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noise/hiss/ T1 / T2

noise/hiss/ T1 / T2

Hello all



I have some strange behavior (hiss/noise) on a COMBINATION of severel T1/T2 amps in a active system (3 Way).



First ==> Each amp alone works almost silent (really almost not hearable, only you put your ear on the speaker, as it should be) and i love those Amps!



They are connectet by a SMPS Power Supply + 36V (I know, a bit high but they work flawlessly on each alone, since long time in Stereo not activeXO)

The 3 amps are star connected/grounded to one SMPS



The noise is kind of like white Noise.

I thought first the DSP active Xover is the problem, because if only one T1 is connected to the DSP there is no noise and the amp does work perfectly (actually each amp does i can change severel amps).



If i connect ANY other amps to the DSP the noise raise to a level which is not accaptable anymore, if you sit 2 meters away.



If i completely disconnect the DSP and connect Ground from the input(left or right) of one T1 to the Input Ground to another T1(as it would be connected by a active XO), the noise is here again. (everything unsymmetrical chinch)





I double checked all kind of Powersupply grounding and one amp at his alone works always perfectly.

Note it doesent matter if i use a T1 to T1, T2 to T1 or T2 to T2) the behaviore is always the same.



Any Idea?



If not may i try Lundahl's, to open the Input ground connection between the 3 amps.



rgs

martin
Hi Martin,
It can be a ground issue, but it could also be the feedback cap's value.
Which power supply is it? We have tested the smps300r powering several amps with no issues.
Hi Martin,

It can be a ground issue, but it could also be the feedback cap's value.

Which power supply is it? We have tested the smps300r powering several amps with no issues.



Hi Nick



Just ordered a T3 (with Mundorf) :-)



It is the C500SMPS from Connexelectronic. (12V for Car)



As i told you; in any combination, if only one amp at time is used there is no problem at all.

I have also 2 from you, the SMPS300r for 230V i will check with this at the next Weekend, but i doubt this will change anything...we will see.

I have also some from China SMUN SMPS 28V

Al SMPS works fine at one amp only.



What do you mean with the Feedback caps value, should i change this? up or down?



regards

martin
Hi,
it might help to use different feedback caps value on each channel. For T1 its C36, C37, C38, C39 (two for each channel). For T2 it's C11, C12, C46 and C47. 180 to 560pF can be used.
Hi,

it might help to use different feedback caps value on each channel. For T1 its C36, C37, C38, C39 (two for each channel). For T2 it's C11, C12, C46 and C47. 180 to 560pF can be used.





ok thanks, i need to try



rgs

martin
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