Interview with Robert Koch of Robert Koda

This took quite some time to finalise, but its finally ready. Matej Isak interviews Robert Koch of Robert Koda about the Robert Koda Takumi K-15 preamplifier and his brand. Enjoy…

It passed some time since our last public corespondency. What happened in between at Robert Koda?

We moved to a quiet village location in the Izu Peninsular. When the wind doesn’t blow it is quite beautiful. I am on the second reform of the listening room and there has been strong interest coming in on the Robert Koda brand. In between all of that I have been trying to spend time with my quickly growing son.

Robert Koda Takumi K-15 preamplifier seems like a logical progression to K-10. But, why exactly?

Because we (humanity) strive to do better. And I figured out a number of ways to improve on K-10.

Together all these improvements spawned a new model, the K-15

What would you say its the main difference between Takumi K-10 and K-15?

Sonically the K-15 develops a more colourful picture with better contrast, focus and field of depth. It is a grander and more exciting listening experience.

Does this make K-10 preamplifier obsolete?

Not at all! K-10 is a wonderful pre-amp and costs about half the price of a K-15. We love the K-10 and will be keeping it in the range.

Gold accents made at Takumi K-15. Why?

I wanted the K-15 not to just sound a cut above K-10, but also to look a little more exotic as requested of a number of customers.

Does Takumi K-15 work in full balanced mode?

Yes it does but that is not to say there are any shortcomings in the single ended mode. There are no conversion processes involved in either mode which is quite neat.

Still same shot warming time as with K-10?

Perhaps a little shorter...

Why now 24/7 on operation like most manufacturer recommends with their solid state preamplifiers?

I do not recommend 24/7 operation. When you want to use it, turn it on. When you done, turn it off unless you plan on using it again soon. The warm up time is not too long and there can only be disadvantages to leaving this, or similar  instruments permanently powered up.

K-10 and K-15 transcend both typical solid state and tube design and sound. Why and how?

Well this was very much in the design brief. We felt we could do better than any existing tube or transistor based designs but only after we managed to identify and find solutions for some of the shortcomings that are inherent within semi-conductors. If we were not equipped with that know-how, then our pre-amplifiers would certainly have a taste of the negative aspects of transistor sound avoided in pure tube amps but replaced with other distortions.

You’ve already described before ITC Circuits, but please do refresh it for our readers and what does bring ITC 2 in Takumi K-15?

ITC is a conceptually very simple and unique arrangement of semi-conductors to form a powerful amplifying engine. It is quite non re-active to the surrounding environment and has an inherent stability – Like a solid foundation. The circuit topology we call ITC is not well suited for use with vacuum tubes but is able to work with silicon very well.

Takumi K-15 performance introduces all new more complex driven volume control?

We use the same resistors but with a switch that offers better contacts. It is fully mechanically driven. In other words, you turn the knob and the volume goes up or down! Not only better contact but more positions and four channels of operation in a L-Pad mode require a configuration of 8 X 34 position switches. Quite a monster!

Same audio dedicated resistors as in K-10?

Yes, same (nude) resistors...

What would you say K-10 owner will benefit from upgrading K-15?

In most cases, yes. Then again there are many customers who are thrilled with their K-10 and have forgotten about the upgrade spiral that is so easy to become addicted to.

You’re among few, that gives a lot of attention and importance to copper as material. What is so special about it? How about the silver?

I guess I have a soft spot for silver wire and copper chassis. Perhaps these are a result of the Kondo influence in my earlier years. I find these to be lovely materials to work with and have found that when silver is used correctly (the solders alloy for example is important), there is no better solution. Copper has excellent high frequency shielding abilities, low skin resistance,is a superb conductor of heat and is quite dense.  All these aspects seem to give copper the edge unless you designing for weight and cost reductions. By the way, there are application areas where silver would be inappropriate or even inferior to copper. So we do not simply use silver everywhere.

Permalloy magnetic shielding?

For sure.If you want to magnetically shield something then a block of brushed aluminium is not  going to be of much help – Even if it is thick since it has the same permeability as air. So a better way is to use something like Permalloy. But it has to be fully annealed after manufacturing. In total Permalloy is a rather expensive yet unglamorous looking solution. Very effective though and that is what we are looking for.

You’ve moved from K-10 6dB to 8dB voltage gain. This is still a small compared to many preamplifiers?

Many pre-amplifiers have too much gain! Six to 12dB is right. A few other brands are starting to pick up on this now.

147dB signal to noise ratio? That is pretty extreme!?

It is totally awesome! But I must put the numbers into context for them to have any meaning.

The K-15 produces a very low output noise, about 114dB below 1V output when measured A-weighted as is a standard procedure. This is an outstanding result (but really only of academic interest). However, K-15 is at the same time capable of generating enormous output levels – Almost 50V RMS! This makes for a so called dynamic range of 147dB.

And even more intriguing THD of 0.0003%?

Not bad for a negative feedback loop free design... But to put things into perspective, it is a mid range distortion reading only and only of academic interest... Harmonic distortion seems to play very little role in sound quality.

True balanced and single ended inputs?

A pre-amplifier intended for universal application really needs to support both. A pre-amplifier of ultimate performance needs to support both superbly well and this was again part of K-15s design brief.

What would be the “right” cable to match the performance of Takumi K-15?

Cables are rather system dependant. We try to minimise system dependencies with an aim to create consistently predictable and excellent results. Still some cables may do rather better than others. Connectors and susceptibility to vibration within the cable are among the many factors to consider.
I personally use cable from Kondo at home.

As with Takumi K-10, Takumi K-15 is keeping the zen like timeless design simplicity, that stands on its own. Would you see it as you design language?

Yes, we are not a bling brand and ascetics that are timeless with an appeal to the viewer increasing over time are what I look for.

Basic role of preamplifier is connecting the audio source and power amplifier. How to understand the role of and difficult decision for choosing appropriate cabling?

Don’t forget volume control and balanced to unbalanced (or vica versa) operation.

Plus the critical role of isolating the source from the load such that they cannot interact with each other. For interlinks, I think a good place to start is to use the same brand of interlinks thru-out.

Which brings us to power cord cables. K-10 is the only preamplifier in my experience, that can work to the extreme even with normal power cable. Please elaborate?

We try to minimise the effect of external imperfections (noisy AC mains etc). K-10 is very gentle on the power cable. This helps to dissolve the poorer qualities of a lesser cable. We do not believe that a component should need a super exotic power cable in order to perform well. Although, within the context of a complete system, more suitable power cables may bring about worthwhile improvements.

What is new regarding the K-15 and what is the importance of the preamplifier chassis design?

I would say it is the circuits design that is of principle importance. The chassis of course is required to house the electronics and allow that electronics to perform optimally. Even the K-15 has susceptibility to vibration – well engineered feet can improve the sound quality. So the chassis is quite involved in this equation.

Do you think ultra high end have finally reached its 21st potential?

We still have a long way to go.

We all know about the importance of power supply. How crucial is in the final sound and performance outcome of Takumi K-15?

The importance of the power supply really depends on the pre-amplifier circuits sensitivity to power supply imperfections. ITC used in K-10 and K-15 is in fact very insensitive and reacts very little with the power supply. None the less, K-15 is given a really nice power supply with an emphasis on reducing radiated noise that might otherwise adversely affect the performance of other components in the audio system. Of extreme importance is to keep ground noise / currents to the absolute minimum.

It seems, that further we're push things in ultra high end audio the less tools we're having on hand. Even on the pure technical plane. So what and how far one can measure objectively?

By measuring objectively one can quickly find faults and design floors.

This makes it very useful for quality control and product development.

But do the tests tell you which amplifier will sound OK and which one sounds great?  Well, no.

There are of course (in my belief) technical and measurable reasons behind the sound.

But they not so easy to measure and of course one has to include the fact that we listen to a complete system, not just a single component. There are many possible interactions that may occur while not occurring on the test bench.

To some extent it depends how much time and money you can throw at the problem. I am sure that if I dedicated my time to developing new measuring systems, I would come up with some measurement that could tell more about the sound than say, THD for example. But it would be a very time consuming and costly task...

We’ve witnessed the fanatical importance to the importance of ground. Please say few words related to this.

Internal to a component, say a phono stage, incorrectly routing even one of the ground paths can seriously reduce measured performance. The same is true for a power amplifier. In a complete audio system there are a number of components and they are necessarily spread over a large loop area (especially if you have powered subwoofers and a network attached). If a ground current arises in the wrong place it will be a noise source and if it is modulating the audio with something more complex than say a 50Hz buzz, say something  that is somehow program related, the noise will not be perceived as just a noise but rather a fizz that sucks the purity out of the music. Indeed important!

One thing, that you’ve managed to capture so uniquely so far is the perseverance of the pure musical impact. This probably have to do a lot more and not only with low distortion?

This has to do with getting many aspects of performance in place securely. There has to be no wobbling around in a way that is program dependant but not in precise time with the program material. I am talking about smearing as being a principle mechanism that is not captured in standard distortion, frequency response tests etc.

Which brings to the distortion. Without going into the design secret, if understood correctly you basically use more transistors per channel to bring lesser distortions in combination with other exclusive approaches?

Well that was mainly with the K-70 power amplifier. We used 64 power devises for a 70W amplifier. That is about 8 to 16 times greater than the norm! There are a number of reasons for us using so many devises.

Would you call your electronically takes esoterica?

For sure. That is what we build...

You’ve attended the The 2nd AE Super HI End Audio Show 2014. Can you share your experience with us?

It was a great show. The system was placed in an untreated and very large conference room. Each session was attended by about a hundred listeners. Now this is no easy task! Energising this kind of environment with truly high end sound that a hundred people can enjoy at the same time! My hat  goes of to Cesarro – Now those are loudspeakers! There was a good content of music, both of analog and digital sources. I was able to meet with my customers in a direct and social way – over excellent food and wine. It is lovely to put a personality to a name. Perhaps above all, it was a great pleasure to meet with the folk behind some of the other brands that Audio Exotics represent. Yamada San (Zanden), so softly spoken – Yet his amplifier had no problem getting the point across. Dietmar of Trinity proved to be an engineer par excellence yet with a great sense of humour and many stories to tell. Miguel and his wife of Tripoint where just completely not what I expected and very humble, enjoyable folk.

Many tried to gave a lesser importance to the role of preamplifier in high-end audio system, but in ultimate sense there is no half way. How do you see the impact of the preamplifier in a high-end audio system?

The pre-amplifier is of paramount importance. But then so is the power amp, the speakers and the room. In high end audio one cannot overlook anything. About the worst thing you can do is use a passive (resistive) volume control to “interface” components.

You’ve set the unique path, that now put you on completely different plane. Satisfied so far with the way your venture resolved?

Yes satisfied but... not quite! I am learning all the time and that would surely imply that past works had imperfections. I enjoy what I have built and so do others. This is enough for satisfaction but does not subdue the will to do better.

Anything changed for you at the Japanese market?

No, the Japanese market is Accuphase and Luxman. And the average owner old enough to be my grand dad (well not quite!). But anyway, the Japanese domestic market is somewhat stagnant. I have started to make friends with other high end manufacturers here in Japan and this is most satisfying.

You’ve been asked many times before, but please try to project few anchor points of what to expect from Robert Koda in near future?

I am working on power amplifiers and a phono stage. It takes time to establish the optimal solutions but I am working on it.

And how do you see Robert Koda in future?

A small privately owned but sturdy company that remains largely unaffected by trends and fashion. I want to build a better, wider range of products that allow listeners to fully engage with their music.

It would be interesting to find a suitable partner so that some of our technology could be retained in less expensive products.

I know you’re not interested in talking about other companies, but still. Anything special came your way?

Well, there are a few recent developments that I find interesting. First is Meridians MQA. I think it is quite ingenious and look forward to some hands on experience.

Korg has developed a new kind of vacuum tube stemming from on vacuum fluorescent display technology and while the parts may not be suited to top of the crop high end audio, it is none the less noteworthy.

Then there is Pono. I like what Neil Young and Co. are doing and hope that the habit of listening to complete albums will again be part of the younger generations appetite.

Any last thought for our readers?

Yes, share your music and high end system with your family. Do not take it too seriously – Relax and enjoy!

Oh and if I may, a short quote I saw on a forum recently that I would like to share. It was written by Martin Colloms.

“Luxuries cannot nourish the soul, and their joy is short lived. Great music continues to satisfy.”