Morley Emerald Echo analog delay

The Morley Emerald Echo Box (they call it EEB for short) is one of the pedals from their late 90s “Jewel Box” pedal series: Emerald Echo, Diamond Distortion, Sapphire Flanger and Crystal Chorus .

It’s an anlog delay based on the MN3205 bucket-brigade and with the NE571 compander. It has only one BBD chip, so the delay time is limited to around 300 ms. The circuit is  similar to the classic analog delays, for example Ibanez AD-9 and Boss DM-2. It’s a buffered bypass pedal, the signal always pass through the input opamp (TL072) buffer.

Looking at the schematic  I found a few things that are a different.

The dry and wet signals are mixed using a blend pot. So when you blend in the wet signal, the original signal is attenuated. So it’s possible to (almost) completely dial out the dry signal and only hear the wet delay signal. In most delay pedals, the wet signal is added to the dry signal, you can only add the delay, not remove the original signal. So, on the Morley pedal, mixing in the delay causes a volume drop on the first, original, signal. Not a big problem I think, you can dial in a good mix.

The feedback signal is fed back through a voltage divider and a trim pot to the NE571 compressor circuit. This is how it’s done in most delay pedals. In the Morley the signal is fed to pin 6, in other pedals to pin 5. Both pin 5 and 6 goes to the inverted input of an internal opamp, the difference is that pin 6 passes a 20k resistor. The number of repeats in the Morley pedal is quite limited and no “oscillating feedback” is possible. The signal passes both the 25k trimpot and the 20k internal resistor.I’ve tested to connect the feedback to pin 5 instead, and it becomes possible to get more repeats. This is a good mod I think, it’s still possible to use the trimpot to get almost the original behaviour.

A really nice sounding analog delay. Perhaps a little to big for your pedal board, but heavy and sturdy if you go old-style with pedals on the floor.

Notes about the CMP-5 compressor (Made in Japan 80s pedal)

The CMP-5 compressor

Here are  some notes about this 80s compressor pedal, and also some tweaks I did to mine to solve some issues.

The CMP-5 compressor was sold under many different brands: Aria Pro II, Axtron, Loco Box and others. I have one that is branded “Vision” (

It’s a Ross/MXR Dynacomp style OTA compressor using the CA3080 chip, built into a cheap but quite durable plastic enclosure. I have rehoused mine in an aluminium enclosure.

It has the standard controls for attack (slow attack is CCW, fast attack CW, so at “0” you get the “default” Ross/Dynacomp setting), sustain and level. When both the sustain and attack are at the higher settings (CW) you can get a crackling noise especially when a note is dying out. See below how I tried to fix that in my pedal.

It has a Boss style soft bypass switching, which means it has a buffered bypass. I did some tweaks to that too, see below.

The transistors used in this pedal are 2SC1815 and 2SK30A (the two JFETs in the switching circuit)

Here’s the pcb with some of the components that I mention in the text marked:

Here are a few observations when I compared the circuit with the original Ross/DynaComp circuit.

Power regulation and filtering

The power is regulated with an emitter follower voltage regulator (Q1 in the picture). The regulated voltage is around 8V and the bias voltage is around 4.3V.


There is an emitter follwer buffer after the CA3080 (Q3 in the picture). That means that the transistor after the OTA doesn’t have to serve as phase inverter, diode driver, and signal output buffer (as in Ross/DynaComp). The buffered bypass switching adds an extra output buffer (Q10) after the level control.

Extra rectifier filter transistor pair

Unlike most other Dynacomp/Ross derivates, it has an extra transistor pair (Q5 and Q6) in the stage that provides the current feedback to the OTA amplifier (Q7 and Q8 are the other transistors in the output stage). The signal is split after the phase inverter transistor. I’m not sure about the advantages of an extra pair. The extra pair has a high pass filtering with a cut-off at 160 Hz.

Buffer mods

I increased the bias resistors (R1 and R2 in the picture) on the input and output buffer stages to 1M (from 470k). This, together with increasing the input cap to 47n (C1) and the cap in the bypass circuit (C2) to 470n (from 47n), the frequency response was changed to allow more bass through (both in active and bypass). The original pedal  cut bass from 150 Hz even in bypass. I haven’t really heard any difference, only verified it with frequency analysis,  but it is more similar to the Boss compressors of the time.

Sustain control mod

I got a crackling noise especially when a note was is dying out when the sustain and attack was in the highest settings (attack in the “fastest” setting). The problem wasn’t reproducible with attack in “slower” settings. My fix was to increase the 15k resistor to reduce the max current that can be fed back to the OTA (I added a 56k in the feedback path). It’s still plenty of sustain.

Replacing backup battery in the Yamaha SY77 synth

I fired up my 90s Yamaha SY77 synth, and was greeted with no or strange sounds and a “Change Internal Battery” message. I don’t think the battery has ever been changed, so after 25+ years I guess it’s ok to do some maintenance. If you had your own sounds and patches, that data is probably lost when you get to this point. Hopefully you have a backup. I had some sounds, but no backup that I know of.


The battery is a CR2032 coin cell that is soldered in place, so you need a battery with solder tabs, to be mounted horizontal on a pcb. Don’t try to solder on a standard coin cell battery, a battery with solder tabs isn’t so expensive.

So I turned the keyboard over and removed the necessary screws to remove the bottom cover. Note that three screws on each end holds the side covers, not the bottom cover. Leave them, and also leave the rubber feet.

With the bottom cover removed, you can see the battery on the large pcb next to the floppy disk drive. To unsolder the battery, you need to remove the cables on the floppy disk drive side of the pcb, and on the keyboard side of the pcb. You can leave the cables on the left side of the pcb. It can be tricky to remove some of the cables, but you only need to pull the connectors (hard). Be careful and do not pull the cables (you may rip out the crimps from the connectors). Remove the screws that hold the pcb, and then you can flip the board over.

Unsolder the old battery. My new battery had two tabs for the plus-side (original battery had one plus tab), but there were corresponding holes in the pcb that I could use. Make sure the tab connected to the top of the battery goes to the “+” hole on the pcb.

After re-assembling everything, you need to do a factory reset. This is done by:

– Turn on the power
– Press and hold the [VOICE] button, the press and hold the [BANK D] button and the [8] button. Now it will display the “Test Program Menu”. (I had to do several attempts to get it to work)
– Now press [COPY] button to reload the factory data.