[skyskraper]

so i've been reading around a bit and im looking to have a crack at a headphone amp after ive done my urei replica phono pre. im just not sure which one would be the better option. obviously pimeta and cmoy are the two im looking hardest at coz im such a newbie at this diy audio game. id rather not just say "which should i build a pimeta or cmoy" because id preffer to learn a bit more about the reasons why i should choose one over the other.

i have no concern with battery life because it will be part of a larger project that will be powered from a wall wart.

my concerns mainly are: ease of component availability in australia, HIGH headroom (will be used in lots of demanding situations by lots of people), good sound quality (yes yes i know the parts i use are likely to have more affect on this then just the design), ease of soldering and pcb creation, and lastly lots of versatility to possibly incorporate a 3 band eq into it.

can someone point me in the right direction to learn more about the different circuitry or tell me a bit more about each design (rather then what ive read in headqize's archive and on tangents site), the sort of design they are, and how i can figure out the advantages and disadvantages of similar designs in the future...

thanks

SS

 

[flecom]

if your looking for a nice wall powered solution you may want to look @ the PPA also, very nice sounding amp and fairly easy to build i guess, its a bit more expensive than the Pimeta tho since it uses a whopping 12 buffers

is this the first time you solder? if your a total beginner i would recommend the CMOY as if you screw up you only lost at the very most like $40~60....

 

[skyskraper]

well i thought against ppa due to the fact 1) im not very experienced with making diy audio stuff. 2) tangents page reccomended the other two for newbies. 3) it's a bit more expensive then the other two and more complex.

im relatively new to soldering but I have done a LOT of it in the last month or so. repairing and replacing stuff on technics turntables a lot lately. i'll be getting into replacing led's on them for a charge shortly

i figure i should be able to handle a cmoy or pimeta...

 

[flecom]

start with the cmoy, easy to build, and a great little amp... from there if you are still not 100% then do a PIMETA, if you feel that you have progressed do the PPA

the cmoy always makes a great portable headamp

 

[skyskraper]

yah i guess if im not happy with the cmoy for my application i can always convert it to battery powered and have a nice little headamp for my mp3 discman

 

[xtreme4099]

suprisingly there is a lot newbies who have started with the ppa as their first amp and made it work on their first try, besides you got a nice big community of diyer's building them everyday, so just ask. It is a paint by numbers amp, all the parts and values are labeled for you, same with pimeta as well, you can start their as well, and move up if youd like, although ive not heard the pimeta.

 

[skyskraper]

cool ill have a think when im away for the next couple of weeks and decide when i get home

which amp has the larger headroom tho? i understand that using ic's you will never have an unlimited supply, but it's essential for me to have as much as possible, less places to distort = better

 

[tangent]

Quote:

which amp has the larger headroom tho?

Probably the PIMETA, but it's pretty much academic.

The maximum output voltage depends on the supply voltage, yes? So let's call the highest supply voltage for op-amps 30V. There are exceptions either way, but it's a common number. An ideal op-amp (or buffer) would be able to swing 30V peak-to-peak signals, or about 10V RMS. (RMS for sine waves = p-p/2.828)

There are two limiting factors that prevent real op-amps and buffers from swinging clear to the rails: design and current.

As for design, most chips aren't designed to go rail-to-rail. There's some minimum distance, typically 1-3V to either side. Let's be pessimistic and reduce our 30V p-p ideal maximum to 24V.

So why does the PIMETA have greater headroom than the CMoy? That brings us to the second limiting factor, current. Buffers are designed to drive higher loads with less sag than op-amps. You'll probably have less than 1V of total voltage sag in a headphone amp due to the buffer, but in the same situation a CMoy amp might sag a total of 2V. This is significant at low supply voltages, but that's not your situation.

Let's take the CMoy situation and take 2V away from our 24V p-p number. That's nearly 8V RMS. I assure you, there are very few headphones that need anywhere near 8V RMS to sound loud. There's only one I can think of off the top of my head -- the AKG K1000 -- and that's only because it's designed to be run from a power amp, not a traditional headphone amp. Even with that one 8V is going to be very loud. A great many "normal" headphones would come apart if you fed them 8V long enough.

 

[skyskraper]

cheers! very informative post.

i will be driving (personally) technics rpdj1200 headphones and sony 7506's, others will be using sony 700's, sennheiser hd25's and probably some pioneer hdj1000's. none of these need anywhere near 8v rms

ill look over the info on your site whilst im away (got it printed for the flight) and make my decision when i come back