Solid State Guitar Amp Forum | DIY Guitar Amplifiers

Agree with G1,
Adding;
Well the data sheet tells it as I suspected,, It's Not an *isolated 115v Tx*

It states very clearly it has 2x115v primaries and 2x 7V secondaries.

So unless I've lost it, ,the only way one could get enough HT to run a valve is from one of the primary windings which means it's a death trap waiting to happen as the circuit runs off the primary. ARRRRGH!!!!
OK sure there are tons of old radio circuits that did indeed run direct from mains but most of those old units where bakalite cases and one would never come into contact with the circuit under normal use but this is an electric guitar amplifier and you ARE in direct contact with part of that circuit so if something fails you could end up Dead.
If you want to build it that is your call but I'm writing this to warm other non teck savvy folks that it's a death trap waiting to happen.

Be very careful grabbing ideas off the net some are really bad designs.

To attain HT for a small valve amp there are much SAFER ways,, here is a better option for High voltage, uses back to back Tx's.
https://valveheaven.com/diy-amp-designs/the-lamington-junior/the-lamington-junior-design/

The added bonus is that it uses a 12Volt wall wart which keeps you a long way away from dangerous main voltages.
HTHelps, Phil.

It should be drawn like antek draws it in the datasheet.


The two 115V windings are on the same side of the transformer, so they are not transformer (inductive) coupled.
Drawing it like they are on opposite sides of the transformer is just wrong.
I think the coupling would be very limited in terms of current, and it is just lucky that it works.

This is my first amp build, but I have about 40 years of experience working with electricity all the way up to medium voltage circuits like 4160-volt motors.   I know how to work safely.

You're right, it's not an isolation transformer, but it's being used as one.   This design has a very low current draw because it is a sub-1-watt amp.  The guy who builds these has used this exact transformer in this way on several small amp builds. One primary set of leads on the transformer gets driven by the mains inducing about 120 volts on the other set.  The 7-volt secondary is dropped to 6.3 volts to run the filament on the tube.  The 6CL6 power amp doesn't require a lot of DC voltage.  I think this supply will put out about 135 volts DC.  The OT is wired using the 1/2 watt tap.

Hang on I just reread the 1st post and as this is your first build,, I'll assume you don't have a lot of teck skill.

Warning!!! RE this;
"The power supply for the amp I'm trying to build features an inexpensive 7-volt Antec Toroid transformer with the 120-volt coils split, making it a small isolation transformer.  The 7-volt side is used for the tube filament."

Unless I've missed something in translation,,,that tells me it is a 120/120 split *Primary* so something sounds wrong

Also the way in which the power Tx is drawn up in that schematic seems strange.
Others here may know more but meantime be careful cause if I'm right as it could kill you.

Normally when a Tx states 120/120 split primary that means it can be wired up to either 120 mains ans 240 mains. It is most likely NOT an isolation Tx
Maybe post a picture of the Tx you wish to use ideally showing the label.
Phil.

I don't think that you have it right as of yet.
The output is cathode biased not fixed as in the Fender.
Why not hook it up as I stated in my last post.