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Colin Wonfor's SECA amp build

I finished the p/s boards this morning and all seems good; no magic smoke anyway:D

There are slight differences with plus and minus readings on both boards but I assume close enough not to be a problem?

Board 1 +17.84v - 18.04v

Board 2 +17.91v -18.05v
 
Those readings look good to go Keith:cool:

So just a matter of some drilling, tapping and you are there.

Looking forward to your thoughts on the sound with and without regulation.

Great work:cool:
 
Marra said:
I finished the p/s boards this morning and all seems good; no magic smoke anyway:D

There are slight differences with plus and minus readings on both boards but I assume close enough not to be a problem?

Board 1 +17.84v - 18.04v

Board 2 +17.91v -18.05v
Click to expand...

Oh dear !!! Perfect results again, well done.
 
Thanks guys.

Drilling and tapping the real fun part;) I will have to order transformers from Airlink at some point.

I will be listening to the amp as is for a while longer before adding the p/s which will probably be after Christmas. Assuming of course that itchy fingers don't get the better of me.What are the odds of that happening I wonder.
 
''I will have to order transformers from Airlink at some point''.

I've had some nice transformers from Airlink in the past at fair prices:cool:
 
[QUOTE

I've had some nice transformers from Airlink in the past at fair prices:cool:[/QUOTE]

Yes they provide a quality; reasonably priced product and I like that you can specify an interwinding screen.

Am I right in thinking that you went with 18V secondaries Shaun?
 
Thanks Shaun. I will have to order a couple after Christmas.

I seem to be going down with what my good lady has had so things will definately be on hold until after the hols :(

A Merry Christmas to all.
 
Time to kick back and enjoy.

have a good one all:)

BTW


I'm now running at 1.9A which sounds even better.


Really starting to cook with gas:)
 
But maybe while we are waiting it would be good to have a chat around setting up the SECA at its optimum.:D

heatsink%20xl.jpg
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The above chart shows (amongst other things) the heat sink specifications required for each operating point.

I managed to have a read of this last night and it seems that it has some other useful info on setting things up.

Just to be sure that I have grasped all of the info.

My speakers are PMCFB1+ which is stated as 93db W 8ohm and being transmission lines are a fairly flat load impedance wise.

So looking along the ‘’Optimum load’’ line and arriving at 8ohm I get

Current 2.5A
Max power OP 24.99W
Power dissipation 100

With the new heatsinks @0.18C/W

Temp above ambient 20deg

Looks like a good point to aim for.:cool:

I think that I’ll be putting the PSU on its own sink to use the main sink for music goodness only.:)

I have my 0.38C/W HS running @ 1.9A ATM (about 14W I think) and I’ve noticed that the sound has got better with each turn of the screw bias wise.

Adding the Regulated PSU has improved things also and is well worth the little extra effort involved.

More detail, better focus, tighter bass (quite unlike most of the Class A that I've heard) are just a few of the highlights that I’ve noticed. Yes I’ve even had a few of those ‘’never heard that in the recording before’’ moments.

Oh have I mentioned that the SECA runs much more quietly with the PSU in place.

anyhow Heatsinks and copper spreaders are in Santa's sack awaiting the long trip from grotto land.:D

roll on Xmas;)

Nice work Colin.:cool:
 
Some copper bar to use as a heat spreader is on order and a pair of transformer will be collected next week so I guess it's time to get my finger out :eek:
 
I should be ready to start the refit next week.

Now that all of the Xmas fun :rolleyes: is out of the way.

looking forward to your thoughts Keith.:cool:
 
Are you sticking with monoblocks Shaun?

I've been wondering whether to rehouse mine in seperate chassis although I might save that as a project for the summer as my workshop is a workmate in the back garden and it's a bit chill at the moment:D
 
Marra said:
Are you sticking with monoblocks Shaun?

I've been wondering whether to rehouse mine in seperate chassis although I might save that as a project for the summer as my workshop is a workmate in the back garden and it's a bit chill at the moment:D
Click to expand...

Yes Keith


Mono's are nearly always my preference and well worth the little extra effort.


I found some time to transfer the First SECA Mono to the new sink.


2.1A:D:D


The copper spreader seems to be doing it's job with the head noticeably more even over the sink.


Running warm but not roasting and cooler than with the old sinks at 1.9A.


One down and one to go.


Tomorrow:cool:


Hope my fingers are up to another session:D


Happy New Year ALL
 
Good to hear Shaun.

Have you left the boards with the mosfets at the bottom or have you turned them through 90 degrees so that the fets are nearer the middle of the sink?

All being well I am hoping to have mine completed by the end of next week(fingers crossed)

Happy New Year folks.
 
Hi Keith

I decided to leave the boards side by side with the mosfets at the bottom of the sink.

same with the PSU.

It just seemed the best way of maxing the sink rather than having them pointing inward.

TBH it's all guess work but seems to be working OK and heating more evenly across the sink once it gets going.
 
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