[GermanGuy]

dear thread members, here it is!
 

THE TU-05 TUBE COMPATIBILITY AND POWER SAVE MOD

 
didn't want to further damage my tubes by connecting or cutting pins, so i modded the tu-05 again
 
- to be compatible with the DF97 or similar tubes
- to be able to use DL91, 1S4, 1S4T and 1L33 tubes
- to use DL92 tubes in power save mode
 
i will not post a tutorial this time, because this mod is near to micro surgery and difficult, so no guarantee, if you try the same be very carefull as i was, i only focussed on getting it done, not on taking pictures for all the steps.
 
to be compatible with df97 tubes while df91, 1t4, 1u4, df904, df96 can be used as before, pin 4 and pin 5 of the df91 tube sockets have to be connected. this is no problem for compatibility because pin 4 is not used in the case of the df91 and compatible tubes:
 

 
to use also dl91, 1s4, 1s4t and 1L33 tubes, pin(s) 1 of the dl92 sockets have to be disconnected from the 1.4 volt heater voltage and then recabled and reconnected to the 1.4 volt heater voltage but providing a switch to switch the pin 1 heater voltage on or off:
 

 
to do this, i disassemled the amp's tube panel and drilled and shaped a hole to assemble a small on/off switch:
 

 
i then connected pin 4 and pin 5 of the df91 sockets, cut the 1.4 volt lines from pin 1 of the dl92 sockets and recabled the pins (2 cables) and the 1.4 volt source point (1 cable) to connect them with the switch:
 

 
now i connected the cables to the switch and reassembled tube panel and amp. you can see the small switch above the battery:
 

 
another view (overexposed) to better see the switch:
 

 
and here is the usual 'horror' picture that may prevent you from doing the same:
 

 
AFTER HAVING IMPLEMENTED THIS MODIFICATIONS
 
- df97 tubes can just be plugged in and used.
 
- for normal operation of dl92 tubes switch has to be set to the 'on' position.
 
- to use dl91, 1s4, 1s4t and 1l33 tubes, switch has to and must be set to the 'off' position, because these tubes have only one heater part getting its power already from pin 5 (pin 5 and pin 1 are connected internally inside the tube), otherwise shorten the pin 1 voltage:
 
remark:
 
i did this accidently when the first time using the 1l33 tubes giving them half a hour of burn-in without listening and at that time not knowing that they need this modification, but the amp was not damaged i think thanks to shikada-san's protection circuit.
 
- you also can use dl92 tubes with the switch in the 'off' position, then only one of the two heater parts is used to heat the cathode, the max. output power of the dl92 is lower, but you need half the power for heating.
 
this i a standard operating mode of the dl92 tubes that now can also be used with the tu-05.
 
btw, i have tested all tube types, combinations and modes before posting this mod.

 

[GermanGuy]

at the moment i am listening to the rft df97 - tesla 1l33 combo with modded amp, but this time unmodded tubes!

 

[ianmedium]

Good grief! I think this is the most complex mod you have done yet! What about biasing the tubes?

 

[GermanGuy]

i had a look at the tube data sheets before testing tubes for compatibility but not to a level that i compared more than pin layout, heater, grid and anode voltage.
 
heater voltage should be 1.4 volt, at the moment using for example the tesla 1f34 (df96, but 1.2 volt heater voltage) would dramatically decrease lifetime of the tube, grid and anode voltage i checked to be at least the 65 / 90 volts of the standard tubes.
 
i think this mod is worth to be done just because you can use the dl92 in power save mode. at least for my headphones there is plenty of power left.
 
and while with the df904 and df96 tubes there are great sounding alternatives to the df91's (and df96's need only half the power for heating), for the dl92 there are no real alternatives up to now, but using df96 with dl92 in power save mode, you need just 150 mA instead of 300 mA for heating!

 

[GermanGuy]

Quote:

Good grief! I think this is the most complex mod you have done yet! What about biasing the tubes?

what means 'good grief!' found no translation!

 

[ianmedium]

It's an exclamation of awe and surprise. In the context I used it also admiration!

 

[GermanGuy]

thanks a lot for that!

 

[GermanGuy]

this is a lorenz df61 mini tube that could also be adapted to be used for the tu-05 (but grid and anode voltage on its limits, resistor needed for the heater) and a df96 for size comparison:
 

 
we should ask shikada-san to build a real portable tu-06 mini version based on this tube!

 

[GermanGuy]

boringer - can't remember if you have received the cleaning kits yet. if not up to now i will again send you some kits (free of cost for you). 

 

[Boringer]

Quote:

boringer - can't remember if you have received the cleaning kits yet. if not up to now i will again send you some kits (free of cost for you). 

 
GG, thanks a lot.
The package has not reach me yet, and I think it stuck somewhere in my local Custom.
The same things also happens with my other shipment packages (tubes and cables).
 
Thanks for the offer, but let's wait for a little while to know what's really happening.
I believe they will release them soon or at least they might contact me for the release.
 
Btw, your awesome work on the TU-05 is really amazing.
If Shikada san could apply it to his production it would be an interesting improvement on the units.
Kudos for you... 

 

[Boringer]

Ian, how do you find your AK120?

 

[GermanGuy]

this is a rather small mod, so no big headline:
 

tu-05 led color mod:

 
as my tu-05 has white led's illuminating the volume knob and the light is also (too) bright shining, i thought of a simple solution and made a ring (diameter 30 mm, center hole diameter 1 cm) out of transparent, colored plastic foil normally used as school book cover and placed it in front of the light emitting ring but behind the volume knob, so now my tu-05 led's appear light blue!
 

 

[GermanGuy]

i sent shikada-san an email with a link to my tube compatibility and power save mod!

 

[ianmedium]

this is a rather small mod, so no big headline:

tu-05 led color mod:

as my tu-05 has white led's illuminating the volume knob and the light is also (too) bright shining, i thought of a simple solution and made a ring (diameter 30 mm, center hole diameter 1 cm) out of transparent, colored plastic foil normally used as school book cover and placed it in front of the light emitting ring but behind the volume knob, so now my tu-05 led's appear light blue!

Thats a really clever idea for anyone with white LED's, it means you can have any colour you want.

One thing with all the modifications which are now turning out to be substantial and very far away from Shikada San's design parameters as far as sound is concerned. How do the latest modifications make the amp sound? Is there any increase in noise or difference in sonic signature, I would really be interested to hear if there is as what you have done now is quite far off the original. I guess the other thing that could make a big difference sonically is changing the capacitors for even higher quality ones.. Of course there has to come a point where this is not a TU-05 any more but something very different.

Looking at what you have done so far I reckon you could easily build your own amp.. Have you ever thought about that? Looking at the modifications you have made already I think it well within your capabilities.

If I am absolutely honest I do think the very different tubes makes it hard to compare to the stock amp now.

I am in awe of your modifications though but I must admit I am more than happy with the stock sound and quite content with just adjusting slightly with different tubes as I feel the standard amp is something very very special indeed.

 

[GermanGuy]

ianmedium - i absolutely agree that the amp is very special as it is and i took great care that the amp is fully compatible with the tubes it is designed for and also took great care not to change anything that could be relevant for the sound.
 
the modification to also use df97 is just connecting two pins of the tube socket internally, pins that are at the same position as before after soldering them together, with no influence to df91 tubes because the df91 internally connects pin 4 and 5.
 
as for the added switch, the added switch only connects or disconnects a static voltage to pin 1 of the dl92 sockets, so if in the 'on' position, nothing has changed. and the additional wires are following the same path as the existing power line, just above it.
 
i changed nothing within the signal path except the additional neutrik 6.3 mm jack because of an obvious reason, and the 6.3 mm out is a real benefit.
 
so the design of the amp is the same as before, no difference, nothing changed on the design parameters, also absolutely no sonic difference, but more types of tubes can be used.
 
if this tubes are compatible to bias and grid and anode voltage is another question, but at least you can listen to them to hear if they sound good or not.
 
so i can see or hear no disadvantage in making this great amp even more universal by modifying the one i bought and own, and while freely sharing my ideas here everybody here is free to modify or not to modify his amp in the same way, i hope modifying my amp will not be seen as a degradation of the great concept and work of shikada-san as just this concept and clear implementation makes this possible and i love this amp as i love the new possibilities testing and listening to even more tubes now.