Guitar pre Rocktron Pro G.A.P. 2 ,noisy..related to display

blisca

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Jul 1, 2019, 11:36:27 AM7/1/19

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Hi to all the people here

I bought the old preamplifier,i remember it as pretty silent,and the
"apparent" S/N ratio is further increased by the proprietary noise gate
called "H.U.S.H."
This is a good pic of the board ,found on a website
https://images.reverb.com/image/upload/s--oH5vkrFt--/a_exif,c_limit,e_unsharp_mask:80,f_auto,fl_progressive,g_south,h_620,q_90,w_620/v1497562015/pq4p7tei1daqvapl3ygx.jpg
I'm finding it a bit too noisy,and this noise sounds as "digital
noise",more than white noise..it sounds like the frequencies composing the
noise are related to the activity of the segments digits of the
display.Adding a piece of wire as antenna to the resistors between IC
driver and display increases some particular frequency to the heared
noise,confirming my impression .
I tried shorting ground points with good cables,it does not change
anything.
I tried adding some metallic shield with minimal or null impact.
I ask your opinion about the decoupling capacitors,they are 1uF ceramic
capacitors,with relatively long leads.Do yout think that it is worth
replacing them?Maybe with SMD capacitor directly to IC VDD and GND?
Another idea is to replace the displays with new ones more
efficient,needing much less current,and then ,to increase the resistor
values,less current=>less noise,but i still dont know if such display
exists.
I would like to know your opinion.
Thanks for your time
Diego

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mako...@yahoo.com

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Jul 8, 2019, 4:22:41 PM7/8/19

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> Another idea is to replace the displays with new ones more
> efficient,needing much less current,and then ,to increase the resistor
> values,less current=>less noise,but i still dont know if such display
> exists.
> I would like to know your opinion.
> Thanks for your time
> Diego
>
> ---
> Questa email è stata esaminata alla ricerca di virus da AVG.
> http://www.avg.com

what type of display LED?

can you use standard signal tracing to determine which audio stage is picking up the noise, does the volume control effect it, tone controls etc.
?
m

tabb...@gmail.com

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Jul 10, 2019, 9:18:48 AM7/10/19

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The simple way to find out if replacing a cap will help is to bridge it with another cap. If the original is ok, it makes no difference. If the original is bad, it solves the problem. Sometimes you can just hold the 2nd cap & touch it onto other caps one after another to dx a fault.

NT

Fox's Mercantile

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Jul 10, 2019, 9:24:57 AM7/10/19

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On 7/10/19 8:18 AM, tabb...@gmail.com wrote:
> The simple way to find out if replacing a cap will help is
> to bridge it with another cap.

That only works if the cap has gone open.

--
"I am a river to my people."
Jeff-1.0
WA6FWi
http:foxsmercantile.com

Phil Hobbs

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Jul 10, 2019, 10:40:24 AM7/10/19

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That's a great way to blow stuff up, too.

Cheers

Phil Hobbs

--
Dr Philip C D Hobbs
Principal Consultant
ElectroOptical Innovations LLC / Hobbs ElectroOptics
Optics, Electro-optics, Photonics, Analog Electronics
Briarcliff Manor NY 10510

http://electrooptical.net
http://hobbs-eo.com

tabb...@gmail.com

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Jul 11, 2019, 3:34:52 PM7/11/19

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On Wednesday, 10 July 2019 15:40:24 UTC+1, Phil Hobbs wrote:

how? I never have that way. Obviously some clue is required, not applying a 400v charged cap to a base somewhere.

NT