Caps question

[evo_lution]

Hi all
Built the power supply below(for a headphone-amp the RJM HeadClone), but i don't have any 1000uF caps, can I use some 470uF Panasonic FCs two a side giving me 940uF?

thanks

 

[jnewman]

That depends whether you put them in series or parallel. You should have them in parallel.

 

[Earwax]

HeadClone, eh?

Let us know what you think of it when you're done.

BTW, does anyone know what those LM7805 and 7905 do?

 

[flecom]

LM7805 + voltage regulator
LM7905 - voltage regulator

 

[MisterX]

Yes, you can replace the 1000uF caps with 470uf ones if you have to.

You gonna stick with the OPA2134 opamp or use something better?

 

[Earwax]

It seems strange to specify a +-12V supply, then regulate it down to +-5 volts, or am I still missing something obvious?

[edit] sorry MisterX, I hoped no one saw my earlier question before I realized why the diagram seemed confusing to me.

 

[MisterX]

Stop editing!
It's a PITA keeping up.... lol


Quote:

It seems strange to specify a +-12V supply, then regulate it down to +-5 volts, or am I still missing something obvious?

I was thinking the same thing.
Especially since the opamp he speced "works better" with more voltage in this type of an unbuffered amp.

 

[MisterX]

Quote:

I hoped no one saw my earlier question before I realized why the diagram seemed confusing to me.

All of that have email not turned on saw it anyhow.

You have a good point.... having a board layout that doesn't match the schematic doesn't help matters either does it?


Most of the schematics we see have the PSU circuit drawn separately so it's easy to get confused when you see one that isn't drawn that way.

 

[flecom]

Quote:

Originally Posted by Earwax It seems strange to specify a +-12V supply, then regulate it down to +-5 volts, or am I still missing something obvious? [edit] sorry MisterX, I hoped no one saw my earlier question before I realized why the diagram seemed confusing to me.

the +12v coming out of the toroid is not regulated... its a 2x 9v toroid, so after rectification it gives you about 12vdc unregulated... voltage regulators need usually like a 3v difference from input to ouput... soooo from 12v you can get 9vdc, and the easiest regulators to find under 9v are 5v...

if you put a bigger toroid that say had 2x 16v windings you could use + and - 12v regulators or just use your imagination

although IIRC adjustiable voltage regulators are less noisy than fixed-voltage regulators, so you may want to do like an LM317 deal paired up with a negative voltage version?

also what app are you using to make those perf-board layouts?

 

[evo_lution]

Thanks for the replies.

Quote:

Originally Posted by Earwax HeadClone, eh? Let us know what you think of it when you're done.

Earwax, i built the "Short-tail version" running on 2x 9v batteries using resistors from an old Sony TunerAmp. It only has gain of 5 because the pot is a large black Alps rated at 250ohms so its too loud. I've attenuated the signal at the headphone jack using Welwyn resistors so this obviously slightly cripples the sound quality.
My friend loaned me a Meridian 206 CD and using his Senn 600s we did A/B against a CMoy(2x OPA627s, WIMA caps,Welwyn resistors, CAT5+silver solder), no contest the CMoy is in a different class. HeadClone sounded more veiled less detailed.

 

[evo_lution]

Quote:

Originally Posted by MisterX Yes, you can replace the 1000uF caps with 470uf ones if you have to. You gonna stick with the OPA2134 opamp or use something better?

MisterX, Using the OPA2134 noticed that i listened for ages with no fatigue(using Senn PX200s) also that i would gradually increase the volume.
Swapped in AD823s(main chip+power supply) noticed more a bit more detail, maybe cleaner sound less laid back, limiting factor here could be my cans.

ps. Senn 600s on Xmas list