Discrete buffers

Ted205 · 30th July 2008, 12:51 PM

Has anyone built the discrete buffer (three transistors - Andrew Rothwell) from decibel dungeon ?

I've simulated it and it seems to work well.
I'm using 3 C549B transistors

However converting over strip board i get very little audio output into a 6ohm speaker. I also get a 'cloudy' sin wave at the input and output (function generator at the input). What could be causing this?

Can anyone help me I've been over the stripboard several times and can't find anything wrong.

thanks

AndrewT · 30th July 2008, 03:19 PM

post a close up pic of both sides of the PCB and the whole preamp.

justblair · 30th July 2008, 04:18 PM

This isn't going to help, but I gave up on this buffer. I tried several builds on stripboard, and then gave up.

I think that Nordic may have mentioned that he had trouble with it as well.

Good luck...

Ted205 · 30th July 2008, 06:33 PM

well i've got it working, though i do get quite abit of ground hum (which can be sorted).

Am i wright in say that this buffer doesn't actually add any gain? and is at unity?

Nuuk · 30th July 2008, 07:17 PM

That's correct, it is a unity gain buffer.

I've built several versions with no problems like hum. There is a bit of DC on the input and I got very small clicks as I turned the stepped attenuator.

Ted205 · 31st July 2008, 08:21 AM

look at it with a scope it looks like unity. When i compare it with my laptop straight to a speaker vs. laptop->buffer->speaker it seems to attenuate the sound. Its louder with out the buffer inline.

Is this correct ?

Nuuk do you have a pcb version?

Nuuk · 31st July 2008, 08:29 AM

I can't comment on the loudness issue as I have not experienced it.

No, I don't do PCB's, and this circuit is so simple it hardly warrants one.

Nordic · 31st July 2008, 09:36 AM

Yep, I gave up on that buffer too.. after numerous diffirent PCB's, PSUs, and transistors, I could not get it to run stable for more than 5 minutes...

I have a friend who uses it sucsessfully though...

Then did the Pedja Rogic buffer, and was about as impressed as I get.

Since then moved to an amp that does not need the extra distortion of another stage slapped infront of it...

P.S. a discrete unity buffer will put out slightly less than the input...

poynton · 31st July 2008, 10:08 AM

What about a premade buffer module ?

http://cgi.ebay.co.uk/STEREO-FET-BUF...713.m153.l1262

Andy

Nordic · 31st July 2008, 10:24 AM

Good old B.I.Y. ?
Buy it yourself.

30th July 2008, 12:51 PM	#1
Ted205 diyAudio Member Join Date: Jun 2008	Discrete buffers Has anyone built the discrete buffer (three transistors - Andrew Rothwell) from decibel dungeon ? I've simulated it and it seems to work well. I'm using 3 C549B transistors However converting over strip board i get very little audio output into a 6ohm speaker. I also get a 'cloudy' sin wave at the input and output (function generator at the input). What could be causing this? Can anyone help me I've been over the stripboard several times and can't find anything wrong. thanks

30th July 2008, 03:19 PM	#2
AndrewT diyAudio Member Join Date: Jul 2004 Location: Scottish Borders	post a close up pic of both sides of the PCB and the whole preamp. __________________ regards Andrew T.

30th July 2008, 07:17 PM	#5
Nuuk diyAudio Member Join Date: Feb 2003 Location: Somerset, SW England	That's correct, it is a unity gain buffer. I've built several versions with no problems like hum. There is a bit of DC on the input and I got very small clicks as I turned the stepped attenuator. __________________ The truth need not be veiled, for it veils itself from the eyes of the ignorant.

31st July 2008, 08:29 AM	#7
Nuuk diyAudio Member Join Date: Feb 2003 Location: Somerset, SW England	I can't comment on the loudness issue as I have not experienced it. No, I don't do PCB's, and this circuit is so simple it hardly warrants one. __________________ The truth need not be veiled, for it veils itself from the eyes of the ignorant.

31st July 2008, 10:08 AM	#9
poynton Magneto the Gravity Man diyAudio Member Join Date: Mar 2005 Location: A life on the ocean waves when I'm not at home in N. Wales (but I'm not Welsh so no sheep jokes!)	What about a premade buffer module ? http://cgi.ebay.co.uk/STEREO-FET-BUF...713.m153.l1262 Andy __________________ If it ain't broke, break it !! Then fix it again. It's called DIY !


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30th July 2008, 04:18 PM	#3
justblair diyAudio Member Join Date: Jan 2007 Location: Glasgow, Scotland	This isn't going to help, but I gave up on this buffer. I tried several builds on stripboard, and then gave up. I think that Nordic may have mentioned that he had trouble with it as well. Good luck...

30th July 2008, 06:33 PM	#4
Ted205 diyAudio Member Join Date: Jun 2008	well i've got it working, though i do get quite abit of ground hum (which can be sorted). Am i wright in say that this buffer doesn't actually add any gain? and is at unity?

31st July 2008, 08:21 AM	#6
Ted205 diyAudio Member Join Date: Jun 2008	look at it with a scope it looks like unity. When i compare it with my laptop straight to a speaker vs. laptop->buffer->speaker it seems to attenuate the sound. Its louder with out the buffer inline. Is this correct ? Nuuk do you have a pcb version?

31st July 2008, 09:36 AM	#8
Nordic diyAudio Member Join Date: Sep 2005	Yep, I gave up on that buffer too.. after numerous diffirent PCB's, PSUs, and transistors, I could not get it to run stable for more than 5 minutes... I have a friend who uses it sucsessfully though... Then did the Pedja Rogic buffer, and was about as impressed as I get. Since then moved to an amp that does not need the extra distortion of another stage slapped infront of it... P.S. a discrete unity buffer will put out slightly less than the input...

31st July 2008, 10:24 AM	#10
Nordic diyAudio Member Join Date: Sep 2005	Good old B.I.Y. ? Buy it yourself.

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