Benson Monarch

[FUCHSAUDIO]

That's not a terribly well designed CF. The workmanship is meh. Looks like Carr sorta...

[Hoodnight]

Have been skimming through this thread - thinking of trying to build a Chimera Reverb, figuring it's the same as the Monarch but adding another set of 6V6's, using a different PT and OT.

After much searching for gut shots etc, I couldn't find anything other than a blurry close-up until I stumbled on this pic of a Chimera Reverb from Reverb - firgured I'd post here to add something back!

[mikeywoll]

This just popped up on Reddit... Nathan Junior.

Looks like the monarch reverb and pre-amp circuits mated to a single ended 6V6 with solid state rectifier. More data points for components and values.

NathanJrGuts copy.jpg

NathanJrOT copy.jpg

NathanJrPT copy.jpg

Mike

[Hoodnight]

Had a crack at tracing out the Chimera's tone stack which has the bass control in place of the voice switch. Looks to be the same bass control as the Benson Preamp running after the tone control from the Chimera, so I copied unknown values for the caps and pots from the pedal.
First time tracing a circuit though, and the source picture (attached) isn't superb, so definitely open to the possibility of errors.

[CraigGa]

Thanks for your work Hoodnight,

That's not much different from the Monarch's voice switch except it's using a pot instead of switching a resistor in and out.
The treble passthrough on the volume pot is an addition though, I've not felt a need to add one of those.

Craig

[unknowntome]

hey Everyone!

I've been following this thread since it pretty much started and, with much preparation, built my first amp! Thank you to everyone who contributed to this long thread... incredible! I used BobL's layout with the only difference being the HV centre Tap going to ground as most of you have done. Overall, hum and noise is 'acceptable' and on par with my Bluesbreaker. I have two issues with the build though...

first: there's persistent crackle. it shifts and is dynamic but there.. doesn't go away... chop sticking doesn't make any difference.

Second: the reverb sounds great up until the last 20% of the sweep where the signal is killed and replaced by a hum.

I used the 290BEX PT and the 1750H OT.. both hammond.
I used CC resistors throughout the build.

I also, as I do, made it more complicated by building it using a completely different layout! see pics... but its pretty much worked out except for the two issues above so am feeling pretty good about that for a first build!

any ideas re above?

https://i.imgur.com/USMBisq.jpg

https://i.imgur.com/n2wylFc.jpg

https://i.imgur.com/jEIjrSM.jpg

https://i.imgur.com/keNybKx.jpg

https://i.imgur.com/DcizkGL.jpg


Cheers
tom

[pompeiisneaks]

I will say that I see a lot of really long wires going all over the place in there. You should try to adhere to a few rules with that:

1. make the shortest most direct run you can, with the other rules respected
2. try and keep signal wires away from or crossing over at exact 90deg angles from other wire types to avoid interference
3. keep heater wires away as best you can from the signal wires. there's a great detail on this by the merlin blencowe here: http://www.valvewizard.co.uk/heater.html

There are probably a lot more as well, but those 3 are some of the most important I've seen.

another side note is that if something is pretty high gain, you want to use shielded wire there for signal as well.

It's often better to start a new thread on a separate amp build so it's less confusing than an existing thread about a different general topic, so that your amp troubleshooting isn't confused with people discussing the amps in general.

[unknowntome]

I will say that I see a lot of really long wires going all over the place in there. You should try to adhere to a few rules with that:

1. make the shortest most direct run you can, with the other rules respected
2. try and keep signal wires away from or crossing over at exact 90deg angles from other wire types to avoid interference
3. keep heater wires away as best you can from the signal wires. there's a great detail on this by the merlin blencowe here: http://www.valvewizard.co.uk/heater.html

There are probably a lot more as well, but those 3 are some of the most important I've seen.

another side note is that if something is pretty high gain, you want to use shielded wire there for signal as well.

It's often better to start a new thread on a separate amp build so it's less confusing than an existing thread about a different general topic, so that your amp troubleshooting isn't confused with people discussing the amps in general.

Thanks for all that! I’ve just posted the above in a new thread.. hopefully it gets some traction!

[unknowntome]

It could be RFI/EMI in general, that often sounds like static or hissing...I have had great luck with a low value (50-100pf) capacitor between the plate and cathode on each triode of V1. That shunts high frequency signals, like am/fm radio, to ground without messing with the audible range.

Mikey,

Did you mean 50-100pF from grid to cathode or actually plate to cathode, as you wrote.

I use a 50pf ceramic cap from plate to cathode. I personally cannot hear any audible change with this setup, except for the lack of RFI. I live on a hill about half a mile from a radio tower serving a large city. My Amps are fm radios without these caps. Values larger than 100pf can reduce audible high frequencies and harmonics. I cannot vouch for the grid to cathode approach, but it makes sense it would work as well. I think you need to use a much smaller value in that case, and maybe in conjunction with a small grid stop resistor?

Hey Mikey.. I’m trying to troubleshoot some hiss/noise in my build. I’ve changed a number of specific resistors from CC to CF without luck… I was reading back through this thread and stumbled across your post. Are you soldering caps on both v1 and v2? Pins 1 to 3 and then 6 to 8?
Cheers
Tom

[mikeywoll]

Hi Tom,

Yeah you have it right. Arguably, you could put the snubber cap across the side of the tube that is exposed to the world outside of the chassis, so the first half of V1 and the return side of the reverb tube. I tend to just try them wherever the pre-amp is significantly amplifying a signal. The potential to pick up and amplify RF is there and there is almost no cost to the little cap, even accounting for the high voltage caps.

Mike

[unknowntome]

Hi Tom,

Yeah you have it right. Arguably, you could put the snubber cap across the side of the tube that is exposed to the world outside of the chassis, so the first half of V1 and the return side of the reverb tube. I tend to just try them wherever the pre-amp is significantly amplifying a signal. The potential to pick up and amplify RF is there and there is almost no cost to the little cap, even accounting for the high voltage caps.

Mike

Great, thanks for confirming that Mike.. I’ll give it a go!

[unknowntome]

Hi Tom,

Yeah you have it right. Arguably, you could put the snubber cap across the side of the tube that is exposed to the world outside of the chassis, so the first half of V1 and the return side of the reverb tube. I tend to just try them wherever the pre-amp is significantly amplifying a signal. The potential to pick up and amplify RF is there and there is almost no cost to the little cap, even accounting for the high voltage caps.

Mike

Great, thanks for confirming that Mike.. I’ll give it a go!

Gave it a shot without luck... the hiss persists!! although I'm not entirely sure if its RFI or not. I've started another thread that has all the info re the issue if anyone wants to chime in

[erwin_ve]

Build one recently as well. Very nice sounding amp. This one is gonna sit in my guitarskool. Simple and fun for my students.

Erwin

[alexrussomusic]

Had a crack at tracing out the Chimera's tone stack which has the bass control in place of the voice switch. Looks to be the same bass control as the Benson Preamp running after the tone control from the Chimera, so I copied unknown values for the caps and pots from the pedal.
First time tracing a circuit though, and the source picture (attached) isn't superb, so definitely open to the possibility of errors.

Hey there - do you know how old this chimera was? Like from what year? Did it have t

[Hoodnight]

Hey there - do you know how old this chimera was? Like from what year? Did it have t

Unsure - actually can't even find my source any more :/ Do you still have the Monarch? Would love some more gut-shots.

I'm actually working on a new schematic and layout for the Monarch Reverb - think I've basically got the thing worked out! Based on some new photos I've found.