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-   -   Nikko Beta 20 preamp (http://www.diyaudio.com/forums/solid-state/197496-nikko-beta-20-preamp.html)

Pure_Brew 28th September 2011 01:15 PM

Nikko Beta 20 preamp
 
Hi,
This preamp has been an old faithful but I've noticed an issue which I don't think is a new one.

Most noticeably, when I listen to piano Music, there are at times peaks that sound like mild clipping. I've had different combos of amps, cd players, cables and speakers and it always comes back to this preamp as being the culprit.

Sounds fine with the matching tuner always. Does this point to a cap issue?

Thanks!

east electronics 29th September 2011 08:07 AM

Nikko is very nice equipment ... nothing that is done in 5 minutes ...designers have been seriously working to create them

in such age you have to replace most electrolytics inside ....easy task to do inexpensive but time consuming ( for an amature if you are )

given the chance many of the capacitors inside can be replaced for a lot better ones and this is expected to alter the sound of the preamp for the best ...

Changes need to be verified by instruments and you need to be prepared to listen to an "other" preamp after the recap or the upgrade

kind regards sakis

Pure_Brew 7th November 2011 11:24 PM

I'm grave digging a bit on this thread, but I didn't stop using this pre. As a matter of fact, I've been using a TT, tape deck, tuner and cd player with it. Now I'm not sure the problem has completely gone away but it's been some time since I've heard it. Maybe using it continuously like I have been lately has caused some reforming? It did sit for a few years and was hooked up on some occasions.

Could be dirty controls that were causing the issue and now with all the use they are freed up a bit.

Thanks

east electronics 8th November 2011 07:03 AM

could be also weather conditions .... lower or higher temp might effect soldering and/or performance

Upgrades in users like you ( people that know and use the equipment daily and know them inside out ) usually are very effective cause the user can listen to the difference instantly .

None of he NIkko i repaired in the past had working capacitors inside all of them where just about ok with more than 15% tolerance...

these are simple facts ... keep them in mind

Kind regards
sakis

Samuel Jayaraj 8th November 2011 08:28 AM

The input signal level might be reduced with a different set of input source equipment!

Pure_Brew 8th November 2011 10:45 AM

Thanks guys.

The pre is driving my tube amp, and come to think of it, the pre is also still hooked up to a big solid state amp that is not being used now. I imagine there must be some resistive load, albeit small, on the preamps output.

No doubt the problem didn't show up from other sources in the past for the reason mentioned Sam.

Ian Finch 8th November 2011 11:51 PM

Pure Brew, You did say your problem is with a CD player, but not with a tuner, right?
I'm not aware of the age of the NIKKO but some equipment that was older than 1983 (intro, of CDs) would clip or rather, just distort more when 2V CD signals were fed where 250 mV signals were expected. A lot of good equipment was sold off or just sidelined when this happened here. Tandy/Radio Shack, I think, also sold a lot of little in-line attenuators

This may not be the actual situation and it may have worked fine some time ago, so failing caps and their related power supplies are still a strong likelihood, as Sakis suggests. Obviously this is a signal level issue and is before the volume control, if it persists at all settings.

I would attenuate the CD input, borrow a player with a level control on the output etc. as the options are available to you and test this first. You may find, even listening to the relative levels of tuner and CD, that this is the matter. The fix then is easy but re-capping, if you like your NIKKO, is still a must in the line/preamp section at least.

One last simple suggestion - play The CD through the tape in/monitor sockets - some pre-amps have less sensitivity there.

Pure_Brew 9th November 2011 02:38 AM

Thanks for that advice, it was defineatly just the cd player on peaks.

adason 8th February 2013 04:03 PM

1 Attachment(s)
I know this is an old thread, but I do have a question about this preamp and I see no point of starting a new one.

I got this preamp of ebay, cheap, I believe I paid $9 +sh for it, and offcourse I tested it and found an issue.
Well, it sounds pretty good on every input, and its phono mm itput is fine, actually I am very pleased with its sound, certainly nicely done phono preamp, just the mc input is very quiet, something is wrong there.
I am using low output benz micro on one turntable, and if I use mm input with step up transformer, it sounds great. When I want to run the cart without step up, just use mc input, its mute. There is some sound comming thru, but its too quiet. So obviously there is somethig wrong with pre-pre. I tested on other turntable with ATOC9, the same outcome. I could live with step up trafo, I have quite a few of those, but I am intrigued as to what could be wrong.
When I looked inside, obviously first think I did, to clean the pots and switches, it lookes like noone ever opened the unit, it looks all original. I assume all the caps are original.
I replaced input and ouput caps in the pre-pre sections, but no inprovement. I checked all the voltages on transistors, all reads fine. I have not taken any transistor out, as I believe they should be fine, if all the voltages are as they should.
Anybody has any idea what should I do? Thanks a lot.

east electronics 8th February 2013 04:11 PM

Recap most of the unit check the secondary supply first stage works in another voltage

kind regards
sakis


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