today's Posts Mark Forums Read

Analog Line Level Preamplifiers , Passive Pre-amps, Crossovers, etc.

Volume Adjustment Thump Troubleshooting
Volume Adjustment Thump Troubleshooting
Please consider donating to help us continue to serve you.

Ads on/off / Custom Title / More PMs / More album space / Advanced printing & mass image saving
Reply
 
Thread Tools Search this Thread
Old 17th November 2019, 05:53 AM   #1
Hypnoglitz is offline Hypnoglitz
diyAudio Member
 
Join Date: Jul 2019
Default Volume Adjustment Thump Troubleshooting

I'm experiencing a low frequency persistent thumping from my speakers and a significant intermittent thump from my subwoofer when adjusting the volume to my preamplifier.

It began a few days ago when I changed out the output coupling capacitors to my dac. I did so in hopes of improving the clarity to my system, I changed the value from a 2.0uf to a 3.9uf. I changed the capacitance value due to the recommendation of a vendor, as my premaplifier has an input impedance of 10k, and it was recommended that a higher value capacitor may be better for my system. I found similar information using the V-cap calculator, as it indicated an optimal capacitor would be much higher than the stock value. I settled with the 3.9 value due to space constraints.

Upon changing the capacitors, I immediately heard the thumping in the system. Once the volume was changed, the sound was very good. However, the volume adjustment noise bothered me so I investigated my connectors. This led to what I thought was a discovery, as I noted the left rca output of the dac was creating a noise through my speakers when disconnecting and connecting. I followed up by purchasing a new set of rca jacks, I soldered them in tonight, and I'm still experiencing the thumping when adjusting the volume.

Curious what I should be looking at for a fix? Is this a problem with my preamplifier's volume control? Or is it the dac? Or something else entirely, perhaps?

Any thoughts would be greatly appreciated.
  Reply With Quote
Old 17th November 2019, 07:56 AM   #2
ubergeeknz is offline ubergeeknz  New Zealand
diyAudio Member
 
Join Date: Aug 2018
It's most likely the capacitors, since it started when you changed them. Did you use the same type of capacitor as the ones which were installed? Why did you change them in the first place?
  Reply With Quote
Old 17th November 2019, 08:20 AM   #3
Douglas Blake is online now Douglas Blake  Canada
diyAudio Member
 
Douglas Blake's Avatar
 
Join Date: Nov 2019
Location: Niagara Region Ontario
Quote:
Originally Posted by Hypnoglitz View Post
I'm experiencing a low frequency persistent thumping from my speakers and a significant intermittent thump from my subwoofer when adjusting the volume to my preamplifier.
This started when you changed those capacitors.
If you have a voltmeter check for DC on the outputs of your DAC.

It's possible you have one or both in backwards. Generally for an output you wan the negative pole of the capacitor on the connector side, not the electronics side.
  Reply With Quote
Old 17th November 2019, 01:32 PM   #4
Mark Tillotson is offline Mark Tillotson
diyAudio Member
 
Join Date: May 2018
Location: Cambridge UK
Some sort of motor boating is happening or an unintended relaxation-oscillator has been created.


What kinds of capacitor are involved? What is the DC voltage across the capacitor? More details should provide clues.
  Reply With Quote
Old 17th November 2019, 02:13 PM   #5
Hypnoglitz is offline Hypnoglitz
diyAudio Member
 
Join Date: Jul 2019
I changed the capacitors to improve clarity, my system was sounding a touch dark. The capacitors I put in are Jantzen Superior 3.9uf, 800vdc. From what I understand, the capacitors are not polarized. I did orient them both in the same direction, per the label writing. I removed the capacitors and checked the capacitance, not sure how to check the DC voltage...is that done in circuit?
  Reply With Quote
Old 17th November 2019, 08:40 PM   #6
Mark Tillotson is offline Mark Tillotson
diyAudio Member
 
Join Date: May 2018
Location: Cambridge UK
And the ones you replaced were what?
DC voltage is measured in circuit.

Those monster film caps claim to be low inductance, yet they are huge wound types so they will have complicated impedance v frequency curve simply due to the length of the foils.

Very large caps can pick up interference or feedback due to the large stray-capacitance of the outside of the thing.

Its a shame there isn't a proper datasheet for the caps, their self-resonant frequency, ESL and ESR are all important to know, and the polarity isn't given (large caps outer foil should be connected to ground if possible, or the lowest impedance side of the circuit if not.)
  Reply With Quote
Old 17th November 2019, 09:20 PM   #7
Douglas Blake is online now Douglas Blake  Canada
diyAudio Member
 
Douglas Blake's Avatar
 
Join Date: Nov 2019
Location: Niagara Region Ontario
Quote:
Originally Posted by Hypnoglitz View Post
I changed the capacitors to improve clarity, my system was sounding a touch dark. The capacitors I put in are Jantzen Superior 3.9uf, 800vdc. From what I understand, the capacitors are not polarized. I did orient them both in the same direction, per the label writing. I removed the capacitors and checked the capacitance, not sure how to check the DC voltage...is that done in circuit?
I looked up those caps... they're not for PCB circuitry. Most likely they're for crossovers or industrial use.

I would strongly suggest you put back the original caps and see if your problem goes away.
  Reply With Quote
Old 17th November 2019, 11:58 PM   #8
Hypnoglitz is offline Hypnoglitz
diyAudio Member
 
Join Date: Jul 2019
Interesting thoughts. I'm likely going to backfill with the old ones. They were proprietary, made by the dac manufacturer. Regardless, I'm still scratching my head, as these dacs, made by MHDTLabs, have hundreds of online pages of modding enthusiasts doing the exact same thing but with satisfactory results. I can't help but feel the change exposed an existing weakness but don't have proof of such a thought.
  Reply With Quote
Old 18th November 2019, 12:32 AM   #9
ubergeeknz is offline ubergeeknz  New Zealand
diyAudio Member
 
Join Date: Aug 2018
It seems that you have DC somewhere and the level is changing when you adjust the volume.

Apart from swapping out those caps, did you make any other change? You haven't accidentally bridged anything with solder or something?

I'm also not sure I understand why changing a 2u output coupling cap to 3u9 could fix a "dark" sound. It seems like it would only improve deep bass response.
  Reply With Quote
Old 18th November 2019, 12:39 AM   #10
Douglas Blake is online now Douglas Blake  Canada
diyAudio Member
 
Douglas Blake's Avatar
 
Join Date: Nov 2019
Location: Niagara Region Ontario
Quote:
Originally Posted by Hypnoglitz View Post
Interesting thoughts. I'm likely going to backfill with the old ones. They were proprietary, made by the dac manufacturer. Regardless, I'm still scratching my head, as these dacs, made by MHDTLabs, have hundreds of online pages of modding enthusiasts doing the exact same thing but with satisfactory results. I can't help but feel the change exposed an existing weakness but don't have proof of such a thought.
One possibility is that your setup has some unique property that exposed the fly in the pudding. Of course, with the low levels of skill prevalent on the net, it's entirely possible others have the problem too and don't even know it.
  Reply With Quote

Reply


Volume Adjustment Thump TroubleshootingHide this!Advertise here!
Thread Tools Search this Thread
Search this Thread:

Advanced Search

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off

Forum Jump

Similar Threads
Thread Thread Starter Forum Replies Last Post
NAD 325BEE Volume pot range adjustment music4cities Solid State 16 25th September 2018 03:36 PM
Volume adjustment on 8ch at once Victorinox Tubes / Valves 11 7th August 2014 07:30 PM
Discussion of CCS control for LED/LDR volume adjustment AndrewT Analog Line Level 0 24th May 2012 01:12 PM
volume adjustment for cabinet lining cast55 Multi-Way 10 30th December 2010 07:02 AM
Volume Adjustment - Please Help Scott_drake Solid State 0 12th August 2006 03:02 PM


New To Site? Need Help?

All times are GMT. The time now is 06:41 AM.


Search Engine Optimisation provided by DragonByte SEO (Pro) - vBulletin Mods & Addons Copyright © 2019 DragonByte Technologies Ltd.
Resources saved on this page: MySQL 15.00%
vBulletin Optimisation provided by vB Optimise (Pro) - vBulletin Mods & Addons Copyright © 2019 DragonByte Technologies Ltd.
Copyright ©1999-2019 diyAudio
Wiki