Karl vd Berg
Super Member
Thank you, Anti_Skate! 
Just notice that the left channel in the unit here was fuzzy, too
Just notice that the left channel in the unit here was fuzzy, too
Kenwood Basic C1 Preamplifier Restoration/Upgrade
- Thread starter Leestereo
- Start date
Karl vd Berg
Super Member
Problem solved. I bought the one you mentioned here...
And, for the record of a missing part number for the stock relay in the service manual, here's a pic of it.
And, for the record of a missing part number for the stock relay in the service manual, here's a pic of it.
vsat88
Like my Bluetooth ?
Went ahead and placed an order with Mouser today for two relays, four 18V diodes, four 14V relays and should get them next week. Gonna open the C 2 back up and put those in and save the rest for the C 1, wish me luck. The C 2 sounds pretty damn good as is but I want to finish it completely out. This is a kickass thread.
Sound Impressions of Restoration/Upgrade
Before I started the Kenwood C1 restoration/upgrade, I listened for a couple of days to it paired to the M1 or a restored harman/kardon hk770 or a Marantz 170DC. The listening sessions used CD and LP recordings that I'm very familiar with (some examples): Steely Dan/Aja; Miles Davis/Kind of Blue; Dire Straits/Love Over Gold; Beatles/Abbey Road; Fournier/Bach Solo Cello Suites; Duke Ellington Orchestra/Digital Duke; Karajan, 1962 Beethoven Symphony cycle. I even took a few notes of these initial listening impressions since I didn't want to rely on just my sonic memory since it would be a couple of months before I could get to the C1 restoration (a Marantz 2235B was currently on the bench). The C1 as received was only fair sounding; with the phono stage noticeably poorer than the line stage. The bass was overly full(bloated), mid-range and treble range were recessed, further back in the sound-stage, the treble had a brash, overly sibilant quality.
The restoration/upgrade of the C1 significantly improved the sound of the preamplifier. It now sounds quite similar to a restored Hafler DH-110 now: overall, very clear and neutral, with a deep and "tight" sounding bass range. The treble range is very natural sounding with lots of detail (e.g., the different cymbal sounds are easily discerned) and the reproduction of the middle frequencies/vocals is now very realistic; singers sound "live" in the living room (the little vocal "ticks" and 'hiccups" are easily heard, and "mumbled" lyrics are easier to be understood, e.g., Morrison in L.A. Woman. Previously, Unican Eric used a tube preamp (http://www.audiokarma.org/forums/showthread.php?t=580444) with the M1 since it was so much better than the stock C1, he has since told me that is no longer the case: the restored/upgraded C1 is more than capable of excellent sound.
Restored/upgraded Kenwood set sitting pretty
Old parts removed from C1
vsat88
Like my Bluetooth ?
Leestereo I would trust if I did not do the work myself. I do not know if he takes these in but best I recall he does. Send him a PM and see. Welcome to AK haukie !
Broesel02
Active Member
Hello,
Leestereo did make a great Job here, very big thanks for that
I have rebuild a Kenwood Basic M1 so i can recommend to replace the snubber condensers (C42 & C41)with PP Types . My OPA selection was:
IC1, Fono: OPA 2604
Flat Amp: OPA 2604
Tone Amp: LME 49720NA
Richard
Leestereo did make a great Job here, very big thanks for that
I have rebuild a Kenwood Basic M1 so i can recommend to replace the snubber condensers (C42 & C41)with PP Types . My OPA selection was:
IC1, Fono: OPA 2604
Flat Amp: OPA 2604
Tone Amp: LME 49720NA
Richard
Karl vd Berg
Super Member
Hi,Yes, no ceramics in my amps is
Richard
I'd like to know if ANY small ceramic cap of, say, 22pF, 33pF or 100pF can be replaced by NP0/C0G ones...
Thanks a lot.
Karl vd Berg
Super Member
Thank you, rjsalvi
I saw Leestereo replacing a few ceramic caps for NP0/C0G ones at first page - here - and I thought that it could be done for every ceramic cap. But saw other restorations (Japanese amp8 restorer does it often) where those green Mylar caps were also replaced by other type of film capacitor, like in the pic below (sorry for that).
Karl vd Berg
Super Member
Many MANY thanks, rjsalvi!
vsat88
Like my Bluetooth ?
That link to the Japanese restorer amp8 is awesome. I could look at that for hours ! Thanks for that. Bookmarked...Thank you, rjsalvi
I saw Leestereo replacing a few ceramic caps for NP0/C0G ones at first page - here - and I thought that it could be done for every ceramic cap. But saw other restorations (Japanese amp8 restorer does it often) where those green Mylar caps were also replaced by other type of film capacitor, like in the pic below (sorry for that).
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Karl vd Berg
Super Member
Vsat88, I like that amp8 site, too. I liked seeing what he did on a couple of SY-88 preamps...
http://amp8.com/tr-amp/toshiba/toshiba.htm
By the way, I "upgraded" the power supply caps C43 and C44 (2200uF/35V) in my Basic C1 unit: I had Nippon Chemicon KMF series, but comparing to other preamp, I didn't like the way it was sounding. Probably the KMF's don't fit well in some PSU's. So, I decided to try two Panasonic caps of same capacitance I had around and the difference is huge. Will go on trying other caps using Panasonic, Nichicon, Vishay, etc, that are really good electrolytic caps.
http://amp8.com/tr-amp/toshiba/toshiba.htm
By the way, I "upgraded" the power supply caps C43 and C44 (2200uF/35V) in my Basic C1 unit: I had Nippon Chemicon KMF series, but comparing to other preamp, I didn't like the way it was sounding. Probably the KMF's don't fit well in some PSU's. So, I decided to try two Panasonic caps of same capacitance I had around and the difference is huge. Will go on trying other caps using Panasonic, Nichicon, Vishay, etc, that are really good electrolytic caps.
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vsat88
Like my Bluetooth ?
Yep, there is most definitely a problem with my C2..I know this is a C1 thread ...hope no one minds.... The volume level has to be turned up way too far for it to get as loud as it should and I bought a 40.00 tube 12V pre amp off ePay and it sounds much better that the C2...Something is wrong, very wrong. I have tried everything I know to figure it out and still no luck. I know this pre amp should run circles around a dOUK aUDIO 40.00 Pre. I wish it would be something like change two caps...I am sick of going into it so I have all but decided to just leave it alone...Lee Audio..Aurex.. Can I send it to you so you can check it out for me or can you guys at least point me in the right direction..
Karl vd Berg
Super Member
I tried two "NOS" Panasonic M of 2200uF/50V in the PSU and the sound improved a lot over the KMF's. Probably worth put newer FC's. Caps feeding the opamps (C45, C46) are now fresh Nichicon's PW...
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vsat88
Like my Bluetooth ?
Installed new Nichicon's (electrolytic) in those positions during re cap. New Op Amps and diodes..None of this helped..Still does not sound right, still have to turn the volume control up to high. It was this way before the restore as well..Hold that thought..Are you speaking of ceramics ?? (" Caps feeding the opamps (C45, C46) are now fresh Nichicon's PW"). My numbers are different because it is a C2 not a C1. I have some stacked caps...Just FYI.
Karl vd Berg
Super Member
I had to do the same with the previous Nippon Chemicon's KMF at PSU, turning the volume up high and there was no bass and weak sound. Now it's different, the sound is much more present, full, nicer. I think that may be room for further improvement, with C0G multi layer ceramic caps, soft recovery rectifiers and a couple of fresh Panasonic FC caps in the PSU...
I have the Basic C1 unit, the C45 and C46 follow the new 16V Zeners, before the opamps, and I'm using here PW's 390uF/35V (stock ones were Elna 330uF/25V).
I have to see the schematic of C2, and will help you for sure
Edit: do you have a thread for your C2 unit?
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