Sony TA-4650 sound quality issues

[noviygera]

Hi there followers of the Sony VFET amps!
I've acquired a working TA-4650 in mint condition. For now, I'm only using the direct amp inputs, bypassing the pre-amp section (removed rca jumpers). Playing some music through it, the sound is somewhat missing bass, and overall sounds a bit flat. Compared to my TA-N7B, it's very noticeable.
Speakers are pretty efficient Tannoys, so I should have plenty of drive power even with TA-4650 in place.

Is this how TA-4650 sounds or it needs some service, replacement of parts? I know about the required replacement of diodes and resistor change, I can do that...

I'm just wondering if it's worth it, if my description is close to how TA-4650 should sound. Light on the bass, flat sound (no 3d space).
Thanks,
Herman

 

[Binkman]

Greetings welcome to AK.. Mint condition might mean not played, too. Give it some time and idle in music low. might only need reforming caps. I've come a across sonys that need time and minor pot cleaning. Direct mode is different than playing through the pre-amp. So how does it sound through that? and preamp needs some run in time, too.

required diode and resistor replacement? usually good unless test bad. or engineering change?

 

[slimecity]

I would agree that it could be the caps, or possibly bias levels have drifted? Not sure if bias is set by the user on these types of VFET amp or not, but that may also require checking.

If it were me, I would give the unit recap anyway.