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?

 

[DSJR]

I may have been linked to this thread from elsewhere (differences in Polish tests compared to Amir?), but I remember that A1 as an awful thing, although I gather that the innards were substantially revised as production went on. They ALL ran too hot and cooked their components to destruction with resultant reliability issues a few years down the line, the frequency response of all those measured, rolled off in the low bass and tapered in the audible top region as well. I'd also suggest that distortion of earlier models was in the -50s rather than the -60? at 1kHz as shown above.

Page 91

https://www.worldradiohistory.com/UK/Hi-Fi-Choice/1983-1989/Hi-Fi%20Choice%20Iss.%20044%20Amplifiers%20&%20Stereo%20Tuners%201986.pdf

The OP drove Magicos with it? I'd suggest it was soft clipping the entire time (as the better equivalent Naim Nait mk1 did into most things) and if any objectivists want to hear an amp which DOES 'sound different' to everything else, try a surviving one of these, as it always sounded to me as if a thin blanket had been placed over the speakers - owners loved that style, however and Sugden continued with that 'tone' in a fairly recent lower model, as I gather that's what tech-ignorant audiophiles think 'Class A' should sound like.. The A100 around at the time, actually had some high frequencies to it and a ductless fan to blow air around the internals. MF did naughty things around the B1 'test sample vs. production' amp and I think it put a lot of dealers off at the time, so I don't remember the B series well at all. It kind-of came good for us ten years later with the X series of 'cylinders,' many of that series being really good in a domestic audio system.

 

[welwynnick]

https://www.worldradiohistory.com/UK/Hi-Fi-Choice/1983-1989/Hi-Fi%20Choice%20Iss.%20044%20Amplifiers%20&%20Stereo%20Tuners%201986.pdf

Oh happy memories! I remember those tests like it was yesterday, and I subsequently owned nearly a dozen of those amplifiers over time.

My friends and I used to pour over the latest HFC tests every other month and devour all the test results, trying to make sense of what the numbers told us. Still trying.

 

[DSJR]

Oh happy memories! I remember those tests like it was yesterday, and I subsequently owned nearly a dozen of those amplifiers over time.

My friends and I used to pour over the latest HFC tests every other month and devour all the test results, trying to make sense of what the numbers told us. Still trying.

You can see Martin Colloms fall increasingly to the dark side of subjectivism ruling his increasingly contradictory tech tests of increasingly expensive US-imported valve gear, this before he jumped to HiFi News for some years. Intro-author Paul Messenger (r.i.p.) straddled both mags and was the first fully subjectivist commentator, I think.

That site had HiFi News scans as well, but I was told by someone here that the powers that be got them taken down, which is a shame, bearing in mind the over-priced stuff they routinely peddle today in their pages.