[pabbi1]

Yeah, probably...

BTW, anyone have an extra matched quad of fets? Might need them to help another build come online.

 

[sachu]

Quote:

Originally Posted by pabbi1 /img/forum/go_quote.gif Yeah, probably... BTW, anyone have an extra matched quad of fets? Might need them to help another build come online.

I know i had atleast a couple of quads of the J271 but gf "cleaned" up the desk..so will have to match again. How soon do you need it?

 

[pabbi1]

Quote:

Originally Posted by sachu /img/forum/go_quote.gif I know i had atleast a couple of quads of the J271 but gf "cleaned" up the desk..so will have to match again. How soon do you need it?

Couple of weeks out. Thank goodness my office is a 'no clean' zone. Once a year is plenty...

 

[luvdunhill]

I'm back.. I'll get this sorted later this week and open a thread and what not for the attenuator.

 

[Sathimas]

I just wired my LEDs and to my surprise they did not light up ...

I have unfortunately used two different kinds of LED, 2 superbright and 10 standard LEDs.
(I wanted it the other way round but messed up the two bags with the LEDs...
But even the superbright LEDs are not bright enough.)
The standard LEDs need 10mA to light, so the power supply does'nt give enough current.

Could I increase simply that current with a parallel resistor? (parallel to the 75kOhms)
I don't want to remove the power supply again from the case.

Would that work with a standard resistor or would that also have to be a 5W resistor?

 

[runeight]

Most LEDs will light at the 4-5mA passed through this circuit. Not as bright as at 10mA but still pretty bright.

 

[Sathimas]

Well mine don't ...

All LEDs are connected in series - the first and the last one are the superbright ones - which light up, all the others don't.

I just checked the data and the normal LEDs I am using here only have a brightness of 3mcd @ 10mA.
The superbright ones are made for 20mA operation and are really much brighter, think they are above 100mcd.

So I'll have to rise the current or replace all the LEDs.
Since installing and wiring took me about 2 and a half hour I'd like to try rising the current first

 

[Beefy]

Quote:

Originally Posted by Sathimas /img/forum/go_quote.gif So I'll have to rise the current or replace all the LEDs. Since installing and wiring took me about 2 and a half hour I'd like to try rising the current first

Raising the current is going to generate an extraordinary amount of heat in the LED resistors.

 

[Sathimas]

Well, if my (very dusty) physics knowlegde is right I'd have to lower the resistorvalue down to arround 30KOhms to get approx 10mA.

If thats not possible I'll have to do all the LED wiring again

 

[Beefy]

Quote:

Originally Posted by Sathimas /img/forum/go_quote.gif Well, if my (very dusty) physics knowlegde is right I'd have to lower the resistorvalue down to arround 30KOhms to get approx 10mA.

That will be a massive 3 watts dissipated by each resistor. Sure, a 5W resistor could possibly handle that heat...... but can the PCB underneath it?

When I was running the original 1.2W through the suggested 75kohm resistors, my PCB was hitting 120C. Not good.

 

[runeight]

Sathimas, sorry about this, but in addition pulling 10mA from the PS at the filter caps will drop the voltage at the input to the regulator. I don't know how much offhand but you'll have to watch for thiss too.

I am surprised that your leds don't light at all at 4-5mA. Really surprised unless you are using super high current leds.

 

[Sathimas]

I just checked the temperature (by finger) and the PCB is already quiet hot - so I'll just leave things as they are.
Thanks for your advice!

Those LEDs are just really cheap ones, I had to search a while to find the datasheet.

Something else - much more joyful: I just gave the offset/balance adjustment another try and this time it seems to work.
Maybe I just forgot to recheck the offset yesterday - i don't know...

Both channels are below 1V now since about one hour, I'll wait another one to be sure...

 

[Sathimas]

Short notice

It's alive !!!!!

From this point one there will be only down and sidegrades in headphones :-D

Thanks again everyone here, especially Alex!

(I just somehow managed to bypass my pot with my loop-in/out circuit, I really have to rethink that wiring ^^)

 

[swt61]

Quote:

Originally Posted by BoilermakerFan /img/forum/go_quote.gif Just imagine how good it would sound on vinyl via a Grado Gold or Denon DL103 cartridge on a modded RB250 tone arm in a modded Planar 3 TT through an AudioSector, TubeCAD Tetra, or Pass DIY Pearl2 phono stage.

Or a 'Colossus' TT w/highly modded RB-300, Zu DL103 and Pass DIY Pearl.

 

[M3NTAL]

Darn you analog guys! All I have is digital and a very small selection of cassettes that are from my pre-teens that are mostly garbage! Praise high end DAC's