[bmichels]

  bmichels - you asked, so here is my answer:

when doing my mod first off all i will rearrange all components inside the amp to minimize cable length and better separate
 
- input from jack to tubes

- output from tubes to output jacks

- power lines from battery to internal power supply pcb to tubes

- improve central ground connection for both channels

the whole input path:

- i will replace all the cables and wires from the input jack to the tubes

- rewiring the connection between input jack(s) and potentiometer

- replacing the thin shielded stereo cable from potentiometer to tubes

- the tube sockets are mounted on the tube panel and decoupled from the electronic parts by thin wires to decouple the insertion movement of the pins from the solder points and electroinc parts:

- as this is start and end of output and input part .... i will replace this thin wires by 0.5mm pure silver wires or lcofc copper ones.

the power lines:

- thicker cables from battery to power switch

- adding capacitors after the power switch and a thicker cable from power switch to internal power supply board

you can keep the cables for the led's for the potentiometer as they are.
 
the output path:

- replacing the wires from tubes to impedance switch to output transformers and output transformers to the output jacks

ianmedium had posted a picture of this nicely modded and recabled tu-05 (can you repost it?), would be a good example for you as the layout is the original one.

 
GG, I think that one important way to clear the signal path will be to remove this impedence switch.  This is really a signal blocker !  see the image posted before by the first guy who rewired his TU-05: the cable go DIRECT from the transformer to the board.
 

 
 
Myself here is my limited plan
 
- Use cooper cable from the transformer to the XLR headphone out. I will use the exact cable for this than the one that has been used to re-wire my TH900 balanced, so the cable is the same on the complete output path (plus the transformer is cooper)
 
- Remove the 1/8 jack so that the ground of the R & L transformers are not anymore connected through the 1/8 jack ( EXCEPT if I can find a 1/8 female jack that disconnect the 2 grounds when there is no 1/8 male jack inserted.  Does this exist ??)
 
- Recabling the cables from the input jack to...as far as I can go.

   BUT here, I don't know what wires to use.  I am not obliged to use the headphone cable, so I can choose something else.  Any suggestion ? 

 

[GermanGuy]

here is the link to the cable theory that is behind the audioquest product design:

http://www.audioquest.com/wp-content/uploads/2012/01/DoNoHarm-whitepaper-1222-11-r11.pdf

it's very interesting, i red through some time ago before making my own headphone cables and interconnects.

 

[GermanGuy]

  as i have received an additional philco 1s4 yesterday (different label color, but internally exactly the same) and waiting for additional four, i had a relaxing evening listening to music with the rft df97 - philco 1s4 combo.
 
i really recommend trying the philco 1s4 or the rca 1s4 tubes. all the 1s4 tubes i have tested have such a rich, full bodied and warm sound with great musicality but more bite, drive, speed than f.e. the philips dl92, the rca especially shines in the area of bass extension while the philco has this extra bit of air and space around everything. 
 
and for me the rf df97's are the masters of detail and soundstage.
 
together a real dream combo.
 
i have decided to rebuild and recable my amp based on the shared experience (i think it was) of detail and soundstage provided mainly by the df91 stage and bass and bass texture the dl92 stage responsible for, so i will recable the whole input section and df stage with mundorf silver/gold cable, and the complete dl92 stage and output path with best of best copper wires (don't forget, that the output transformers are also copper wire ones).
 
btw, at the monent i am listening to my pf viii with that combo and they match perfectly. listening to dvorak, symphony no.9 i have the feeling to sit in a large concert hall with some distance to the orchestra slightly above looking down and listening to the music, the presentation is so real, relaxed, beautiful, but again so life-like and real like really beeing there. amazing!

 
you are right, i also thought about possible problems with the impedance switch:
 
the real no sorrow solution would be to use the same outout jacks as for loudspeakers to set impedance but then needing eight ones for all three impedance settings connecting them with this bi-wiring bridge cables or a short cable with bananas (this connector type).
 
but on the other hand this side of the output transformers has an impedance of usual 4 to 5 KOhm, current is rather low, voltage rather high, so will try a 4x6 switch i will use also as input switch, which is copper hard plated with pure silver made out of one piece, only 0.025 ohm internal resistance, up to 0.5 ampere.
 
the sound degradation due to impedance mismatch is much larger than the one of a carefully selected switch.
 
and also if using only a specific headphone type as my grado's with 32 ohm impedance you can use the impedance switch to finetune the sound warmer - brighter.
 
and at last i have headphones from 8 to 300 ohm impedance and also asked shikada-san to check the availability of output transformers (if within his design concept) with resulting additional 300 to 600 ohm impedance setting to make my next mod really the final one and the tu-05 usable for headphones like hd800 and beyer t1.
 
it is easy to modify a 3.5mm female jack with switch that the switch is on or off like you want by bending the outer part of that contact. if you want to avoid ianmediums problems he got with his input jack with switch, add a small switch to connect / disconnect ground as i will do.

 

[bmichels]

  some new tubes arrived today:
 


these are all matched pairs and one additional philco 1s4. the 3q4's are dl95's i want to test if they work.

 
 
What " matched pair " means exactly  ?  Is it important ?   
 
and... how can you be sure that they are really matched pairs  ?   Do eBAY vendors offer "matched pairs " or do you have to go some special vendors ?

 

[GermanGuy]

just by chance the tubes were matched pairs! no special idea behind. matched pair means that important electrical properties like amplification are matching, i.e. the same.
 
ebay sellers offer matched pair tubes.
 
to verify that a matched pair is a matched pair, you can buy a good tube tester and check it!
 
if you don't trust your sellers at least until a bad experience, it gets hard to even buy some bread and butter!

 

[ianmedium]

I am very glad that you got your " precious " back.  Now you can have fun with us again...

What tube combo have you used for this new start ?

My favourite pairing that I know so well.. Phillips/Lorenz

3Q4's???

 


yes, 3Q4 = DL95!

at the moment i am listening to the RFT DF97 - General Electric 3Q4 combo which means the DL95 tube type can be used in the DL92 stage and works!

GG, just to clarify, do you mean the DL95 can be used with no modification to the amp or tube and just slot in as a direct replacement for the DL92?

On to another topic. I think I may try the "Stamp Brimars" today though I have to be honest on my pair the stamps looked decidedly tacky so I have carefully removed them with a warm towel. The printing was not great on my pair either so I was not too concerned about losing it if it came off but I am happy to say it remained intact and can report that there was no printing on the stamp side of the tube as none was on the stamp when I removed it.

Before I slot them in what do people who have them think of them?

I have to be honest I was not enamoured with the seller, everything came safely but he was very poor on communications I thought

 

[GermanGuy]

 
would be interested in your impressions how they sound. after my brimar df91 arrived i gave them one hour of burn-in and listened to them with different dl92's or compatible tubes but was not that impressed, i missed soundstage, bass and bass texture, all combinations somewhat bright and soundstagewise flatter sounding.
 
maybe they need more burn-in time.

 
for the dl95 (3q4), the tube is pin compatible to the dl92 and can be used, also in powersave mode, but ... after testing with different records the bias, grid and anode voltages seem not to be optimal or fitting, the tube starts to distort for example with bass heavy organ music at slightly more than modest to medium volume level, so can NOT be recommended.

 

[GermanGuy]

at the moment i am listening to the rft df97 - sylvania 1s4 matched pair combo and must say that from the start i got and get more and more addicted and fascinated by the sound.
 
i bought the sylvania 1s4 tubes because the philco 1s4's are made by sylvania.
 
this combo has a rich, full bodied, highly textured airy and spacious, warm but clear, precise but relaxing, highly detailed but beautiful sound on par with the philco 1s4's, from top to bottom end. i will give them some time to burn-in, but i must say that i find the 1s4 tubes (except the tungsram) superior sounding to any dl92 i have.
 
edit:
 
at the moment i am listening to rimsky korsakow, scheherazade, 1960 live recordings, chicago symphony orchestra, from hdtracks, and feel like molten cheese floating down my chair, it sounds so beautiful!

 

[ChrisSC]

@ Anakchan (or anyone else who has heard both):
 
Can you shoot a quick sound comparison of the TU-5 and the ALO RX-MK3B?  I've got the rxmk3b and am going to be running it fully balanced with my ak120b (the mod's done and should be shipping back to me tomorrow) and LCD3s, and am wondering whether the TU-5 would be a significant upgrade to this balanced setup.  Thanks! 

 

 

[bmichels]

My favourite pairing that I know so well.. Phillips/Lorenz...

you mean Lorenz DF96 + philips dl92  ?  
 
better than   mazda 1T4 + philips dl92  or mazda 1T4  / Mullard  ?

 

[smial1966]

I really wouldn't worry too much about CE certification as there are a number of European owners of this amp from various countries, e.g. France, Germany and the UK, who have all received their amps without a CE mark and no customs interference whatsoever. I think that the CE mark is primarily a European compliance directive and not necessarily something that's stringently applied to goods imported from outside of the E.U.

Cheers,
Andy.

Thanks for your thoughts. Portability is a huge plus in my book. I listen to music in different parts of my house. I have a AK120, so I'm not so keen on spending money on the dac side of WA7. But I will check out a bit more of what other headfiers thinks about it.

The only thing I worry about is if the customs in Norway will stop equipment without CE approvement... Are there anyone here from Norway who has bought such gear?

 

[GermanGuy]

ianmedium - up to now i sometimes had a problem to understand your postings when you name a specific tube combo, but i just understood and think that you are always use the dl92 / df91 sort order to name a combo while i and at least bmichels use the opposite naming - df91 tube / dl92 tube ?!

 

[ianmedium]

you mean Lorenz DF96 + philips dl92  ?  

better than   mazda 1T4 + philips dl92  or mazda 1T4  / Mullard  ?

I have not done the tubes that need modification and have no interest in that part. I will leave that to you and GG. The combination I mean is the Phillips DL92/ Lorenz DF91 that I have loved for so long. For my tastes that combination has not been beaten but I hate to say "best" as that is subjective I feel.

As far as I am concerned of all the tubes I have had so far the only one that I would say was "bad" was the Telefunken DL92. I liked the Telefunken DF91 but I seen to have no luck with the brand as the ones I had were too noisy despite the seller saying they measured well!

Oh, I contacted the seller you mentioned.. Outrageous prices he wants for his tubes. There is no way a pair of Telefunken's of the types we use are worth 79 Euros a pair!!! :eek:

 

[ianmedium]

ianmedium - up to now i sometimes had a problem to understand your postings when you name a specific tube combo, but i just understood and think that you are always use the dl92 / df91 sort order to name a combo while i and at least bmichels use the opposite naming - df91 tube / dl92 tube ?!

Your right GG, I normally do DL/DF but sometimes I forget. I guess I just assumed most would know what i meant as I have mentioned that combination ad-nauseam !

 

[GermanGuy]

As far as I am concerned of all the tubes I have had so far the only one that I would say was "bad" was the Telefunken DL92. I liked the Telefunken DF91 but I seen to have no luck with the brand as the ones I had were too noisy despite the seller saying they measured well!

Oh, I contacted the seller you mentioned.. Outrageous prices he wants for his tubes. There is no way a pair of Telefunken's of the types we use are worth 79 Euros a pair!!!

 
are you looking for or searching a specific tube type ? the standard tubes get more and more rare and expensive on ebay.