Kenwood L07C ll Pre Amp?

Hi and sorry to resurrect an old but extremely interesting thread. I have a question.
When you say best are you referring to measurements or sound quality ? sorry for asking. No provokation intended, i am really curious about top quality preamps of the 70s-80s.
I think maybe wrongly that good solid state preamps are less common than good solid state power amps. I dont know why by the way.
Any other suggestion of top quality SS line stage would be welcomed and much appreciated.
Thank you very much indeed.
Kind regards, gino

I meant sonically since I have not done measurements (yet) as above; but I am pretty confident that the L-1000C measures best as well.
However, as opposed to the L-07CII, the L-1000C is not a fully solid state pre-amp; it is also using a number of IC (integrated circuits)
Nothing wrong with that by the way, when done properly like in the L-1000C.

If you want to know about alternative decent solid state pre-amps, then JVC P-L10 or some of the P-3xx series from Onkyo come to my mind (P-388F being tops).
The Yamaha C-2/C-2a/C-2x are overrated in my opinion; but some are religious about as it is associated to the famous B-1 and B-2 amps.
Anyway, for vintage Yamaha collectors, they have no other option. Yamaha has been particularly lean in the 70's/80's with releasing quality pre-amps (as opposed to Sony)
You can never go wrong with a Sony TA-E86 or E88, or TA-E901, or TA-ER1 (and the list goes on.....).

Single weak point with Sony pre-amps is often their volume pot; it was very high (best) quality (sometimes even specially custom made for Sony), but the wipers are too fragile and age badly.
I own all of the above..... and know this issue well (not limited to Sony though)
For an experienced DIYer not really to panic, but it complicates your ownership if you are not into serious rebuilding vintage gear (i.e. depending on remote specialists to help you out)

Which is one of the strong L-07C(II) points: a stepped attenuator
Should last for life (with occasional cleaning).
 
I meant sonically since I have not done measurements (yet) as above; but I am pretty confident that the L-1000C measures best as well.
However, as opposed to the L-07CII, the L-1000C is not a fully solid state pre-amp; it is also using a number of IC (integrated circuits)
Nothing wrong with that by the way, when done properly like in the L-1000C.
If you want to know about alternative decent solid state pre-amps, then JVC P-L10 or some of the P-3xx series from Onkyo come to my mind (P-388F being tops).
The Yamaha C-2/C-2a/C-2x are overrated in my opinion; but some are religious about as it is associated to the famous B-1 and B-2 amps.
Anyway, for vintage Yamaha collectors, they have no other option. Yamaha has been particularly lean in the 70's/80's with releasing quality pre-amps (as opposed to Sony)
You can never go wrong with a Sony TA-E86 or E88, or TA-E901, or TA-ER1 (and the list goes on.....).
Single weak point with Sony pre-amps is often their volume pot; it was very high (best) quality (sometimes even specially custom made for Sony), but the wipers are too fragile and age badly.
I own all of the above..... and know this issue well (not limited to Sony though)
For an experienced DIYer not really to panic, but it complicates your ownership if you are not into serious rebuilding vintage gear (i.e. depending on remote specialists to help you out)
Which is one of the strong L-07C(II) points: a stepped attenuator
Should last for life (with occasional cleaning).

Hello, thank you very much indeed for the very kind and helpful advice. Line preamps are an old passion of mine (I do not listen to LPs a lot these days). Actually i read some doubts about op-amps but i understand from your words that correct implementation is the key for great sound also with op-amp. I like clean, transparent sound with great 3d ability (with the right recordings of course).
To find these hidden gems among the moltitude of units is like treasure hunting
Very impressive the internals of the PL-10 ... Amazing unit indeed

1329539-jvc-laboratory-ml10-pl10-amp-and-pre.jpg

Thanks a lot again.
Kind regards, gino
 
If you want to do some more with the Kenwood L-07 C II:

The Tone Amp has a diffential amp at the incomming stage with a Lontail- Resistor to adjust the current. Ri17/10kOhm. The Voltage come up from -40V to -0,2V = 39,8V. So the Current will be 39,8V/10000 Ohm = 3,98 mA

Stromquelle.JPG

You can use an LM 334 Current IC to deliver this current. The RSet for an LM 334 at this position will be about 18 Ohm for a in Case Temperature in the L-07 C 2 of 40°C.

Stromquelle.jpg

here it is in Place on the PCB
you wil hear the Difference!

Richard
 
For me, and my TheVintageKnob buddies, all of us owning a lot of high-end 70's/80's gear, this Kenwood L-07CII is a jewel.
It's taking dullness out of a boring system; it's like an angle landed.
It's defeating the Sony TA-E88 and TA-E901.

And yet, going for so very little money ($300 to 600)

The L-07CII has an amazing dual phone equalizer circuit (one for MM, one for MC) , starting off with a dual cascode FET (yep, 4 fets that is) differential input stage with a mirrored current sink, followed by a decent VAS stage and class-A output stage.

But damned, it's getting hot! First unit which has a "hot" volume knob !! (well, it's also above a Sony TA-N902 amp in my rack :biggrin:)
And the open source selection switches needs TLC.

The II model is the last one built as full solid state, and all-metal.
The L-08C is an all-plastic disaster (with non-understandable controls, even for an engineer :oops:), but circuit-wise the L-08C was the next generation (some hifi buddies like the L-08C even more.)

Then, the next (and last) generation of that series came out: the incredible-ugly L-1000C (some Kenwood engineer should have gone to jail for that).
That pre-amp is really the best of the series. No all-solid-state anymore, but several opamps well used and well-built (but yet still the same basic circuit design of his predecessors)
And with the BIG advantage of a remote control and balanced XLR outputs

The CII model is slightly above the C model (and so black that I have a spot light next to it for operation, no joke)
However, the 07CII is the last of an all-metal-all-solid-state era; a must have pre-amp if only for sonic reference, and built quality !

I could go on forever about this unit!
It's the power supply that is getting hot, I added extra heat sinks to the existing ones, plus added 2 small adjustable cooling fans mounted on the outside of the case blowing across the heat sinks. The damn power supply does get sizzling hot even after a total recap. Power output from supply is exactly where it should be also.
 
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I’ve had this unit for several years and I really enjoy it. I had it re-capped as well and I’m happy I did. The phono stage is exceptional, and I imagine I would have to spend a fair amount of money to get any kind of improvement.

I have not been quite as satisfied with the line stage. The soundstage isn’t as wide and the overall sound is overly clinical (or less warm). I’m comparing this to the phono stage, of course. Perhaps the reason for this is the source components? I’m currently using an older Panasonic DVD player and a Topping D30 deck for digital music. Flac files played from my laptop and through the d30 are slightly better, I think.

I’m curious about everyone’s impressions of the unit’s line stage.
 
It's the power supply that is getting hot, I added extra heat sinks to the existing ones, plus added 2 small adjustable cooling fans mounted on the outside of the case blowing across the heat sinks. The damn power supply does get sizzling hot even after a total recap.

That ain't normal !

If the heatsinks gets bloody hot, then the TO-220 series regulators dissipate much more energy than they ought to.
This can be for two reasons:
1) Either the reference voltage is way below what it should be (i.e. faulty/fainting zener diodes or regulating opamp)
2) Or the regulating transistors are getting old and more resistive inside.

Oops.... 3 reasons:
3) One consumer (circuit section) has an issue and draws way too much current

In any case I would change out the zener diodes in the entire unit

Qk5/6 subs are KSD526 and KSB596

Are the power rails at +/-48.5V ?
Oh, and once there was a guy running a 100V japanese unit at 115V mains....
Which means 15% higher voltage drop to be dissipated by Qk5/6: really not recommended

Then, C22/23 in the power supply: from factory they used different types.
Some units have polystyrene caps, other units have the infamous "black flag" caps.
Well..... both go south over time.
Replace by a C0G cap, for example Kemet C317 series.
 
That ain't normal !

If the heatsinks gets bloody hot, then the TO-220 series regulators dissipate much more energy than they ought to.
This can be for two reasons:
1) Either the reference voltage is way below what it should be (i.e. faulty/fainting zener diodes or regulating opamp)
2) Or the regulating transistors are getting old and more resistive inside.

Oops.... 3 reasons:
3) One consumer (circuit section) has an issue and draws way too much current

In any case I would change out the zener diodes in the entire unit

Qk5/6 subs are KSD526 and KSB596

Are the power rails at +/-48.5V ?
Oh, and once there was a guy running a 100V japanese unit at 115V mains....
Which means 15% higher voltage drop to be dissipated by Qk5/6: really not recommended

Then, C22/23 in the power supply: from factory they used different types.
Some units have polystyrene caps, other units have the infamous "black flag" caps.
Well..... both go south over time.
Replace by a C0G cap, for example Kemet C317 series.
Like I said the rail voltages are fine, the entire amp has been recapped with quality caps, it does run hot at the power supply, not sizzling, that's an exaduration. Not going to go & replace zeiner diodes in the entire amp. Just power supply. I'll try replacing regulators if that doesn't work. Other than that I've been using this unit all the time this way & it sounds great. This is the only issue. Thanks
 
These have 2 sided circuit boards, it's easy to ruin a feed through when replacing parts, not an easy thing to replace parts, have to be careful. People who replace part after part must have a lot of time, plus really unnecessary to replace everything.
 
These have 2 sided circuit boards, it's easy to ruin a feed through when replacing parts, not an easy thing to replace parts, have to be careful. People who replace part after part must have a lot of time, plus really unnecessary to replace everything.

Oh yeah, very true.
This unit is even for the senior professional a PITA to (de-)solder in.
A lot of patience and skills required for that part.
As much as I worship this pre-amp, I hate it deeply for the PCBs in it.
The combination of ultra-fine PCB vias and tracks, combined with glued components is a true hell.
 
No one of them come near to the L-07 C II. I have had most of them,- and some more. These Preamps are very fine ones. But i have a total rebuilded L-07 CII. The Kenwood pre is just better. But: For me it is about 50 hours and 500 Euro to make a total rebuild of a Kenwood L-07 C II. If you hear it in the original condition you could hear something else. I have rebuild the Yamaha C-2, the sansui CA-F1 and many many Luxi´s. There had no Chance

Richard
It is always interesting to hear the opinion of someone who has compared a lot of the Japanese preamps. Have you ever compared the Luxman C-5000A?
 
I really like my L-07CII. It was recently rebuilt and sounds fantastic. It did get a bit on the warm side,
however after the rebuild it runs much cooler.
I use it in conjunction with either my L-07Ms or
L-09Ms. Here is a photo I poster before.20190118_161621.jpg
 
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I had a pair of L-05's that were in need of some serious tlc and still sounded as good or better that any amp Ive owned (besides one particular McIntosh). Id love to get a set of 09's or 07 and a preamp...
 
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