Integrated Amp help

The amp MAY sound very loud, bright and straining because it is clipping or it may be a result of one of the constraints of a single-ended circuit. Single ended amps distortion levels increase substantially as they move closer to their maximum power output, even before clipping.

Some other information will also be useful:
Is the efficiency rating you quoted (89-90) for an 8 or 4
ohm load?
Does the actual impedance vary significantly w frequency?
How big is your room and how far are you from the
speakers?
How loud is "a decent volume level"? Remember a 3dB
volume increase requires a doubling of power.

And yes, it is possible to have too much gain.

Zd, that looks like what he has, and according to the company website this unit can drive "traditional speakers", however his speakers may not be tube friendly due to their impedance/phase angle relationship.

Is the impedance switch on the back of the amp set to 4 or 8 ohms? Sometimes 8 ohm speakers with an impedance that drops severely at certain frequencies will sound better on the 4 ohm tap of a tube amp. Have you tried both switch positions? And switch only with unit powered off.

Also, here is something you may try with the Pioneer.

Connect to video, then in the menu for 5.1 adjustments, set front L&R to "large", then center, surround, and sub to "none". Now use front L&R out instead of the 2ch L&R out.

I think it's the speakers that need upgrading

However, it is very bright and very straining to listen to at decent volume levels.

Also agree with Swampwalker, depending on distance and volume level, amp may be clipping, therefore, not enough power.

Good comments by the others. I would particularly emphasize the question by Swampwalker about how the speaker impedance varies with frequency, if that can be determined.

A lot of two-way speakers have considerably lower impedances at most of the frequencies that are handled by the woofer than their impedance at most of the frequencies that are handled by the tweeter. The impedance often being around 4 ohms at lower frequencies and around 8 ohms at higher frequencies. That can often signify that the speaker is best suited for use with solid state amplification, as the interaction of that kind of impedance variation with the relatively high output impedance of a tube amp, especially a SET amp, will tend to result in excess brightness.

That effect will be somewhat less if the 4 ohm taps are used rather than the 8 ohm taps, so as was suggested you should definitely try the 4 ohm taps if you already haven't. And if you are presently using the 8 ohm taps, going to the 4 ohm taps would also help with respect to the gain issue, although probably just slightly.

Good luck. Regards,
-- Al