AD-900 Delay MN3008 version

[armdnrdy]

A few years ago, I put together a smaller build of the AD-900. (MN3005 version)
Since that time, the price of MN3005s has skyrocketed!
MN3008s can still be sourced for a reasonable price..so...I decided to explore the AD-900 MN3008 version.

Using soulsonic's schematic from the other site, I figured out the differences between the two versions by studying component side images of the MN3008 version. I was able to produce a schematic..but wanted to verify the drawing before I posted it.

I made a request on the other site in the "I'd like to see the guts of" thread, for any trace side images, and Dirk Hendrik was gracious enough to provide trace side images...and more! Thanks again Dirk!

With the info that Dirk provided, I was able to verify the schematic. (The circuit was correct but I had some of the component numbering wrong)

Dirk also provided an overlay (silk layer) that I took the liberty of adding component designations to, and the trace side art which was unfinished. (There were a few areas that were highlighted in red that the "artist" was unsure about)
I also took the liberty to fix these "problem" areas.

I'm not sure who put together the silk layer and trace side art but...credit and thanks go out to you!







I have PDF files of all of the above. If needed...please request. Also...if there are any talented forum members out there that are good at resizing the trace side board image while keeping high resolution...I have a large BMP file if needed.

[armdnrdy]

I've had a few PM requests for the schematic in PDF form so....

Here it is for anyone else interested.

https://dl.dropboxusercontent.com/u/53299166/DIYstompboxes/AD-900%20MN3008%20version.pdf

This info is for the original Maxon AD-900......stock.

I'll be putting together a project with TBP, a tails footswitch, and a regulated power supply, which will allow the use of unregulated wall adapters from 12-18 VDC.

[armdnrdy]

Here's the schematic and board overlay for a "modified" MN3008 version AD-900.







True bypass, tails footswitch, and voltage regulator added.

[armdnrdy]

I decided to revisit and finish some of the projects that I have had boxes of parts "laying" around for.

Here is the trace side and component side of the AD-900 (4) MN3008 version.
The enclosure is a bit larger than the original Maxon. 1590XX





If anyone is interested....I'll put together a project for this.

[Luke51411]

Epic! Love it! Want.

[mth5044]

Man oh man that biasing is going to be fun 

[armdnrdy]

I have the factory alignment docs.

It's really not that bad....eight of the trimmers are bias and balance for the BBDs.

You do one BBD...then move on to the next. The whole set up shouldn't take much longer than 10-15 minutes.

What I'm not looking forward to is the offboard wiring! Almost all of the boards I've been designing lately include all board mounted components. This one...I kind of stuck to the original because the routing is textbook! Good separation of "problem areas" and separate grounds for the clock/BBDs and the signal path.

[mth5044]

Three pots, two wire bypass, power, in and out? You've gotten too soft 

Very kidding, it's hard to believe the PCB doesn't route itself with how fantastic it looks.

Do you use an oscilloscope for the bias and balance, or simply by ear?

[armdnrdy]

Yeah...I've spoiled myself with my recent builds!

Yes..I use a scope. I picked up an old used Kenwood (remember the stereo company) that suits my needs just fine. I paid $25 for it.

As far as set up goes (bias and balance)...once you've calibrated one BBD based circuit...they are all the same. You really don't need factory docs for that. What is needed is the clock frequency for each particular circuit so you can "dial" it in as per the original.

[armdnrdy]

Finally found the time to box, wire, and calibrate this build.

Now I'll have to "unbox" it and paint it.
It fired up with no issues which is always a plus with a larger build! I even put the ICs in before I started calibration! 

This is a great sounding analog delay! A little darker sounding than the Carbon Copy but a great delay by any standard!

Some months back I purchased a batch of 3mm flat top LEDs. This is the first opportunity that I've had to use them.

[mth5044]

Damn that is gorgeous. What is the second foot switch for?

[armdnrdy]

Thank you!

The extra switch is a "tails" switch as shown on the modified schematics. (Reply 2) (B-3.5 on the drawing)

I added a 12 volt regulator, TBP, indicator LEDs, and the tails switch. The rest of the circuit is original.

Here's a shot of the original Maxon.

[Govmnt_Lacky]

OK...ok...ok...

Challenge accepted Larry!!! 

Can you send me the documents for the build (pdf)?

PM me if you need email or deets! 

[armdnrdy]

I still have your email Greg.

Do you have an oscilloscope?

I wouldn't want to dial this in by ear!

[Govmnt_Lacky]

I still have your email Greg.

Do you have an oscilloscope?

I wouldn't want to dial this in by ear!

You know it brother! 

I got the tools... now I need the deets and the willpower 

[armdnrdy]

I have the adjustment procedure docs from Godlyke (Maxon rep) but, I'll rewrite new docs with scope shots I took during the process...

Give me a bit to get it all together.

[teknoman2]

Usually I don't post here but this project is awesome mate,
I have the maxon 4 BBD 3xx8 version and its a killer, there isn't any audible clock freq even in max delay settings due to filtering but the downside is that it cuts too much high freq.
Now regarding your build I believe you don't need the two 100k resistors R51 and R50 their purpose is only when there is a switch there to prevent pop and for output impedance.
Also nice idea adding tails to this project and make it TBP. Why did you put a 10M on the tails switch?
Again great work.

Cheers,
Panos.

[armdnrdy]

Thanks Panos.

If you look at the original drawing, there is a 4.7µf capacitor and a 100K pull down resistor on either side of the switch.
The negative side of the capacitors are facing each other making a bipolar cap when the switch is closed. The two 100Ks are in parallel when the switch is closed making them a 50K.
To keep things as in the original, I decided just to leave the components "as is" as if the switch was engaged.
I figured a couple of 4.7µf caps would be easier to source than a 2.2µf non polar...same with a couple of 100K resistors.

The 10M across the switch is to keep it from popping when engaged/disengaged.
I could have went with a couple of pull downs on either side of the switch but, I wanted to try this method.
I nicked the idea from the Dunlop 535Q. There is a 1P6T rotary switch which switches in different caps. There is a 10M resistor across each switch position to keep it from popping when switched.

The 10M is almost like JFET switching...the JFET is always in the circuit but the resistance goes high causing the signal not to pass.

[Govmnt_Lacky]

I have the adjustment procedure docs from Godlyke (Maxon rep) but, I'll rewrite new docs with scope shots I took during the process...

Give me a bit to get it all together.

Sweet! Always the professional Larry! 

Looking forward to the build...   

[armdnrdy]

Looking forward to the build...   

1/8 watt resistors or 1/4 watt standing on end!