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My system has a noticeable turn on thump and I have always powered things up (and down) manually and in order.  I now want to be able to power everything up at once and so I examined my system component by component.  I found that the preamp is causing the turn on and off thump.  (Without the preamp, there is a very small thump that I can live with.)  The culprit is my Sumo Athena preamp, which sounds great and seems to be working well except for this problem.  So, I would like some help in diagnosing and repairing  this problem.  Can anyone direct me to posts or articles on this subject?

BTW, I don't have schematics for this piece.  Apparently, Sumo never released them and they are very hard to come by.

One common strategy for avoiding preamp turn on spikes is to turn the power amp on after the preamp has stabilized.  There are power management devices that do that.  This device looks about right:

Another strategy is to ensure that the power supply of the preamp stabilizes very rapidly or very slowly. Either strategy can work, or not. The theory of the fast stabilizing strategy is to let the preamp get stabilized before the power amp starts passing signals. The theory of slow stabilizing is to try to reduce the rate of stabilizing until it is so slow that  any thumps that are created are at such a low frequency that they are below the bandpass of the power amp and get lost in its low frequency roll-off. Neither approach has to necessarily work, but either often may work.

Common means to accomplish these strategies is to make the power supply and coupling caps in the preamp either as large or small as possible consistent with general goals for adequate frequency response.

One common set of circumstances is that the electrolytic caps in the preamp degrade over time as they are naturally prone to do, and this essentially changes the design of the preamp. This is one way that re-capping or capacitor upgrades can yield real improvements. The sound is really no different, but the thumps may be reduced or eliminated.

Other strategies include simply throwing this legacy crap away and getting good modern gear that works right. A lot of modern gear does this by design. For example my fairly modern AVR is so digital that it has to boot which takes time, and it has a relay that doesn't hook up the speakers until the AVR finishes booting. This takes about 3-5 seconds.  The other components in  my system could be thumping away to high heaven, and by the time the speakers get hooked up, the excitement is all over.
General Audio / Re: Parametric EQ and Crossfeed for Android?
Last post by lélé -
I gave a try to Neutralizer and I'd like to thank you because it proposes a very interesting approach.

As far as I understood Neutralizer relies on Android EQ.
It seems to work fine with all my streaming applications: very good point!
I just regret it is limited to 12 bands which does not allow 'fine tuning' in the highs, where my (current) IEM frequency response curve is quite 'bumpy' and where my audition suffered more of abuse and time.

Equalizing every bump and null, and/or within a fraction of a dB does not necessarily contribute significantly to listening pleasure.

Our ability to even detect a frequency response discontinuity goes down as it gets narrower. 

Freedom from detection is a far more sensitive to what is required for the perception of natural balance, or listening pleasure.

I am still looking for a solution for cross feed that can be used with my streaming application by the way...
Any suggestion?

Fix the tracks.  Many audio editors have channel mixing features. Ideally, you'd access the .wav versions, add a little cross feed, and then re-apply any compression that you might have chosen.

IME there are not a large number of tracks that don't have any crossfeed at all or are objectionable because they have way too much separation.  For example, there are all those old Beetles tracks that are essentially two channel mono, with all of the instruments and voices slammed to one channel extreme to the exclusion of the other.  Those represent a short term phase, and for a variety of reasons including mono compatibility and compatibility with cheap LP players, that phase mostly went away pretty quickly.

Some recordings with extreme channel assignment and mixing or un-mixing are still made, but it seems like they were intentional, and part of the artistic experience of listening to them.


Many thanks for your answer.

As for the connection of 'bumps' and 'dips' in the highs, they can have very large amplitude (but narrow bandwidth) with headphones and, even worse, with IEM. Plus I guess those can be quite user dependent with IEM (depending on tips used, filters used and insertion depth). I would have been curious to see if it can be corrected with an EQ like Neutralizer.
But you might be right and the most important remains the general presentation. Plus I guess correction of large amplitude on narrow bandwidth may worsen things instead of correcting them (and introduce artefacts?).

Regarding excessive stereo separation, unfortunately, I cannot fix the tracks because I use streaming platforms. At the moment I am trying Qobuz and Spotify to assess which service suits me better. I will probably give a try to Tidal too.
In any case, I don't want to go back to the 'old fashioned way' for a lot of reasons, including:
  • I listen to music from my android device several hours per day. I enjoy discovering artists and albums that I don't know. For such purpose, streaming is very convenient and very cheap.
  • Ripping or downloading is too time consuming and too expansive(assuming you go for legal offer).
So I am still looking for an Android application that offer a good cross feed feature and can be used in parallel with streaming platforms apps.

Welcome to room sound. You have two choices: Either believe what reviews and marketing and "general forums" say about EQ, or you can educate yourself to point where you will completely dismiss all that "fake news" (sorry)

Then you save 100 bucks and buy a measurement microphone. You have a computer obviously.

You moved your speakers, now you have new "standing waves". The "bettering of bass" you experience after fiddling with decoupling is only your brain adjusting to the new sound. Keep going and one day it will simply feel "right". Its not of course. This burn-in of your brain to the new sound ... (get where I am going with this?)

For starters, you should read up / Google about "room modes" and "standing waves". If you want to go a bit further, read Floyd Tooles book:   Sound Reproduction: The Acoustics and Psychoacoustics of Loudspeakers and Rooms (Audio Engineering Society Presents) 

I do like your 3 spikes idea - won't help with your problems of course, but the "self leveling" is a cool idea. Makes for tippy speakers if someone bumps into them.

When you're done reading, you measure your room with and without the spikes. Mark the speaker locations! Report back! It will be interesting to see the data.
If changing the language code to 'eng' is all it needed, well that's one of the changes 3.100 will have out of the box.
Go to Preferences/File/Add Location/

and write something like:      spotify:album:401DhjeJg1yVIfBN2A55JY

where 401DhjeJg1yVIfBN2A55JY is the album code. To get the album codes I open Spotify Web Player. You need a premium account.

It works fine.

General Audio / Re: Diagnosing Preamp Turn-on Thump
Last post by dhromed -
15 seconds sounds like an extremely long time though. My amp only takes ~3 seconds to click on after I press the power button. Maybe it's a typo and should read 1.5 seconds?
That might be a possibility too. I'd expect for someone to at least know what tags are.
Frankly, from the original posting (what you call "faulty logic" yourself), I would not bet money on the OP being right about what is called "tags" and what is merely order of appearance in a playlist.

A suggestion that will work if it is a "well-known" album:
Install MusicBrainz Picard - which is a useful application anyway, I'd say - and let it tag based on audio fingerprint.
Then auto-rename the files.
General Audio / Re: Diagnosing Preamp Turn-on Thump
Last post by cresco -
Check out this article

It states there is no switch on (or off) thump, so I assume there is a problem with your amp if it is indeed responsible for the thump

"I generally leave preamplifiers on all the time, and did so with the Athena as well. But for those who don't, the Sumo preamp has no turn-on or turn-off pulse; the output is muted for 15 seconds at turn-on to allow for stabilization of the circuitry—a welcome feature."
As I said, read the thread again. This is getting really stupid. Everyone here except you and OP seem to know it's just wrong tag titles and track numbers with the numbers and titles shifted one place. So that gets confused to a "sorting" problem with the tracks having "wrong audio". Seriously??