Naylor Presence circuit

[Gaz]

Can anyone explain to me how this works?

[Cliff Schecht]

I see a low-pass filter formed by the .005uF cap and 10k resistor in parallel with an adjustable lowpass filter formed by a 22uF cap and a 5k pot. The higher the value of resistance the pot is set at, the less effective the presence circuit is (i.e. more highs get through). I think the .0015uF cap is to form either a high-pass filter or perhaps some sort of shelving filter to cut bass output (lets more mids and highs through, makes the amp sing more). These are guesses without calculating anything though..

[martin manning]

The 22u is so big that the 5k pot is controlling the level of FB across all frequencies... a FB control rather than a presence. The 0.0015 with the 10k tail high-pass is also causing some phase shift, which is sometimes used to flatten the response of the power amp. 10.6kHz knee means it's taming the high end, but then the 0.005u to ground is reducing that effect.

[Darkbluemurder]

I asked a similar question in a German tube amp forum and got the comment "not a good idea - it's bound to oscillate." I have never played a Naylor though and have not tried this circuit.

Cheers Stephan

[martin manning]

I got curious about this and ran some numbers.

The usual presence circuit has a low-pass shelving response, with the lower break point fixed, and the upper one sliding down a 6dB/Octave slope.

This thing is a high-pass shelf, but the low end is attenuated so much (~100dB) it is basically a high-pass filter. The knee is at around 10-11kHz when the pot is at max resistance (the 0.0015u and 10k), and turning the pot slides the knee to the right along with the 6dB/Octave slope. Interesting variation... anyone know what it sounds like?

[Gaz]

Thanks for the info! I actually wired it up really quick, and thought it sounded nice, only affecting the really high-highs. I didn't try it too loud because it was late, and didn't keep it in because the amp has a PPIMV, making the control useless/ineffective at low settings. I thought it was very intriguing though.

[azatplayer]

Im in the middle of planning a naylor build, actually drilling out the chassis now.
Im wondering if theres the usual phase issue with plate leads on this feedback circuit. Will report when i find out!
Looking forward to this build, should be killer.

[bcmatt]

I stumbled across a youtube clip of a Naylor SD60 yesterday and I'm rather intrigued with what effect this style presence circuit would have in a JCM800 or an Express. Has anyone played with it to any degree in a real amp?

My Express currently has the Presence circuit completely removed in favour of no NFB and just a cut control (just like I did and loved on my Liverpool). I think it was an improvement on my Express, but not necessarily the gamechanger it seemed to be on my Liverpool.

[bcmatt]

So I just installed this Naylor SD60 presence circuit in my Express (with VVR) and after playing it for the last 20 minutes, I'm still unsure if I love it or hate it. It does feel like it brings down the overall gain in the amp a bit as well as thinning the sound significantly at some settings.
It's a weird control to get used to because it's not like it is directly controlling the "sizzle" or even the obvious brightness per se. But if you strum while turning the presence knob it is obviously affecting some brighter frequencies in the tone.
When you're super used to your express and have usual settings, it does throw that off and causes you to twiddle all the controls again. It still sounds like a great amp, but it is different.

[bcmatt]

Ok, I buttoned the amp back up and played it a whole bunch more with 3 different guitars.
I actually do quite like the sound of it and the Express still has all its character. However, without doing a real A/B against the original presence circuit, I can't say exactly how it sounds different. Especially since for the last 6 months I've had a cut control instead of NFB and presence.

After playing for awhile, I'd say there is no concern about lacking low end, but it is quite controlled.
I feel like it does add a certain "smoothness" to the tone. Maybe it is adding sustain too? (But that could be due to playing it a bit louder this last hour.
I do feel like it's a bit misleading to simply call it a presence control since I feel like it is more like a control for a lower-highs push almost like there is a parallel cocked wah added to the tone as well. I don't know; I'm struggling to describe it.
Having a cut control instead was definitely more intuitive. This presence control isn't exactly something you can reach for to simply add or subtract overall brightness. A cut control is way more efficient and simple that way. I'd actually be tempted to keep this as well as a cut control at the same time... but for now I'll just leave this in and see how used to it I get.

I'd be tempted to give this Naylor Presence a more cryptic name like a "contour" control or something.

[cdemike]

Glad you were able to experiment more with it -- I was hoping someone would try it an share the results. Based on how you're describing the circuit's behavior in an actual amp, I wonder if this would work better when reconfigured to operate more like a presonance circuit.