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Post subject: GT40: High frequency noise. Comming from power supply?
Posted: Wed Dec 27, 2017 3:43 am
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Hi all,
I got a GT40 Amp to Christmas. When I power on the Amp, there is a (changing) high frequency noise which seem to come from the power supply area (maybe transformer?). It is definitely not coming from the boxes. The noise is not loud but recognizable in quiet environments. Does your Amp's also doing such noise or is my one broken?

Best regards

Jan


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Post subject: Re: GT40: High frequency noise. Comming from power supply?
Posted: Sun Dec 31, 2017 2:15 pm
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I have not this amp, but it should be quiet.

Best is return to the store.


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Post subject: Re: GT40: High frequency noise. Comming from power supply?
Posted: Sun Dec 31, 2017 2:16 pm
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I have not this amp, but it should be quiet like any amp or electronic gear.
Transformer could be the issue.

Best is return to the store.


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Post subject: Re: GT40: High frequency noise. Comming from power supply?
Posted: Sun Dec 31, 2017 3:09 pm
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These amps have no transformer. It's likely one of 2 things....interference from something in the place you are playing it or it needs to be updated. Even if its at the latest update you can refresh a corrupt firmware install by doing a forced update. First thing i'd do is try it as far away from there as possible in case something locally is interfering, preferably a different building. Then if no good, update it or do a forced update if it;s already on the latest firmware. If neither of those does it then return it.


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Post subject: Re: GT40: High frequency noise. Comming from power supply?
Posted: Sun Dec 31, 2017 5:10 pm
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oczad wrote:
These amps have no transformer.



125 volts ( or 240 in Europe ) from wall outlet goes direct to amp circuit :lol:


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Post subject: Re: GT40: High frequency noise. Comming from power supply?
Posted: Sun Dec 31, 2017 5:49 pm
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It's done via SS devices. Open it and look. I've had the chassis out, theres no PT. The entire chassis weighs 3 Lbs. A PT would weigh thatmuch. So it's not me your smilie is laughing at.


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Post subject: Re: GT40: High frequency noise. Comming from power supply?
Posted: Mon Jan 01, 2018 2:32 am
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Pardon my ignorance but I did not want to be rude.
This is the first time I've heard of SS as a power transformer. :oops:

I can't find any shematic or picture


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Post subject: Re: GT40: High frequency noise. Comming from power supply?
Posted: Mon Jan 01, 2018 8:42 am
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Have you not seen the many simple devices that plug into your AC wall socket and output small voltage DC power to charge phones or batteries? How do you think they do that? They certainly don't put a power transformer in that tiny device. https://www.walmart.com/ip/Insten-Unive ... -/32237107


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Post subject: Re: GT40: High frequency noise. Comming from power supply?
Posted: Mon Jan 01, 2018 8:56 am
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oczad wrote:
How do you think they do that? They certainly don't put a power transformer in that tiny device.


Why not ? I often see very very small P.T


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Post subject: Re: GT40: High frequency noise. Comming from power supply?
Posted: Mon Jan 01, 2018 9:33 am
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How do you figure they take a 500vdc tube amp supply and reduce it to double digits in those power scaling devices? They do it with transistors. Do you see a tranny of any sort in this kit? I have built these myself before and trust me, i did NOT need a transformer. http://www.londonpower.com/power-scalin ... thode-bias

I'm not going to try and convince you any further that high voltage can be reduced w/o a transformer or that i'm not lying that theres no PT in the GT. Investigate it if further yourself you wish. It's 2018. There are cars that run w/o gas too in case you weren't aware. :mrgreen:


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Post subject: Re: GT40: High frequency noise. Comming from power supply?
Posted: Tue Jan 02, 2018 3:38 am
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oczad wrote:
How do you figure they take a 500vdc tube amp supply and reduce it to double digits in those power scaling devices? They do it with transistors. Do you see a tranny of any sort in this kit? I have built these myself before and trust me, i did NOT need a transformer. http://www.londonpower.com/power-scalin ... thode-bias

I'm not going to try and convince you any further that high voltage can be reduced w/o a transformer or that i'm not lying that theres no PT in the GT. Investigate it if further yourself you wish. It's 2018. There are cars that run w/o gas too in case you weren't aware. :mrgreen:



Working from higher DC voltage to a lower DC voltage with solid state is well know and in use since 40 years and more (?) . Like scaling power amp as you write.
We can't lower DC voltage with a Power Transformer, this work only with AC so use of S-State or tube is a must.


It is another story from AC wall outlet to insulating AC to feed a amp or any electronic gear.

I did not say you are wrong about the GT, I say I never hear or see any power supply with solid state only , no Power transformer.

A picture of your power supply will help.
I did not find any GT40 schematic on the web neither USB charger or small cell phone charger


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Post subject: Re: GT40: High frequency noise. Comming from power supply?
Posted: Tue Jan 02, 2018 10:00 am
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Almost all AC powered electronic devices use a power transformer to safely isolate the AC line from the user.
But the large, heavy, 60 cycle power transformers you are used to seeing aren't used in modern amps.
Digital amps use high frequency transformers that are much more efficient, lighter, and smaller. They are golf ball to match book size and are wrapped in yellow tape for guitar amps. I've seen them as small as a pea.
While you can't hear the ultrasonic operating frequency, they can cause sympathetic whines.
If it's just outta the box, take it back for an exchange


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Post subject: Re: GT40: High frequency noise. Comming from power supply?
Posted: Tue Jan 02, 2018 12:17 pm
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TimsAudio wrote:

Digital amps use high frequency transformers that are much more efficient, lighter, and smaller.



So GT40 use transformer :lol:

Thank you TimAudio your knowledge is always a gift for us.


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Post subject: Re: GT40: High frequency noise. Comming from power supply?
Posted: Thu Jan 04, 2018 1:33 pm
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OCZAD is correct. These days most guitar amps don't have AC Power Transformers in the mains power supply. Mains AC is wired right to the power supply PC board without first going though a Power Transformer. Some power supply designs will utilize small (typically with yellow tape wrapping) open transformers to develop and split the DC power into plus and minus voltages that are used for most modern ICs but those aren't the AC Power Transformers being discussed. I haven't opened a GT40 (yet) but I have been inside both the Mustang II and III. The Fender schematics for that whole pre-GT Mustang range are available on the internet. You'll see those two models had similar "Power Transformer-less" designs. Transformers are comparatively "expensive parts". There's always a push to cut production costs so those huge transformers for the Power and Output are being designed out of existence. OK with me, I'm not going to haul my 66LBS Super Reverbs anywhere anymore. The Mustang III and now the even lighter GT100 are so easy to move!


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Post subject: Re: GT40: High frequency noise. Comming from power supply?
Posted: Thu Jan 04, 2018 1:51 pm
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Thank's Myrel.

That is you are talking about ?

ImageMustang V by


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