HH Scott 388b Amp 4 ohm load issues

[c-atle-79bay]

I recently tried running some 4 ohm speakers, AR Classic 30's, with my Scott 388b, however I'm not happy with the sound. I've read that some amps don't do well with a 4ohm load, even if they say they can run a 4 ohm load.

The sound quality is almost angular, crystally and harsh, very good separation of all the instruments but not in a good way. Dynamics are still good though. Could be partly the speakers and the separation but the quality of it is just not good.


The Scott can run a 4 ohm load think it was advertised this way for higher power specs, but now I'm assuming it's sound quality is an indication it really can't.

Any experience with the 388 or other of the early 70's 3XX receivers and 4 ohm loads?

Confused, I usually love how this receiver sounds, ditched my 2285b over this and it's really about to beat out my MAC1700, although the tuner is a big part of my scoring.

 

[Trio]

Are your audio cables just the typical 18 gauge wire? If so move up to a larger gauge to reduce voltage drop. 12 would probably be best.

 

[c-atle-79bay]

That I would not have thought to do, have some larger gauge speaker wire around will give it a try. (I'm a wire skeptic though) Is there a code word for that? Or a signature item.

 

[dr*audio]

The Scott solid state receivers that were made in USA were early, primitive transistor designs. They do not have very low output impedance, and because of that they will not drive a 4 ohm load well. The distortion will go up. That's what you are hearing, and you can use thicker gauge speaker wires but they will not help. They would help if you were using a better designed amp, but the situation with these receivers is such that they have this limitation. If you really like this receiver, use it with 8 Ohm speakers. Scott kept recycling the same basic amp for all the US built receivers so another model will be no different.

 

[Naptown Rob]

Interesting. That model has (granted early) FET's, and all of the Scott advertising listed their power ratings at the 4 ohm measurement, not 8 (I know - way to cheat).

 

[c-atle-79bay]

That's s bummer. It's such as good tuner SBD SQ is good. I think I'm going to use it as a tuner for now. Or keep my eyes open for a 312 tuner. Either way will be coming out of this system for now.

 

[ConradH]

I don't know the amp, so don't change or adjust anything based on what I'm going to say. In general, solid state amps require more bias current to avoid crossover distortion with low impedance loads. IOW, the bias current required for 8 ohm loads isn't sufficient for 4 ohms loads. Usually the bias current is chosen accordingly, but back in '68 (I think) maybe the 4 ohms performance wasn't great, and higher bias might have caused problems. It could be something completely different, but that's what I see when looking at distortion residuals when setting bias. IMO, distortion numbers don't predict much sonically, but crossover distortion in particular can be audible. (anybody got a schematic?)

 

[dr*audio]

If you like the vintage vibe but want better sound and the ability to drive 4 Ohms, check out a Sansui Model Eight or Eight Deluxe. Even better tuner and a superb amp.