O2 LiPo Daughterboard - Page 2 - diyAudio
Go Back   Home > Forums > Amplifiers > Headphone Systems

Headphone Systems Everything to do with Headphones

Please consider donating to help us continue to serve you.

Ads on/off / Custom Title / More PMs / More album space / Advanced printing & mass image saving
Reply
 
Thread Tools Search this Thread
Old 19th June 2013, 07:36 PM   #11
diyAudio Member
 
gastro54's Avatar
 
Join Date: Nov 2003
Location: Atlanta, GA
Nice points, Amperage.

The adaptive regulation is interesting. What are you using in the feedback loop to prevent the DC-DC output basically toggling very fast at audio frequencies if the headphone output voltage is swinging above/below 3.5V? There would have to be some sort of envelope detector with hysteresis built in I would think...
__________________
Bipole Transmission Line TangBand 871s
  Reply With Quote
Old 19th June 2013, 08:33 PM   #12
diyAudio Member
 
Join Date: Mar 2013
Quote:
Originally Posted by gastro54 View Post
Nice points, Amperage.

The adaptive regulation is interesting. What are you using in the feedback loop to prevent the DC-DC output basically toggling very fast at audio frequencies if the headphone output voltage is swinging above/below 3.5V? There would have to be some sort of envelope detector with hysteresis built in I would think...
A diode prevents negative voltages from discharging the circuit and a small capacitor charges and keeps the mosfet turned on for a short period after the voltage falls coming from the headphone output. The value of the capacitor and circuit leakage will obviously change the "on" time but in my particular application it holds the higher voltage level for approximately 5 seconds before the mosfet turns back off. I posted the circuit a while back in this thread and a later addon that gave a visual indication if it was operating in low or high power mode (power light pulses on and off when in low power mode).

Audio controlled voltage mod.

I've been running the circuit in a couple of amps for a while and measured the output on the scope looking for odd transients from the voltage shift. At worst from dead silent to a really loud burst there is a bit of clipping on the first half of the wave while the voltages come up from the DC-DC converter but it's inaudible. During normal listening there generally isn't such abrupt volume changes and the voltage shifts well in time to prevent clipping of any sort.
  Reply With Quote
Old 19th June 2013, 08:36 PM   #13
ryuji is offline ryuji  United States
diyAudio Member
 
Join Date: Feb 2011
Location: massachusetts
I got most of the parts in but i will need to design and have a pcb fabricated to do testing. I will work on that on and off over the next few weeks as i get time to do so. Meantime i have a soundblaster ZxR coming later this week that by chance has a tpa6120 so i will get to try out just how well it can run my high impedance headphones and i can go from there in my designs, perhaps instead of a upgrade for the o2 i will be essentially building a 6120 amp

really cool feedback circuit you got there amperage

Last edited by ryuji; 19th June 2013 at 08:40 PM.
  Reply With Quote
Old 19th June 2013, 08:44 PM   #14
diyAudio Member
 
Join Date: Mar 2013
Quote:
Originally Posted by ryuji View Post
I got most of the parts in but i will need to design and have a pcb fabricated to do testing. I will work on that on and off over the next few weeks as i get time to do so. Meantime i have a soundblaster ZxR coming later this week that by chance has a tpa6120 so i will get to try out just how well it can run my high impedance headphones and i can go from there in my designs, perhaps instead of a upgrade for the o2 i will be essentially building a 6120 amp
I quite enjoy the sound from my 6120 amps. It's certainly not the easiest on power consumption but it's capable of enough power output to brute force even the greediest of headphones. One modification I did make vs the recommended circuit configuration in the datasheet was to use 5ohm output resistors.. I haven't run into any stability issues at all with a number of diff loads and it's a much more acceptable output impedance for low resistance headphones.
  Reply With Quote
Old 19th June 2013, 08:50 PM   #15
ryuji is offline ryuji  United States
diyAudio Member
 
Join Date: Feb 2011
Location: massachusetts
reading through the datasheet earlier, i recall reading that the output resistors were to protect the 6120 from capacitive outputs and short circuits. since the datasheet cites using it as a pre-amplifier this is for the situation where the following stage is protected from dc offsets using a input capacitor, and for headphone usage can be reduced to 1 ohm or even omitted?
  Reply With Quote
Old 19th June 2013, 08:58 PM   #16
diyAudio Member
 
Join Date: Mar 2013
Quote:
Originally Posted by ryuji View Post
reading through the datasheet earlier, i recall reading that the output resistors were to protect the 6120 from capacitive outputs and short circuits. since the datasheet cites using it as a pre-amplifier this is for the situation where the following stage is protected from dc offsets using a input capacitor, and for headphone usage can be reduced to 1 ohm or even omitted?
I haven't tried completely eliminating it. The 6120 is a high speed op amp and as such is pretty sensitive to layout and oscillation issues. The chip itself has output short circuit protection so the resistors are mainly to protect it from load capacitance (even headphones have some small amount of capacitance). You can always add pads for the resistors on the pcb layout and bridge them just to test.
  Reply With Quote
Old 20th June 2013, 06:46 PM   #17
ryuji is offline ryuji  United States
diyAudio Member
 
Join Date: Feb 2011
Location: massachusetts
Just sampled my headphones on the integrated tpa6120 amp in my sound card. plenty of volume. I think i might be indeed be making my project tpa6120 based instead of o2.
  Reply With Quote
Old 20th June 2013, 08:26 PM   #18
diyAudio Member
 
Join Date: Mar 2013
Quote:
Originally Posted by ryuji View Post
Just sampled my headphones on the integrated tpa6120 amp in my sound card. plenty of volume. I think i might be indeed be making my project tpa6120 based instead of o2.
That soundcard is running the 6120 Very conservatively also. If you check the specs here you can see even with 600ohm load it's rated for 2Vrms output. Not sure how they claim 80mW output into 600ohm. The tpa6120 is capable of it but when driven at +/- 12v. 2Vrms isn't going to do it

Creative Sound Blaster Z Sound Card Review | techPowerUp
  Reply With Quote
Old 20th June 2013, 11:16 PM   #19
ryuji is offline ryuji  United States
diyAudio Member
 
Join Date: Feb 2011
Location: massachusetts
Quote:
Originally Posted by Amperage View Post
That soundcard is running the 6120 Very conservatively also. If you check the specs here you can see even with 600ohm load it's rated for 2Vrms output. Not sure how they claim 80mW output into 600ohm. The tpa6120 is capable of it but when driven at +/- 12v. 2Vrms isn't going to do it

Creative Sound Blaster Z Sound Card Review | techPowerUp
that's running a MAX97220A
the ZxR is completely different hardware
  Reply With Quote
Old 20th June 2013, 11:43 PM   #20
ryuji is offline ryuji  United States
diyAudio Member
 
Join Date: Feb 2011
Location: massachusetts
Creative Sound Blaster ZxR Review - Closer Look

contrast between the two pcb's is interesting. the Z looks like barely anything on it in comparison =P

The software has a high gain setting, but specifically says not to use it on anything but 600 ohm headphones, and that the other setting is for up to 300 ohms(mines closer to 300 ohms)

Last edited by ryuji; 21st June 2013 at 12:01 AM.
  Reply With Quote

Reply


Hide this!Advertise here!
Thread Tools Search this Thread
Search this Thread:

Advanced Search

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Trackbacks are Off
Pingbacks are Off
Refbacks are Off


Similar Threads
Thread Thread Starter Forum Replies Last Post
LiPo batteries, help separating facts and myths Peter Pan Everything Else 16 5th February 2012 10:44 PM
Solar powered (charging) circuits with LiPo/LiFe/Li-ion battery Narkki Construction Tips 3 15th November 2011 08:51 AM
LiPO battery charging Atilla Power Supplies 2 4th September 2009 05:37 AM
What DIP plug to use for a daughterboard? leadbelly Parts 1 27th October 2004 07:53 AM
standard daughterboard size for an unsiversal preamp sonnya Solid State 7 9th January 2004 11:33 AM


New To Site? Need Help?

All times are GMT. The time now is 05:52 PM.


vBulletin Optimisation provided by vB Optimise (Pro) - vBulletin Mods & Addons Copyright © 2014 DragonByte Technologies Ltd.
Copyright 1999-2014 diyAudio

Content Relevant URLs by vBSEO 3.3.2