Slow audio playback on Windows 95 with PPTP

[DemS98]

When testing DOOM IPX PPTP net play, between Win95 and Win98 clients, I encountered lag on audio playback, regarding MIDI and SFX, on the Win95 client.
The game seemed to run fine, so the problem only concerns audio.

I've posted audio recording in this Vogons thread.

Moreover, as reported in the same thread, I experienced this only on Windows 95 and with DOOM, DOOM 2 and DUKE3D (Quake was fine).

No problem whatsoever using UDPSETUP.EXE with the above games.