Threshold Sa3.9e

@spersanti276 

If you're a diyaudio forum member, you can download the E-Series Operations Manual. Click on the link and go to posts #16.

Threshold Amplifier - Overview and Schematic Collection of all Models

Thanks!

I am particularly worried about the possibility of driving the 3.9e from my Aleph P1.7 preamp in balanced mode, because I have read that the xlr input impedance of the power amp is only 600 ohm while in the P1.7 manual it is recommended to keep the master volume in the position of least attenuation (where it has the highest output impedance!).

Please take a moment read the manual, the Aleph P1.7 should has no problem driving the 3.9e, you also can play with the gain setting for best performance.

https://www.passlabs.com/wp-content/uploads/2020/05/apman.pdf

Thanks

LOL, uploaded the e series manuals a long time ago. Glad to see they are still up in the DIYA site.

Used a 3.9e for about 20 years back in the day. Doubt your Aleph pre will mate well with the 3.9e using XLRs given the pre’s high output impedance relative to the 3.9e’s 600 Ohm input impedance via XLRs. Will sound a bit lacking in bass.

Still, the 3.9e was a great amp.

This is what I feared, even if the Aleph manual explains (confusingly to me) that, with proper adjustments of the gain knobs and the master volume, a very low output impedance can be obtained.
Thanks,

Stefano

You can connect via XLR but flip the switch on the back panel of the 3.9e to RCA. It will work (as if using the higher input impedance on the 3.9e). But I always thought it was not a good idea. I know others that have changed the internal resistor at the inputs to change the value from 600 Ohms.

😨

...it gets worryng for me...