strange buzz...goes away at volume 98 99

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guf

strange buzz...goes away at volume 98 99
« on: 13 Jan 2019, 01:54 am »
I have a weird hum, buzz something. That I think is unrelated to my preamp. but when its at max volume it goes away to dead silent. This is my desktop system so I sit about 2 feet from my Omega speakers. any thoughts?

the hum issue I could discuss in another thread but I have tons of stuff connected to my system, regen, rendu, pre, tube amp..... but the interesting  thing is just having an ifi power supply plugged in all I have to do is touch the tip of the plug and the hum increases. 

Samoyed

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Re: strange buzz...goes away at volume 98 99
« Reply #1 on: 13 Jan 2019, 03:20 am »
Nice dogs!

guf

Re: strange buzz...goes away at volume 98 99
« Reply #2 on: 13 Jan 2019, 05:29 am »
 :D  thanks.  down to one. but he's a handful like 2  :duh:

Markwatkiss

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Re: strange buzz...goes away at volume 98 99
« Reply #3 on: 13 Jan 2019, 11:26 am »
I had a buzz last nite,gone this morning.

Elizabeth

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Re: strange buzz...goes away at volume 98 99
« Reply #4 on: 13 Jan 2019, 02:10 pm »
Questions: Do you have all the equipment from one AC duplex? (or if two, are they definitely the same circuit? Are you certain that outlet's GROUND is connected to the Whole house AC ground?

Have you inspected the AC duplex wiring? is it 'tight'. (Sometimes that hidden away wiring gets loose(r))

Is your stereo power on a separate circuit (at least not on the same as any appliances?)

The fact the noise gets louder TOUCHING ANYTHING is actually a good sign. You KNOW it is ground related!

It also may have to do with a AC plug in one bit of kit being wired HOT and Neutral in reverse.

As to why it vanishes at max volume is a mystery in the design of the preamp, but not really a major factor IMO.

tortugaranger

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Re: strange buzz...goes away at volume 98 99
« Reply #5 on: 13 Jan 2019, 04:45 pm »
The fact the noise gets louder TOUCHING ANYTHING is actually a good sign. You KNOW it is ground related!

My thought exactly. It suggests not every component in a system is at the same ground level.

That the buzz goes away at 98/99 (the last couple of steps in the 100 step attenuator) is probably because the output impedance of the preamp drops off significantly over the last few dB close to max volume. That drop off in output impedance near/at full volume is characteristic of all potentiometers as well.

guf

Re: strange buzz...goes away at volume 98 99
« Reply #6 on: 13 Jan 2019, 08:15 pm »
Thanks guys. yes all plugged into the same duplex and not connect to any appliances. I think the problem started from adding my m rendu.  actual when I touch the case of it it get louder.  I will inspect further and see what happens.

and transfer the thread to that circle.

guf

Re: strange buzz...goes away at volume 98 99
« Reply #7 on: 14 Jan 2019, 12:08 am »
after a bunch of experimenting plugging stuff and not.... when I take the Tortuga out of the picture there is no hum.  Amp, and all accessories plugged in and no hum at all.  Could it be something with my Pre?

tortugaranger

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Re: strange buzz...goes away at volume 98 99
« Reply #8 on: 14 Jan 2019, 02:09 pm »
after a bunch of experimenting plugging stuff and not.... when I take the Tortuga out of the picture there is no hum.  Amp, and all accessories plugged in and no hum at all.  Could it be something with my Pre?

Humming/buzz and such is not a common problem with Tortuga preamps, especially single-ended models. However, there have been a couple of instances where customers had direct coupled amps (no blocking/coupling cap on the amp's inputs). Those direct coupled amps were unhappy being connected to a passive preamp with the relative high output impedance typical of passives compared to actives. In those instances the hum also disappeared at step 98/99 when output impedance plummets.

One approach to mitigating this is to reduce the Tortuga's impedance level to something lower than the default 20k. Another approach is to add a buffer between the preamp and amp (essentially creating an active low output impedance preamp).  Yet another approach is to confirm if your amp is indeed direct coupled and use  an AC coupled amp instead - at least to confirm that this is cause.

Passive preamps will never be a universal fit with every combination of source/amp but it's fair to say passives work well with the vast majority of sources and amps. We've never been able to make our preamps hum in our shop but then again we've only used a small sampling of equipment.

guf

Re: strange buzz...goes away at volume 98 99
« Reply #9 on: 1 Feb 2019, 09:07 pm »
So, i did change my setting to 25k and the buzz/hum went away. If I set it to 20k then the buzz is worst than the higher settings, mostly in the right speaker.  I did recalibrate. more confused but happy to have solved the problem.