[regal]

Quote:

Originally Posted by vlb /img/forum/go_quote.gif Is it a good idea to use one triode for left and one for right channel in the same tube? Pros cons? I would like to thank you all for this tread, it has helped me a lot.

No but the Bijou has different phases in the same tube so the same concern is somewhat revalent. This has been discussed and there is probably little loss in SQ doing this, the # I remember is 60dB stereo separation in a single tube. No one could prove that we should hear a difference between 60db and 100 db. So for budget it is fine, for all out no compromises don't do it. With the bijou you would have even less a problem because any cross-talk is just going to cancel. Sorry to take the thread off topic.

 

[TimJo]

Quote:

Originally Posted by vlb /img/forum/go_quote.gif Is it a good idea to use one triode for left and one for right channel in the same tube? Pros cons? I would like to thank you all for this tread, it has helped me a lot.

I asked this question last year, and here is what Alex said...

Quote:

Originally Posted by TimJo /img/forum/go_quote.gif Alex, I was wondering if you would mind talking about the pros and cons of using a dual triode as a 'stereo' two channel tube (ala CTH) versus using it as a 'two-stage' tube with one tube per channel (ala Bijou and SOHA II)? After building the CTH, I am impressed with the sound quality with both channels of the input stage being shared by a single tube. Is there such a thing as crosstalk within a dual triode? I bring this up here because I am contemplating doing the Bijou as a PTP build, and was considering a topology where one tube would handle both channels of the input stage, and one tube would handle the job of phase splitting. Any thoughts on this notion, or should I just stick to an equivalent topology of your single channel boards? Edit: Just to clarify my thoughts a bit, I got to thinking about this with the idea that you could roll input tubes (like on the CTH) independently of the phase splitter tube. I began to wonder if there could be an interesting level of control and 'boutique' tweaking by dividing the two tasks into separate tubes...

Quote:

Originally Posted by runeight /img/forum/go_quote.gif Interesting you should ask this. My proto PTP Bijou does exactly what you want to do. The input stages are in one tube and the phase splitters in another. I don't think this generates any significant crosstalk and is a much easier way to do the PTP.

 

[particleman14]

Hey all, i am getting ready to take a crack at a Bijou build.  after reading through tons of text, I had just a couple questions regarding mods and tweaks to the bijou. 
I plan on getting the glassjar kit. however , I see some guys using fairly large poly caps on the amp boards.  i am just wondering if there is a big difference between those caps and caps i would receive in the glassjar kit. is it worth it to try out some "boutique" caps? any recommendations?

 

[adamus]

film caps are better for the outputs, but you have spend ALOT to get them big enough.

 

[regal]

Actually if you are using a headphone with an impedance of 300 ohms or more I had a huge improvement over the electrolytics by using 100uF ASC Oil Motor Run capacitors.   They sound great,  get decent reviews by some of the cap experts but you need a big chassis and cap ring holders. They were the best mod I did on my Bijou.  You theoretically add a little phase distortion below 50hz or so but it is well worth it in the improvement of sound.    Best thing is they only cost $15 bucks or so a piece.    For lower ohm phones you could put 3 or 4 of them in paralell per channel,   to my ears they actually sound better than most of the costlier film caps available in these sizes.  One caution is I did this on a NFB delete Bijou since it was intended for high impedance phones only,  I think the NFB would require larger caps since the output impedance drops,   but build a SOHA II or EHHA for low ohm phones anyway.
Quote:

film caps are better for the outputs, but you have spend ALOT to get them big enough.

 

 

[rolotube]

I agree with adamus & regal re improvements brought by using large film caps.  I too am running high impedance phones (650's) & they work superbly with 330uF MCaps which, whilst providing better sound than the stock electros, come at high cost, both in terms of $'s & space required to mount them (they are BIG).  An alternative may be to use the stock electro but with a high quality bypass film cap.  There are quite a few previous posts on this subject.

 

[dean0]

 
Quote:

Actually if you are using a headphone with an impedance of 300 ohms or more I had a huge improvement over the electrolytics by using 100uF ASC Oil Motor Run capacitors.   They sound great,  get decent reviews by some of the cap experts but you need a big chassis and cap ring holders. They were the best mod I did on my Bijou.  You theoretically add a little phase distortion below 50hz or so but it is well worth it in the improvement of sound.    Best thing is they only cost $15 bucks or so a piece.    For lower ohm phones you could put 3 or 4 of them in paralell per channel,   to my ears they actually sound better than most of the costlier film caps available in these sizes.  One caution is I did this on a NFB delete Bijou since it was intended for high impedance phones only,  I think the NFB would require larger caps since the output impedance drops,   but build a SOHA II or EHHA for low ohm phones anyway.
 



 

 
Sounds interesting, have you got a source for the caps? By using these caps in C5 would I still need the bypass cap in C6?
Thanks

 

 

[adamus]

whilst not necessary, you may still want to play with a bypass.
 
With 300ohm phones, as regal says you can easily get away with 100uf. Drakvoice amps use 30uf film outputs.
 
 
 

 

[particleman14]

ya  been doing some more reading..my problem is I am debating whether to just use my high-z headphones.  or incorporate big enough caps to accommodate my k701..
I would prefer no nfb, but maybe I'll just experiment with it.  but building an ehha or soha for low z phones seems like another fun project too!  So i am thinking maybe 2 of those motor run caps would be a reasonable mod for not too much extra $.   
should I grab 2 of these?  http://cgi.ebay.com/New-100UF-100-UF-RUN-OIL-CAPACITORS-CAPACITOR-370V-/380229945477?cmd=ViewItem&pt=LH_DefaultDomain_0&hash=item5887788885
 
also any other recommendations for caps for the other positions? or should i just worry about output caps?  about to empty my wallet for the parts on this build

 

[adamus]

no harm in trying!
 
I didnt like lowZ phones with the bijou, Purely personal taste but the magic with phones such as the hd650 or the high z Beyers just seemed to go when i tried grados and akg k701. To be honest i was pretty repulsed by the grado bijou combo! However, it is my amp of choice with the senns, really nice sound.

 

[ujamerstand]

Increasing cap values in other position will help with frequency roll off too. But if you decide that you will be mainly driving high impedance cans, then I agree with others, you don't have to spend money on large value caps.

Quote:

Quote:

Originally Posted by runeight /img/forum/go_quote.gif At some point increasing the size of the O/P cap doesn't really buy you much more. The 1db point with 470u is about 6Hz. That's pretty low. Larger caps will make it lower. However, there are three other caps in the circuit that also matter to LF response: C1, C3, C4. Increasing C1 to even just 22u should help a little. Increasing C3 and C4 to 220n will also lower the bass cutoff.

Increased C1 to 33u. Replaced C3 and C4 with .22uF Clarity caps. It did improve the lower end response (In my case using Grado 325i) , but is probably insignificant for most setups. I imagine this might improve somewhat as the Clarity's break in.

I'd like to hear comments about a comparison between the Bijou and the SOHA2. dBEL84 obviously you've heard both...do you have a comparison somewhere I can reference?

 

[regal]

Those look like ASC's,  they are getting harder to find in 100uF that looks like a good deal to me.  Remember they are big.
 
Quote:

ya  been doing some more reading..my problem is I am debating whether to just use my high-z headphones.  or incorporate big enough caps to accommodate my k701..
I would prefer no nfb, but maybe I'll just experiment with it.  but building an ehha or soha for low z phones seems like another fun project too!  So i am thinking maybe 2 of those motor run caps would be a reasonable mod for not too much extra $.   
should I grab 2 of these?  http://cgi.ebay.com/New-100UF-100-UF-RUN-OIL-CAPACITORS-CAPACITOR-370V-/380229945477?cmd=ViewItem&pt=LH_DefaultDomain_0&hash=item5887788885
 
also any other recommendations for caps for the other positions? or should i just worry about output caps?  about to empty my wallet for the parts on this build

 

[tamu]

its Alive!
 

 

[ujamerstand]

Cool! Congratulations! I'm surprised you didn't go with a choke supply with that transformer though. Any problems with hum?

 

[tamu]

Havent listened yet. Im gonna leave it for a while as says in the instructions.
 
Still thinking about painting the front plate in black
 
what do you guys thk?