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Kenwood L-08C Pre-amplifier Review (Vintage Audio, QuirkAudio restored)

Koeitje

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Cut it out. We had dbx with 110dB dynamic range, Dolby C came out before CD and gave us in the 70dB+ S/N. And open reel.
Oh nice, formats that wear down during use. Great.
 

milosz

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Cut it out. We had dbx with 110dB dynamic range, Dolby C came out before CD and gave us in the 70dB+ S/N. And open reel.

dbx playback had quite a lot of audible artifact - gain pumping, swishing, etc. So did Dolby S and Dolby C. Dolby B is a little better in this regard. Open reel - well, for example a 4 track Revox A77 ( considered one of the best hifi reel to reel machines made, kind of a pro-sumer unit ) has a S/N ratio of 62 dB at 7½ ips. So, yes, 20 dB better than vinyl- but still 40 dB worse than good digital. And at 7½ ips it rolled off by 3 dB at 20 kHz and more like 6 db down at 20 Hz. So, nothing really to brag about. 15 ips is better, but no commercially pre-recorded tapes back then were done at 15 ips.

So sources back then were not really all that transparent.
 

restorer-john

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dbx playback had quite a lot of audible artifact - gain pumping, swishing, etc. So did Dolby S and Dolby C

dbx wasn't perfect for sure, but 'gain pumping' or 'swishing' on Dolby C? I don't believe it for a second. Give me an actual example. I have multiple well aligned decks and recordings I did now over 35 years ago (on top quality TDKs) that sound as good as the CD they were recorded from.

Dolby S, I never pursued it. I was into DAT by then and cassette was dead to me... ;)
 

Mart68

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Preamplifiers are a shadow and I mean a shadow of their former selves. Not even close. Okto, Topping and Benchmark 'preamps' are just linestages with hardly any functionality. Where's the MM stage, the MC stage, the tone controls, the filters, the loudness contours, the multiple inputs, headphone stages and processor loops? Notably absent. They are a tiny sub facet of a real preamplifier.
A proper pre-amplifier yesterday:



(from 1979 although gain has been reduced and a few components replaced with modern variants)
 

beagleman

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dbx playback had quite a lot of audible artifact - gain pumping, swishing, etc. So did Dolby S and Dolby C. Dolby B is a little better in this regard. Open reel - well, for example a 4 track Revox A77 ( considered one of the best hifi reel to reel machines made, kind of a pro-sumer unit ) has a S/N ratio of 62 dB at 7½ ips. So, yes, 20 dB better than vinyl- but still 40 dB worse than good digital. And at 7½ ips it rolled off by 3 dB at 20 kHz and more like 6 db down at 20 Hz. So, nothing really to brag about. 15 ips is better, but no commercially pre-recorded tapes back then were done at 15 ips.

So sources back then were not really all that transparent.
A lot of classical Music masters were done at 1/2"OR 1"tape width at 30 ips.

No idea what specs THAT would give, but heard some that sounded great even from the early 60s
 

AudioSceptic

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They've been building phono stages for a while and know what they are doing. I'd say they consider a typical overload from a scratch/pop as something that you really don't want to fully reproduce if you want to keep your tweeter voicecoils in one piece.

I could argue for a high overload capability and a low overload/soft clipping capability equally validly. Vinyl just doesn't have the dynamic range needed in real terms and clicks and pops are faults anyway. A bit like the so-called 'intersample overs' needing headroom in a DAC. No, you don't need headroom for IS overs- you need recordings that aren't faulty in the first place.
It seems that vinyl recorded velocities can reach 50 cm/s, which would be 50 mV for a typical MM cartridge. Why shouldn't a phono stage be able to accommodate that? (Scratches or other faults are another matter, of course.)
 

anmpr1

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Preamplifiers are a shadow and I mean a shadow of their former selves. Not even close. Okto, Topping and Benchmark 'preamps' are just linestages with hardly any functionality. Where's the MM stage, the MC stage, the tone controls, the filters, the loudness contours, the multiple inputs, headphone stages and processor loops? Notably absent. They are a tiny sub facet of a real preamplifier.

I agree with you from an historical standpoint. However, for digital sources, preamplification signal modification functions can be done in software.

The problem arises when one introduces an analog signal path into the setup. Typically this means a phono input. We've mentioned this before, but a phono source requires adjustments (balance, mono switch, subsonic filter, loading etc.) in order to properly integrate into the overall system. These features are generally unavailable in even most separate phono stages.

A tape loop suitable for dubbing, with appropriate filters, is less important for the vast majority of audiophiles, since there are no high quality tape machines (either open reel or cassette) made. At least one manufacturer is making Type II tapes, however the best Type IV cassette tapes are no longer available (as far as I know). In any case, anyone using analog tape is probably out of 'feature luck' with any pre or integrated amplifier made today. Top of the line Yamaha (and even more expensive Lux/Accuphase products) will not help. In that case, a legacy preamp or receiver is the only way to go.

I'm not a headphone uber alles fan, but my guess (and it is only a guess) is that modern headphone amplifiers are much better than what was usually available in integrated gear from the '70s and '80s.

Tone controls were always questionable in actual use, with some exceptions (early Pioneers offered dual mode selectable turnover controls, and I think Sansui too). In the analog world, useful tone modification was typically done via external EQ, either graphic or parametric.

For what it's worth, featureless preamplification was pushed by the high end press. Features were supposed to make the device 'sound bad'. I think manufacturers liked it, because it made their job easier, not having to include features. Compare something like the multi-flexible LNP-2 with the later ML-6a, and then back to the future again, with the Cello Audio Palette.
 

restorer-john

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I agree with you from an historical standpoint. However, for digital sources, preamplification signal modification functions can be done in software.

The problem arises when one introduces an analog signal path into the setup. Typically this means a phono input. We've mentioned this before, but a phono source requires adjustments (balance, mono switch, subsonic filter, loading etc.) in order to properly integrate into the overall system. These features are generally unavailable in even most separate phono stages.

A tape loop suitable for dubbing, with appropriate filters, is less important for the vast majority of audiophiles, since there are no high quality tape machines (either open reel or cassette) made. At least one manufacturer is making Type II tapes, however the best Type IV cassette tapes are no longer available (as far as I know). In any case, anyone using analog tape is probably out of 'feature luck' with any pre or integrated amplifier made today. Top of the line Yamaha (and even more expensive Lux/Accuphase products) will not help. In that case, a legacy preamp or receiver is the only way to go.

I'm not a headphone uber alles fan, but my guess (and it is only a guess) is that modern headphone amplifiers are much better than what was usually available in integrated gear from the '70s and '80s.

Tone controls were always questionable in actual use, with some exceptions (early Pioneers offered dual mode selectable turnover controls, and I think Sansui too). In the analog world, useful tone modification was typically done via external EQ, either graphic or parametric.

For what it's worth, featureless preamplification was pushed by the high end press. Features were supposed to make the device 'sound bad'. I think manufacturers liked it, because it made their job easier, not having to include features. Compare something like the multi-flexible LNP-2 with the later ML-6a, and then back to the future again, with the Cello Audio Palette.
True. Great post for balance and perspective . :)
 

restorer-john

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I use tape outs for testing as they are prior to the the volume, balance, filter, tone and line stages. Otherwise the results would be worse.
 

anmpr1

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From a 'feature' standpoint, in an analog world, there was no limit to what you could get. No doubt one of the (over the) top consumer devices in this regard was the C-1. Back then, the well equipped audiophile likely had two record players (a changer for 'casual' listening and a manual for 'serious' use), two tape decks (in various combinations), and a tuner. So you needed some switching capability, for sure.

Aczel, scratching his head at all the buttons quipped: Look at it this way: a Krohn-Hite 4100a push-button oscillator costs $695.00; a General Radio 1382 white/pink noise generator costs $675.00; a DB Systems preamp costs $425.00. Total: $1795.00. So for five dollars less than the price of the C-1 you can get two superb professional lab instruments, plus a preamp. And the Kronh Hite has 40 controls on its front panel, nine more than the C-1...

His advice--if you want a Yamaha, save some dollars and go for the C-2! :)


c1.jpg
 

sarumbear

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They've been building phono stages for a while and know what they are doing. I'd say they consider a typical overload from a scratch/pop as something that you really don't want to fully reproduce if you want to keep your tweeter voicecoils in one piece.
1- The issue is not the amplitude but the clipping sound.
2- Peaks as short as ticks will not burn twitter coils on a matched Hi-Fi system.
 

Spkrdctr

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From a 'feature' standpoint, in an analog world, there was no limit to what you could get. No doubt one of the (over the) top consumer devices in this regard was the C-1. Back then, the well equipped audiophile likely had two record players (a changer for 'casual' listening and a manual for 'serious' use), two tape decks (in various combinations), and a tuner. So you needed some switching capability, for sure.

Aczel, scratching his head at all the buttons quipped: Look at it this way: a Krohn-Hite 4100a push-button oscillator costs $695.00; a General Radio 1382 white/pink noise generator costs $675.00; a DB Systems preamp costs $425.00. Total: $1795.00. So for five dollars less than the price of the C-1 you can get two superb professional lab instruments, plus a preamp. And the Kronh Hite has 40 controls on its front panel, nine more than the C-1...

His advice--if you want a Yamaha, save some dollars and go for the C-2! :)


View attachment 234286
Wow! That is a beauty to behold. All that fiddling you can do with no computer! Dang youngsters and their digital stuff, why back in my day we just listened to AM radio on our fillings in our teeth. Plus we walked to school uphill 5 miles both ways in the snow.

Seriously, this is a piece of beauty.
 
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ConnorG

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Kenwood's marketing team was very clever. What better way to cheap out on the chassis than to claim that it's the superior way of doing so, while pushing beauty shots in magazines. They were capable of making the L-08C a stellar preamp on the physical front, even while pushing the "anti magnetic" aspect to avoid eddy current induced distortion, by making the chassis and top plate out of aluminum. But they failed wonderfully. Almost every L-08C I have seen has had a /melted/ top cover from the heat generated by the hot running circuit - because it is plastic... They likely felt they could get away with it as the L-08C didn't dissipate enough heat to make it necessary :facepalm:

The L-08C, while measuring and sounding terrific, is a flop internally and externally. It is really built like a clock radio. It uses an awful volume slider mechanism, much like the string and dial scheme of older analog tuners and receivers. Because the faceplate and top cover are mostly plastic, they didn't hold up to wear and tear. Eventually the legend will fade from the faceplate (much like a well-used keyboard) and reading what each button and lever does will become almost impossible.

Kenwood L-08C.jpg


Luckily, they aren't using the "black flag" polystyrene capacitors like in the L-07MII. Although, knowing Kenwood, they probably had a poorly executed grounding scheme which could send the circuit into ultrasonic oscillation much like what happens with the L-07M/MII if it fails.

What's cool about the L-07C is the fact that they had a Sigma sense line going to the RCA output, and there was also a very very rare version of the L-08C that accepted an external power supply called the L-08CPS. (Much like what the L-08M had, as well as the KA-1000) The external power supplies for the L-08M and L-08C are extremely rare, and were a Japanese market version only. You can see the external power supply hookup port on some L-08M's.

Speaking of the KA-1000, I have one with me that I restored. It sounds extremely good, but is built even worse than the L-08C! Truly abysmal internal and external construction, although I really like it's looks when in good shape. Kenwood unfortunately dropped the ball on this series as this was during the first of Kenwood's many downfalls.

Everything after the L-07M, build wise, was a compromise. Ease of service and layout / construction took a back seat in favor of saving money which is extremely disappointing when seeing how well the later models preformed. I would like to have a set of L-07MII's measured. I am still waiting to get my own QA analyzer. Maybe soon!

Here's a few photos of one of the L-07MII's I have recently restored for reference:

IMG_6701.JPGIMG_6702.JPGIMG_6703.JPGIMG_6704.JPGIMG_6705.JPG
 

AndreaT

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Cut it out. We had dbx with 110dB dynamic range, Dolby C came out before CD and gave us in the 70dB+ S/N. And open reel.

Preamplifiers are a shadow and I mean a shadow of their former selves. Not even close. Okto, Topping and Benchmark 'preamps' are just linestages with hardly any functionality. Where's the MM stage, the MC stage, the tone controls, the filters, the loudness contours, the multiple inputs, headphone stages and processor loops? Notably absent. They are a tiny sub facet of a real preamplifier.

I have plenty of real preamplifiers- you should try one yourself. And today (because it's pouring rain), just for fun, I'm measuring phono overloads because a bunch of people are interested. Guess what? The worst one so far is a 2015 product. The best one so far is a 1980 product!
DBX added horrible fake quality to music. Tone controls for treble and bass were often not defeatable and added more problems than they solved. MC and MM amplification was often noisy and the RIAA (or inverse RIAA) input FR commonly with 2-3 db of error. I am happy now and I was not so much until late 1990’s when they finally mastered CDs right and DACs began to perform well enough. There is nothing, xcept my youth, that I miss from those old days.
 

MerlinGS

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Perreaux had very wide range amplifiers...

View attachment 234251
Back in the early 80s I was trying to purchase a Perraux amp, and went to a dealer that advertised it, only later to find out he no longer carried it. Being a "High-End" dealer, he had moved on to better SS amps. I should not have listened to him, because the amp he sold me twice needed substantial repairs over a 10 yr period. I still have the amp in storage (I paid $1300 back then). He also tried to convince me to buy a tube amp instead, but I didn't like the necessity of changing tubes; however, if I had listened to him at least I could have re-sold those mono amps and not lost too much money, whereas my ss amp (which was well reviewed by Absolute Sound) is basically ballast.
 

Jimi Floyd

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Cut it out. We had dbx with 110dB dynamic range, Dolby C came out before CD and gave us in the 70dB+ S/N. And open reel.

Preamplifiers are a shadow and I mean a shadow of their former selves. Not even close. Okto, Topping and Benchmark 'preamps' are just linestages with hardly any functionality. Where's the MM stage, the MC stage, the tone controls, the filters, the loudness contours, the multiple inputs, headphone stages and processor loops? Notably absent. They are a tiny sub facet of a real preamplifier.
YES

h4sgdtjy25g4l9pidrqc.jpg
 
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