Koo Audio System
Koo audio system, audio setup is unique in that the power amplifier only puts out 0.75 Watt! The above picture was taken 7 months ago when the audition was made. I doubt there are any similar systems in Malaysia! Koo is very passionate in music enjoyment. He would rather spend time listening to music rather than upgrading the equipment neither checking with this and that tweak. This is something I really respect! Unlike me, I’m always on the hunt for better designs and gears. Shame on me!
- Source – Philips CD160, Philips CD614 plus prototyped non-oversampling TDA1545-based DAC with solid state i/v conversion
- Amplification – Ad815 preamp / Darling (1626) tube amplifier / Quad 306
- Speakers – Isophon FSB3001 (FSB20/8)
- Subwoofer – Audio Pro PS-175
- Cables – silver coated copper helicopter wires with shield screen as interconnect, Astro coaxial cable for digital signal to the DAC
As far as I know, the Quad 306 was no longer in use in Koo audio system, audio setup and he has switched back to Darling tube amplifier which is rather invincible in all areas other than paunchiness. A subwoofer was added to help in the bass region to compliment the low perhaps under-powered setup.
Subwoofer deployment, adjustments and tunings are still in progress and need more time but that really helped in the sound as a whole. One can chat in person with Koo if they’re interested to know more about the subwoofer setup in his system.
From left to right:
- Pic1: toplessloading Philips CD160 with CDM2/10 (solid brass clamp)
- Pic2: toplessloading Philips CD614 with CDM4/19 (aluminum clamp)
- Pic3: toplessloading Philips CD614 with CDM4/19 (shaped brass clamp)
Koo has recently done some simple yet very daring and effective modification to his source – CD player. With the “arm” (one holding the original clamp) attached to the body of CD player, the CD mechanism essentially does contaminate the music signal picked up by the lens as the “arm” makes a means to transmission of vibrations from the body / chassis to the lens.
From this simple logic, it is necessary and generally beneficial to have the “arm” emancipated from the CD player chassis and convert it topless loader to allow “free-weight” clamp (without arm) to press on the spinning CD. Therefore, much lesser vibrations is transmitted to the CD mechanism and spinning CD and therefore much lesser contamination to the music signal!
The effects are very apparent after with this modification:
- Definitive imaging / sound staging
- Increased depth, width and height
- Improved sonic density
- Lower noise floor / background noise
- Much improved musicality
Now comes the question – who else is daring and willing to venture into Koo’s path? Owners of expensive front loaders? Haha! While conversion to topless loading is reversible, the sonic benefits Koo has tasted and treasured have rendered the deployment of the free-weight clamp IRREVERSIBLE! He will never revert to the “armed clamp” for sure!
This is the Darling tube amplifier used in Koo audio system, audio setup. This is the biggest irony: the power amplifier actually puts out hardly 1wpc. So where is the power? If you do not know what this is, just Google for “Darling tube amplifier” and you will find hundreds of links related to Darling tube amplifier. There is a huge following on this amplifier and many have built many versions of this tube amplifier. The fever started when Bob Danielak wrote an article in Sound Practices magazine
The heart of Darling tube amplifier used in Koo audio system, audio setup is the famous 1626 tube. 1626 is an IDHT indirectly heated transmitting triode (I like transmitting triode!). It uses an octal 8-pin base with a ST12 bulb shape (a.k.a. coke bottle) glass case. The price of the tube has shot up several times since then from ~U$3 a piece to ~U$30 now.
1626 vacuum tube
Koo uses the Lundahl LL1663 output transformer (yummy!) in his amplifier, along with other goodies like vintage Cornell Dubilier paper in oil capacitors and etc. On the driver seat, a Telefunken 5965 tube is deployed though his then owned Philips Miniwatt pinch-waisted E180cc was a keeper for couple of years. In any case, there are plenty of choices for this job. One can choose the driver to suit their own taste. I might probably choose the 6SN7 or 5687 for high efficiency speakers, and 5842 or 6C45PI for the medium efficiency speakers.
The 1626 is a very interesting tube. If you look at the average plate characteristics, it can actually be driven into class A2, just like the other transmitting tubes. In class A2, the grid will start to conduct current and it can actually be seen on graph number 2 above. When it goes into class A2, the output power will be increase considerably and will be useful since the original output power is just 0.75wpc.
Although for 1626 in class A2, the linearity suffers (look at the region when the grid is driven positive), but in audio, nothing is absolute! You will never know how it sounds until you tried it. I’ve got several 1626 in my stash that I’m planning to try later.
This is the Isophon FSB3001 used in Koo audio system, audio setup. These speakers are generally perceived to be very musical without any hint of listening to hifi, or perhaps they’re not hifi-ish enough. The signature of these speakers is just beguiling. It makes Koo misses it whenever he is not listening to them (please do not tell his wife about this!), whether he is at work or not home.
The highs sound rather natural (never hear it standing out from the harmonic structure of the music), though to some guys, it is a little or seriously lacking depending on their levels of hearing impairment suffered haha! The midrange is not to die for but juicy enough to keep Koo listening on and on. The lows only reach around 60 Hz (by checking with some technical track) but the specification indicates 42 Hz (without revealing the roll-off gradient).
Even the speaker cable is original – made by Isophon! This is a more than 40 year old cable (probably full oxidized already) teriminated with 2-pin DIN plug. One end with the original connector is coupled to the speaker and the other end is connected bare-end to the Darling amplifier.
This is the 1st revision of Koo audio system, audio setup that I visited many, many years ago.
These two are the older setups that Koo has. One was with the Back Loaded Horn Coral Flat 8A (Eastmarinedrive design) and the other was with the open baffle Coral Flat 8A. Notice the metamorphosis? If not because of his intense music enjoyment, he could have given up this passionate pursuit long ago, seriously I reckon.
This is a picture of the listening seat of Koo audio system, audio setup with a frequency visitor (not me!) from overseas (South China Sea). The picture is edited for privacy purpose. This is not an invitation to visitors but he welcomes all bona fide HIFI friends.
The listening room has a very cozy ambience with a good sense of taste! Koo does not mind locking himself up in this room for the whole day, soaking himself in his music daily and nightly. Koo has a few hundreds of original CDs and is pretty proud with his music collection.
There has been quite a number of praises from fellow audiophiles from the North and South on the good performance and warmth on this setup. If you happen to drop by Kuala Lumpur and know Koo via the internet or KLANS@Yahoogroups, pay Koo a visit!
Alright, that's it on Koo audio system, audio setup page!
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