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post #166 of 570

I finally got around to getting the plates printed for my pimeta, and here's the results:

 

front back

 

I only wish I had gone with some larger knobs, as the alignment pins on the crossfeed and volume shafts are visible. But I'm fine with that!

post #167 of 570

Nice build.  Where / how did you get the plates printed?

post #168 of 570
Quote:
Originally Posted by tcpoint View Post

Nice build.  Where / how did you get the plates printed?


I sent them to a metal etch company in my city. Just provided him with a pdf of the design, as well as dimensions of the plate... the case is a Hammond case.

post #169 of 570

 

My build is finished. Pix:

100_2149.jpg picture by weldnrod

100_2150.jpg picture by weldnrod

100_2152.jpg picture by weldnrod

100_2153.jpg picture by weldnrod100_2154.jpg picture by weldnrod

100_2156.jpg picture by weldnrod

100_2158.jpg picture by weldnrod

100_2159.jpg picture by weldnrod

 

Opamps are AD8066/65. C2's are 470uF/25V FM's; 16mm tall and they fit. Barely.

Signal wiring is SPC.

 

iPod is 5G diyMod w/Blackgate cap's in the LOD. Now I'm on the hunt for a pair

of sealed cans. Maybe the Phiaton MS400's to match.

post #170 of 570

Very nice! The red case matches your red iPod :D

post #171 of 570

Quote:

C2's are 470uF/25V FM's; 16mm tall and they fit. Barely.


Sweet.  I guess you didn't bevel the board edges to help with this?

post #172 of 570



 

Quote:
Originally Posted by tangent View Post


Sweet.  I guess you didn't bevel the board edges to help with this?



Nah. Didn't need to.

post #173 of 570

Wow, truly nice stuff. I am kicking myself for not getting mine done already......I've had the PCB for about 4 months now.

Just now getting a digikey order made up. I should tell you that the one 3.5mm jack listed from digikey on the BOM (the high quality one) is no longer available.

 

My plan is to try to make the best sounding portable I can, using the standard case (of possibly one without the 9v compartment) and use the biggest li-po battery pack I can get to fit. 4 cells should give ~16.8v fully charged, and ~12v at the low voltage cut-off. I am wondering if the OPA627 will work ok with those figures? (I'm thinking they will).

Opamp recomendations and biasing options for the *best* sound are greatly apriciated!

 

I know a 14.8v 500ma pack will fit, as i have those cells and thay are almost exactly the same size as a 9v battery, but looking at the case, i may be able to go with a bit wide cell and bumo it up to 800-1000ma.

 

I have a mini3, and love it, can a pimeta be built to sound even better?

 

now to deside on resistors......

post #174 of 570

Hmmm, I am wondering what the best way to byass the opamps is.

 

with the options available, is there a prefered method? is there any detriment to using CRD's instead of resistor's/trim pot?

 

I am trying to keep the bulk down, so using the smallest components possible on the bottom, or mounting them in the scratch pad area, is what i want to do.

 

My idea here is that if I can leave a large portion of the top of the board free of components, I can use this area for a stack of lipo cells.

 

Honestly, I'm starting to consider buying a couple extra boards and build a couple of versions......

 

Love this sesign, as far as tweek-ability anyway. can't wait to hear it!

post #175 of 570

"The maximum safe output current for this buffer is 300 mA, and the output current limit increases as the resistor value increases, so the smallest safe value for R11 is 667 times your power supply voltage. These formulas are based on single-voltage power supplies, so if your power supply is 24 V, use 24 for V+, not 12, as you would if it were referring to the ±12 split supply. This is why the formulas above differ from the ones in the datasheet, by the way; National’s formulas assume a split supply"

 

sorry for all the questions. not quite a nood to DIY, but new enough that i know its better to ask then make an assumption.

I'm trying to understand this, as the way i read it it sounds kinda contradictory to itself.

 

So if I undersand correctly, to keep the output current limmited to the "save 300ma" level, I need to choose a value that is 667xV+, a higher value resistor will allow the buffer to exceed 300ma?

 

So, with a 16.8v battery, i need to select a value for R11 of ~ 11.3k-11.4k?  a larger value will allow more than 300ma from the opamp if output is shorted, and a lower value will limmit the amount of current available to drive headphones?

 

Hope I have this right. thanks

 

post #176 of 570
Quote:
Originally Posted by H22 View Post

 I should tell you that the one 3.5mm jack listed from digikey on the BOM (the high quality one) is no longer available.

 

 



     Slightly new number: http://search.digikey.com/scripts/DkSearch/dksus.dll?lang=en&site=US&WT.z_homepage_link=hp_go_button&KeyWords=cp5-43502pm-nd&x=23&y=22

post #177 of 570

 

Quote:
 My idea here is that if I can leave a large portion of the top of the board free of components, I can use this area for a stack of lipo cells.

 

You could just leave the "Class A" suffs out.

I built one a while back with a "stealthy on off switch" for that and the difference was very subtle.

 

 

switch.jpg

 


 

post #178 of 570

 

 

Quote:
Slightly new number

 

 

Thanks, funch, fixed.
 

Quote:
Originally Posted by H22 View Post

should give ~16.8v fully charged, and ~12v at the low voltage cut-off. I am wondering if the OPA627 will work ok with those figures?

 

Yes.

 

Quote:
Originally Posted by H22 View Post

Hmmm, I am wondering what the best way to byass the opamps is.

 

with the options available, is there a prefered method? is there any detriment to using CRD's instead of resistor's/trim pot?


What, pray tell, are you talking about?

 

The only "bypass" on the op-amps is the bypass caps, C3 and C5.

 

It sounds like you're talking about class A biasing instead, but the docs don't talk about CRDs for this, so I don't see why you describe it as an option, as if you're being made to choose.  There's only one standard bias circuit: Q1-4, RBIAS, RBLIM and friends.
 

Quote:
Originally Posted by H22 View Post

a higher value resistor will allow the buffer to exceed 300ma?


No, the greater the resistor value, the greater the current limiting.  You may want to look at page 16 in the LMH6321 datasheet.

post #179 of 570

 

Quote:
 What, pray tell, are you talking about?

 

The only "bypass" on the op-amps is the bypass caps, C3 and C5.

 

It sounds like you're talking about class A biasing instead, but the docs don't talk about CRDs for this, so I don't see why you describe it as an option, as if you're being made to choose.  There's only one standard bias circuit: Q1-4, RBIAS, RBLIM and friends.

 Um..... wow, thats what i get for trying to post while im at work doing 3 other things!

Yes, I was asking about biasing. I re-read the assembly notes and think I have a little beter understanding, I thought the CRDs could be part of the circuit, as in some other amps (B22, Lisa3). but as i understand it now, one would just use a CRD in place of a resistor to assure no LED dimming?

 

 

Quote:
 

You could just leave the "Class A" suffs out.

I built one a while back with a "stealthy on off switch" for that and the difference was very subtle.

 Yes, but I did a little experiment with express PCB last nite, and a SOT 23 (2n3904) could be mounted on the bottom of the board using the TO-92 through holes as pads. The SOT 23 would be mounted, but oriented at a right angle to what would look "normal"

 

 

Any sugestions on good 1206 sized resistors? thick film or thin film or other? metal film in  1206 are very pricey, and i would use them in the audio path, but they are very limmited in what values are offered.

 

 

                                                                             


Edited by H22 - 8/19/10 at 9:51am
post #180 of 570

Yes, that's one use for CRDs.

 

There are lots of other ways you can mod the standard PIMETA v2 circuit to make use of CRDs.  If you want feedback on circuit mods, best to post new schematics instead of just proposing ideas in prose, since there are no standard options here to refer to to make sure everyone's on the same page.

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