Tone tweaking section
barry (Administrator) 12-30-2013 at 12:03 AM.
Post: #1
The N5X has a simple signal path and that makes it very easy to tweak to personalise your amplifier's tone. Use the ideas below as your guide.
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barry (Administrator) 01-20-2014 at 06:42 AM.
Post: #2
[Image: n5xtt01.jpg]

Power valve biasing
As standard, the N5X comes with relatively conservative biasing for the octal power valves. It's designed to work with the 'industry standard' 6V6 Champ value of 470Ω/3W (R17). This should ensure that any popular octal power valve that you want to try works without risk of burning out.

However, you may want to experiment with a warmer bias for bigger valves - 6L6, EL34, etc. If so, you can lower the value of this resistor - perhaps to 270Ω. Keep an eye on the cathode voltage and if you start to approach the 3W resistor rating, consider upping the rating to 5W.

When you do replace the R17 resistor, make sure to carry out the measurements and calculations shown on the Final testing page, and compare the figures you see to the datasheet of the valve you are using.
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barry (Administrator) 01-20-2014 at 07:39 AM.
Post: #3
More gain/distortion
The N5X, like the old SE-5a, used just two valves to get a surprising amount of distortion. The N5X adds a Bypass switch to switch out the tone stack for even more gain, and with the N5X's Power level control (using a VVR circuit), you can get that fully-cranked distortion at lower room volumes. No need for an attenuator!

But there are still a few ways to get a little more distortion:
1) lower the 470k R7 resistor (e.g. to 100k)
2) increase the 100k R4 resistor (150-220k)
3) increase the 100k R10 resistor (150-220k)

[Image: n5xtt03.jpg]

Try each in turn and play for a while to see how you like it.

For a different approach to distortion tone, you can also experiment with lower value for the 820Ω R9 resistor. Try values of 560Ω/680Ω.
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barry (Administrator) 01-20-2014 at 07:53 AM.
Post: #4
More bass
With a big octal valve, you may want to adjust the circuit to pass more bass. Switching the Boost switch to the down position provides a simple bass boost over the normal N5X response, but with a few capacitor value changes, you can go further.

First, the basics: the capacitors that are in-line with the guitar signal act to restrict (attenuate) low frequencies. C3 and C9 (both 22nF as standard) work with the resistances to ground (R7+VR1 and R14, respectively) to create what's known as a high-pass filter. Increasing the value of the capacitors acts to lower the frequency of the filter, allowing more bass through to the next stage.

[Image: n5xtt04.jpg]

So the simplest approach is to increase one or both of C3 and C9 to perhaps 47nF or even 100nF. Choose them capacitors rated for 350V or more.

TIP: Capacitors higher than 22nF tend to be physically larger, and can seem awkward to fit. But just bend the leads back under the body to mount on the turrets.

[Image: n5xtt05.jpg]
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barry (Administrator) 02-01-2014 at 08:14 AM.
Post: #5
Make a bigger difference
The Boost switch on the N5X has three settings:
1) Up = Bright (boosts upper mids and highs, and is the original SE-5a mode)
2) Middle = None (cleaner tones)
3) Down = Fat (boost most frequencies including bass)

To achieve this, the standard values for the cathode bypass caps on the N5X are 1uF (for the Bright mode) and 47uF (for the Fat mode). The general idea is that the 1uF mode works well with humbuckers, and the Fat mode gives some extra thickness for single-coil pickups.

But if you want to create a bigger difference for the two settings, you can alter these capacitors. For example, change the 1uF capacitors to 0.47uF and the 47uF to perhaps 100uF and you will accentuate the difference. (Any voltage rating over 10V is fine.)

As always, it's easy to adjust these values to taste.
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