Guesstimator Posted November 20, 2020 Report Share Posted November 20, 2020 Hi all, I heve been offered a pair of Nad 2155 power amps at a very reasonable price (250€ the pair). I was curious if anybody has ever tried these (or something similar) in bridged mode with ar3's ? I currently use a galactron mk10 integrated amp, whose current delivery ability are kind of an unknown. I like the sound but can't help feeling I'm missing the deeper bass.... Cheers all Quote Link to comment Share on other sites More sharing options...
Aadams Posted November 20, 2020 Report Share Posted November 20, 2020 55 minutes ago, Guesstimator said: I'm missing the deeper bass.... Deep bass from an AR3a is mainly a function of placement with respect to room boundaries. If you have adequate power now, for your room size and listening position, then more power won't provide deeper bass. Quote Link to comment Share on other sites More sharing options...
genek Posted November 20, 2020 Report Share Posted November 20, 2020 Do the specs for that amp actually say it's rated for 4 ohms in bridging mode? Most bridging amps that are rated for 8 or 4 ohms in standard mode only support 8 ohms when bridged. Quote Link to comment Share on other sites More sharing options...
Guesstimator Posted November 20, 2020 Author Report Share Posted November 20, 2020 The user manual explaines that the impedance in bridged mode is halved and says to set the output resistance to 8 ohm in bridged mode regardless of speakers used. It states that a 4 ohm speaker will in effect be seen as a 2 ohm and that two 4 ohm speaker in parallel will be seen as a 1ohm impedance load. However it only suggests not to run more than one speaker per amp in bridged mode and seems to consider single 4 ohm speakers as acceptable...."for best results the bridging mode should be used with only a single 4-ohm or 8-ohm speaker in each channel".(user manual) At the same time the service manual does not give power ratings for 4 ohms in bridging mode. Quote Link to comment Share on other sites More sharing options...
Guesstimator Posted November 20, 2020 Author Report Share Posted November 20, 2020 The amp itself is rated down to two ohms in non bridging mode ... Quote Link to comment Share on other sites More sharing options...
Guesstimator Posted November 20, 2020 Author Report Share Posted November 20, 2020 1 hour ago, Aadams said: Deep bass from an AR3a is mainly a function of placement with respect to room boundaries. If you have adequate power now, for your room size and listening position, then more power won't provide deeper bass. That's the thing....I'm not sure the amp is up to the job. Manual rates it at only 8 or 16 ohm loads, but an ex designer of this company swares it's fine with the ar3a and to be honest I've never had any overheating or other problems whatsoever. Speakers have been refoamed and recapped with the vintage AR kits from fleabay. I have worked over three years with rew, and several bass traps I made and have managed satisfactory frequency response soundstage and imaging with monitor audio bx6 bronze, JBL l40 and ar4x. Curiously the pneumatic suspension speakers have similar placements which differ from those of the ported designs. With ar3a I have achieved a good frequency response and I find they have a nicely detailed bass but was expecting more in the 40 to 60 Hz region ....and again not sure about amp capabilities...250€ is fairly cheap even just for a test but was wondering if anybody ad ever tried this combination... P.s. Ar3a are on 32 cm stands (12.5 inch) Quote Link to comment Share on other sites More sharing options...
Aadams Posted November 20, 2020 Report Share Posted November 20, 2020 37 minutes ago, Guesstimator said: With ar3a I have achieved a good frequency response and I find they have a nicely detailed bass but was expecting more in the 40 to 60 Hz region The 3a is strong at 40hz. The vast majority of recordings have nothing lower than 42hz and it looks like your amp can supply around 100 wpc which is plenty in most home listening spaces. If you have a pair of decent over ear headphones compare the 3a to the headphones. Good flat bass is just there, not prominent unless it is the featured part. Quote Link to comment Share on other sites More sharing options...
Guesstimator Posted November 21, 2020 Author Report Share Posted November 21, 2020 Specs for my amp are all over the place. On vinylengine the power rating is incorrect. Max power is 70w per channel into 8 ohm. Also the Freq response curve is not fantastic by today's standards. From 100hz it drops by 2 dB at 40 Hz....although I wouldn't have thought that would be significant Problem is not just my sound perception....the response measurents show the same....I know it's not a cancellation because with the tone controls I can definitely increase the output in this frequency region...but it then feels bloated...... But I'll give the headphone test a go thanks. Quote Link to comment Share on other sites More sharing options...
Aadams Posted November 21, 2020 Report Share Posted November 21, 2020 19 minutes ago, Guesstimator said: Problem is not just my sound perception....the response measurents show the same....I know it's not a cancellation because with the tone controls I can definitely increase the output in this frequency region...but it then feels bloated...... It sounds like you know what you are looking for so I'll cave and say it may be your amp which I believe is 1970s vintage. I personally would be leary operating 3as with any old unrefurbished amp considering there are reliable new ones with warranties at reasonable prices. The headphone comparison works for more than just the bass. Decent headphones can give you a good reference for setting the frequency balance of the speakers in the room. Quote Link to comment Share on other sites More sharing options...
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