AH! NJOE TJOEB 4000 MODIFICATION
Before we inform you about what we did with the
OEM cd-4000, we suggest you read about the modifications
we did on the OEM CD-38
to understand more about our general
"modification" philosophy. Than read on from here.
The OEM CD-38, having been the basic machine for our AH! Tjoeb '98 and '99,
has been discontinued now (november 1, 2000) for a few months and only because
we had invested in a huge stock of more than 2,000 machines, we were able to
continue delivery of the AH! Tjoeb with CD-38.
Now (november 1, 2000) we have reached more or less the point that we have to
change from the OEM CD-38 to its follow-up, the new basic model CD-4000. We
have tried to avoid this as long as possible, simply because CD-4000 is 20% more
expensive to start with than model CD-38. And due to the weakness of the Euro
(thank you politicians!) it will even go up soon another 15%!!!
We have been experimenting with the OEM CD-4000 machine already for about 9
months to find the weak and strong spots. Besides that we have been listening
very well to all comments we received from many of our AH! CD-38 Tjoeb
customers. The result of all this is a new remarkable AH! NJOE TJOEB 4000. I
will try to go through a number of points to show you what I mean.
What we absolutely wanted to keep is the affordable low price of the Tjoeb. We
even wanted to try to improve on price/quality ratio. We carry an excellent
record for reliability and after-sales service. That's something we want to keep
and will keep and where possible will improve too. Most people think that the
"looks" of the OEM CD-4000 are better, so that's something you get
as a free extra by this change.
The outputboard of the AH! NJOE TJOEB 4000 is (of course) still based around the
Philips Jan 6922 Military Grade NOS tubes. Also we kept the optimal mix of
SMD-parts and "traditional" components were we found this was
necessary and best choice. Now the outputboard is designed in such a way that
the OEM CD-4000 can be upgraded without a soldering-iron! No internal analog
signal wires are used anymore. Mounting of the board is very easy (1 screw!)
without use of self-adhesive supports. This all means shortened assembly-time.
For the "tech-interested" I have the following details:
Overall improved supply with a total capacitance > 30,000 uF (which is for comparison not only higher than the filterbank of the well-respected Krell KAV-300i, but it also proved to be the "right" quantity according to the listeningpanel). We tried several filterbanks and it was proven that there was a "right" filterbank for our new design. We found that soundwise a filterbank simply could be too large!
The high voltage supply is stabilized (before it was not) and we use a slightly higher voltage for improved performance of the tubes;
We use an independent logic stabilization for display, dac and drive;
We use an improved filament supply. Tube filaments are now in parallel, while these were in series before. For the filament supply we apply a higher filter capacitance: we went from 3,000 uF to 6,600 uF, which again proved to be the "right" quantity according to the listeningpanel.
The supply-voltage of the I/U converters is now stabilized. It is no longer drawn from the drive-supply, but from the high voltage supply for bigger supply rejection;
We apply a separate stabilization for the left and right I/U converter;
On board we have several measurement points for easy checking in case a problem occurs.
We experimented very much with parts of different manufacturers and different
grades. We noticed that sometimes a so-called "audiophile-grade"
component worked as expected while sometimes a "standard-grade"
component worked better. This time-consuming work has resulted in a choice of
parts we will keep on using during the life-span of the AH! NJOE TJOEB 4000.
Significant improvements we got by using Vishay/Ero input signal capacitors and
Wima MKS4 output capacitors. Also the choice of diodes was very critical for the
sonic result of the board.
Everybody has noticed the big sonic improvement of replacing the
muting-transistors with a relay. Much more open sound and much more detail.
Higher dynamics, specially in mids and highs. But, oh that little
"click" between the tracks. Well, that's gone. The relay is still
there, but the (relay)click is only there when you start up the cd, pause the cd
and / or stop the cd. No more clicks between the tracks with your AH! NJOE TJOEB
4000. Besides that, we use now a new relay which is very "soft" in the
"click".
Lots of people agreed it was nice to have all the information about the inside
and what could be done with it. But Oh those nasty (but good!!) Torx screws!
Several people had a problem to find the tools for that. Solution: the AH! NJOE
TJOEB 4000 will be supplied with a Torx 10 screwdriver. This is probably not a
big deal, but at least it will make your life a little easier if you need or
want to open your AH! NJOE TJOEB 4000.
The outputvoltage of the early Tjoebs started "rather" high. Why?
Simply because our listening-panel decided that that sounded best. We did not
realise we were using a very good pre-amp which simply could not be overloaded
by that high output signal. In real life several Tjoeb owners noticed an
overload of their preamp-input, reason why we lowered the output to 2.5Volts. In
the new design we decided to adjust the output with fixed resistors instead of
potmeters. It sounds better and is more reliable in the long run. The AH! NJOE
TJOEB 4000 comes standard with 2.5V output, but if wanted you can make your
choice of outputvoltage (in total 4 possibilities: 5V - 2.5V - 1.25V - 0.7V) by
soldering / desoldering small "bridges" on the board (no wire is
needed, just solder).
Several Tjoeb-owners experiment heavily with different tubes. While most AH!
TJOEB 98 and 99 models were supplied with Philips Jan 6922 Military Grade NOS
tubes (except for the first 100 which were supplied with Sovteks), still some
people wanted to go beyond that. This means that in the long run the
tube-sockets can suffer from all theses "changes". The tube-sockets in
the original Tjoeb were not chosen for that, so sometimes the "heavy
user" had to replace them. But now knowing this, we searched the world for
the best tube-sockets available. And did you expect else from us? We have them!
What a difference! What an improvement! And …. these tube-sockets together
with the (lower) mounting of the new board, make it also possible to use the
larger Philips or Siemens E288CC SQ GoldPins, which are our favorites. However
due to price, availability and reliability, we will continue to supply the AH!
NJOE TJOEB 4000 machines with the known Philips Jan 6922 Military Grade NOS
tubes. The new tube-sockets we use will not easily suffer from tube-swapping.
And hell, these sockets have really tight and strong contacts!
For the Tjoeb-owner who likes to experiment himself we offer the possibility to
play around with numerous different types of OpAmps. While we used a dual OpAmp
(BurrBrown OPA2604) in the AH! TJOEB 98 and 99, we decided to use single OpAmps
in the AH! NJOE TJOEB 4000. As the standard choice we use again BurrBrown
(OPA604), but another favorite is the AD797 from Analog Devices. Other OpAmps
from different brands can be used (a list will be available in due time) and as
we used ic-sockets these are user-replacable parts. Also the DAC is mounted in
an IC-socket, but this is NOT an user-replacable part!!!!
We noticed that more than 80% of the AH! TJOEB 98's and 99's sold were installed
with an AH! AC NoiseKiller and an AH! SuperCrystal. Around 60% of all these
Tjoebs had also a coax digital output installed. To allow us to continue to
offer the AH! NJOE TJOEB 4000 at an attractive price-level, we will deliver all
of them with AC NoiseKiller, SuperCrystal and a Standard Coax Digital Output
installed. As an option a Transformer Coax Digital Output (+version)
is available.
What does this all mean in real life (read: money)?? Well the basic AH! Tjoeb 99
was retailing (overhere, including 17.5% salestax) for Hfl 899,-. The basic AH!
NJOE TJOEB 4000 in 220/240Volts will retail for Hfl 999,-. Add to that (like
before) Hfl 125,- for the SuperCrystal, Hfl 50,- for the Coax Digital Out and
Hfl 75,-(yes, this is a little more expensive) for the AC NoiseKiller and you
end up with a retail of Hfl 1.249,-. Still we will have some extra options for
those who want to get these: TjoebSjoes, Transformer Coax Digital Output and AC
Cord (we don't have yet a "funny" name for that). And … we still
hope to come up with a dampingkit for both the AH! TJOEB 98, 99 as well as the
AH! NJOE TJOEB 4000.
And how about the final "NJOE TJOEB" result?
Well, as said the AH! NJOE TJOEB 4000 is an unique follow-up of the AH! Tjoeb
99. We improved the good qualities as much as possible and we worked on the
(minor) remarks we got from current AH! TJOEB 98 and 99 owners. After we decided
"This is it!" we did the final listeningtests. Follow
this link to "hear" the first impressions of some Tjoeb '99 owners
about the Njoe Tjoeb 4000.
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