My first Kenwood and first preamp : Basic C-2

[Bert 1100]

I just got this yesterday, from our local swiss auction site.
It's my first Kenwood and my first real preamplifier
I was pleasantly surprised by the build quality, it looks all pretty solid, with metal knobs and a feel of solid quality.
Apart from a few tiny nicks on the top edge of the faceplate it is pretty much like new.

It's all working very well, just a tiny bit of scratchiness from the balance control, I'll see if it gets cured with deoxit, otherwise I'm confident to try dismantling the pot to see if I have a case of wipers coming free. Or at the worst I can bypass it, I never use it anyway.

I plan on giving it a complete restore and clean up, I still have to do some reading on whether there is anything to be gained by changing the op-amps.

For now it is feeding the main-in of my restored Yamaha CA-810. I have a freshly rebuilt NAD 216, I'll try this combo on the weekend.

It has a mild case of tobacco smell, but at least it does not diffuse the smell in the whole sitting room since it does not really warm up and has no ventilation grills. The smell test was passed when my wife came home after it had been on for a few hours and she did not notice anything (usually she notices straight away if I put into rotation some smelly vintage amp ...)

Sound-wise it seems to be quite nice. Good tonal balance, good detail, good stereo imaging.
Maybe a bit flat and lacking dynamics and spaciousness, though.
I'll see how it sounds with the NAD.

 

[Roadrash]

I like my C2 a whole lot. As soon as I get the right cables it will be feeding my newly acquired pair of L-09Ms. I have the exact opposite opinion regarding the dynamics and spatiality. Maybe it just doesn't pair well with the Yamaha. I have an Onkyo P306RS that sounds great with my Citation 22 amp, but sounded the way you describe the C2s sound with a Citation 16. The C2 pairs wonderfully with the Citation 16. I hope it changes your mind when you change amps.

 

[Wolverine]

Congratulations! The Kenwood Basic series is anything but that. It was their version of the Sony ES or Pioneer Elite series. The Kenwood Basic M2 was the matching amplifier for that preamp.

 

[johnebravo]

If you're not already aware of it, and you're feeling really ambitious, some genius here posted this:

http://audiokarma.org/forums/index....ting-my-kenwood-basic-c2.473466/#post-6349814

I had mine bypassed a few years ago, and it worked out just fine.

 

[Bert 1100]

I have the exact opposite opinion regarding the dynamics and spatiality.

Don't get me wrong, it does sound very nice.
I hooked it up to my rebuilt NAD 216, it's noticeably nicer than with the CA-810, especially when it gets louder
Maybe my C-2 has not been used for years and years and needed to settle in a bit.
Now the only reproach I have is with the high treble. It lacks a bit of sparkle, and....how to describe it.....it's a bit on the "tsshhhiiiing" side when I'd like a "dziiiing"
But I do really like it. My usual amps are : Marantz PM8005, fully and nicely restored Marantz 1060, 2220 and Yamaha CA-810. My source is mainly my Rega Apollo, speakers are Monitor Audio Silver RX6.
From the date codes on the Elna caps, my C-2 was made in the second half of 1987.
With all the amps and receivers I restored, I noticed a BIG improvement in the sound. So this C-2 will get at the very least a high quality recap.

Thanks for the links about the balance problem.

More photos, here on top of the masked NAD 216

 

[Wolverine]

Don't get me wrong, it does sound very nice.
I hooked it up to my rebuilt NAD 216, it's noticeably nicer than with the CA-810, especially when it gets louder
Maybe my C-2 has not been used for years and years and needed to settle in a bit.
Now the only reproach I have is with the high treble. It lacks a bit of sparkle, and....how to describe it.....it's a bit on the "tsshhhiiiing" side when I'd like a "dziiiing"
But I do really like it. My usual amps are : Marantz PM8005, fully and nicely restored Marantz 1060, 2220 and Yamaha CA-810. My source is mainly my Rega Apollo, speakers are Monitor Audio Silver RX6.
From the date codes on the Elna caps, my C-2 was made in the second half of 1987.
With all the amps and receivers I restored, I noticed a BIG improvement in the sound. So this C-2 will get at the very least a high quality recap.

Thanks for the links about the balance problem.

More photos, here on top of the masked NAD 216

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Perhaps it will get "brighter" over time but my experience with it was the same as yours. I had a Kenwood Basic M1D/C2 combo for a couple of years and I didn't realize how "dark" it sounded until I got a Adcom set up that I could compare it to. Still all in all it is a more than capable preamp.

 

[Bert 1100]

I don't need or want it to get brighter, the tonal balance is good. Bass is very nice, and if needed the bass tone control is very nice.
Usually if I'm listening in the sweet spot, I have it all flat, the bass is plenty. But if I'm around in the room I like a bit of bass boost.

It's just it seems the treble could be a bit cleaner, maybe.
As it is it's very enjoyable and very good looking .

 

[slimecity]

Now the only reproach I have is with the high treble. It lacks a bit of sparkle, and....how to describe it.....it's a bit on the "tsshhhiiiing" side when I'd like a "dziiiing

Symptomatic of a recap being required IMO.

Like you said earlier too, op-amp rolling will also produce improvements. I did this with a Technics SU-V6 input stage - opened it right up.

 

[icenine]

I just found one for $14 two weeks ago. I have it matched with my Mitsubishi DA-A15DC power amp.

 

[Bert 1100]

I just found one for $14 two weeks ago

You got a great deal ! I got mine for just about 10 times as much ...

 

[Bert 1100]

op-amp rolling will also produce improvements

Do you have any recommendations for the C-2 in particular ?

 

[slimecity]

You will need to do a lot of research on this - critical to get a good match - pinouts and operating voltage.

There are some experts on this on AK. Heres the thread to my replacement for guidance:

http://audiokarma.org/forums/index....552-op-amp-in-amplifier.749244/#post-10164494

 

[Bert 1100]

During the winter holidays I gave the C-2 a complete restore :

- Complete disassembly to clean everything up
- all electrolytics replaced (Nichicon FG, ES, Elna SIlmic II)
- small value lytics replaced with Wima MKS2 films
- Bipolar output caps bypassed with 1uf Wimas
- Put in sockets for the op-amps (original op-amps still in use)
- All ceramic caps replaced with C0G/NP0 ceramics (AVX series SR15) (might not have been necessary everywhere or at all, but since I was in there, with everything dismanteled...)
- balance pot rebuilt (I was loosing the right channel when balance was to the right)
- new relay
- IEC plug installed instead of the built-in cord
- new solid aluminium feet
- ultra-fast, soft recovery diodes installed for the main rectifier.

Pictures

 

[Bert 1100]

More pictures

 

[Bert 1100]

And more ......
It was when I was putting the buttons back on that I realised I had put together the balance pot wrongly, the shaft is turned 180° and the knob is the wrong way up
I'll need to put it right....
Also, the case needed a tiny bit of grinding to fit the new IEC mains connector...

 

[Bert 1100]

And the sound ?
It has really improved for the better. I had found the treble lacking in clarity and sparkle, that is now solved.
All in all it is really nice sounding, I tried it with my NAD 216 (with the wooden face), with my Marantz PM8005 (main IN) and my newly acquired Hitachi HMA-7500 Mk2.

For now I have reinstalled the original op-amps, but I do have some NJM2068DD in stock, I wonder if using them will make a difference ?

As for voltages to the op-amps, I measured them at 18.4 and 18.6 VDC, op-amps in circuit.
I have 16V Zeners as well. Or will the 18.6 VDC be OK for the 2068 (specs are max 18VDC) ?

The stock op-amps rated at 18VDC as well don't seem to suffer at all from the slightly high supply.
They just only get warmish in use (with no load, though).

I have a Yamaha C-4 waiting for a full resto as well, will it better the Kenny C-2 ?

 

[Bert 1100]

The factory 2114Ds are actually a really good low noise package

For the flat amp, my factory original is 2041DD. Would a 2114D be a "plug and play" op-amp ?
the other 3 are different, can't remember which now...

I really like how it sounds now, the top end is very nice, all the rest as well, so I'm not in a hurry to go op-amp rolling....

 

[Bert 1100]

Nice job.

Thank you !
So, the 2114 should be a straight forward replacement for the 2041? can it replace the 4560 as well ? (originals are one 2041DD and three 4560DN)
Or is it a more complicated question, with the whole circuit to be taken in consideration so as to avoid oscillations and other hidden difficulties ?

 

[hopjohn]

A small addendum to rjsalvi's advice - If you put the little bypass caps in from the opamp rails to ground it's always recommended to keep these leads as short as possible, particularly on the rail side, to minimize series inductance.

 

[Redone90]

Great write up Bert

I have a Kenwood C2/M2A and a C1/M2 and was considering a complete resto for the C1 after having a ground loop hum issue.
I since fixed the ground loop problem, but after reading feedback on the DRM audio page and your experience I still think it's something that's worth the time and effort.
I've got to ask...did you get the parts from the DRM audio site as a package or chase them down yourself?
http://www.drmaudio.com/parts-kits
I ask because being in Australia getting access to some of these parts in the correct spec and in good quality can be difficult.

Cheers

Andrew