Mini Portable Headphone Amplifier, with Discrete Diamond Buffers

cetoole · 24th May 2006, 10:12 PM

Been working on this layout for about a week so far. Features are:

DIP8 opamps for L/R
SOIC opamp for ground, either use a high current single opamp, or a low current opamp with a class B emitter-follower in its feedback loop
Bypassing on all opamps via 0805 ceramics right at the power pins to ground
1206 resistors everywhere
Discrete Diamond buffers for L/R, with crd ccs, all transistors in SOT23
2 channel design, eliminates the need to isolate the input/output jacks, and reduces current draw
No parts requirements that require sourcing from only one place, so no shortages like recently with the BUF634, TLE2426, and OPA551
PCB measures 49mm x 25mm, so fits my favorite case for portable, the Hammond 1455C801, with 8xAAA batteries for a long runtime, and plenty of voltage swing into the majority of headphones we use portably.

I know the schematic shows a PNP transistor for T1, T2, T5, and T6, but it is really this SOT23 CRD, I didnt have an eagle library part for it, and didnt take the time to adapt one specifically for that part.

Prototypes have been ordered, and should be here in about a week.

peranders · 25th May 2006, 06:41 AM

I have commented this design at Head-Fi.org but I didn't notice that you have SOT23 output devices. This is not a particulary rugged output stage, easy to break. I have used SOT223 types, 1 A transistors.

cetoole · 26th May 2006, 10:03 AM

Thanks for the suggestion peranders, looking at the datasheets for some of the transistors I was looking to use, like the MMBT3904/MMBT3906 complimentary pair, confirms what you said, the SOT223 package can dissipate nearly 3x the power of the SOT23, and reading other places, the SOT23 can only handle 100mA or so, while the SOT223 can do 1A. Because of this, I made some changes tonight, but it was quite hard to route the PCB in the space I wanted, and use these output transistors. Anyways, here is what I came up with. Note the incorrect part is again used for the CCS, both on the diamond buffers, and now replacing the DO-35 package CRD, because I just couldnt make it fit while routed reasonably.

cetoole · 30th May 2006, 07:32 AM

Just a minor update to the layout, and I also finally have the schematic all correct; I finally made a library part for the SST502 CRD.

24th May 2006, 10:12 PM	#1
cetoole diyAudio Member Join Date: Mar 2005 Location: Maryland, USA	Mini Portable Headphone Amplifier, with Discrete Diamond Buffers Been working on this layout for about a week so far. Features are: DIP8 opamps for L/R SOIC opamp for ground, either use a high current single opamp, or a low current opamp with a class B emitter-follower in its feedback loop Bypassing on all opamps via 0805 ceramics right at the power pins to ground 1206 resistors everywhere Discrete Diamond buffers for L/R, with crd ccs, all transistors in SOT23 2 channel design, eliminates the need to isolate the input/output jacks, and reduces current draw No parts requirements that require sourcing from only one place, so no shortages like recently with the BUF634, TLE2426, and OPA551 PCB measures 49mm x 25mm, so fits my favorite case for portable, the Hammond 1455C801, with 8xAAA batteries for a long runtime, and plenty of voltage swing into the majority of headphones we use portably. I know the schematic shows a PNP transistor for T1, T2, T5, and T6, but it is really this SOT23 CRD, I didnt have an eagle library part for it, and didnt take the time to adapt one specifically for that part. Prototypes have been ordered, and should be here in about a week.

25th May 2006, 06:41 AM	#2
peranders Electrons are yellow and more is better! diyAudio Member Join Date: Apr 2002 Location: Göteborg, Sweden Blog Entries: 4	I have commented this design at Head-Fi.org but I didn't notice that you have SOT23 output devices. This is not a particulary rugged output stage, easy to break. I have used SOT223 types, 1 A transistors. __________________ /Per-Anders (my first name) or P-A as my friends call me

Thread Tools	Search this Thread
Show Printable Version Email this Page	Search this Thread: Advanced Search

Similar Threads
Thread	Thread Starter	Forum	Replies	Last Post
Portable headphone amplifier project!	Inocybe	Headphone Systems	2	6th July 2008 09:11 AM
A question about diamond buffers	darian	Solid State	41	3rd July 2008 02:20 AM
Diamond buffers	Nordic	Parts	7	13th March 2007 03:13 PM
Discrete buffered portable mini headamp, for Lansing DN1	cetoole	Chip Amps	3	3rd August 2006 05:39 AM

New To Site?	Need Help?
Register to Participate Search Privacy Statement Contact Us	Frequently Asked Questions Did you forget your password? Mark Forums Read


	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

26th May 2006, 10:03 AM	#3
cetoole diyAudio Member Join Date: Mar 2005 Location: Maryland, USA	Thanks for the suggestion peranders, looking at the datasheets for some of the transistors I was looking to use, like the MMBT3904/MMBT3906 complimentary pair, confirms what you said, the SOT223 package can dissipate nearly 3x the power of the SOT23, and reading other places, the SOT23 can only handle 100mA or so, while the SOT223 can do 1A. Because of this, I made some changes tonight, but it was quite hard to route the PCB in the space I wanted, and use these output transistors. Anyways, here is what I came up with. Note the incorrect part is again used for the CCS, both on the diamond buffers, and now replacing the DO-35 package CRD, because I just couldnt make it fit while routed reasonably.

30th May 2006, 07:32 AM	#4
cetoole diyAudio Member Join Date: Mar 2005 Location: Maryland, USA	Just a minor update to the layout, and I also finally have the schematic all correct; I finally made a library part for the SST502 CRD.

Currently Active Users Viewing This Thread: 1 (0 members and 1 guests)