gyraf

Re: G-PULTEC problems, please help!
« Reply #760 on: March 24, 2020, 12:51:20 PM »
I'm seeing a -3dB point of maybe 95 Hz? Too high, should reach down to ca. 25Hz at least

What transformers are you using? Driven by what source impedance?

Amplifier output coupling capacitors?

How is your frequency response BEFORE the output amplifier (so that we know where it messes up)?

/Jakob E.
..note to self: don't let Harman run your company..


Re: G-PULTEC problems, please help!
« Reply #761 on: March 25, 2020, 04:04:23 PM »
Hello Jakob,

I don't know exactly why but today the frequency response is better. ;D
Maybe because the connection of the (bad) header from the filter board on the main board wasn't good...
 
What transformers are you using?
By the way, my power transformer is from Don-Audio. And the audio transformers are the Lundhal LL5402.
As you did.

Amplifier output coupling capacitors?
The coupling cap (if you mean the big 4,7uF/250V ) is a big red WIMA MKP4

Driven by what source impedance?
The signal is coming from my RME and it's a 75 Ohm output.

How is your frequency response BEFORE the output amplifier (so that we know where it messes up)?
Check the curves BEFORE and AFTER the output trafo
« Last Edit: March 25, 2020, 04:12:57 PM by lars on »

Re: G-PULTEC problems, please help!
« Reply #762 on: March 25, 2020, 04:09:05 PM »
I know it's less than one db difference but I wonder from where this bump and hollow are coming from.

gyraf

Re: G-PULTEC problems, please help!
« Reply #763 on: March 26, 2020, 02:01:04 AM »
Looks correct now. The bump is transformer inductance vs. coupling capacitance, you can tune vith out capacitor value if you like, but 4u7 and LL5402 sounds pretty nice.

/Jakob E.
..note to self: don't let Harman run your company..


 

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