Balanced F5 question

NYCOne · 29th August 2010, 10:50 PM

I've asked a few times in the main F5 thread, but I didn't have a schematic. I put together a rough sketch of my question on the attachment.

Briefly, I have a standard F5 set of parts, and I'm interested in whether two boards can easily be converted to one balanced channel. I've seen Patrick's balanced F5 schematic, but he uses the Toshiba outputs, I have the IRFs.

Can the attached setup work without substitution of a lot of resistor values, or is the effort more complex?

I'd appreciate any input, as modeling circuits is well beyond my abilities.

AndrewT · 30th August 2010, 09:31 AM

the two halves of the single ended input are connected at the source resistors to form an LTP. But there is a tail missing to carry current to the other supply rail.

NYCOne · 2nd September 2010, 07:49 AM

Is this solved by connecting the +24v and -24v rails on both sides of the circuit, or is there more to it than that?

AndrewT · 2nd September 2010, 09:54 AM

Oh Sh..., Oh dear, is allowed.
I noticed that I had misread your partially inverted pdf. I intended to come back with an "oops" and ask you to explain what was happening to the two sides of the inputs.
But, I forgot. Sorry!

If the left side is restored to non-inverted, then the two new links get twisted to form the X, that is part of this balanced arrangement.
If you draw that part with the X and with both sides non-inverted, how does your proposal compare to the other examples of balanced topologies? I think there are about 4 ways to make this balanced work.

Itsmee · 04:38 PM

Is it me or does a balanced F5 look like a variation of an UGS

NYCOne · 4th September 2010, 08:30 AM

I guess I can always try it out. I'm new to amps, I hope I don't blow something up.

EUVL · 4th September 2010, 09:38 AM

The balance topology is basically correct.
As shown, it delivers its full power for a 15 ohm load.
If you have a lower load impedance, then you are not using the rail voltage to the full, and you could have used with more current.

This is why the circuit I published has 16V rails and 2A bias.

But it will work.
And I suggest you ground the intersection of the "X" to start with, trim everything properly, before you float the X for final trimming.

Good luck,
Patrick

PS This balanced circuit requires a balanced input signal.

.

AndrewT · 11:36 AM

Quote:

Originally Posted by EUVL

......And I suggest you ground the intersection of the "X" to start with, trim everything properly, before you float the X for final trimming.

is this your recommended setting up procedure?

Ground the X and set up the amp resistors/currents.
Then unground the X and trim to final currents/offsets?

If ungrounding shows up an error, can we read the errors to work out where they are coming from and make circuit adjustments to correct the circuit errors, eg. change the value of a source resistor rather than simply trim out an offset.

EUVL · 4th September 2010, 06:53 PM

Yes, grounding the X basically means that you separate the balanced circuit into 2 individual single ended circuits.

This is must easier to set up one by one.
Once you are satisfied that they are working on their own, you can then float the X and do the final trim.

Patrick

NYCOne · 4th September 2010, 10:24 PM

Thanks Patrick. If I want to drive an 8 ohm load, are there simple resistor changes that will get me where I need to go?

3rd September 2010, 04:37 PM	#5
Itsmee diyAudio Member Join Date: Feb 2009	Is it me or does a balanced F5 look like a variation of an UGS Last edited by Itsmee; 3rd September 2010 at 04:38 PM. Reason: missed a word out

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
F5 bias question	richD	Pass Labs	12	4th March 2013 12:57 PM
F5 - Antek 4218 Wiring Question	vdi_nenna	Pass Labs	17	7th May 2011 12:05 AM
F2 and F5 heat question	trusound	Pass Labs	14	1st July 2010 02:28 PM
F5 Output Connection Question	rtate	Pass Labs	1	5th January 2010 11:58 PM
question re: sony ps-f5 portable turntable	voicegyrl	The Lounge	0	31st July 2008 09:36 PM

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

30th August 2010, 09:31 AM	#2
AndrewT diyAudio Member Join Date: Jul 2004 Location: Scottish Borders	the two halves of the single ended input are connected at the source resistors to form an LTP. But there is a tail missing to carry current to the other supply rail.

2nd September 2010, 07:49 AM	#3
NYCOne diyAudio Member Join Date: Jul 2010 Blog Entries: 1	Is this solved by connecting the +24v and -24v rails on both sides of the circuit, or is there more to it than that?

2nd September 2010, 09:54 AM	#4
AndrewT diyAudio Member Join Date: Jul 2004 Location: Scottish Borders	Oh Sh..., Oh dear, is allowed. I noticed that I had misread your partially inverted pdf. I intended to come back with an "oops" and ask you to explain what was happening to the two sides of the inputs. But, I forgot. Sorry! If the left side is restored to non-inverted, then the two new links get twisted to form the X, that is part of this balanced arrangement. If you draw that part with the X and with both sides non-inverted, how does your proposal compare to the other examples of balanced topologies? I think there are about 4 ways to make this balanced work.

4th September 2010, 08:30 AM	#6
NYCOne diyAudio Member Join Date: Jul 2010 Blog Entries: 1	I guess I can always try it out. I'm new to amps, I hope I don't blow something up.

4th September 2010, 09:38 AM	#7
EUVL diyAudio Member Join Date: Oct 2003	The balance topology is basically correct. As shown, it delivers its full power for a 15 ohm load. If you have a lower load impedance, then you are not using the rail voltage to the full, and you could have used with more current. This is why the circuit I published has 16V rails and 2A bias. But it will work. And I suggest you ground the intersection of the "X" to start with, trim everything properly, before you float the X for final trimming. Good luck, Patrick PS This balanced circuit requires a balanced input signal. .

4th September 2010, 06:53 PM	#9
EUVL diyAudio Member Join Date: Oct 2003	Yes, grounding the X basically means that you separate the balanced circuit into 2 individual single ended circuits. This is must easier to set up one by one. Once you are satisfied that they are working on their own, you can then float the X and do the final trim. Patrick

4th September 2010, 10:24 PM	#10
NYCOne diyAudio Member Join Date: Jul 2010 Blog Entries: 1	Thanks Patrick. If I want to drive an 8 ohm load, are there simple resistor changes that will get me where I need to go?