Go Back   Home > Forums > Amplifiers > Solid State

Solid State Talk all about solid state amplification.

Please consider donating to help us continue to serve you.

Ads on/off / Custom Title / More PMs / More album space / Advanced printing & mass image saving
Reply
 
Thread Tools Search this Thread
Old 10th September 2003, 06:27 PM   #11
tiroth is offline tiroth  United States
diyAudio Member
 
Join Date: Dec 2001
Location: Pittsburgh, PA, USA
It may not seem like much but the LED and bleeder resistors are wasting valuable battery life. For SLA I wouldn't bother removing them, but those 9V get expensive fast.
  Reply With Quote
Old 10th September 2003, 07:11 PM   #12
00940 is offline 00940  Belgium
diyAudio Member
 
Join Date: Sep 2003
Location: Paris
Well, I've no problem removing the led, it was just cool.

The choice between a voltage divider and the ps below is more tricky. If a battery went to fail, we'd have a severe problem of voltage balance. I know this way is used in the grado ra-1 but most diyers on headfi or headwize would use a setup like in the two posts above. Is it too much of a fear ?
Attached Images
File Type: jpg ps2.jpg (18.8 KB, 557 views)
  Reply With Quote
Old 10th September 2003, 07:59 PM   #13
diyAudio Moderator Emeritus
 
jean-paul's Avatar
 
Join Date: Sep 2002
Location: Germany
The input caps should be 1 uF instead of 0.1 uF.
__________________
It's only audio. Official member of the Norske Brillegeit Gang.
  Reply With Quote
Old 10th September 2003, 10:57 PM   #14
diyAudio Member
 
Join Date: Mar 2001
Location: Brazil
Quote:
Originally posted by 00940
Well, I've no problem removing the led, it was just cool.

The choice between a voltage divider and the ps below is more tricky. If a battery went to fail, we'd have a severe problem of voltage balance. I know this way is used in the grado ra-1 but most diyers on headfi or headwize would use a setup like in the two posts above. Is it too much of a fear ?
Yes, using a continuously lit LED with 9v batteries will drain them. You may use blinking types.

If you use batteries you may also think on some way to know when they get below a certain voltage. Most modern ICs work down to +/-4.5 or less though, but you will lose some dynamics.

A voltage divider is certainly a good option, but it's far from simple. Now that you put capacitors at the input and output you may go back to it.

The chance of a battery failing is almost as likely as an AC supply failing. A battery should go down slowly, and both at the same time. What you should never do is not putting fresh same type batteries for BOTH units when you change them. Same type and same charge.

In any case DC is a seriosu problem in two cases:

1) If you send DC to an MM or MC cartridge

2) If you send DC to a power amp.

That doesn't mean you should noe prevent that.

Personally I think you should only use blocking capacitors at the power amp input and use low offset chips all along the preamp chain.


Carlos
  Reply With Quote
Old 11th September 2003, 05:39 AM   #15
Werner is offline Werner  Europe
diyAudio Member
 
Join Date: Jan 2002
Location: Belgium
Quote:
Originally posted by jean-paul
The input caps should be 1 uF instead of 0.1 uF.
The input caps should go, as we trust it
that the sources are reasonably free of DC.

Please use JFET-input opamps that are known stable at unity gain.

With a better-controlled power supply you could drop the output caps, but I guess that with batteries this could become a risky business.
  Reply With Quote
Old 11th September 2003, 08:20 AM   #16
diyAudio Moderator Emeritus
 
jean-paul's Avatar
 
Join Date: Sep 2002
Location: Germany
Quote:
The input caps should go, as we trust it
that the sources are reasonably free of DC
It can be dangerous to trust unknown things.
__________________
It's only audio. Official member of the Norske Brillegeit Gang.
  Reply With Quote
Old 11th September 2003, 08:33 AM   #17
Werner is offline Werner  Europe
diyAudio Member
 
Join Date: Jan 2002
Location: Belgium
Sure. But the source is known. Either a commercial source with belts-and-braces protection (made in Japan-style), or else a DIY source that is definitely known and where it is your very own responsibility to keep the output free of DC.

And anyway, given the presence of the output coupling caps, the input ones do nothing useful once JFET opamps or opamps with nulled biased current are used.
  Reply With Quote
Old 11th September 2003, 09:30 AM   #18
MBK is offline MBK  Singapore
diyAudio Member
 
Join Date: Apr 2002
Location: Singapore
Forgive me, but the 0.1 uF caps for the PSU I hope do go to ground and not in series with DC...?
  Reply With Quote
Old 11th September 2003, 01:36 PM   #19
cdl is offline cdl  Denmark
diyAudio Member
 
Join Date: Aug 2003
Location: Copenhagen
00940, you might want to consider putting a little bit of gain in to compensate for loss in the pot (depends on the sensitivity of your power amp).

Furthermore, I would heavily recommend getting a couple of opa627's as free samples from TI - they are very nice sounding, and expensive... but who cares when you get them for free?
Separating the two channels in distinct chips should give better channel separation.

I don't really think you need those coupling caps - as long as you are careful with changing the batteries, and remember to monitor for DC every time you change something. Newer sources do not output DC, but measure for yourself!

I have the prototype shown here playing, and it is pleasant (with opa627 instead of op37). You might not want the "cheap" class A biasing 15k resistor from output to -, though... and you can make do with 100 ohm output resistor instead of 470.

Your RF input filter is probably a good idea - do keep it.

Despite a small +/- voltage imbalance in the power supply that I haven't got around to fixing yet, DC levels are below 0,1 mV measured with my DMM. My power amp doesn't have a problem with that at all (although it is DC coupled, yes!).

cheers - cdl
  Reply With Quote
Old 12th September 2003, 05:30 PM   #20
00940 is offline 00940  Belgium
diyAudio Member
 
Join Date: Sep 2003
Location: Paris
I forgot those samples well, it's repaired, I've a pair of op627ap and a pair of buf634p on their way from TI, no questions asked. I also took a pair of lm317/337 voltage regulators.

With those pieces saved, I could try something slightly better. I'm planning to use the zero distortion power supply. No more problems about batteries. For the rest, I could go for this (pcb perhaps still available from macura) :

Click the image to open in full size.

Thanks a lot to all of you, your comments helped me a lot.
  Reply With Quote

Reply


Hide this!Advertise here!
Thread Tools Search this Thread
Search this Thread:

Advanced Search

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Trackbacks are Off
Pingbacks are Off
Refbacks are Off


Similar Threads
Thread Thread Starter Forum Replies Last Post
Intrest Check : Pretty Simple Digital Preamp / Volume Control rhysh Chip Amps 69 20th December 2008 06:14 PM
Check: Simple Circuits Devil_H@ck Parts 19 9th June 2004 02:54 PM
check my simple circuit svokke Solid State 5 25th March 2004 06:19 PM


New To Site? Need Help?

All times are GMT. The time now is 08:13 PM.


vBulletin Optimisation provided by vB Optimise (Pro) - vBulletin Mods & Addons Copyright © 2014 DragonByte Technologies Ltd.
Copyright 1999-2014 diyAudio

Content Relevant URLs by vBSEO 3.3.2