[fortney]

If you are using low impedance phones and a source of reasonable power output (e.g., computer or portable CD player...) I would suggest a gain of 2 or 3. With a gain of 11 you will barely move the volume control and the audio will be blasting. If the stereo volume control is not perfectly matched you may find that at low volume one channel is noticeably louder than the other.

I like opamp OPA2227. Definitely use a socket mount for the opamp.

Low impedance headphones don't need an amp, but I built several for the entertainment value anyway. Be careful not to damage your hearing.

F

 

[nate911]

Quote:

Originally Posted by fortney /img/forum/go_quote.gif If you are using low impedance phones and a source of reasonable power output (e.g., computer or portable CD player...) I would suggest a gain of 2 or 3. With a gain of 11 you will barely move the volume control and the audio will be blasting. If the stereo volume control is not perfectly matched you may find that at low volume one channel is noticeably louder than the other. I like opamp OPA2227. Definitely use a socket mount for the opamp. Low impedance headphones don't need an amp, but I built several for the entertainment value anyway. Be careful not to damage your hearing. F

Hmm ok. I may do the gain at 11 then experiment with 6 and 3 to see how those work out. 11 seems the easiest for troubleshooting initially.

 

[Spacehead]

Gain 11 can be very noisy, you might not understand why it keeps such hard hiss. I need to lower gain to 2 - 3 to get noise free amplifier. I have 32 ohm Sennheiser HD438.

It is very annoying to remove that r4 resistor. Instead soldering it to the board you could use sip socket strips, 4 pins together and solder only 1 and 4 , then insert R5 resistor there. Then you can quickly swap resistors. I know, it is very hard to keep the board clean if you tweak it a lot.

here is picture of the strip http://media.digikey.com/photos/Mill...-41-001000.JPG

If you want to balance the input currents for "nasty" op amps,
with 140K input resistor (R2) , R4 can be 470K ohm, R3 200K , then you have gain of 3
even LM6172 can work with these resistor values. It will give some offset, like 30-60 mV , I guess.

 

[nate911]

Quote:

Originally Posted by Spacehead /img/forum/go_quote.gif Gain 11 can be very noisy, you might not understand why it keeps such hard hiss. I need to lower gain to 2 - 3 to get noise free amplifier. I have 32 ohm Sennheiser HD438. It is very annoying to remove that r4 resistor. Instead soldering it to the board you could use sip socket strips, 4 pins together and solder only 1 and 4 , then insert R5 resistor there. Then you can quickly swap resistors. I know, it is very hard to keep the board clean if you tweak it a lot. here is picture of the strip http://media.digikey.com/photos/Mill...-41-001000.JPG If you want to balance the input currents for "nasty" op amps, with 140K input resistor (R2) , R4 can be 470K ohm, R3 200K , then you have gain of 3 even LM6172 can work with these resistor values. It will give some offset, like 30-60 mV , I guess.

Yeah I didn't understand all of that

Which socket strip should I get from Mouser (since I'm ordering my parts from there)? Do I just need to solder that on and just take the R5 on and off? or what...I'll have to do some research I guess hah.

Until I get some new IEMs, I'll be using JVC marshmallows..which have an impedance of 14ohms :S. Also have some Yuin PK2s that are semi-broken...gotta re-do the plug for those. Looking to get an RE0 or something in the future. So pretty low impedance.

What gain do you think I should start out with, then?

 

[Spacehead]

Quote:

Originally Posted by nate911 /img/forum/go_quote.gif Yeah I didn't understand all of that Which socket strip should I get from Mouser (since I'm ordering my parts from there)? Do I just need to solder that on and just take the R5 on and off? or what...I'll have to do some research I guess hah. Until I get some new IEMs, I'll be using JVC marshmallows..which have an impedance of 14ohms :S. Also have some Yuin PK2s that are semi-broken...gotta re-do the plug for those. Looking to get an RE0 or something in the future. So pretty low impedance. What gain do you think I should start out with, then?

I quickly staged an example how to use socket strip for easy resistor swap.
you solder this piece you cut from a longer strip, in place of R4. You can only solder the outermost pins.

You can probably get good volume with gain of 2.

For example 310-43-164-41-001000 Mill-Max IC & Component Sockets
that would be what I found from Mouser that could fit.

 

[mewrei]

RE0's rock. And they're easy to drive so if you do choose a lower gain, you'd not be hurting for volume.

 

[nate911]

Quote:

Originally Posted by Spacehead /img/forum/go_quote.gif I quickly staged an example how to use socket strip for easy resistor swap. you solder this piece you cut from a longer strip, in place of R4. You can only solder the outermost pins. You can probably get good volume with gain of 2. For example 310-43-164-41-001000 Mill-Max IC & Component Sockets that would be what I found from Mouser that could fit.

So do you just solder the pins in the board...is the actual resistor soldered in the socket or what? (stupid question?)

Quote:

Originally Posted by mewrei /img/forum/go_quote.gif RE0's rock. And they're easy to drive so if you do choose a lower gain, you'd not be hurting for volume.

Good to know.

I'll probably go with a gain of 3...since I might use it with my AD700s also.

 

[Beftus]

The resistor isn't soldered. This setup allows for fast switching of the resistor for testing purposes. Once you've settled on a resistor value solder it.

 

[nate911]

Quote:

Originally Posted by Beftus /img/forum/go_quote.gif The resistor isn't soldered. This setup allows for fast switching of the resistor for testing purposes. Once you've settled on a resistor value solder it.

Ahh ok, thanks

that sounds like a good idea..I'll probably get the socket then.

 

[rembrant]

I have all the parts to build ten of these things. They are all in my soldering tacklebox awaiting PCBs that I have designed but yet to order. I have heard a lot of mixed things about the 2227. None the less, I bought five of those. I also have five Pcs of opa2132. I should probably get one of these put together on some proto board so I can hear for myself. I have always enjoyed my music a bit fat on the bottom. From what I have heard, both of these chips sound that way. Of the two, which would you guys say has better highs? I can't stand it when my cymbals get all wonky.

 

[nate911]

Hopefully this is my last round of questions...

What awg wire should I use to wire up the panel for the cmoy? Any particular place where I should buy it?

And what should I use for the interconnect? (source to input) I know you can make cables..but I'd rather get into that after building a few amps. Suggestions?

 

[nate911]

^Bump

 

[Mullet]

I ended up going for a 22 gauge stranded wire from the rat shack. We'll see how that works. Got most of the necessary tools gathered. Just waiting on my Mouser order. I'm going to have a read through Tangent's directions a few times. I still have no idea how to read a schematic. I figure I'll pick it up through the process. Here goes nothing...

 

[nate911]

Quote:

Originally Posted by Mullet /img/forum/go_quote.gif I ended up going for a 22 gauge stranded wire from the rat shack. We'll see how that works. Got most of the necessary tools gathered. Just waiting on my Mouser order. I'm going to have a read through Tangent's directions a few times. I still have no idea how to read a schematic. I figure I'll pick it up through the process. Here goes nothing...

Haha. I barely know how to read a schematic, if at all. You're in the same position as me

I may order my soldering equipment/cmoy parts today so let me know how it goes.

 

[nate911]

Can anybody else confirm 22 awg is good for wiring up things? And anybody know of a good place to find a interconnect from amp to source?