Accent towards Presence

[jazzbass]

Hi everyone,

now that I am building an amplifier inspired by the SSS and the John Mayer / Wonderland I discover a unique feature of the first creations of H. Dumble, the "Accent" function which in the following amps becomes "presence".
If I'm not mistaken, the first function acts on the medium frequencies while the second acts on the medium frequencies.
It is the first amplifier that I build with this function and I wonder what to expect sonically speaking, what will actually be the differences between these functions perhaps with some "sound" examples taken from some performance of artists who are using Dumble amps with these functions.

Thanks

Franco

[martin manning]

I discover a unique feature of the first creations of H. Dumble, the "Accent" function which in the following amps becomes "presence".
If I'm not mistaken, the first function acts on the medium frequencies while the second acts on the medium frequencies.
It is the first amplifier that I build with this function and I wonder what to expect sonically speaking, what will actually be the differences between these functions perhaps with some "sound" examples taken from some performance of artists who are using Dumble amps with these functions.

"Accent" is basically a fixed (full up) presence with on/off functionality. The size of the accent cap and the NFB/PI tail resistors control the range of frequencies that are affected and how much boost occurs for that range.

[jazzbass]

Thanks Martin,

i realized what effect the capacitor has. What range of values would you suggest in an amplifier derived from the SSS?

Thanks
Franco

[martin manning]

What range of values would you suggest in an amplifier derived from the SSS?

In the end it's up to you :^) SSS 002 used 1uF over a 270Ω.

[Bombacaototal]

What range of values would you suggest in an amplifier derived from the SSS?

In the end it's up to you :^) SSS 002 used 1uF over a 270Ω.

Martin, #002 didn't have a presence cap, and 1uF on that circuit is horrible unless you add a presence pot

[erwin_ve]

What range of values would you suggest in an amplifier derived from the SSS?

In the end it's up to you :^) SSS 002 used 1uF over a 270Ω.

Martin, #002 didn't have a presence cap, and 1uF on that circuit is horrible unless you add a presence pot

The presence, accent is labeled "mid" on the handrawn Japanese schematic(full of errors) and useless. I think Richard came up with the idea this might be a presence/accent cap. I changed it accordingly and this setup is much more useable icw the step filters.

[martin manning]

Of course I looked at the 002 schematic I'm maintaining, which has the accent with 1u. Maybe I should have said on SSS 002 people are using 1uF over a 270Ω. That makes much more sense than the 1n mid switch, and it's similar to other amps documented here that have the Accent switch.

[Bombacaototal]

In my personal amp I added a 15pF in place of the 1n. Works like the bright cap across the master like a few ODS. Very nice and much better than the 1uF presence (without the pot) to me personally at least. I use it as an "in between" high filter position

[jazzbass]

Hi everyone,

then summarizing: the best solution is to have an accent "function" consisting of a potentiometer whose central lug is connected to a capacitor from 1uf / 63volt to ground, but the difference with the cut / presence circuit is still not clear to me. Are you getting similar sounding results or will they act differently?

Sometimes we take things for granted that we are used to knowing but that really need a deeper reasoning.
For example, why did H. Dumble leave Accent for Presence? Did he think it was more useful in managing sound?

A hug and Happy Easter to you all.

Franco

[Richard1001]

Hi everyone,

then summarizing: the best solution is to have an accent "function" consisting of a potentiometer whose central lug is connected to a capacitor from 1uf / 63volt to ground, but the difference with the cut / presence circuit is still not clear to me. Are you getting similar sounding results or will they act differently?

Sometimes we take things for granted that we are used to knowing but that really need a deeper reasoning.
For example, why did H. Dumble leave Accent for Presence? Did he think it was more useful in managing sound?

A hug and Happy Easter to you all.

Franco

In the Dumble schematics i have seen, and like Martin said, the accent switch is essentialy the same as the presense. The difference is that the variabele resistor that was user on the presense control gives more tonal variation because you can vary the amount of feedback in the high/mid range that is shorted to ground. Dumble also made accent switches with internal trimpots, keeping the switch, but allowing to set the desired sound.

There are also other manufacturers (Mesa boogie comes to mind) where the presense control is not in the feedback loop at all, but is in fact wired as a high cut filter. In some Dumble amp's something similar can be found, but as far as i know here it only has effect when the overdrive is engaged and it is called 'hf taper'.

[talbany]

https://ampgarage.com/forum/viewtopic.p ... 99#p399399

Hoyt Dumble.jpg

accent%20revised.jpg