What's the effect of keeping it at high? And does it produce a different output?

higher gain implies higher multiplication factor. The signal is simply louder.

So it increases the volume? That's it?

Voltage swing is increased. Useful for high impedance headphones, which you think is too soft with low gain. Higher gain would also amplify the noise, so keep it low if you can.

Yes, you see, Vout = Vin * Av (Av = gain). The higher the Av, the higher the output is.

The reason why you should keep it as low as possible is because:

1) Volume pots are more linearly matched between channels at higher levels. So when you need higher volume with lower gain, you end up turning the volume knob more towards the higher level. If you have high gain, a tiny twist of the volume knob would have given you too much volume.

2) Lower noise.

3) Higher gain means you risk clipping the output because most people these days listen too loud.

4) If I can live with a gain of 1 for almost every sources with my HD650, most of you with anything higher than that is really listening too loud. That's going to kill your ears.

Culprit found for the hiss. My metal film resistors are new and they come with tapes. The adhesive material remain stuck on the leads. Used my finger to scrape of the adhesive and it's fine. I also added rail to rail capacitors (cheap 100uF electrolytics). DC offset is very healthy@0.1mV. No hiss at all.

Now the hard part comes, how to improve the amp to ensure that the output of the amp is definitely better than unamped.

The objective of the amp is to improvise CMOY-based amp into something bigger, bolder, better.

and then finally you end up building a triple channel PPA V2/M3.

trust me I've walked this path before and it's exactly like this.

And then you waste many years reading books in hopes of one day you can finally design a fully discrete amplifier that you like using complex topologies.

EDIT: If you're really serious about building stuffs, I have a few pint boards that I can give it to you for free. They are fully SMD though.



This post has been edited by LittleGhost: Dec 28 2010, 10:27 PM

I just want to build a dual mono CMOY if possible the coming months...before aggravating myself building a DIY single tube amp

Even if it sounds bad, it still can bring a bit of shine in the room

Fucuk, the buzz suddenly came back by itself. Arrgh

aiyo so marfan. If you have prior soldering experience, just get a compact tube hybrid and be done with it. CMOYs really a waste of time.

I've estimated around RM500-600 for a wholesome package.


let's assume your layout is perfect, have your considered maybe it's due to cheap potentiometer?

No pots implemented yet. I plan to control digitally after I am done with the microcontroller.

It is indeed poor connection. Took out the resistors and cleaned the leads, then back to normal. Sigh

Perhaps I should really solder them onto PCB.

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Added on December 28, 2010, 11:19 pmOoh interesting! Tell me more about it

This post has been edited by mengsuan: Dec 28 2010, 11:19 PM

it's on tangent's site.

Just dig around for it. It was discontinued the last time because AD8397 was really hard to use.

You can substitute the ground with something else though

Alright I will check it out first.

Goodness, the breadboard is already so messy. http://twitpic.com/3kk7k8

Lol...the CMOY is to regain some of my rusty soldering skilz although I'm not at all a fine solder guy...I used to play around with my guitar, taking out and putting back in the pickups and adding/replaced some of the pots and resistors just to change the sound a little...

the RM500-600 does it includes the PSU

The regulators and the multiplier circuit is already in the PSU, so you only have to spend RM30 to get a teletron AC to AC adaptor.

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Added on December 29, 2010, 12:01 amleads too long. Antenna for RFI.

This post has been edited by LittleGhost: Dec 29 2010, 12:01 AM

Haha, the components are expected to be on PCB later on so I didn't cut them off yet.

All tests was done on a lousy Edifier clip on headphone. After confirming a DC offset of only 0.6mV, I'm hooking up to my Senn HD555. Honestly, I think it is better than my X-Fi Titanium unamped for the vocal clarity.

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Added on December 29, 2010, 2:18 amNow the amp hums when the input are left hanging. Humming stops when plugged into a source or when the input are grounded. I haven't exactly noticed that the amp would hum when not connected to source earlier. Not normal I guess?

This post has been edited by mengsuan: Dec 29 2010, 02:19 AM

Thanks for the explaination guys. I only need high gain if the headphone is too soft right? Half the volume on the amp is very loud already for my Alessandro MS1i at low gain

So gain is basically increasing the volume, not that much on the quality (or not at all?)


Btw, quote from GoVibe's thread
This post has been edited by FaezFarhan: Dec 29 2010, 03:45 AM

I'll tell you this. Most people are misinformed or ignorant about how these stuff works. As i've mentioned earlier, simply keep it as low as possible.

You only need high gain if you have a ridiculous source with very low output (which is very rare in these times).

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Added on December 29, 2010, 11:35 amit's normal because without a source connected, the high impedance input picks up all kinds of noise.



This post has been edited by LittleGhost: Dec 29 2010, 11:35 AM

The hum is quite loud. As loud as music

3.5mm jack have contact switches, I could ground the input whenever interconnects are not inserted. But problem comes when the interconnect is inserted but not into the source. I cannot be having such an embarassing amp.

I feel the only way to tell, is to solder it at least to a perfboard or stripboard. The connection is too wanky on breadboard

I see, thanks a lot bro. You've been really helpful Mengsuan too