Dynaco ST-70 and Magneplanar 1.6QR

My MG 1.6 sound much better with a 350 watt Adcom amp than with a 100 watt Adcom amp having similar specs except for power. The message is clear...get more watts.

I am sure that the various audiophile 100 to 150 watt amps mentioned above may improve performance in subtle ways. However, for the same, or less money, you can have 350 watts of Adcom amp. The difference will not be subtle.

By the way, when you get your new amp I'll take the Dynaco off your hands!

Seriously, the Dynaco is a nice piece, but just doesn't have the muscle needed for the Maggies. However, before you dispose of it, you might try biamping the MG 1.6. The Dynaco would suffice to power the tweeters, and you would retain that "tube sound" (warm-sounding harmonic distortion).

Andersd...Volume means voltage gain (not really power) so it's possible that your preamp is just not driving the power amp with enough signal. One thing that you could try would be to connect your 4 ohm speakers to the 8 ohm outputs of the power amp. This will get you more voltage to the speakers although the power amp wattage capability (which may not be the limiting factor) will be less.

It's a long time since I played around with tubes, but I suspect that there is a 12AX7 input stage in the power amp. I hope you don't have a 12AU7 pluged in by mistake: that would lower gain. The driver for the output stage is probably a 12AU7: they might be swapped around.

You really ought to be able to play those speakers loud with your amp, and the symptom of insufficient power would be distortion, particularly clipping, rather than low volume.

All this being said, I still suggest you try a much more powerful amp, and find out how good your speakers really are.

Andersd...My amp is the GFA-5503, which is the three-channel version of the GFA-5502 that you probably want. These amps are rated at 200 watts into 8 ohms, and 350 watts into 4 ohms (which is what the MG 1.6 are). I paid only $875 for my amp which was "B stock" (demo or mfg repaired) and it came from an authorized dealer with full warrantee, and I have no problems. (Someone "broke it in" for me, if you believe in that).

Magneplanar speakers are a very "easy" (resistive) load for the power amp, so I doubt that some of the very expensive amps would do much better than the Adcom when used with Magneplanars. If you were driving the MG 1.6 with the Adcom you would have a valid basis of comparison if you ever were to consider one of the very high end amps.

Go look at the Adcom website www.adcom.com for full details.

If you can get the 5503 for less than a 5502, do it. The amp doesn't mind having one channel unused. Also, if you ever get into multichannel sound, the 3 channels will be useful.

The 555 was very well regarded when it came out, but that's a long time ago. I think you would be better off with a current model.

Regarding Jolida...any amp will "drive" the MG 1.6, but not all will do it in a way that extracts the full capabilities of the speaker.

Andersd...David says that the Dynaco st-70 uses a tube type 7199, not the more common 12AX7 which I mentioned. I assume he is correct. Whatever the proper tube is, my point is that you should make sure you have the right kind plugged in. Many small dual triode tubes will work, sort of, when substituted, but parameters like gain will be affected.