[SBoy]

Hello,
To all that had modified or maxxed out this lovely amp. i was wondering if you can give me some advice on maxing out my bijou as well.
I built this amp 2 years back (stock) and am loving it with DT990/600 and i want to max it out.
I've been reading this form occasionally and had came across some of the options like changing the coupling cap, tubes, amphead's mod.

I don't mind spending some cash on the upgrades cause this amp is a keeper. what i have in mind is:
changing tubes to amperex bugle boy 6DJ8
and some bad ass caps. 
 
Also, will these upgrades justify the sound improvement?
 
I need some guidance here. Thanks alot.

 

[yiancar]

some good bypass caps (C6) is the best change ivemade , replaced the wima with some silver in oil Mcaps

 

[vlb]

Hi fellow bijouers!
 
 
This is my Mods so far, Im happy to tell more about them if anyones interested. But this is my first serious build so my knowledge is limited.
 
One Ps per chanel
Replaced c1 with 40uf film
Replaced c5 with 120uf film
One 20uf film paralell with incomming 250V
Regals mod
 
All of theese mods have improved the sound
 
Ive just installed negative feedback and its a big improvement, without feedback the soundstage was a litle messy. With feedback applied the sound is much more relaxed and the freq response seems more linear.
How do I calculate how many dbs of feedback Im applying?
 
Is it possible to replace R3 and R7 with a constant current source ( Im not sure of the english name).
This would give me lover distortion and the possibility to apply more bias current without changing b+, am I right?
 
Does the choke med affect the sound or will it "only" give me more available power? If so, how much more?
 
Thanks!

 

[Coupe]

Hello all,

I have the board mostly populated. I was wondering if anyone would be willing to build and cut a case for me. I would obviously be willing to pay. Thank you for reading.

-Steve

 

[particleman14]

You should try what most people here do.. buy a case (par-metal, hifi2000 etc.) and then use http://www.frontpanelexpress.com/ for all your milling needs...

 

[pabbi1]

If you want to go cheap and quick, NABU is the answer. Then, take your time figuring out a permanent solution. It is almost perfect for adding a wood front panel,

 

[S3TUP]

Hi, tomorrow is the day.
I have already powered it up, but it smoked a bit, so i'm asking for your advice:
Should i let him smoke for a hour?
By "smoke" i mean the scent of something getting hot. Burning oil on the tube's surface, paint on power supply resistors e.t.c?
Probably i should clean the tubes prior to letting it run...
 
Case from WonderCo: http://stores.ebay.com/wonderco-buy79/Metal-/_i.html?_fsub=2037457011
Trafo from Antek.
 
That wasn't an easy task to
 - Put everything inside such small enclosure
 - Do "symmetrical" look with asymmetrical boards
 
Have anyone tried Nichicon KX caps in the C5?
 
Anyway, see the pics:
 



 
 
 

 

[balderon]

Quote:

Hi, tomorrow is the day.
I have already powered it up, but it smoked a bit, so i'm asking for your advice:
Should i let him smoke for a hour?

You have a nice, clean, and compact build S3TUP! I think it unlikely anything good would become of keeping it powered on for any duration. Something is probably wrong. Did you power up the PS by itself (with the 100k resistor across the B+ terminals) and measure/adjust the voltage? Were you able to easily set the voltage at 250v? Did you smell or see anything at that time?

 

[walangalam]

Nice build.  But smoke is not good. You should power off and check.
 
I hope you got the orientation of your mosfets right, because you mounted them at the bottom, then you should have mounted them facing the other way.
 

 

[S3TUP]

The mosfets are right, caps too...
 
 
Cleaned-up the tubes, removed thermal insulation tubes off PS CRCRC resistors - the amp quit smoking 

 
Hm...
The behavior of +250v of mine:
Slowly rises during startup (10-15 sec), up to 252v. (it stays at zero for 5-7sec , then rapidly rises, reaches maximum and stays there for 3-5sec, and then start to drift down)
Then slowly decreases (30-60 sec) to 248v.
 
I'm unable to "easily" change the +B voltage, as i don't have isolated screwdriver
Otherwise, it has tendency to change when i turn the trimmer between startups/shutdowns.
 
Everything is with all the tubes in place, no 100k load resistor.
 
Tubes:
EZ81
6n6pi
6n1p
 
The transformer outputs 510v unloaded, before rectifier. could this be an issue?
I'm running it off 220v mains.
 
 
 
I feel myself really silly with this amp
When i first powered the PS section, i haven't seen any glow nor the voltage won't rise - i turned it down and rechecked everything.
Then again and again i did this procedure, swapping EZ81, cleaning contacts etc. In the end i have figured, that it won't start up in the moment you push the power button - it needs time to heat-up, and then you'll get everything working (or smoking).

 

[S3TUP]

Ok, it seems i'vefigured out what's the problem.
The transformer seems to be weak.
 
The trimpot regulates well the 240-246v, but it won't let me rise the voltage up to 250v - nothing happens when i turn it futher.
 
I've got pretty high load with these russian tubes, so maybe CRCRC resistors drop too much voltage with such current demand - i'll have to investigate it futher right now.
 
Are there any other solutions? I don't really want to recalculate the resistors in the amplifier for 220v B+ neither want the power dissipation of 25v difference between 246 and 220v... Maybe someone already did it for 240v B+ operation?
 
C6 300v
C5 277v
C4 255v
C1 247v
 
 
UPD:
I've found in this thread that there is no much difference between 240v and 250v operation, as long as i have enough voltage on regulator's input. So i'll stick with 243v setting, having marginable control (up to 246v) and not much power wasted on regs.
Now it's time for the listening session
 
I've got some caps to roll:
Jamicon LP 470u 400v
Mundorf M-Lytic 560u 400v
Nippon Chemicon KMH 330u 200v
Phillips 159 43221 220u 250v
ROE EYF 470u 200v
 

 

[vlb]

Yes, I used those both in PS and as C5 in the amp. I later changed c5  to 120uf film wich was much better. Using hd-650.
 
Quote:

 
Have anyone tried Nichicon KX caps in the C5?

 

[balderon]

Quote:

Ok, it seems i'vefigured out what's the problem.
The transformer seems to be weak.
 
The trimpot regulates well the 240-246v, but it won't let me rise the voltage up to 250v - nothing happens when i turn it futher.
 
I've got pretty high load with these russian tubes, so maybe CRCRC resistors drop too much voltage with such current demand - i'll have to investigate it futher right now.
 
Are there any other solutions? I don't really want to recalculate the resistors in the amplifier for 220v B+ neither want the power dissipation of 25v difference between 246 and 220v... Maybe someone already did it for 240v B+ operation?
 
C6 300v
C5 277v
C4 255v
C1 247v
 
 
UPD:
I've found in this thread that there is no much difference between 240v and 250v operation, as long as i have enough voltage on regulator's input. So i'll stick with 243v setting, having marginable control (up to 246v) and not much power wasted on regs.
Now it's time for the listening session
 
I've got some caps to roll:
Jamicon LP 470u 400v
Mundorf M-Lytic 560u 400v
Nippon Chemicon KMH 330u 200v
Phillips 159 43221 220u 250v
ROE EYF 470u 200v

Glad you discovered the source of the smoke! The low B+ is not uncommon especially with the Regal mod and russian tubes. I recall a post from Alex Cavalli stating B+ at 240v or greater should be ok.

 

[S3TUP]

Yay, it's working On my ol' 565 sens - just for testing.
Weirdly enough, it doesn't produce any hum although the power transformer is so close to the circuit.

Probably star grounding and shielding signal wires helped a bit...
 
The thing which worries me - are the clicking/popping noises when you take out/plug in the headphones.
They sound unhealthy for my hd650s...

 

[zzffnn]

Can a Bijou builder kindly tell me the minimum part cost for a balanced bijou? I am selling mine and want to provide my buyer some accurate info. Thanks so much.