BoSoZ is working.......

[lykkedk]

Hi, just want to tell, you that i just tested my Balanced Line Stage, and it worked.

I would like to tell, that i have done some modifications to the PCB, so that I could use some bigger resistors, and bigger heatsinks. To bad i do not have any digital-camera..

Instead of R3 - R4 in serie and R5 - R6, which is 2 x 750ohm, 3watt, i use one 1.5Kohm 11watt (Still got hot !!!)

Instead of R1 and R2, i use 2 x 1.5Kohm 3watt in parrelell, which gives me 6watt (Still got hot !!!!)

I have used some pretty good heatsinks for the four IRF610 at the main PCB, they do not get very hot !!!

At the PSU, i used some very small heatsink's which i have to replace, cause they got pretty hot (Fried i guess)

I only plan to use this circuit unbalanced so i shorted the R14 (actually R14 isen't there at all) on both -IN. I did not make any changes to the -Out, just dident use it.

I used my computer-speaker as power-amp , and i noticed, that there was some humming whitout the sortcut between R8 and GND (Where R14 normally is placed)

I think, i noticed some klicks when unplugging the PSU, even when volume P3/P4 at min and P1/P2 at min... maybe it's because of the testing wiring, and the lousy computer-speaker..

I find it rather strange, that theese resistors, and the IRF610/IRF9610, on the PSU, turn so hot (Ok, when i have replaced the heatsinks on the PSU, they will not anymore.

OK, anyone experianced the same heat-problem ?????

OK, BTW i used no P5, and 430ohm at R15 for GAIN at 10.

Everything seem to work fine, nothing wrong with the sound I think (Hard to tell with my 10dollar loudspeeker

Hope to have some reply...

[jwb]

The heat sinks Nelson Pass recommends for the power supply are marginal. They run the junction at nearly their rated limit. I used the next size up.

I wouldn't worry about the power resistors getting too hot. They are designed for that.

Regarding the turn on and turn off transients, they are very real. You will need some protection on the output.

[lykkedk]

What kind of protection, do i have to use, so that i could be completely safe ?

I have for 6month used an homemade Leach-amp 4.5, power-amp, where i plan to build in a loudspeaker-protecktion relay /DC-safety kit from Velleman K4700 inside, actually i allready got the kit.

But I was woundering, what they do in normally amps, for avoiding theese, also i would like to connect my new sound-card, through it. When i turn my computer off/on, it could be very dangerous right !!! - any suggestions ?

[Mad_K]

Regarding the turn on transient, there is a chap, easy and very good working solution: Turn the preamp on before the poweramp. Reverse procedure when powering down.

[moe29]

Mads - that's what i do!

i think if you use P1 and P2 in the circuit, you can turn
them all the way down before turning on.

i still haven't put my BOSOZ in a case yet because i've
been to busy listening to it! ...just the hazards of
DIY i guess



m.

P.S. am i the only one who's ever built the BOSOZ using
all the pots like in the article? The amount of control you
get with them is really cool - tweaks that really work
Thanks once again Mr. Pass!

[Mad_K]

Originally posted by moe29



P.S. am i the only one who's ever built the BOSOZ using
all the pots like in the article?

quess so...

(The DACT's are a liiiiiittle biiiittle too expensive to put everywhere)

BTW, I'm building a bridged OPA549 power amp that my BZLS will get the pleasure of driving.

[moe29]

i'm just using the Clarostat pots from digi-key. Having essentially
two mono pots for each channel is a little interesting when
adjusting the volume, but i feel it doesn't pose any huge
problem.

In the end i think i'd like to get a DACT for the P3-4 combo, since
that's what i use for every day volume. Once P1-2 are set for
your signal source level you can leave them be. (if like me you
have one sorce, a CD-Player)


m.

[DavidMM]

Jesper,

Since you are using your BOSOZ in the unbalanced mode, to achieve a gain of 10, you might want to lower R15 to 220 ohms.
For the balanced version, the 430 ohms will give you the gain of 10dB. But simulation shows that for the unbalanced, 220 ohms will give you 10dB.

I have also experienced the high heat and agree with the above posts. The resistors can get to 90C without much problem.

Dave

[lykkedk]

I just finished, replacing my small heatsinks, on the PSU, tomorrow i will try to fire it up again. !!!

BTW. any suggestion, for turn off/on tumbs ?

Hmmm.... I was woundering howto make an stereo 5 Kohm volume-pot, with 1% Resistors, in an 2pole 11step - switch.

[ElectroNick]

Hi Jesper,

i've got my BETA version of the BoSoZ working too !
only problem i have is the difference in output voltage on the hot and cold output, when using unbalanced input.
What value you got on outputs ? Also different or nice equal values ?

Input : 2 Vtt (1000Hz sine)
Output HOT : 6 Vtt
Output Cold : 5.2 Vtt

Can't be right
Ajusting gain with P5 won't help much. Should i place an extra pot on the HOT output ???
Any tips ???

Grtz,
Nick