Musical Paradise MP-701 Mk II Tube Preamp

Introduction

Musical Paradise is a cheerful company that serves up tantalising components to audiophiles on a modest budget. According to their website, they state the following, "Our mission is to design and manufacture high quality audio equipment to fulfill critical audiophiles' demand with competitive prices." 

This is the first Musical Paradise product that I've owned and so far I have been impressed by their innovation, quality of build, sound quality and totally outrageous value-for-money. 

Description

Looking like a very tall oversized shoebox, the MP-701 Mk II measures 31 cm (W) x 39 cm (D) x 14.5 cm (H). Construction is really good, with a solid aluminium alloy faceplate and panels. Weight is a reassuring 12 kg. 

The MP-701 Mk II is said to be the product of two years of research and development. It is a three tube design with zero negative feedback. The power supply is tube rectified. There are plenty of conveniences, including XLR sockets in addition to the usual RCA sockets, as well as a remote control.

Parts quality is very good throughout, with a 150 W shielded toroidal transformer, Vishay resistors, Nichicon and Rubycon electrolytic capacitors, and Obbligato Gold film coupling capacitors. There is also an option to upgrade the coupling capacitors to Mundorf Silver/Gold/Oil capacitors for a premium.   
This is the point where the usual list of features ends and things really get interesting. 

Want to roll your own capacitors but don't know which end of the soldering iron to hold ? No problem, just undo the binding posts and change the capacitors yourself. 

Can't get the gain matched properly in your system ? No problem, just change the gain settings by flipping a DIP switch. 

Want to roll different tube types ? No problem, change your preamp or rectifier tube heater voltage settings by accessing a switch too.

Here is a list of rectifier and preamp tubes that can be used in the MP-701 Mk II :-

Rectifier tubes

6.3 V - 6Z5P, 6X5
5 V -  5R4, 5U4G, 5AR4, GZ33, GZ34, 274B, 5Y3, 5Z3P

Preamp tubes 

6.3 V - 6N11, 6N1P, E88CC, E188CC, CCA, 6922, 6H23, 6H6, 6H30, (6SN7 with 6SN7 to 6922 adapter).

12.6 V - 12AU7, 12BH7, E80CC, (12SN7 with 6SN7 to 6922 adapter).

Don't forget that as each rectifier type has a different voltage drop, the resulting plate voltage will also change. As this shifts the operating point of the tube, the rectifier choice will alter the sound. This means that the possibilities on tweaking the sound are endless ! Similarly, you can get a more classic tube tone with tubes like the 12AU7, or a more modern and linear sound with the 6N1P or 6H30 tube. 

Both the two output coupling capacitors and two film capacitors that bypass the main electrolytic power supply capacitors are mounted on speaker binding posts that unscrew to allow easy replacement.

Impedance is specified at 100 Kohms (input) and 2 Kohms (output) with a recommended pairing with a power amp with a minimum 10 Kohms. I personally think that is a bit too liberal, and at least 47 kohms may be more appropriate.

Operation

The MP-701 has no mute relay to suppress start-up noise, so please remember to switch on the unit at least two minutes before switching on your power amp, and remember to switch off your power amp first before powering down the MP-701. 

There is also no power LED, although the prominent tube rectifier should serve as enough visual indication. I also found that the knob markings to be too discreet to be seen - time to get out your felt marker.

The XLR inputs and outputs are there merely for convenience. This is not a balanced circuit design, but at least you do not need to use an adapter if your source or power amp only have balanced connections.

Lastly, do bear in mind that you need a lot of height clearance on your rack if you choose to use very tall tube rectifiers.  

Sound Quality

The stock Chinese tubes supplied had a very subtle high-pitched whine, so I replaced them with some vintage Voskhod 6N1P-EB tubes instead. Otherwise everything else was stock, include the rectifier tube and film capacitors.

In my system, I got the best results with the lowest gain setting (my Totaldac D1-Six DAC has higher than usual output voltage). My set was pre-owned, but I still put in an additional 24 hours of use before doing any serious listening. 

The MP-701 in stock form has a confident tone, with very firm and powerful bass. The midrange has a subtle warmth to it, with a little bit more body and projection to it than my Conrad Johnson GAT S2 preamplifier. 

High-frequencies have very nice openness and sparkle, with good transient strike and decay. 

Dynamically, this is one powerful and agile little tank, with a hefty and tight bass, with plenty of articulation and speed too. Fast-paced music never caught it flat-footed, although separation does suffer a bit compared to my much more costly preamps on hand.

From a price-performance perspective, the MP-701 does very well and easily takes on contenders at double or triple the price. It does not play the overt tube card, and has plenty of resolution and dynamics to please listeners.

You can read below to find out how far you can push the MP-701.

Taking into account its asking price and tuning options, this is a no-brainer save for two caveats. Firstly, you should avoid pairing this with power amplifiers with low input impedance. Secondly, this is not a balanced design - the XLR sockets are there for convenience only and are wired in parallel with the single-ended inputs / outputs.   

Tuning Options

Accessing the gain switches is quite easy. A long bamboo skewer or toothpick is able to reach the switches through the top most tube cut-out. If you are clumsy, removing the tube makes this even easier. Similarly, the rectifier heater voltage switch can be accessed in the same manner. The signal tube heater voltage switch does require removal of the top-cover though.

Changing out the coupling or power supply bypass capacitors should only be done by users with a certain degree of technical skills and understanding of electricity. After unplugging the set from the mains and depressing the power switch to drain the capacitors, I measured close to 100V DC on the coupling capacitors and more than 180V on the power supply capacitors. The capacitors discharged to a safe level after a few hours, so I highly recommend that you take necessary precautions to check the residual voltages and to drain the capacitors safely before working on the set.  

According to Musical Paradise, the coupling capacitors should be between 1.5 uF to 4.7 uF and have a DC rating of at least 350 V, while the power supply filter bypass capacitors should be between 0.1 uF - 10 uF and have DC rating of at least 350 V.

My unit came with Obbligato gold coupling capacitors of 2.2 uF and Bennic power supply capacitors of 6.8 uF. I would advise users to use power supply filter bypass capacitors of at least 400 V DC. I measured about 350 V DC across these capacitors although this will vary depending on your choice of tube rectifier and your local mains power supply. 

The value of your coupling capacitor is dependent on the input impedance of your partnering power amplifier and is inversely related. You can use this handy calculator at VH Audio's website to calculate the minimum value of your coupling capacitor :- https://www.v-cap.com/coupling-capacitor-calculator.php

The two power supply bypass capacitors at the bottom of the board are wired in parallel with each other. The theory of power supply bypass capacitors is that the performance of the large electrolytic power supply capacitors can be improved by adding small film capacitors in parallel. Film capacitors have much lower ESR and would "speed up" the power supply. 

The jury is still out, so feel free to remove these film capacitors altogether. You can also add two different capacitors. The common practice is to use a capacitor of 1 % or 0.1 % of the value of the capacitor being bypassed. If you are upgrading the coupling capacitors, feel free to move the stock Obbligato capacitors down to the power supply also.

Musical Paradise also advises that different signal tubes (so long as they have the same heater voltage) can be mixed too. The lower two tubes handle the left and right signal, and have to be the same tube, but a different tube can be used in the top position. The circular cut-out for the tubes is quite large, so you can also use large rectifier tubes that use "coke-bottle" envelopes.  

The Works ! 

While the MP-701 is perfectly listenable in stock form, is it worth upgrading, and how well can it perform ? 

Using some parts on hand, I changed the output coupling capacitors to VH Audio's excellent TFTF capacitors, and the power supply bypass capacitors were changed to a Mundorf Supreme and a Multicap RTX. I left my Voskhod 6N1P-EB tubes in place (I tested and matched them for tight section and pair matching BTW), although I did change the stock rectifier for a vintage GE 5U4G tube.

You can expect a significant upgrade, with a marked improvement in transparency, speed and control. The warmth and body I previously noted were absent, and in place was a sparkling clean and clear midrange. The uplift in resolution and soundstaging dimensionality to me far outweigh the cost spent. Consider this a wholehearted endorsement to lavish attention on your MP-701. 

Conclusion

The MP-701 is an incredibly versatile preamp with outrageous performance for the money. The tuning options means that tweaking options are limited only by your imagination. Devoting a modest sum of money also allows you to lift the performance of the MP-701 from excellent to outstanding !

The Musical Paradise just goes to show you that you really can have it all without breaking the bank (rest assured I didn't miss out any digits in the price below). Having a relook at their mission statement, I can only say, "Mission Accomplished !" - Best Buy.

Musical Paradise MP-701 II

Price : USD 699 with free worldwide shipping

http://www.musicalparadise.ca