Kenwood KA-9100/9150 sound experiments...

pakko

Member
Hello everybody!

After updating several Kenwoods I started to make some experiments the last years. Mostly to get better sound out of the old units.
This time I overworked my KA-9150 in a special way. After recapping the whole unit I decided to optimize the Signal Path dramatically. I did this already with some KA-7300 and other smaller Kenwood amps with great results. Now I wanted to figure out how much you can get out a big KA-9150 - a good sounding amp anyway... so after the standard treatments (cleaning the Vol. Pot, full recap with Panasonic FC´s ...) I shortened the signal path in the unit. The signal goes a long way from the inputs through all the switches to the pre outs - the power ams - back to the relay board and then again through the LS-selector switch and finally to the outputs. Long way.
I made two tests and pick up the signal once directly at the Volume pot and then in a second try at the control board after the flat amp. The difference of course was the amplification, because at the Vol. Pot you have only 150 mV and after the flat amp you find 1 V output.
In the first try I was impressed how clean and silent the amp plays - of course with less power, because the output was dramatically reduced (around 5 times less power). In this case you reduce around 1 Meter cable way and most of the switches. You can hear this!
In the second and final setup I included the flat amp and picked up the signal at 1 V (minus of Ci9/Ci10) and optimized the output caps and feedback caps (Ci7 to Ci10) to Elna silmic II. I went from there directly into the Power amps.
And I shortened the signal path one more time from the relay board and went from there directly into the LS-outputs (to avoid the speaker select switch, because I installed much better speaker bindings just for only one speaker set). I used a good solid silver cable to do this (blue in the pics).

Now - after a few days burn-in time the result is more than good.
The Kenwood plays now with much more transparent and a lot more detailed.

For everybody who thinks I disturbing my nice Kenwood....yes I own some more KA-9100´s - most of the in a 100% original condition. And because of this it´s easy to listen to the sound differences from the original to the updated amp. I can tell you - it´s a big step!
Of course you loose some functions - but honestly I never use the Tone controls and Filter options - all time I listen as strait as possible to the music!

Just for testing I added a Furutech Gold plug and power cable to see if it makes a difference - and yes - it gives you some more details and sound potential in the bass cellar. This is a lot of work, because you need to cut a bigger hole into the rear panel but to be consequent I had to test it;)

OK, here he is the beauty in a nearly mint wooden case - enjoy!

Greetz from Hamburg / Germany

pakko/eckart
 

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Welcome to AK pakko!

Great looking work on the 9150! The wood cases add a nice touch don't they! I would LOVE to find a wooden case for mine... and another for the matching 9900 tuner.
 
Welcome to AK pakko!

Great looking work on the 9150! The wood cases add a nice touch don't they! I would LOVE to find a wooden case for mine... and another for the matching 9900 tuner.

...thanx - and by the way the KT-9900 is not the matching tuner for the KA-9150. The front panels are different. KA-9150 is bronze and the KT-9900 is gun metal (darker). Although it´s a different series (you can tell by the knobs). The matching tuner would be the KT-7550.

Here a pic of the gun metal series sold in the PX-shops:
 

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You are absolutely correct about the knobs from the 7550 matching the 7150/8150/9150. My 2 9900's are bronze though! Might be a difference between the US and Euro models?

I have a KR-9060 inbound and I am hoping that it is bronze as described... looked kind of gun metal grey in the picture though? Fingers crossed!

I might quit collecting if I come across a set of Supreme 650's :D
 
I think there is a difference - the gun metal Version sold here in Germany at the US Army Bases (PX-shops). They are 110-240 V switchable and do have the darker front panel. If you see both front panel version next to each other you can tell the difference.
Probably because of the small production they are not all 100% the same. I had two KT-9900 Euro version in gun metal and they look a bit different.
The bronze front panel is way much lighter.
The funny thing is than the matching tape deck (KX-1003) is not compatible to the KA-9150 and KT-7550 - even when it´s the same series.
For the older KT-9800 and KT-9900 Kenwood never released a matching tape deck....
 
Crazy... now that I get them all in one place there are some differences. One of my 9900's and the 7550 are the darkest bronze of the bunch. The one 9900 on top of the 9150 though is a near perfect match to it.


I have seen a couple of the gun metal grey versions on this side of the pond and they are a pretty dark silver grey. I have none of those.

5579725133_77e901ee5a_b.jpg
 
Kenwood front panel colors

Here an other set - a KA-8150 in bronze and a KT-9900 in "gun metal light".
In this case the gun metal is close to the bronze.
As we see there are variations in this versions.
My PX-Shop Set is much darker.
 

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Very interesting post pakko. I have thought about, but never experimented with, similar mods.

I would be interested in hearing more about your earlier experiments with this concept. What have you learned to be beneficial and what may not be worth the effort, etc.

.
 
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several roads lead to Rome...

If you follow the idea to optimize the sound reproduction of these old vintage gear you will figure out after a while than not all changes do work the same way even inside one brand.
I concentrate myself most of the time to Kenwood gear and try to invest as much time listening to what I did, as I invested working on these projects.

And this can be time consuming if you like to reach a certain point.
Someone who thinks he is ready just with recapping an amp with new caps is in my opinion only on the way....

Every change needs your ears to hear what really happened. Often the unit and the new parts need time to burn-in for some days.
You find this with caps as well as with cables and transistors etc.

As I said before the units don´t react the same way just by changing basically the same parts. A KA-9100 works and reacts different to a 700M, or ever the smaller KA-3700 etc. - (and I wanne reduce it here to the amps - thesame with tape decks, tuner etc.)
Of course there is no need to test so much - but for me it´s part of the fun to see/hear exactly this differences.

Every little change can improve your result and in total it´s a big step forward.

To put it into sections you should have a look at the following areas:

1. Power Supply
- Power supply board and sometimes Power Amp Modules -> change caps, transistors, diodes - try to reach perfect Voltage output with low ERS
- add voltage regulators (not tested up to now!)
- replace Power cable and Plug -> can change a lot in soundstage and resolution. Mostly you need to work on the back panel and cut it open for bigger diameters.

2. Signal Path
- check the path: input/output coupling caps, feedback caps, Input transistors/resistors etc.
- change caps and Resistors (to 1% versions) in the direct audio path.
Here is a big sound potential by the selection and positioning of the caps.
- Bypass caps (works very good with Nichicon Muses ES! I lov them;)
- think about changing/shortening the signal way. Like I said above as example - the cable way to and from the Pre-outs is a bit and you have a little switch in between etc. If you don´t need it really - cut it out.
- change relais! it´s easy and a sound killer when old

3. Pre/Phono- and Power Amps.
Sometimes it´s necessary to have a closer look at these boards and test a little bit more (as example I made very good experiences with Sonicaps in a KA-7300, or Elna silmic II in the Phonostage of the KA-9100)
Replace zener diode with voltage regulators

4. Cleaning
- switches, switches and switches - unsolder & open them - clean and conserve

4. Body work
- insulate the top/side/button covers
- insulate the power transformer (rubber feet)
- maybe try different feet for the case

5. Outputs
- in good project I always change the speaker Terminals to good banana WBT versions (needs a new ground-plate for the terminals...lot of work if you have no CNC)
-shorten the way to the terminals with bypassing the speaker selector switch

6. other
- Replace main caps
- Main caps bypassing -> see Echowars

Only your ears can determine what you like or not.
I test my mods always in the same setup of speakers and speaker cable.
With some listening practice and time investment you can point out the differences in what you did in the last step.
And comparing a modified amp with the original give me the power go on on testing and search for the best sound.

To answer your question - I never tried to change the input side. Just because I don´t want to loose my input options.
But if you wanne reduce it to the maximum - this it it! You would skip the input selector switch and this could calm down the amp anymore.

A lot of ideas I found here in this great forum and of course Echo helped me out more than one time.
But there are more crazy electropimpers here in German and all over the world. EVERYBODY HAS AN IDEA...
 

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Here an other set - a KA-8150 in bronze and a KT-9900 in "gun metal light".
In this case the gun metal is close to the bronze.
As we see there are variations in this versions.
My PX-Shop Set is much darker.

Wow,I love that gun metal color.I'm digging the mods you did too,very nice work.
 
I've been doing a 7 year wander through some of Kenwood's amplifiers.They sound nice.I would imagine that a 700C would sound improved(it already sounds great) if the excess switching/signal routing etc was simplified.
 
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