Modding a Logitech Transporter
Posted: Sun May 16, 2021 3:19 pm
I'm not sure if anyone will be interested in this but here goes...
I've been into the Logitech Squeezeboxes for a long time, having three SB3s, a Duet and 2 SB radios. (I never did get the boombox or the touch) The "Transporter" was always the one lusted after and way out of my price range.
Years go by...
Things have moved on and Logitech dropped the ball and I found a guy on Ebay selling the Transporter "special edition" that doesn't have the twirly-wheel for a fraction of the original cost. I just couldn't resist. I know, it's old tech by today's standards but somehow the original urge to own one way back when won out.
Of course the lid had to come off just as soon as you can say "stripped screw remover".
They must've put the screws in with one of those air-driven things they use for car wheelnuts!
Anyway, initial sound-wise this thing had potential and it has all sorts of interfaces including balanced and unbalanced analogue, SP/Dif optical and co-axial and AES/UBU in and out. Plus word clock input! I guess the clue is in the name "Transport-er".
So I listened to it for a while and thought, hmmmm, a bit jumbled and lacking in coherence. So that's when the idea to try experiments to see if I could improve it came along. The Transporter uses an AKM4396 DAC and looking up the datasheet I could see that they had simply used the reference line output circuit as-is with no changes. In fact the datasheets has two circuits, one for unbalanced and another for balanced + unbalanced. It was this latter one they have used. The downside is that the circuit is more complicated than it needs to be if you only want unbalanced and there are electrolytic caps in the path.
So my idea was to try some alternative output stages. The first one I tried was based upon the "FETishator" which I just tried to find links for again but all that comes up is porn sites. lol. Believe me is a real thing and by the Lampizator guy.
Anyway, I built a couple and tried them out:
It was an interesting change to the sound and although was smooth and very laid back it wasn't my scene so back to the drawing board. Next up I decided to reproduce the simpler of the circuits in the datasheet, dedicated to unbalanced.
Of course I made a mistake with the pcb desgn and had to bodge it but oh well..
The sound was now the best I've had from the unit. Very dynamic and exciting but not harsh or jumbled.
Then more reading the web and deciding to see if transformers could be the way forward? My friend had some spare cheap line transformers which he gave me to try out:
The poor transporter was starting to look very abused by this stage! Anyway, the transformers brought a whole new level of realism in the midranges, voices really sounded fabulous, as did piano. Bass was a little light but expected from such small transformers. So at this point I took the plunge and bought some Lundahl high level line transformers from Sweden. These took a long time to arrive but they came last week and this is the final result:
I now have two of the modes connected, the op-amp circuits go to the existing phono sockets (disconnected from the original cct) and the transformers go to a separate set of phonos.
The sound from the transformers is sweeter and more natural than that from the op-amp drivers but there is a "family" likeness that shows I have found the sound of the DAC itself (rather than the associated circuitry) and I will let it run in and test it out with all sorts of music.
It was an enjoyable journey and has got me back into DIY and electronics after a long drought period.
I've been into the Logitech Squeezeboxes for a long time, having three SB3s, a Duet and 2 SB radios. (I never did get the boombox or the touch) The "Transporter" was always the one lusted after and way out of my price range.
Years go by...
Things have moved on and Logitech dropped the ball and I found a guy on Ebay selling the Transporter "special edition" that doesn't have the twirly-wheel for a fraction of the original cost. I just couldn't resist. I know, it's old tech by today's standards but somehow the original urge to own one way back when won out.
Of course the lid had to come off just as soon as you can say "stripped screw remover".
They must've put the screws in with one of those air-driven things they use for car wheelnuts!
Anyway, initial sound-wise this thing had potential and it has all sorts of interfaces including balanced and unbalanced analogue, SP/Dif optical and co-axial and AES/UBU in and out. Plus word clock input! I guess the clue is in the name "Transport-er".
So I listened to it for a while and thought, hmmmm, a bit jumbled and lacking in coherence. So that's when the idea to try experiments to see if I could improve it came along. The Transporter uses an AKM4396 DAC and looking up the datasheet I could see that they had simply used the reference line output circuit as-is with no changes. In fact the datasheets has two circuits, one for unbalanced and another for balanced + unbalanced. It was this latter one they have used. The downside is that the circuit is more complicated than it needs to be if you only want unbalanced and there are electrolytic caps in the path.
So my idea was to try some alternative output stages. The first one I tried was based upon the "FETishator" which I just tried to find links for again but all that comes up is porn sites. lol. Believe me is a real thing and by the Lampizator guy.
Anyway, I built a couple and tried them out:
It was an interesting change to the sound and although was smooth and very laid back it wasn't my scene so back to the drawing board. Next up I decided to reproduce the simpler of the circuits in the datasheet, dedicated to unbalanced.
Of course I made a mistake with the pcb desgn and had to bodge it but oh well..
The sound was now the best I've had from the unit. Very dynamic and exciting but not harsh or jumbled.
Then more reading the web and deciding to see if transformers could be the way forward? My friend had some spare cheap line transformers which he gave me to try out:
The poor transporter was starting to look very abused by this stage! Anyway, the transformers brought a whole new level of realism in the midranges, voices really sounded fabulous, as did piano. Bass was a little light but expected from such small transformers. So at this point I took the plunge and bought some Lundahl high level line transformers from Sweden. These took a long time to arrive but they came last week and this is the final result:
I now have two of the modes connected, the op-amp circuits go to the existing phono sockets (disconnected from the original cct) and the transformers go to a separate set of phonos.
The sound from the transformers is sweeter and more natural than that from the op-amp drivers but there is a "family" likeness that shows I have found the sound of the DAC itself (rather than the associated circuitry) and I will let it run in and test it out with all sorts of music.
It was an enjoyable journey and has got me back into DIY and electronics after a long drought period.