Musical Fidelity A1 mk3 and B200 vintage amps measurements

[elberoth]

I have just measured those two. The MF A1 has a cult following, and was designed by Tim de Paravicini

Here are the details:

1. Musical Fidelity A1 mk 3 (1994; 20W Class A amp according to the manufacturer), fully restored with modern parts:

Rated power (1% THD + N, 1 kHz) [W]

1 channel / 2 channels:

8 Ohm 14W / 14W
4 Ohm 9W / 9W

Sensitivity (for maximum power) [V] 0.25
Signal / noise ratio (A-weighted filter, with reference to 1W) [dB] 92
Dynamics [dB] 102
Damping factor (relative to 4 ohms) 17

2. Musical Fidelity B200 ( ca. 1994; 60W Class AB amp according to the manufacturer), original condition:







Rated power (1% THD + N, 1 kHz) [W]

1 channel / 2 channels:

8 Ohm 113W / 85W
4 Ohm 111W / 74W

Sensitivity (for maximum power) [V] 0.2
Signal / noise ratio (A-weighted filter, with reference to 1W) [dB] 71
Dynamics [dB] 91
Damping factor (with reference to 4 ohms) 34

 

[Apesbrain]

I remember well the A1:

You could grill burgers on top of it.

 

[elberoth]

Both amps get pretty hot (45-50'C). A1 just idling, B200 driving my Magico M3 speakers (at normal listening levels).

 

[DonH56]

Are you sure the LF roll-off is not in your measurement system?

 

[elberoth]

Compare the A1 vs B200 FR plots. The B200 one does not have this early roll off.

This was done by a friend of mine, whom I've asked to measere those for me - he has been doing measurements for Polish AUDIO magazine for 20 years or so.

 

[amirm]

Ah, I remember that Avatar anywhere. Welcome to the forum Elberoth. Do you still organize the Polish audio show? If so, how is it doing?

 

[elberoth]

Yes I do. The show is doing great!

https://www.soundstageglobal.com/index.php/shows-events/audio-video-show-2017-warsaw-poland

 

[amirm]

I am glad to hear. As you may know, our regional audio shows in LA/west coast are a mess right now.

 

[elberoth]

I am glad to hear. As you may know, our regional audio shows in LA/west coast are a mess right now.

Yes, I've read about this. Could not stop shaking my head.

 

[restorer-john]

Are you sure the LF roll-off is not in your measurement system?

The B1 was not that bad- I've swept them and that roll-off is not representative of the units I tested.

OP, please clarify the FR and THD sweep test parameters (1W, full power, arbitary level single channel/both channel?).

 

[elberoth]

I will check and let you know. Here you can see 250 amps measured (only a fraction of amps tested):

https://audio.com.pl/testy/stereo/wzmacniacze-stereo

- most of them have ruler flat FR.

So I doubt this is a measuring setup error. It is also worth remembering, that the B200 is a 25 year old unit in original condition, so god knows how the 'lytic caps are doing inside.

If you have any B200 measurements on hand, please post them. I would very much like to see them and compare.

 

[elberoth]

Are you sure the LF roll-off is not in your measurement system?

I highly doubt (of course, everything is possible).

Two other components measured using our trusty Neutrik A2D:

$60k Soulution 710 power amp:

$500 Pioneer SX-N30 receiver:

 

[elberoth]

OP, please clarify the FR and THD sweep test parameters (1W, full power, arbitary level single channel/both channel?).

1. Frequency characteristics:

The reference level (0 dB) is 2.83 V output voltage. One channel measured.

2. THD + N vs power:

Distortion (+ noise) for the assumed output power range, from 0.1 W up to rated power. One channel measured.

Measured using Neutrik A2D

 

[DonH56]

Thank you. Main reason I asked is because the first two measurements I saw that you presented both had significant LF roll-off.

 

[preth30]

Hello, this is the first time I am writing in this forum. I have a MF A1-S (A1 signature series) and a B200 too. I have compared both side by side and I found that in spite of having a higher wattage in B200, the A1-s is a clear winner here with better definition in the mid and highs. The B200 is more of a neutral sounding amp having the lows mid and highs in a straight line, while the A1-s has a slightly forward mid which help in focusing more on the vocals which I like. What are your opinions on this. I would love to hear from you.

 

[elberoth]

The A1 I have is not a regular A1. It has been fully restored, with lots of new parts fitted and the famous A1 potentiometer issue corrcted:

http://ftbw.de/workshop/hifi-highend-service/musical-fidelity-fix-price/david2-revision.html

That said, my A1 sounds much cleaner, more transparent with more open hights than the B200. The B200 sounds almost closed in in comparision.

I could only wish the A1 had more power. It is OK if you are listening to chamber music or vocals. Speaker efficiency plays a big role here of course.

 

[SIY]

Hello, this is the first time I am writing in this forum. I have a MF A1-S (A1 signature series) and a B200 too. I have compared both side by side and I found that in spite of having a higher wattage in B200, the A1-s is a clear winner here with better definition in the mid and highs. The B200 is more of a neutral sounding amp having the lows mid and highs in a straight line, while the A1-s has a slightly forward mid which help in focusing more on the vocals which I like. What are your opinions on this.

How did you do the level matching?