sopht amp 12v layout help?

[machinist82]

I'm working on the sopht amp 12u7 12k5....and I really don't know what I'm doing.

The part I can't really figure out is the transformer/heaters/12v connections.

What I've got right now definitely isn't right.

Heaters go to 12v
Pins 5 and 6 on the 12k5 are labeled as the grid output connected to 12v, seems like the heaters shouldn't also be connected to this same 12v, but I'm not sure how else to do it.  4 turrets on the right hand side are the transformer, I'm using a slightly out of spec 500/3.5 ohm transformer as I had one laying around.

 Also I substituted the 1m and 2.2m resisters for gain/volume.  Not sure I have these correct either.

Not pictured is a 7812 circuit for filtering on the 12v input.

edited - 12k5 is correct

[shooter]

http://tubedata.milbert.com/sheets/093/1/12K8.pdf
should help, pics n everything 

[PRR]

For lurkers: the 12K8 connections look wrong but ARE correct. It works different.

> grid output connected to 12v, seems like the heaters shouldn't also be connected to this same 12v

ALL the electricals in your car are connected to the same 12V battery. Spark-coil, cigar lighter, trunk light, navigation system....

Yes a car is a little more complicated so there are several "groups" and dozens of fuses so you can play the radio even when the headlights are shorting-out. But a little amp does not need such frills.

[machinist82]

http://tubedata.milbert.com/sheets/093/1/12K8.pdf
should help, pics n everything 

I don't know how I got 12k8 in my head it's 12k5.  Sorry.

http://www.sophtamps.ca/mambo/index.php?option=com_content&task=view&id=25&Itemid=37

http://www.r-type.org/pdfs/12k5.pdf

[DummyLoad]

Not pictured is a 7812 circuit for filtering on the 12v input.

just curious, but why? you need at LEAST 14.5V supplied to regulator input for the 7812 to operate and regulate. typically charging systems run @ 14.4V. your regulator may not regulate. 

you could try a low dropout type (LT-1082-6), however, your car's battery is all the filter you need. `a noise suppression circuit may be what you really want. 

--pete 

[DummyLoad]

LT1086 datasheet.


--pete

[machinist82]

Not pictured is a 7812 circuit for filtering on the 12v input.

just curious, but why? you need at LEAST 14.5V supplied to regulator input for the 7812 to operate and regulate. typically charging systems run @ 14.4V. your regulator may not regulate. 

you could try a low dropout type (LT-1082-6), however, your car's battery is all the filter you need. `a noise suppression circuit may be what you really want. 

--pete

It's not for a car in particular.  My plan is to run off a dedicated battery or power supply and generally the power supplies I have laying around are noisy.