F5X -- the EUVL Approach

alazira · 2013-09-29 1:35 am

Thanks Patrick.
I think you mean one 24V DPDT or DPST relay can handle two channels?
In a stereo power supply (as opposed to dual mono), would one be able to get away with a single SPST by tying together the L&R speaker negatives?

EUVL · 2013-09-29 2:04 am

> I think you mean one 24V DPDT or DPST relay can handle two channels?

No.
DP because you can switch both outputs of ONE amp at the same time.
DT because you can choose to disconnect (series) or short circuit (shunt) the amp output in case of fault.
Most people use series, so the relay is in the signal path.
I use shunt, because it is non-invasive. But a safty trip will no doubt kill all your output devices.

> In a stereo power supply (as opposed to dual mono), would one be able to get away with a single SPST by tying together the L&R speaker negatives?

Of course NOT.
We have balanced amplifiers here.

Patrick

alazira · 2013-10-01 12:24 am

EUVL said:
> In a stereo power supply (as opposed to dual mono), would one be able to get away with a single SPST by tying together the L&R speaker negatives?

Of course NOT.
We have balanced amplifiers here.

Ok, not for balanced amp. Will it work for SE F5?

alazira · 2013-10-01 12:27 am

EUVL said:
> I think you mean one 24V DPDT or DPST relay can handle two channels?

No.
DP because you can switch both outputs of ONE amp at the same time.
DT because you can choose to disconnect (series) or short circuit (shunt) the amp output in case of fault.
Most people use series, so the relay is in the signal path.
I use shunt, because it is non-invasive. But a safty trip will no doubt kill all your output devices.

I'm not 100% sure on what you mean by shunt. Perhaps like this?

EUVL · 2013-10-01 1:12 am

Post#823 is in theory possible, but you are using common Gnd for both stereo channels.
This people do in headphones.

I don't understand your motivation.
You want to save the cost of one relay ?

All the relays you have drawn above are SPDT, not DPDT.
File:Relay symbols.svg - Wikipedia, the free encyclopedia

Patrick

pmchoong · 2013-10-01 2:20 am

Can I use 12v SPDT? I have two which are 12V.

EUVL · 2013-10-01 2:47 am

You need to use two (left & right channel) in series.

Patrick

alazira · 2013-10-02 1:33 am

pmchoong said:
Can I use 12v SPDT? I have two which are 12V.

I think you would leave 87A (center) unconnected

alazira · 2013-10-02 1:37 am

EUVL said:
Post#823 is in theory possible, but you are using common Gnd for both stereo channels.
This people do in headphones.

I don't understand your motivation.
You want to save the cost of one relay ?

All the relays you have drawn above are SPDT, not DPDT.
File:Relay symbols.svg - Wikipedia, the free encyclopedia

Patrick

Not really concerned about the cost of one relay ($5)

Just an exercise in the possible. Plus I find fewer parts more elegant.

alazira · 2013-10-02 1:42 am

EUVL said:
> I think you mean one 24V DPDT or DPST relay can handle two channels?

No.
DP because you can switch both outputs of ONE amp at the same time.
DT because you can choose to disconnect (series) or short circuit (shunt) the amp output in case of fault.
Most people use series, so the relay is in the signal path.
I use shunt, because it is non-invasive. But a safty trip will no doubt kill all your output devices.

Patrick

Is this what you mean by short circuit (shunt)? Would disconnecting the power supply to the amp also work?

EUVL · 2013-10-02 2:20 am

Shunt means short circuiting the positive and negative terminal using the NC contact of the relay.
Amp will NOT work in any case if auxillary supply is disconnected.

I suggest you do use the series type protection, as published.

Patrick

johnwmclean · 2013-10-09 12:57 pm

I’ve managed to collect nearly all my F5X parts,
I started building tonight with the protection board, I’m a complete novice at SMD, with some good tweezers, a thin soldering tip, loads of flux paste, good solder wick and a leap of courage...

EUVL · 2013-10-09 1:54 pm

John,

This is most excelllent for a first-time effort.
Many congradulations.

I cannot wait to see how perfect your final article will look.

Keep us posted.

Patrick

Horio · 2013-10-10 3:49 pm

John,

I was worried about my lack of SMD experience as well when I started to populate the protection board. But like you said, the right tools (flux is so important) and some patience goes a long way.

Good luck and let us know how it turns out!

johnwmclean · 2013-10-10 8:03 pm

Thanks Patrick and Greg,

Like you said Greg patience and working slowly is key, I’ll update once I have the protection board up and running.

BTW for those that are still after auxiliary transformers, I got a custom made version from SUMR (Canada) to spec, core banded, epoxy filled centre with 650mm secondary leads (will reach the protection board without re-termination). $45USD.

johnwmclean · 2013-10-13 1:27 am

I made good progress this weekend, if I hadn’t ordered the wrong 120kohm resistors instead of the 120ohm I would of found time to test.
I did a diode test, the bi-coloured LED will only aluminate red, I assume this is because of the current state of the circuit setting?

Some progress pics... and yes I need to clean that flux off!

Horio · 2013-10-13 5:38 am

John, do you have updated protection boards with the fix?

johnwmclean · 2013-10-13 5:58 am

Yes Greg I have updated PCBs (Version R4).

EUVL · 2013-10-13 6:23 am

You should make some square-on shots.
Then I can also use them.
Isn't it gorgeous layout ?

Very well sone.

Patrick

ashaw · 2013-10-13 9:31 am

John, you do not have the fix implemented on your pcb, you will still have to do the mod.

Also you should be able to get the blue led just by pressing the button a few times, not you should wait 20 s after applying power for this to work.

F5X -- the EUVL Approach

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