Roland - AP-2 ( Phase-II )  [schematic]

Discussion regarding early stompbox technology: 1960-1975 Please keep discussion focused and contribute what info you have...
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Brainbender
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Post by Brainbender »

can someone make a layout out of schematic, please? :wink:

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Post by Greenmachine »

chicago_mike wrote:Cool! Im building a jetphaser as I type this 8)
Cooool. If you ever want to share a layout for that I'd be grateful!

:D
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Post by candidate »

Bernardduur wrote:[ Image ]
what values are cut off at the bottom right hand corner?

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Post by Cub »

Hello chaps,

Not to derail the Pete Cornish P-2 thread any further with talk about the AP-2 buffer, I thouht I'd take it to this thread. It all started with this post by analogguru. Particulary the last bit sounds very promising.
analogguru wrote:Overall it can be expected that the "AP-2-Buffer" has:

a higher input impedance,
a lower output impedance,
less noise,
less distortion,
and even a small gain

compared with the "mythical Cornish Buffer" - with only 2 additional components.
That could be a fun little project! analogguru's redrawn schematic is nowhere to be found, so I found the full schematic, enhanced it a bit and redrew the bit with the buffer, keeping the components names and values from the original schematic intact.

I did manage to track down a layout and traces on a Japanese blog that I can't seem to find any more. It was said that the redrawn schematic from analogguru was used to create these. They're attached as well, but I'm not certain if they're correct. R10 in the schematic is named R7 in the layout and BOM and the real R7 is not to be found in the Japanese layout. What do you make of this?

Lastly, perhaps there's room for a little 21st century improvement? Here's what I'm thinking, but I'll be the first to admit that I know very little on this subject, so please do chime in if my ideas are rubbish and / or if you have any suggestions.

- The Japanese bloke already added a 2M pull down resistor for those who would like to make it switchable, splendid!
- A 100pF cap parallel with this pull down resistor to block RFI could be welcome as well, right? Better safe than sorry.
- Other transistors than the stock 2SC1000GR. The Japanese Layout suggests 2N5088, are there any other suitable candidates?
- Then the power filtering. Do you think we need a larger value for C30? I'm thinking 470µF or perhaps even 1000µF, or will 100µF be sufficient?
- Let's give C30 a little friend and put a .1µF parallel with it to reduce the high frequency noise.
- Also in the filtering, R55 might be a bit on the large side. Will 100r or 220r will be enough here?

I know I could breadboard this and find out for myself, but as a paint-by-numbers type of kit builder, I don't have many components in stock. My usual supplier is a bit swamped with orders at the moment. It seems everybody is staying in and soldering and I applaud them for it! Then there's the delivery people, who are also swamped.
If I order today, it might be several weeks up to a month before the package arrives. So you understand I'd rather hear from you more experienced people before I put together a definitive shopping list.

Thank you all for your help and stay safe.
Attachments
Roland AP-2 Phase II (full schematic)
Roland AP-2 Phase II (full schematic)
Roland AP-2 Phase II (buffer) redrawn for FSB
Roland AP-2 Phase II (buffer) redrawn for FSB
Roland AP-2 Phase II (buffer) layout by Bridge Fx
Roland AP-2 Phase II (buffer) layout by Bridge Fx
Roland AP-2 Phase II (buffer) layout by Bridge Fx.gif (11.38 KiB) Viewed 6775 times
Roland AP-2 Phase II (buffer) traces by Bridge Fx
Roland AP-2 Phase II (buffer) traces by Bridge Fx
Roland AP-2 Phase II (buffer) traces by Bridge Fx.gif (1.84 KiB) Viewed 6775 times
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Post by Cub »

Cub wrote:analogguru's redrawn schematic is nowhere to be found, so I found the full schematic, enhanced it a bit and redrew the bit with the buffer, keeping the components names and values from the original schematic intact.
Or, so I thought... There are two C5 caps! The 10µF one should be C3, the 1µF one is only C5. I'll make certain to change this in the schematic with the 21st century improvements.

Speaking of which, do you think these two caps should be film type instead of electrolytic? I notice that a lot in Tube Screamer mods, but I don't know if it's for sound or for mojo.
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