Building amp with 9 volts pedal socket output.

[Latole]

Yesterday I met a guy who builds amps (and fixes them).

In some of its amps it has integrated a 9 volt power supply circuit for effects pedals.
The socket is on the back of the amp.

I think the idea is very interesting, if not brilliant because we all use effects pedals.

[JB]

I did this many years ago with an old Selmer Treble 'n' Bass 50W head.  I had a 1U half width effects unit mounted on the side of the head, a PSU inside for 12VAC for the fx unit, and 9V DC for the pedal board and midi foot controller.  Multiway connector on the back of the amp that took audio, power and midi to and from the pedalboard. Was pretty quick and convenient for settup at a gig.   Single mains connection to the amp and the multicore cable out to the board. 

[PRR]

One of the not-small g-amp companies did that 10-20 years back. It did not sell top of the charts. I can't find it now.

If it works for you, great. But it may be tough to sell to others.

[Latole]

I posted the topic here in the Tube amp Building because building an amp for yourself can be interesting.

I understand that for a large manufacturer that would force them to increase their prices too much and no longer be competitive.

[Leevi]

That is a good idea but I think it is better to use a separate power transformer/secondary for the 9V source.

/Leevi

[Latole]

Better ? I don't know, it is two different thing.

For a DIY amps builder, parts for a complete circuit will cost less than $10

[Leevi]

I mean that don't use the same secondary that you use for the amp.
E.g. using the 6,3 heater secondary both for heaters and ~9V output might cause disturbances.
/Leevi

[Latole]

I mean that don't use the same secondary that you use for the amp.
E.g. using the 6,3 heater secondary both for heaters and ~9V output might cause disturbances.
/Leevi

You could be right.

[JB]

I installed a small toroidal transformer when I did it, basically in parallel with the HT transformer primary so it used the amps mains fuse and power switch.

[Leevi]

Is the output grounded to the amp or is it floating?
/Leevi

[JB]

On mine, I ripped it out a while ago to revert the amp to stock and sell.  From memory, pretty sure I had it floating, though of course the 9V will ultimately connect back to the amps ground in the effects pedals.  But at least if it's floating within the amp then you're not creating a big loop.  No difference really in that scenario to an external pedal supply, you're just sharing the mains input/fuse/switch in the amp.

[Leevi]

The output could have the following switches:
- ground lift
- polarity
/Leevi

[Williamblake]

If i have the space avalaible i put it in. Everybody and myself likes my tuner and what not. / Also i put the additional power transformer next to the main pt in a way it rather cancels than adds hum but you might only notice that if you have a reverb tank in the amp.