Other models

Musical Fidelity A1 (12K)This page carries brief details of related Musical Fidelity products that are related to the A1. You'll note that the information here relates very much to Musical Fidelity's earlier products; if anyone is able to offer information on their later products, I'd be fascinated to hear from you. I'm keen to see what configurations they are using today, especially knowing how well-reviewed their products currently are.

A1 David

Thanks to Marc Huske for supplying the following pictures of a "David" and a "David II". As far as I can establish, this was a tuned version of the A1 that sold to the German market. The pictures here show the original version of the A1 circuitry.

Front view of the David (7kB)
Top view of the PCB (14kB)

From the front, there is a "David" logo in place of the "A1" designation. Inside, things look normal at a glance, but you can just see two large black polypropylene capacitors hanging off the right-hand end of the PCB which appear to be connected in parallel with the main smoothing capacitors. Also, there are bigger loudspeaker binding posts and an IEC mains inlet instead of the captive two-core lead - the case of this unit is connected to mains earth. This mains transformer looks like it might have 4 primary wires, meaning that it could probably be converted to 120VAC operation - most examples I have seen, including my own, have just 2 primary connections, meaning a new mains transformer would be required for 120V operation.

The quad op-amps in both the phono preamp and the main line preamp are in sockets, but apparently they are still the standard TL084s.

These pictures show a Mark II David:

Top view of the David 2 (15kB)
Close-up of the phono preamp (14kB)

Looking at the PCB, it says David II on the silkscreen, between the input sockets and the power supply. From a recent examination of a MK3 A1, it's clear that the PCB is MF's latest version.

Note how the primary lead-outs of the mains transformer and the rest of the mains wiring have been double-insulated using what looks like heat-shrink tubing. I can't see if there are four primary wires, so I don't know if this model could be re-wired for 120VAC operation. The large polypropylene capacitors have been accommodated on the PCB, and the power supply has an extra pair of smoothing capacitors and 0.47Ω dropper resistors - the output of the first smoothing capacitor is split two ways, so that each supply has its own capacitor - almost dual-mono, perhaps...

The line preamp has moved slightly, and has an extra 4 transistors to implement a simple power-on mute. Here, Marc has upgraded the TL084 to an OPA4134. The 1uF input capacitors on the power amplifier have been changed for polyester units (like I did when I replaced my preamp). The phono preamp is slightly different - they've dropped the complicated regulation arrangement that the original version had, and there is a pair of TO92 voltage regulators supplying the dual op-amp instead.

A1 Final Edition

Many thanks to Marcus Ackel for these pictures of his Final Edition. As you can see, this is the B200 circuit, with an outboard power supply that gives higher supply rails and a higher output - 40 watts per channel.

Top view of the Final Edition (17kB)
Bottom view of the PCB (20kB)

The first image shows the general view with the cover removed - click these images for a larger view. The "Final Edition" sticker can be clearly seen on the PCB. The connection from the outboard PSU appears to be a 3-pin XLR - raw AC from the external transformer is switched by the power switch, meaning that the transformer is continuously powered when it is plugged into the mains supply.

Looking at the enlarged version of the picture showing the underside of the PCB, you can clearly read "B200 MK2 ISS 4" towards the bottom-right of the image.

Close-up of the power amp (18kB)
Close-up of the output MOS-FET (14kB)

These two picture show the output stage, with the LM318 op-amp and BUZ900/BUZ905 output MOS-FETs. The smoothing capacitors are 6800uF each, and a bridge rectifier is used instead of the 4 discrete diodes of earlier models. They retained the Alps "Blue Velvet" volume potentiometer...

Thanks to Justin Goh for submitting this picture of a Final Edition with a striking silver/chrome finish:

Final Edition (12kB)

And according to the accompanying certificate, here are the differences between the standard model and the Final Edition:

  1. Special Output transistors
  2. Specially selected PCBs
  3. Special 10th anniversary polypropylene bypass capacitors
  4. Large mains transformer
  5. Special IEC mains input socket
  6. Special gold plated loudspeaker terminals
  7. Mirror finish chrome plated front panel
  8. Machines aluminium black anodised knobs
  9. Special anniversary feet
  10. 10th anniversary print and signature on front panel
  11. Brushed aluminium side plates - black anodised

From a purely engineering point of view, some of these are clearly of dubious merit! But, as only 200 of these were ever made, they are quite collectable, and raise good money on places like eBay...

The A100

Released in 1986, the A100 is a beefed up A1 in a slightly taller case producing 50 watts per channel. To achieve this, there's a bigger transformer giving higher supply rails. Musical Fidelity claim that it operates in class A 99% of the time, but I suspect that this refers to the time spent outside of class A operation in typical use with music rather than test tones; in other words, we almost certainly can't infer anything about the standing current from that statement!

There are two fans which become noisy with age, and when the bearings get tired, they slow down and innevitably the reduced airflow leads to reliability problems. Also, they suck dirt and dust through the case...

The output transistors seem to be the same 2N3055/MJ2955 combination as used in the A1. I'm surprised at this frankly, but it certainly explains why failures are all too common - it's definitely worth upgrading to MJ15003/4 pairs. All other comments about the A1 apply to this model, so check for noisy controls and dried up electrolytic capacitors...

Something that amuses me - reviews often state that the phono stage was much-improved compared to the A1, but it's exactly the same!

The MA50

This is a monoblock amplifier built into an A1 case, released in 1985. It's just an A1 with a bigger power supply - the PCB is the same, just the components relating to the pre-amp aren't fitted. Both power amp sections are fitted, and the outputs are wired in parallel. Apparently they are even less reliable than the A1!

The B200 and Pxxx MOS-FET models

These all use Musical Fidelity's "op-amp plus MOS-FETs" power stage - another Tim de Paravincini design. This includes the P140 (70Wpc), P170 (85Wpc), P180 (80Wpc), P270 (135Wpc), P370 (185Wpc) and the B200 - no-doubt there are others too.

The design was gradually refined over the years, but follows the basic topology explained on the Technical Page.

This is a picture of the insides of a P180 - you can see the multiple output MOS-FETs all on their individual heat sinks. Somehow, they don't seem big enough for an 80W amplifier but at least there will be a saving in thermal resistance because the devices won't need to in electrically insulated from the heatsink. The outboard PSU appears to have an XLR connection to the umbilical lead that connects to the main amplifier.

Musical Fidelity P180 (48K)

I don't recall where this image came from, so if you recognise it, please let me know and according to your wishes I'll either credit you, or remove the image.

The B1

This was Musical Fidelity's budget model at the time of the A1, and I remember considering this when I purchased my A1. Compared to the A1, it's positively awash with facilities despite the lower cost (£199 IIRC), including a record-out selector and a headphone socket - although rather annoyingly, this is on the rear panel! The power output was quoted as 32 watts per channel. Cost cutting was evident - for example, the extension rods for the selector switches were plastic rather than metal, and felt rather cheap as a result. The case is thin steel and plastic mouldings, and lacks the appeal of the A1.

Musical Fidelity B1 (56kB)

Thanks to Kat Manton for this picture of the B1.

Technically, it's another quirky design. The output stage consists of four 2N3055s per channel, mounted on individual heatsinks that are directly on the PCB. In terms of topology, it has much in common with the A1, with dual long-tail pairs and dual feedback paths.

The line preamp is simpler (but better) that the A1, using a single op-amp per channel providing gain after a conventional volume potentiometer. And the phono preamp is similar, using a transistor gain stage ahead of an op-amp using shunt feedback. This version appears to be more complicated than the A1 version, having complimentary transistors and heavy supply filtering of both rails. There is an MC option, and it's implemented in the same way (changing the emitter impedance of the input transistors).

The schematic is available from (at least) a couple of places, so I'll link to them rather than hosting my own version:

  1. First, it can be found on the excellent Hi-Fi Engine website. You have to join up, but this is free, and well worth the effort.
  2. Secondly, this amplifier was discussed on the UK Vintage Radio Repair and Restoration forum, where I contributed a fair bit to the discussion. If you need to learn more about how it works, it's worth studying the thread - there's no sense duplicating it here, but I have saved the text of the discussion locally should that thread be removed in the future.

The B1 Mark 2

I don't know what electrical changes happened with the move to the Mark II - it might have little more than just been a PCB revision - but you can tell them apart from the position of the knobs on the front panel. Compared to the earlier example pictured above, the three rotary controls have moved across to the right, so only one of the extension shafts travels between the heat sinks.

Musical Fidelity B1
      Mark 2 (58kB)

You'll note two other changes for this version: first, the ridiculously-placed headphone socket has been deleted; secondly, the extension shafts have been upgraded to what looks like metal. The volume potentiometer has been moved forward so that all three shafts can be the same length. The power transistors have moved back to make space for the power supply just behind the front panel. From other close-up pictures that I have seen, the op-amps are now the TL072, and the output transistors are 2N5882.

If anyone knows anything more about the Mark II, please get in touch...

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