Audiofile

Review

Stand up and dance in joy

What's the reason for all the fuss? What's the reason behind two writers working on one review? Well it's a newborn babe. We'll let ANTHONY LIM and KULDEEP SINGH tell you the story. Take it away boys ... but Anthony first

HOW many times have you lusted after great sounding hi-fi equipment, only to scamper away, tail between your legs, when you find out you can't afford it, unless you take out a mortgage on the home (assuming you have one) or starve yourself for what could easily be an eternity?

Well, fear this no longer. Imagine a great sounding product and a tubed one at that at a real world price, one you can easily afford. Now you don't have to use those "I really, really like it, but can't cough up the dough for it" or "Aieee, look at my weight!" excuses any more.

Here are just a few of the many testimonies from people who have heard this revolutionary product in action:

"The first time I heard it, my jaw fell off. I haven't found it since then." A. Lim (avid hi-fi buff; reply was typed).

"I'm sorry, I can't even begin to tell a cretin like you how good this thing sounds. You just wouldn't understand. You never do, all of you." Anthony L. (famed hi-fi sociopath).

"Oh, my! I can see clearer than before. There's no glare ... what an incredible product!" A.L. (confused hi-fi enthusiast, talking about wrong product, naturally).

What is it that had these normally sane folk raving rabidly? (By the way, Anthony, what are your initials? Ed;) anyway, here's the deal: a preamp under one and a half grand is a scarcity these days, a tubed one, virtually nil.

Given this state of affairs, you can imagine my utter consternation when the people at Octave Electronics showed me the pre-production M7i samples, let me have a listen, and then bounced the price off me. At that point, I went ballistic.

Now, despite what Andrew Wong thinks or says, upper market products don't always cut our hair snip-snip. There's nothing more that gets us AudioFile types all hankered and buttoned up than a good ol' cheap smoke. 

Features

Since the crafty K-nine is gonna carve out the technical roast, I'll carry on with the other set o' ramblings, and just run thru' a brief description of the M7i. It's a tubed line-level preamp, with four sets of inputs and two outputs, all single-ended RCAs, and all solid, heavy-duty types.

The sparse fascia contains just three rotary knobs (for power on/off, volume and input selection) and one lil' classy-looking blue LED. Neato, and the review sample's casework came with a textured dark grey finish. Oh, the mains receptacle is a detachable IEC type, so you can tinker with different power cords. Cool, I say. 

Sound

In a word, delectable. Now, if this amp cost RM2,500, I'd say it was pretty good, but nothing too spectacular. But at RM1,450, gee-whiz, it's stunning. (It's also available in different kit forms at different prices check out Kuldeep's description below.) Unless you expect it to sound lushly warm and smoothly limpid, that is. In which case, stop, turn off this TV and get on the freeway right now.

No, things are a little more incisive here; while there is no mistaking the sense of tubed euphony, the resultant overall texture isn't at all thick and syrupy. The amp has none of the boring, extreme politeness that can virtually pull the plug on musical excitement.

Elsewhere, tonally, the M7i has a balance that falls slightly upfront in terms of image perspective, but isn't unduly or aggressively forward. This isn't a slow sounding amp, and the high-ish gain helps heighten the sense of dynamics.

But it is the midband that will claim you first; at once communicative, voices are solid and display good shape proportion characteristics. That said, I'd have preferred the image edges from disappearing a little abruptly (I know I'm nitpicking rather unfairly this is in comparison with the N.E.W P-3, a unit costing almost four times more than the lil' M7i). 

Conclusion

In truth, the only real shortcoming this preamp has is in terms of its noise floor, which is far from being dead quiet. I think the transformer is the main culprit (you can feel the mechanical buzz through the top plate). The Shakti electromagnetic stabiliser, a.k.a. the Shakti Stone (a passive EMF absorber/dissipator) returned excellent results, and elevated its performance level to a completely higher plane. Not only does it remove residual grain and etchiness, but with such masking aspects now removed also helps impart a greater sense of contrast and focus.

Still, even in its original form, the M7i is a real grand job, and at RM1,450, gets my vote as being the budget ticket of '97. Very warmly recommended. 

Kuldeep wrenches the mike from the Limster and comandeers the TV cameras:

AS Anthony attests, the M7i is a bargain. But wait, even more savings can be had if you're willing to wield a soldering iron. I, as always, have a warm soldering iron to go home to, so off and running we went. 

The circuit

The M7i is a derivative of the famous Marantz M7 preamp which attracted a cult following during its production run and has since ascended the throne of an audio legend. So much so, Marantz has even recently released a limited edition run of the same preamp together with the power amp, the Marantz 9. How much? Well, if you have to ask, you can't afford it ....

I was curious to see what elements of the original was retained in the kit. After a spell poring over schematics, it was apparent that the crucial line amp section was identical. The original's point-to-point wiring had now been replaced by PCB construction though.

The M7's line-stage, in case you didn't know, is based around three triode sections in cascade, with the last section in a cathode follower configuration.

This helps lower output impedance allowing the preamp to drive most loads comfortably. Most crucially, it will happily drive the lowish input impedance of most modern solid-state amps something which many preamps from the golden days of tubes can't do.

The rest of the small signal circuitry used in the original M7 is not reproduced; not many people will find a use for the extensive tone controls these days, methinks.

There is a major change implemented in the M7i, and it's the use of a regulated solid state supply. Here, the HT is regulated using a combination of discrete and integrated linear voltage regulators. Even the heater voltage is regulated so that there's no AC running around in there.

The parts quality is pretty much top notch you ain't gonna see an Alps Black Beauty sealed volume pot on any mainstream commercial product anywhere near this price, so this was a surprise. Supply capacitors are Nippon Chemicon while signal caps are either Philips film caps or Wima Red Bricks. The high-voltage rectifiers, meanwhile, are the expensive fast-recovery types rather than the usual 1N series silicon foot-soldiers wot luxury, eh?

The one thing that I have some doubts about is the ultra-thin teflon coated wire-wrap wire used for signal wiring many DIY types will have problems stripping this unless they have some pretty sharp pre-settable cutters. Still, it does sound much better than the ordinary thick stuff, so it's worth the wrestle. I tried using my teeth and it didn't work .... 

Construction

The whole shebang comes in two packages, one containing the powder coated heavy gauge steel chassis and the other, everything else. I like the fact that it comes complete (down to the last nut and bolt) and even a length of silver loaded solder. The thick fibreglass PCB looks really quite nicely done it's pre-tinned and has a solder mask, so accidental solder bridges shouldn't be a problem. Heck, there's even silk-screened legends to tell you where everything goes.

Building up the PCB was a doddle as the instruction manual was clear and lucid. The manual has little diagrams which I found quite useful as I could use them as reference while going along. Be advised that deviating from the recommended build-up sequence will invariably have you holding components in as you solder since there're so many differently sized parts on board.

Since all the mounting holes are pre-drilled, the hardware mounting did not present much of a problem. The source select switch is located right next to the RCA input sockets to reduce the signal path length a nifty touch. There are a lot of connections to be made here, but a little patience, Grasshopper, is all it takes.

The only other tricky bit was wiring up the heaters you have to do this manually. The heater wiring carries substantial current and it's not usually a good idea to have so much juice running down thin PCB tracks. It was a chore having to do this as the wires have to be cut to length quite accurately to ensure neatness. Suffice to say I'm not a neatness freak. 

Switch on!

Set-up was a doddle and simply involved twiddling one pot until I hit the target HT voltage. And that's it.

Somewhat surprising though was the fact that it worked first time most DIY jobs usually entail tedious amounts of jigging to eradicate hum, at least. 

Conclusion

As far as a kit goes, this one definitely ranks as more thought out than most. Little helpful touches along the way like pre-fitted heatsinks on semiconductors make building a doddle.

Novices shouldn't find the going too difficult but this kit is not suitable for those with no building experience. It's worth bearing in mind that the kit is one of those easy-build jobbies where everything is done for you. Effort is required and this is why the kit is a whole RM250 cheaper than the built-up version. Your time is cheaper than any manufacturer's.

In my book, RM1,200 is an absolute steal for what you're getting and if you've been on a long holiday from DIY, I can't think of a better reason to return to the warm clutches of a soldering iron.

In case you have even more time and less money than most folk, Octave sells a stripped down version of the kit M7i. This basic version retains almost all the features of the more expensive model but uses Matsushita valves instead of Tesla and this is the cruncher: you have to drill the chassis yourself .... Aaargh! Well, maybe the RM800 price tag will help ease the pain.

There's no built-up version of the basic model, so don't bother asking, just get the damned drill out. 

Note: Octave Electronics has informed us that the mains transformer is now supplied with a screen to eliminate the EMI nasties reported by Anthony.

Review sample courtesy of OCTAVE ELECTRONICS (03-793-7939), 81 Jln 1/12, 46200 Petaling Jaya. The standard built up version of the M7i costs RM1,450 while the kit costs RM1,200 and includes a one-year warranty. A basic kit with stripped down chassis is also available for RM800.

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