TOPIC:

Hi!

I needed to change gain structure after I removed preamp.
Now I have balanced from DAC to DDRC-88A and balanced/pseudo-balanced from DDRC-88A to power amps.

Theissue is significant hiss = noise.
I made noise measurements and the wide band noise output from DDRC-88A is ca. 4mV RMS
After 27.5dB of gain that results a quite loud 2.5 mW into 4ohm tweeter which is masking tintinnabuli from the likes of Arvo Pärt or other performances with pianissimo partutures.

I may be mistaken but the noise seems to be Johnson noise. I have not yet checked the analog paths of inputs/outputs for resistor values and the opamps used for gain and balun sections nor other parts for potential noise source.

Can anyone advise a course of action? I could not find any posts on this on the forum. No attenuators please, DDRC is already just barely driving the power amps and I often use all the headroom for listening.
I can easily do HW modifications and can measure THD+N down to -120dB to report/verify results.
However, if there is a simpler solution or even a good suggestion on conf correction or HW mod, that'd be great!

Thanks!