Yamaha C-4
Natural Sound Stereo Control Amplifier (1979-81)
Specifications
Frequency response: 5Hz to 100kHz
Total harmonic distortion: 0.0035%
Input sensitivity: 0.1mV (MC), 2.5mV (MM), 150mV (line)
Signal to noise ratio: 77dB (MC), 85dB (MM), 100dB (line)
Channel separation: 85dB (MM), 85dB (MC), 85dB (line)
Output: 150mV (line), 2V (Pre out), 10V (Pre out Max)
Dimensions: 435 x 116 x 376mm
Weight: 8.6kg
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Reviews
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Reviewed Oct 31st, 2020 by Tepez
A few years ago I sold my Yamaha c-2. Great, though a slight channel balance issue at the Very bottom of the volume range (could not clean It away...). I recently accuired a PC2002m - i had been on my Bucket list for years. All I could find from the C-series was the C-4, and I was s bit hesitant to pick It up I must admit. I heard It with the M-4 many years ago and wasn’t too impressed (laid back...
A bit boring and polite ...). Well, I’m glad I did. It sounds marvellous with my PC2002M - a match made in heaven:) The C-4 is exeptional. In every way. I prefer It to the c-2, actually! Speakers? The NS1000M - what else!?:)
Reviewed May 31st, 2020 by gvwrighty
This is a superb Pre-Amp.
I managed to acquire a C4 / M4 set and have rebuilt them both, recapping, checking all components and rebuilding all switches, double diodes and replaced all relays with modern silver switched relays.
The sonic quality is superb and as an all discrete amp it is a rarity. If you check the circuitry of Yamaha's latest range, the 3010 for example you'll see that Yamaha have come back to the MC and MM circuitry used in this amp. However you will also notice an unusual feedback circuit that uses an inverse RIAA filter that feeds back to the loading circuitry for the MM amp section. This is a trick which synthesizes input load ranging from 100, 33k, 47k, 68k and 100k, but supplies around -20times output signal to a 1M resistor to synthesize a 47kOhm resistor. This has the effect of reducing input noise by about 3db.
In checking the RIAA circuit, there was considerable drift in the resistors and the caps in the EQ feedback circuit, and in calculating the Time Constants for the feedback circuit, there were some compromises. The circuit uses 2 parallel RC filters in series, which make up 4 Time Constants. Doing the maths these work out at 3259us, 319.6us, 75.2us and 2.21us. The ideal values are 3180us, 318us and 75us, so they are pretty close. There is no IEC amendment (good) and no 'Neumann' pole at 3.18us, but there is one at 2.21us or 72khz.
I corrected mine to be close to perfect, to do this adjust the first filter set to be 0.05417uf & 58704Ohms, 0.01548uf and 4845Ohms, and 82Ohm resistor in series with the filters is okay at 82Ohms, but if you can find one of 82.9Ohm you will get time constants of 3179.996us, 318.0000us, 75.0006us and 2.145us 74.19kHz. Gain is virtually unchanged with an increase of just 0.2db.
Of course you don't need to make these changes at all as the standard EQ with the standard resistors is fine the 3180 time constant is a little higher, so the bass response will be a little higher than expected, but by a tiny amount, the 318 time constant is a little higher, but again by only a tiny amount, and the 75us time constant is pretty much bang on anyway. I like that they've got high enough gain to set a high frequency flattening pole at 72kHz rather than the Neumann pole at 50kHz as at this frequency it would affect signals at the 20kHz level. It would be easy to remove this pole as well if you wanted to, by adding a filter after this stage at the HF pole frequency.
I love this amp, the bass is accurate and deep - all the way down to DC, and there is a subsonic filter if you need it. Treble it crisp and accurate.
If you find one and have the patience to rebuild it, it is worth the time and effort.
Reviewed Aug 15th, 2018 by Vanningale
To me this is one of the great pre-amps. The MC moving coil Preamp is absolutely superb, it's the principle reason to own this unit, if your a vinyl lover, and you've moved up to the vastly superior MC cartridges from the MM Moving magnet stylus cartridge then a critical front end is essential. I used to own the Yamaha HA-1 MC preamp for my Yamaha C-1, however I sold that and the HA-1, and still have what I think is the best of all worlds with this pre-amp. I'll reserve the score of 10 to the Yamaha C-1 for technical reasons. However the C-4 is sonically impressive in it's openness and transparency. Compared to the C-2a it's a close second, and easily superior to my other reference Preamp the Hitachi HMA-7500 which I also love.
C-4 is an honest unit, grossly over designed as is all Yamaha hi -end stuff of the era. Example: The front end preamp has 8 paralleled transistors just to linearize the characteristics of each transistor to be averaged out to be the perfect single transistor, and biased current mirrors for incredibly tight bias and thermal tracking, heck the regulated +/- 30v power supply alone has more components, and transistors in it than many preamps of the era and today. Today it's all chips (IC's).
A classically great preamp. Get one if you can!
Reviewed Jul 17th, 2017 by plattenladen
Excellent Pre-amp with a plethora of functions, now long absent from pre-amplifiers like:
Dual switchable pre-outputs...
Semi parametric EQ that can be entirely bypassed...
3 (!) Phono inputs including a very good MC input...
Hard to find in a good condition, especially cosmetically.
Together with an M-4 (or M-2) Yamaha power amp a very good combo that sounds great for the money, even with Horn Speakers.
re: C-4
Hi ! after reading so many positive reviews i would be interested to give a look at the C-4 flat amp schematic (i am only interested in line stages these days as i listen exclusively to digital sources).
I see only the regulation stage of power supply in the service manual here.
However i am also impressed by the high voltage rails (+/-40V) used in the more expensive C2A.
Its line stage looks very very serious at the point that i wonder how great these preamps could sound with all the costume jewelry stripped down (i.e. the f.... tone controls).
I would be extremely thankful if someone could direct me to the Yamaha preamp with the best sounding line stage of all.
Kindest regards, gino
P.S. of course i would appreciate if someone kindly would suggest me a great solid state line preamp to search for.
re: C-4
You have to try the Yamaha C 70
Full parametric tone control.
Hard to find however.
re: C-4
Classic piece of Yamaha gear, especially for the vinyl lover. I bought mine in 2009 from a guy in Arizona and had it shipped to me in PA. In 2011, I sent it to an excellent tech in Iowa who specializes in Yamaha gear. He did a total recap and reflowed the solder connections, among other things. I've used it in my main system since I bought it, except for the 3 weeks when it was receiving the "spa treatment". This pre will probably outlast me. I'll never sell it. I also have a good friend who bought one of these and sent it to the same tech in Iowa for a recap. He feels the same way as I do about his C-4.
I'm using two turntables, one with a MM cart and the other with a MC. This pre also has cartridge loading capability. The phono stage is outstanding. I would connect a third turntable but I don't have any room close enough, so it's in another system. I use one of the outputs to a power amp and the other to my subs. The output on-off switches are very handy if I want to turn the subs off, or the speakers when dialing in the subs.
Yamaha C-6 Pre-amp
Does anyone have a comparison between this C-4 and the C-6. A fellow employee has a Yamaha C-6 which he offered to me once he locates it in storage. He said there was a manual with it so I have an idea what to do with that since there is no C-6 manual on here.
re: Yamaha C-6 Pre-amp
Hello,
I've owned the Yamaha C-6, it's a really solid preamp. Great sonically. Different features and front panel layout to other earlier models, (C-1, C2a, C-4) but still and outstanding preamp in the industry.
I would be happy to own another one.
Great unit if you like the aesthetic layout and features... Can't go wrong.
Vannin
I always have mine bought in
I always have mine bought in 1978, it is in perfect condition, packed in Cellophane since many years ...
Thanks a lot for sharing !