Benson Monarch

[chasbenson]

Hey gang...just happened to check back today, we use 22uf on the OT supply, a 1k dropping resistor, 47uf on the screens, and then it goes off to the preamp filtering nodes with larger value resistors (usually 4.7k / 22uf to the PI and then 4.7k / 22uf to the preamp. I find this yields the benefits of a somewhat loose power section while still pinning the screens where I like them, and has the added benefit of allowing less ripple to reach the split plate circuit. BTW that trashy looking amp in the pic someone posted from Premier Guitar was a sloppy job I made for myself that didn't even use the same components as even the early amps, and just happens to be the first thing that comes up when I search for gut shots. Theres a lesson in there somewhere

[mikeywoll]

Screenshot_20210412-002500.png

Looks like the input on pins 2 and 7 on V2 are swapped on the layout posted on page 5. Can anyone confirm? That could explain why some have noticed the balance pot is increasing noise as resistance is increased.

Mike

[didit]

Hey gang...just happened to check back today, we use 22uf on the OT supply, a 1k dropping resistor, 47uf on the screens, and then it goes off to the preamp filtering nodes with larger value resistors (usually 4.7k / 22uf to the PI and then 4.7k / 22uf to the preamp. I find this yields the benefits of a somewhat loose power section while still pinning the screens where I like them, and has the added benefit of allowing less ripple to reach the split plate circuit. BTW that trashy looking amp in the pic someone posted from Premier Guitar was a sloppy job I made for myself that didn't even use the same components as even the early amps, and just happens to be the first thing that comes up when I search for gut shots. Theres a lesson in there somewhere

Thanks Chris. So no front-end PI filter. Curious if you're curious about trying it, or did and didn't feel it works.

Best .. Ian

[pullshocks]

Thanks to Chris for posting up that info, and hats off for a fantastic sounding amp.

Based on Chris's post I updated my power supply as shown below, and tried it out for an hour. The amp is really fun to play.

EDIT:

With the power supply change and running my PT 6.3V center tap to the 6V6 cathode connection, the hum issue is gone.

For a permanent build I would add the DC heaters, but it is working very well with the elevated AC heaters.

[T Wilcox]

edit, nevermind I read your schem from left to right.

[dorrisant]

Thank you Chris! You are a gem!!

[chasbenson]

Like a pi filter in front of the OT node? I haven't had reason to incorporate that in the Monarch (since the production ones don’t hum appreciably), but I do enjoy the sound and feel of some series resistance or inductance in the power supply path in other designs. The 5E7 PSU circuit for instance is so wrong but so right.

Hey gang...just happened to check back today, we use 22uf on the OT supply, a 1k dropping resistor, 47uf on the screens, and then it goes off to the preamp filtering nodes with larger value resistors (usually 4.7k / 22uf to the PI and then 4.7k / 22uf to the preamp. I find this yields the benefits of a somewhat loose power section while still pinning the screens where I like them, and has the added benefit of allowing less ripple to reach the split plate circuit. BTW that trashy looking amp in the pic someone posted from Premier Guitar was a sloppy job I made for myself that didn't even use the same components as even the early amps, and just happens to be the first thing that comes up when I search for gut shots. Theres a lesson in there somewhere

Thanks Chris. So no front-end PI filter. Curious if you're curious about trying it, or did and didn't feel it works.

Best .. Ian

[didit]

Like a pi filter in front of the OT node? I haven't had reason to incorporate that in the Monarch (since the production ones don’t hum appreciably), but I do enjoy the sound and feel of some series resistance or inductance in the power supply path in other designs. The 5E7 PSU circuit for instance is so wrong but so right.

Anything that works cannot be so wrong, so you're right. That's one excellent example. Was more so referencing some fairly common use of CRC PI filters in old-school single-ended designs. And also a Gibson GA50 inspired project put together a few years back - https://ampgarage.com/forum/viewtopic.php?t=30164. A 6-8dB ripple reduction at the OT node, to me, seems well worth cost and effort.

Best .. Ian

[pullshocks]

Hum is now GONE!!!

Even with AC heaters, and breadboard construction. Ran the PT 6.3 V center tap to the 6V6 cathode connection.

DC heaters may be even better.

Sorry for any confusion caused by my post yesterday. I will edit accordingly.

[BobL]

Hum is now GONE!!!

Even with AC heaters, and breadboard construction. Ran the PT 6.3 V center tap to the 6V6 cathode connection.

DC heaters may be even better.

Sorry for any confusion caused by my post yesterday. I will edit accordingly.

Help me get a grasp on this... to which side of the 25uF/250r pair did you run this?

As for the filter caps, trying to figure out the best way to get another node onto my board... hrm...

[pullshocks]

Between the tube cathodes and the cathode resistor and cap.
Merlin Blencow has on this page (scroll down to Heater Elevation). http://www.valvewizard.co.uk/heater.html Robrob also shows it on his 5e3 pages.

[pullshocks]

Screenshot_20210412-002500.png

Looks like the input on pins 2 and 7 on V2 are swapped on the layout posted on page 5. Can anyone confirm? That could explain why some have noticed the balance pot is increasing noise as resistance is increased.

Mike

Since the connection from the 0.1uF coupling capacitor goes to pin 7, I think the plate connections need to be reversed like this. (But double check.....

EDIT--Yes you could change the grid connections at the tube socket, but I think it would be easier to change the plate connections as shown.

[BobL]

Between the tube cathodes and the cathode resistor and cap.
Merlin Blencow has on this page (scroll down to Heater Elevation). http://www.valvewizard.co.uk/heater.html Robrob also shows it on his 5e3 pages.

Doing this w/o any other changes did not solve hum, FYI.

[dorrisant]

Between the tube cathodes and the cathode resistor and cap.
Merlin Blencow has on this page (scroll down to Heater Elevation). http://www.valvewizard.co.uk/heater.html Robrob also shows it on his 5e3 pages.

Doing this w/o any other changes did not solve hum, FYI.

How did you configure your B+ dropping/filter string? Maybe post a pic.

[BobL]

Between the tube cathodes and the cathode resistor and cap.
Merlin Blencow has on this page (scroll down to Heater Elevation). http://www.valvewizard.co.uk/heater.html Robrob also shows it on his 5e3 pages.

Doing this w/o any other changes did not solve hum, FYI.

How did you configure your B+ dropping/filter string? Maybe post a pic.

It's as per original schematic and layout, not updated.