[krisjan]

I am new to the DIY stuff - but have decided to venture into this area - hoping to build my first amp (probably a cmoy) soon - i already purchased some equipment and 4 the moment i am just looking at an existing cmoy i purchased (eBay View About Me for biosciencegeek).

Ok so one of the issues in this whole amp is re the power supply source. After reading Op-Amp Power Supply Quality Considerations and also considering the obvious disadvantages of batteries (depleting and causing distortion) i decided to try wall-power to see if there are audible differences. I asked BSG re the wall-wart (on the site he recommends Regulated and Filtered Universal 300mA AC Adapter - RadioShack.com - is this one switch-mode?) since i live in ZA and obviously different shops here etc. He was very helpful but didn't mention that linear-regulated is the way to go for audio amps...so in the end i just took an existing ac/dc adapter intended for powering a handheld spotlight - specs 12V,300ma - i modded the plug, making sure of polarity, and tried it - it seemed great...if i turn up the volume very high (with no source coming in) i hear some noise, but this is identical to the noise with a 9v battery loaded, so doesn't seem as if (audibly) anything is added by the psu.

Then i read about the whole regulated/unregulated thing, i purchased a multimeter and did the measurements - the modded psu read much higher than the indicated spec value of 12v (about 17v) - so i suppose meaning it's unregulated...I went to the electronics store and tried to get a linear regulated psu - LOL the electronics "expert" in the shop didn't even know that you get switch-mode and linear - he didn't know what i was talking about, and i ended up buying a psu very similar to the one bsg recommends ( i think specs are exact) - it states it is regulated, but not what type. Now according to Op-Amp Power Supply Quality Considerations a good switch-mode could actually be acceptable - so i thought let me try it...result: MAN is it noisy! - i just switch the amp on and immediately there's hiss - even at low volumes - it's basically unusable - so i presume it must be aswitch-mode and then a BAD switch-mode in Op-Amp Power Supply Quality Considerations 's book...

So my q's are -
if i use an unregulated supply and i honestly can't hear any noise added - does it matter?
Could the increased voltage due to low load of the amp cause components to fail? I know the opamp (2227 in the bsg) can handle the 17v easy according to the spec, but maybe depending on the resistors/caps he used some of those might fail?

 

[Pars]

I can't think of anything in a Cmoy other than the electrolytic caps that you would need to be concerned with. Those I would say 25V would be fine. Resistors, etc. are usually good for at least 200V; most are good to 300 and higher.

 

[millwood]

Quote:

if i use an unregulated supply and i honestly can't hear any noise added - does it matter?

if you cannot tell the difference, there is no difference.

all the talks on regulated vs. unregulated, switching vs. linear, don't really matter to you if you cannot tell them apart.

I personally have used mostly unregulated for high power amps, and sometimes switching mode power supply (almost all regulated) and I am happy.

Quote:

Could the increased voltage due to low load of the amp cause components to fail?

12v vs. 17v isn't going to make much of a difference. the IC is good for 30v (assuming you used +/-15v ICs), the electrolytic caps are good typically upto 120% of their ratings, and resistors are good as long as their rated power isn't exceeded - very unlikely unless you have used some really low wattage and small resistors.

 

[tomb]

Quote:

Originally Posted by krisjan /img/forum/go_quote.gif <snip>So my q's are - if i use an unregulated supply and i honestly can't hear any noise added - does it matter? </snip>

Yes, it does ... but it's subtle and one of those things you may not notice - without very sensitive measurement - or through direct comparison. Every AC-powered supply has ripple - the question is how much. Every bit of ripple that's present - even if inaudible - means bass that's less tight, detail that's obscured. A truly quiet, linear-regulated supply will minimize ripple below what can be easily measured. The result will be higher-fidelity sound.

Whether you can distinguish that difference depends on a lot of things - your hearing, your ability to discriminate differences other than outright noise, and the PSRR (Power Supply Rejection Ratio) of the amp circuit.

 

[NelsonVandal]

Of course you don't want the sound of mains hum. A regulated wallwart costs about the same as an unregulated. Why buy an unregulated if you're not going to build a regulated supply yourself?

Focus on what matters in an audio circuit. Topology/grounding and active parts are in my oppinion much more important than power supply and passive parts. Some claim to hear a difference between different batteries and wallwarts. I don't, but I can quite easly hear the sound of different transistors or opamps. Some claim all "good" amplifiers sound the same.

Happy DIY'ing. To me it's like tasting wine or chocolate.

 

[krisjan]

Quote:

Originally Posted by tomb /img/forum/go_quote.gif Yes, it does ... but it's subtle and one of those things you may not notice - without very sensitive measurement - or through direct comparison. Every AC-powered supply has ripple - the question is how much. Every bit of ripple that's present - even if inaudible - means bass that's less tight, detail that's obscured. A truly quiet, linear-regulated supply will minimize ripple below what can be easily measured. The result will be higher-fidelity sound. Whether you can distinguish that difference depends on a lot of things - your hearing, your ability to discriminate differences other than outright noise, and the PSRR (Power Supply Rejection Ratio) of the amp circuit.

yes - look it makes sense, but i guess i either need to listen to the amp + unregulated supply and compare with batteries over time - my immediate response on a very "subtle" level would be that the unregulated supply ws better than the current battery in there, but the battery might be a little flat already, etc. Else, I may simply not be at the "level" where I can discern the audiophilic qualities mentioned...

 

[krisjan]

Quote:

Originally Posted by NelsonVandal /img/forum/go_quote.gif Of course you don't want the sound of mains hum. A regulated wallwart costs about the same as an unregulated. Why buy an unregulated if you're not going to build a regulated supply yourself?

Maybe in your country - but where I live it's very difficult to get a hold of a (linear) regulated supply - as mentioned the guy in the electronics shop didn't even know what it was...
Quote:

Focus on what matters in an audio circuit. Topology/grounding and active parts are in my oppinion much more important than power supply and passive parts. Some claim to hear a difference between different batteries and wallwarts. I don't, but I can quite easly hear the sound of different transistors or opamps.

cool yes - this makes sense to me - let me start soldering...