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Forum Home > Layout Gallery - GuitarPCB Build Documents, Mods and Tips > Apollo Tremolo

Site Owner
Posts: 8793

The Apollo Tremolo is a highly advanced version of one of the most popular music effects ever made! We took the original Tremulus Lune version to a new advanced level by adding several versatile features!


It adds an instantaneous SPEED SHIFT for a dramatic change and a "KILL" switch to remove the effect while maintaining a high quality buffered throughput. The awesome buffer makes this a 2-1 pedal . Use footswitches for both SPEED SHIFT and the KILL Switch! True-Bypass is of course always an option.

Imagine having access to these dreamy wave tones and have an awesome buffer in the same pedal. Hit the kill switch and use it as a stand alone buffer or simply disengage for True-Bypass.


There are many more exotic sounds available.


Watch Video #1 below. Stay tuned for Video #2.

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Apollo Tremolo Build Document

Updated 3/3/17 - Substituted NE5532s for TL072s. Some people were experiencing a noise or pulse issue with the NE5532 chips. This problem seems to be hit or miss so we decided to substitute the NE5532s for TL072s which are a great sonic chip with absolutely no chance of any type of noise.

Must Have Components:

Apollo Tremolo NSL-32 OptoCoupler - (1 )

TL072 Dual Opamps - (2)

Trimmers - 2k and (Optional 10k) - (1 or 2)

If using Toggles for Mods - SPST &SPDT - (2)

Build Notes:

* Use either a Gain Potentiometer or Trimmer (your choice – see below) Do not use both!

** There is no D2 in this build version. There is only D1 and D3.

*** NSL-32 is the recommended Vactrol, you may also use a *VTL5C2 if you have access to one.


Gain – You have two choices. Many will want adjustment of the overall level on the outside of the enclosure to keep the Tremolo at Unity Gain or otherwise. Those that are looking to make a (4) knob Apollo may use the convenient on-board Gain trimmer instead. Do not use both! You may then set and forget the master volume.

Speed – This adjusts the rate of speed of the Tremolo waves. Use this in conjunction with the Speed Shift!

Speed Shift - Switch [SW1] - The speed shift switch allows you the option of kicking an extra capacitor in parallel with C5, which has the effect of changing the speed range of the LFO circuit. This option adds more flexibility. I would also recommend using this as a footswitch for instant Speed Shifting on the fly, instead of a toggle switch.

Depth – Adjusts the overall strength of the Tremolo sounds.

Spacing – Adjusts spacing between volume pulses

Smooth – Blend between full on/off square wave "chop" to smooth buttery sine-tri-round wave

BLEVEL Trimmer: Adjust the Level of the Buffer in “Kill Mode” at [SW2]


The NSL-32 Vactrol is comprised of an LED and a photo resistor. As the LED changes intensity, the photo resistor changes resistance. This change in resistance is what manipulates the audio signal to give us a tremolo effect.

Note you may also use a VTL5C2. If using the VTL5C2 Vactrol then make R17 a Jumper wire instead of 1k.

The NSL-32 , TL072 Opamps and BiColor LEDs for Mods can usually be found at GuitarPCB’s PCB Shop.

It must be an NSL-32 with no additional numbers or letters attached to the product code!

Mod Idea:

Socket and play with C4 and C5 to change the spread of the Speed Control

This is a "two in one" pedal circuit:

I cannot stress enough that besides being the "Ultimate Tremolo" you can use the "Kill Switch" and have the "Ultimate Buffer". It will make your guitar and amp rig sound fantastic!

Add to this you can install a "Speed Switch" that when used on a footswitch instead of a Toggle you can instantly change speeds on the fly for an extra "moody" musical passage.

Symmetry Mod option:


The components aside from the 500k pots are diodes with the white stripe being cathode. A 1N4001 would be fine.

Another link showing similar mod:

This version uses a single B500k pot with the diodes off of lugs 1 and 3, so that putting the pot at noon gives a symmetrical wave shape, and turning the knob left or right will shift the peak left or right as well.

The above Symmetry Mods have not been tested by me personally but should work.

If you try this mod please make a post in the Show Off Your Finished Pedal section of the forum.


Recommended accessories:

1. Barry's Famous Pot Condoms™ .

2. 3PDT Wiring Boards .

3. Barry's Best Pedal Hookup Wire.

4. DPDT Wiring Boards - Perfect for Mods

5. DC Power Jacks 2.1mm

6. Common Anode LED (Optional to Standard LED)

7. Plastic Bezels for Common Anode LEDs

8. Pot Condoms for mounting in tight quarters over potentiometers

9. GPCB Secure Mounts - For mounting with room to spare

April 2, 2016 at 12:50 AM Flag Quote & Reply

Site Owner
Posts: 8793

Apollo Tremolo Build Document has been updated above as of 3/3/2017.

It contains a newer wiring guide. We have substituted NE5532s from the old document to TL072s as some people had heard a noise associated with the NE5532 chips.

There were no other changes made to the document!

Enjoy the Wilkie1 Symmetry Mod - Courtesy of Wilkie1

Mods are not guaranteed to satisfy everyone but those wishing to explore give it a go.

April 7, 2016 at 12:26 AM Flag Quote & Reply

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