Balanced F5 question

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#883
EUVL said:
> Question: is it important to keep the connection of the X short ?

If you want to use floating X, yes.

> I would like to put the two half of the balanced circuit on opposite sided of a monoblock chassis to maximize the use of the heatsinks.

Our PCB (to be available via the forum) will fit a mini-tower monoblock 85mm wide.
This will still allow optimum PCB layout while using two heatsinks for the 4 MOSFETs.

> I am speaking about 20 cm wires.

Then you should considered using the grounded X, which is essnetially 2 separate single-ended F5's in bridge mode, one amplifying the positive signal, the other the negative.

There is little to choose between grounded and floating, so I would not worry too much about it.


Patrick
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So an F5X balanced is the same as 2x F5, one of each using th + and - of a balanced input? If it is the same, why caring about it? It should be easier to make two F5.
The point seems to be in the "essentially" word, there must be something I am missing 🙂


PD. Regarding my question about halving the output voltage, what's wrong in using a resistor divider at the input? Nobody has said it's right to do that, so something tells me that I am missing something (again). If my knowledge don't betray me, it should be the same as using an input potentiometer.

Best regards,
Regi
 
#886
I am just as happy that you like the standard F5, or just want to bridge two of them for balanced signals.

As to having the signal level, there is nothing wrong using a potential divider (say 2x 5k). But then I assume you have volume control somewhere. So maybe you could just lower the volume.


Patrick
 
#888
regiregi22 said:
So an F5X balanced is the same as 2x F5, one of each using th + and - of a balanced input?............... there must be something I am missing i
Click to expand...
A balanced amplifier is designed and built to run with balanced signal all the way through the amplifier from input to output.
A bridged pair of amplifiers can never approach the performance of a properly designed balanced amplifier.
The way a balanced ClassA amplifier draws current from the power supply is fundamental to that performance improvement.

Note that Cordell also splits amplifiers into 3 types: single ended, bridged and balanced and says why they are different.
However I think there is a mistake on p532 last line referring to power supply advantages of ClassAB balanced amplifiers.
Which reminds me. I need to send an Email.
 
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#889
then there is balanced single ended amplifiers also ;D special in that a balanced amplifier even with properly matched devices will still never react the same over frequency and temperature, because even 'matched opposite' devices behave differently. SuSy solves this problem by using the same devices cross-coupled (the X) so they track thermally and over frequency (as well as many other shared characteristics), especially if they share a heatsink. so CMRR is much more effective than even properly balanced amplifiers can manage.

not trying to preach to the converted here, I am totally out of my league in this company, but just speaking out loud as I believe the above is the main benefit right? i'd be happy to hear more, but I suppose that would be off topic
 
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#892
no problem, it took me a little while to get my head around it also

@ Patrick, no problem, i'll keep an eye out for it. i'm a bit all over the place these next few days, so please give me a day or so to respond, I will do so as soon as possible
 
#893
Another short update :

I have contacted the well-known source for 2SK3497/2SJ618 to confirm price & availability, before contacting the GB members for payment. This might take a few days as a lot of people are off for Chinese New Year in South East Asia.

I also saw the first draft of the F5X main board done anew with PCB software. It was immaculate. Thanks Dave for the great effort. It is now off for second check. So we are one PCB short (control & protection board for regulator users) before we can go for PCB prototyping.

I hope Marc (Variac) is watching this. He has not responded to emails for months. At some stage, my work is done and someone representing the forum has to take over.


Regards,
Patrick
 
#897
EUVL said:
We shall publish everything in due course, when all tests are finished and conclusive.
Avoid a lot of unnecessary discussions, for which I do not have the time.

Will take a while (a lot of work involved), so please be patient.


Patrick
Click to expand...
Would be interesting to post a preview of the board, we are quite enough so it is possible to give interesting suggestions. Like optional conexions, pads, etc.
 
#900
Half way to one channel

Well, I've been pretty busy with my day job, so progress has been slow.

I settled on a design 3 days ago.

I etched the PCB two days ago.

I'm about half way stuffed tonight.

In retrospect, I wasted months trying to glean information from a few folks to no avail. Finally, NP was gracious enough to answer my basic questions (a few days ago), and I was off to the races.

The design is straightforward. Most of my concerns were easily addressed by NP, and the build is quite easy. I'd guess I'll be testing a channel by tomorrow. My biggest mistake to date...not moving forward months ago.

By the way, I welcome "unnecessary discussions". I think its the best way to learn. While I'm swamped at my day job (18-20 hour days lately), I find DIY Audio relaxing and enjoyable. I'm not the most savvy fellow with electronics, but I take risk for a living, so I like to experiment.
 

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