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Old 12th June 2012, 12:03 AM   #781
AndrewT is offline AndrewT  Scotland
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Quote:
Originally Posted by Stormrider View Post
As far as I can tell from Andrew's posts, his calculations were based on an EF2, two pair output stage.
The post2 schematic shows 2pair. That's where I got the information.
Is the post2 schematic wrong?
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Old 12th June 2012, 12:28 AM   #782
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Default Output Pairs

The CB and build manual show 3 OP pairs
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Old 12th June 2012, 12:41 AM   #783
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Default post 2 wrong?

Andrew,

I don't know that the post 2 scheme is wrong... I believe it has just evolved
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Old 12th June 2012, 02:02 AM   #784
SoIL4x4 is offline SoIL4x4  United States
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Quote:
Originally Posted by bmcevers View Post
Just my 2 cents...If you've chosen a reputable manufacturer...It is properly sized...It will get the job done!! There will always be some voltage sag at high loads, that's life. There will always be losses, that's physics..

I would be more concerned with proper mounting location and ensuring you will not be injecting hum into the amp circuitry. Also, I would take caution not to inadvertently introduce a shorted turn with your mounting technique, this will surely take out fuses and/or your breaker...not good

Remember, many 'mid-fi' manufacturers intentionally undersize the XFMR because they know it won't be driven at high levels continuously

Hope this helps,

Regards
Yes this helps. My tentative on paper build consists of two 400va 45v x2 antek transformers with covers. The antek covers take care of the shorted turn issue, though in my opinion only if mounted to a metal base of appropriate thickness.
Should this discussion be moved to the build thread?
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Old 12th June 2012, 03:49 AM   #785
AJT is offline AJT  Philippines
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Quote:
.If you've chosen a reputable manufacturer...It is properly sized...It will get the job done!! There will always be some voltage sag at high loads, that's life. There will always be losses, that's physics..
i make my own traffos for all my amplifier builds.....i can make them any size i want.....

voltage sag happens the instant your circuit draws current, this is physics and this is unavoidable...

i asked the question in this forum many years ago about the proper sizing of power transformers, and the answer i got from the gurus, "get the biggest size that will fit in your box".....

there are other answers to that question in these forums......

the relationship between power transformer size and output stage robustness is a balancing act.....

get a small transformer and a robust output stage and your traffo burns out, get the biggest traffo and your output stage burns out....

now which is easier? replacing traffos or replacing output trannies?

the choice is yours.......

Last edited by AJT; 12th June 2012 at 04:15 AM.
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Old 12th June 2012, 04:28 AM   #786
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Default XFMR size

Tony,

There are many problems with the "get the biggest XFMR that will fit in your chassis" philosophy.

1. We have foregone doing a few calcs to come up with the correct size based on the application

2. The "law of diminishing returns" takes effect. Once the optimum XFMR based on calcs is put aside to opt for "bigger" the cost starts to become exorbitant for the amount of performance gained.

If you have a 20^2 Meter box, that XFMR would be pretty big...j/k

Tony, kudos for being able to wind your own toroids! I am sure that is quite an art!

Regards,

Brannon
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Old 12th June 2012, 04:44 AM   #787
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Default balancing act

Tony,

It does require a few calcs, but it's fairly straight forward to find the optimum XFMR size:

1. Power output
2. Power Losses
3. Power of auxiliary circuits

Output transistor's have SOA's, and heatsinks should be implemented that are representative of that. This is not as straightforward as optimum transformer VA, but it is achievable. There are several good texts (and posts on this site) that relate the laws of thermal dynamics wr to audio amplifers ( Self, Cordell, etc..)

Regards,

Brannon
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Old 12th June 2012, 05:02 AM   #788
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Default re:

Quote:
Originally Posted by Tony View Post
i make my own traffos for all my amplifier builds.....i can make them any size i want.....

voltage sag happens the instant your circuit draws current, this is physics and this is unavoidable...

i asked the question in this forum many years ago about the proper sizing of power transformers, and the answer i got from the gurus, "get the biggest size that will fit in your box".....

there are other answers to that question in these forums......

the relationship between power transformer size and output stage robustness is a balancing act.....

get a small transformer and a robust output stage and your traffo burns out, get the biggest traffo and your output stage burns out....

now which is easier? replacing traffos or replacing output trannies?

the choice is yours.......
I would regard any amplifier that "burns up" transistors and transformers on a regular basis as an "ill conceived design", I'm sure you would too
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Old 12th June 2012, 05:10 AM   #789
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Quote:
Originally Posted by SoIL4x4 View Post
Yes this helps. My tentative on paper build consists of two 400va 45v x2 antek transformers with covers. The antek covers take care of the shorted turn issue, though in my opinion only if mounted to a metal base of appropriate thickness.
Should this discussion be moved to the build thread?
Quite possibly, that will be up to the mods

Regards,

Brannon
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Old 12th June 2012, 09:26 AM   #790
AJT is offline AJT  Philippines
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Quote:
Originally Posted by bmcevers View Post
I would regard any amplifier that "burns up" transistors and transformers on a regular basis as an "ill conceived design", I'm sure you would too
oh, yes.....but you know how these amps can be abused.....no design is ever bullet-proof in the hands of the abusers.....

years of troubleshooting and repairing commercial amps tells me so...
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