Saturday, July 18, 2015

Rethinking the Sumo Charlie Tuner

The Sumo Charlie tuner produces good sounds: very quiet, and yet also very dynamic and tuneful, even on weak college radio stations.  In comparison, a Yamaha T-80 (the penultimate model just below the famed super tuner T-85) has more noticeable noise on just-above-stereo-threshold signals, and even without the high filter (which I cannot bear at all because of how dull it makes everything) seems slightly dull and tuneless but has more real 3D ambience if you listen for it.  The Charlie seems to bring the musicians into my living room, stripped of their original ambient environment, but close up so you see them better, as part of achieving the low noise yet dynamic (passionate!) sound.  It isn't really what I want, I want to be transported in my imagination to the musical venue, but it's an interesting trick, since not much else seems to be lost.  In particular the Charlie does not sound "filtered" (as in held back) in any way, indeed the dynamic sound seems exactly the opposite, full of life, moxie, and musicality.  It is not especially lacking highs, though the bass does seem a bit bumped up and loose from everything else, and you might wonder if the highs aren't slightly reduced, but there's no pervasive dullness.  I like the Yang sound more than Yin sounding tuners like the T-80 (the T-85 is a Yang sounding tuner like the Charlie, actually not quite as much as the Charlie, but not an ambience minimizer).  You only notice the missing ambience if you have previous experience with good hifi and good tuners, as I do.  (Interestingly, just as this tuner was being made James Bongiorno left the hifi business and started talking about how he enjoyed his own grand piano better.)

I noticed this lack of ambience in the Charlie output, and then noticed that others have made the exact same observations at FMtunerinfo, that the Charlie sound falls down from lack of ambience and depth.  It is said to sound "flat" (meaning lack of depth and 3D).  It is said to have bumped up sounding bass (which actually measures flat).

It's also doing extremely well for a 35 year old tuner that has never had any kind of refurb.

I do not observe a general lack of sensitivity and weak stations come in remarkably quietly (if not the actual quietest).   However the muting is very fussy about actual quieting and will mute even the strongest of stations if there is an interfering signal nearby.  The best solution is to enable the narrow IF when this happens. Unfortunately the narrow IF does have a negative effect on the sound, but many stations require the narrow IF anyway.  If instead you disable the muting, then you get the problem of stereo intermittently dropping out, and there is a temporary muting when stereo goes in and out, which is annoying.  Furthermore, neither the muting nor stereo thresholds are adjustable externally.

Many Yamahas and many other Japanese tuners would automatically engage the Narrow IF in situations like this, or at least have an "auto" mode which would.  Bongiorno leaves all controls fully manual, and not even retained in the station memory, so you have to remember which stations need Narrow and which work even better in Wide, and you must manually engage the correct IF even when using the 5 presets.

This might not have turned out exactly the way Bongiorno wanted.  Full manual and presets would have been OK if the stereo could come in and out without much effect.

I think the muting may have been less fussy when I first bought this tuner in 2000.  But maybe I was also less observant and more inclined to just use Narrow (which I didn't hear any difference from then, either).

I'm now thinking the fussy IF and the in-your-room sound are two sides of the same coin (design).

The development of this tuner was a life's work for Bongiorno, given his history of working as an assistant on legendary tuners including the Marantz 10B, the SAE MkIV, and as a primary designer of the SAE Mk VIII (aka 8000).  He joked about the Charlie tuner when I first met him at the first GAS company in 1976, and a GAS prototype was built, but it was not until the Sumo stint that Bongiorno finally got to do things the way he wanted…or maybe not quite (and perhaps it's no coincidence that Bongiorno's association with Sumo ended just before the last batch of Charlie's could be personally adjusted by Bongiorno himself).

I know Bongiorno was interested in tuner IF stages because…he got me interested in them!  In one of the most memorable experiences in my life, Bongiorno was the presenter at a San Diego Audio Society meeting (sometime before I became President of SDAS) around 1981.  He talked about tuners and different kinds of IF's, and I'm sure I asked him a question or two that suggested to him a deep ability to misunderstand what he said.

I don't even necessarily remember him pushing The Charlie.  At that meeting he praised recent Kenwood tuners as much as Marantz, etc., and singled out the L-01t and L-02t.  Well he was always a windbag and mostly a self-promoter, but he nailed that one, way back then, as it took me years to discover.

I imagine the development of The Charlie to have been a battle between Bongiorno and the manufacturer, and even the very thing that led him to leaving the company and the hifi business.  It is not a fully successful realization of what Bongiorno had imagined it could be.  And I chalk this off to the lack of awareness at the time (and even through the marketing of the designs Bongiorno had previously been associated with) of the importance of tuner front ends and the pervasive weaknesses of varactor based front ends.

So it's not the most wonderful tuner ever.  But it is relatively unique in the singularity toward which the IF was designed.  It uniquely suppresses hiss despite the weak front end.  Unlike the Pioneer F-93 and similar tuners which used very complex processing to achieve a similar effect, and I should also mention Carver who long did similar things, Bongirno was able to achieve similar effects merely by the way he tuned the IF.

As people have said regarding the F-93, though it has weaknesses, there may be stations it renders more listenable and enjoyable than other tuners, despite limitations.

Though right now it seems I enjoy the presentation of other tuners, especially my F-26 and L-1000t better, on the stations I actually listen to.

One of the things that blew my mind regarding Frequency Modulation a few years ago was learning that FM produces not just 200 kHz of modulations…but an infinite spectrum of modulation.  To really decode FM properly would require unlimited wideband…with open airwaves at all other frequencies.

With a fully continuous signal, such as a 880 kHz sine wave, all these sidebands are going to basically contain the same information.  But with a constantly changing signal, they are going to represent small differences in time.

So having a very high Q filter in the IF, which restricts these sidebands severely, the effect is going to be that things that are more changing are going to be discarded.  That nicely suppresses noise, but it simultaneously suppresses correlations only seen in the very wide IF--the ambience!

My mysticism tells me the Charlie should not have needed that 280 Mhz ceramic, which is messing the whole can.  But that would suggest I have the Q thing backward, or perhaps if you're going high Q you have to high Q all the way.

But perhaps it had to have the 280 Mhz ceramic because of the weak front end.  A nice air capacitor front end could have done wonders.


It lacks remote, which I need in my setup.  But it looks cool, the 100 kHz steps are cool in some ways (you don't feel a need to mess with fine tuning--since you can't anyway), it is far simpler (and easier to deal with) than the Kenwood KT-6040 I'm now using as my remote tuner  With the Charlie, I tune in the station and press Narrow if needed…done.  On the Kenwood there are scads of different combinations of settings including off tuning that may be helpful, and for some reason I off tune every station now.

It does seem that Bongiorno didn't just buy off-the-shelf front end…he got them to do particular things. And it does seem that it's been quite stable, over time, to work as well as it does now, 34 years or so after having been made.  Bongiorno was a stickler for lack-of-drift in the frequency domain.

I was just about to sell mine, but after listening to it's unique presentation I've decided to keep it for now in my tuner Collection Museum and even get a Bongiorno Tuned unit if I can.  I sometimes joke that I could use it, in a closed FM circuit, as a special effect processor--ambient stripper.  But IF I maintain a collection of 10 or so tuners, which I'm thinking is ok (though many of the ones I have now should go).  The the real angle is the same as the F-93 one.  There might someday be a station it gets better than other tuners in it's unique way.

Regarding the off tuning of the Narrow IF…I think this was a deliberate if partly unsuccessful attempt to utilize the effect of closely tuned--but not exactly tuned--serial filters in making a super filter.  This is rarely attempted.  It has failed to reach objectives I fear, and especially in its sonics.  One can hear a similar effect with off tuned crystals…though the crystals are more inherently effective.

As it turned out, the lousy sounding Narrow IF is worth avoiding if you can, and I can avoid it most stations but not the college radio stations I now use the Kenwood KT-6040 for.  So it can replace neither the F-26 nor the KT-6040 in my setup, but if I had a dozen tuners online it would be an interesting one, especially if I could add remote to it.

**** Update 9 PM

I have won a second Charlie, one with the handles which means it was given the final alignment by Bongiorno himself.  It has an amazingly low serial number too.  Actually my unhanded unit has a serial number in the 1400's…which makes me wonder about production estimates I've seen that put the number of handled units over 2000.

I don't know why it didn't occur to me back when I was blogging daily at the FMTuners group, back when Bongiorno himself was participating, and I complained about not having a handled unit (he made me an offer for tuning AND upgrade which I never followed through on) having the magic adjustment, why I didn't just get a second unit?  Well back then the handled units did command a considerably higher price, and the unhanded ones too, and I had read all the complaints about the tuner and how it's performance was substandard (some of which may be explained by not setting the Narrow switch when needed). And, I didn't believe a Charlie would solve the strange whistle I had been hearing in KPAC, which had been my motivation for trying so many tuners.  I had hoped that a fully (or at least nearly fully) LC type IF would eliminate the problem, and it clearly didn't, or the unhanded Charlie would do it too.

(Many tuners later, and a big experiment, I determined the problem was with the station transmission system.  The Charlie, which attenuates the gaussian, wouldn't help.  The Sony XDR-F1 eliminated it entirely…but falsely, which is the problem of open ended noise elimination systems, they always reduce real information along with the noise.)

Now I'd like to know, among other things, what is the difference?  Is the Narrow tuned to sound better, for example???

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