I wonder how it sounds? Mine is a little boomy with the KefR300 that I use with the vintage units.
EDIT: Increasing the capacitance of the output-coupling caps definitely increased the bass response, in this case in an unwelcome amount. So, I've switched back to using output-coupling caps of the same capacitance as original and I'm much happier for doing so.
The test speakers I had on my workbench up til now were a pair of refoamed and recapped Infinity RS-10 2-way speakers from the 1980s. Never thought anything was wrong with them. Connecting the newly restored/modified HK330B to them brought in a lot more bass than I'm used to. I had to turn down the bass control on the HK330B for most source, just 1/16th of a turn maybe. And the Infinity RS-10s sounded better at higher volume settings, of course.
Reference Standard 10
Introduced: 1982
Dimensions: 34 x 21 x 20 cm
Bass: 1 x 16 cm
Highs: 1 x Polycell
Suggested for amplifiers with: 15-65 Watts per channel
Frequency range: 59 Hz - 22 kHz
Crossover frequencies: 3000 Hz
Suggested price (pair): RS 9: 196 $
RS-10 are bookshelf speakers 17.7" tall
So, I swapped in a dinky pair of Infinity SS-2001 speakers I had lying around and which I'd recently refoamed and recapped and, of course, one of the woofers was bad and I hadn't noticed until listening critically to hear if the HK330B was working properly. Sigh.
So, eBay to the rescue for a replacement set of drivers, SimplySpeakers to the rescue for another refoam kit, and
now I have a more-neutral-sounding set of workbench speakers.
SS-2001 Sterling Series 2-Way Speaker
Nominal Impedance: 8 ohms
Power Rating: 10-60 watts
Sensitivity: 90dB
Crossover Frequencies: 4500Hz
Frequency Response: 74Hz-20kHz +/-3dB
1x - 1/2" (1.27cm) Polycarbonate Tweeter
1x - 5-1/4" (16.3cm) Woofer
Dimensions: 9"H x 11-5/8"W" x 6-5/8"D
Introduced in 1993
Discontinued 1996
Original Retail Price: $159.00/pair
And these don't sound too boomy. So, I'm guessing the mods to the HK 330B have unlocked more bass response, especially at the higher volumes the RS-10's demanded.
The change I made to the output coupling caps actually predicted this new behavior. I'd read somewhere here on AK that "the use of 2200 uF of capacitance or less in the output coupling position will cause a roll off (of some amount) of the lower audio frequencies." So, I chose higher capacitance electrolytic caps and I believe that is why, or they are at least contributing to, more bass.