Buchla 111 Ring Mod Layout

ericcoleridge · Joined: Jan 16, 2007 Posts: 889 Location: NYC

Yep, that's a ring mod alright. No question Very Happy

Doesn't someone sell matched transistor pairs now? I think maybe MFOS.

vtl5c3 · Posted: Wed Feb 29, 2012 9:30 pm Post subject:

Bridechamber too.

LektroiD · Posted: Fri Mar 02, 2012 2:01 pm Post subject:

Maybe I was lucky but I managed to calibrate mine down without matching transistors. However, if you really must, why not build the Frijitz transistor matcher, save yourself some money...
http://electro-music.com/forum/download.php?id=25772

fluxmonkey · Joined: Jun 24, 2005 Posts: 708 Location: cleve

i shd be getting my prototype boards next week... any details on how to trim this?

RSFC · Joined: Sep 02, 2010 Posts: 63 Location: space lab

hey flux, do you plan on offering PCBs for sale?

fluxmonkey · Joined: Jun 24, 2005 Posts: 708 Location: cleve

emdot_ambient · Joined: Nov 22, 2009 Posts: 667 Location: Frederick, MD

I'm sure there'd be plenty of interest if you posted a PCB sale notice here and on muff's. thumb up

fluxmonkey · Joined: Jun 24, 2005 Posts: 708 Location: cleve

any additional hints on how to trim this thing up? i'm not clear on the actual function of each of the 4 trimmer pots...

b

-minus- · Joined: Oct 26, 2008 Posts: 787 Audio files: 13

I'm bread boarding this at the moment just to check that it works before I lay out a stripboard design.

On the original Buchla schematic, R14 is labelled as 10K and R19 is just labelled 10. Is this 10 Ohms? I noticed vtl5c3 has both these resistors as 10 Ohms. I assume that what ever value they are meant to be, they are to be alike. Any opinions on this? I'm still breadboarding through the night... just waiting for sunrise and the local store to open so I can get more 680 Ohm resistors. In the mean time I'll try with 10 Ohms and and then with 10K just to see.

-minus- · Joined: Oct 26, 2008 Posts: 787 Audio files: 13

I have this working on bread board. Well at least I think it is working. It sounds similar to the clip posted on page 1.

I'm unsure about the trimming. Those trim pots were put in the circuit for a reason. The 20K one seems to affect the sound the most when turned. R10, R14 and R19 appear to be fine tuning to balance the matched transistor pairs. I used Yves simple method, but spent a bit of time matching about 40 transistors.

http://electro-music.com/forum/post-276867.html

So I guess there are some measurements to take with a voltmeter around these matched pairs. I'm wondering if it matters which input the carrier signal goes into. Also, I'm using triangle oscillators as I have yet to get around to building ones which output sine waves. I was unable to calibrate until no sound was present as LektroiD did. I'll post further findings here.

-minus- · Joined: Oct 26, 2008 Posts: 787 Audio files: 13

YAY! Just got it working! Cool

CARRIER into signal input 1

Sounds great. Really bell like. I'll play around with the trimming and see what happens. I'll be strip boarding this in the next couple of days I imagine. I'll post the diagrams in case anyone else wants to make one.

fluxmonkey · Joined: Jun 24, 2005 Posts: 708 Location: cleve

checking against the schematic: under each of the 2 transistor pairs in the upper left (Q1/2 and Q3/4), there are 2 resistors tying the emitter pairs together, in parallel w/ the two 1k trimmers. on the layout, both of these are shown as 10 ohm; on the schematic one of these is 10k. those of you who've built this successfully: what are you using?

-minus- · Joined: Oct 26, 2008 Posts: 787 Audio files: 13

OK... On my breadboard I tried both the 10K and the 10 ohm resistors. I even tried one 10K and one 10 ohm. I don't think it matters a hell of a lot to be honest. My gut feeling is that they should be 10K. It seems more than likely a K was omitted than a K was accidentally inserted. Confused

I've stripboarded this and will be posting a diagram in the next few hours. I have used 10K on my stripboard and the circuit seems to be working fine. Be prepared for an hour of tuning those trimmers trying to figure out what is what. Laughing

...and just ignore my carrier into signal input 1 comment:oops:. I don't think it matters. I'm feeding both inputs triangles and it goes "WWWWWeeeeeeOOOOOOOowwwwwwWWWW" regardless.

vtl5c3 · Posted: Wed Oct 24, 2012 10:04 am Post subject:

I'm pretty sure I used 10 ohm resistors. I have an earlier version of the 111 schematic and it shows 10 Ohm under both pairs.

-minus- · Joined: Oct 26, 2008 Posts: 787 Audio files: 13

All right. I might pull out the 10K resistors and try 10 Ohm. Perhaps it does seem a little large a value going across the pot outer legs.

EDIT: Just did parallel resistance calculation.

With a 10 Ohm resistor across a 1K trim pot we get:

9.900990099009901 Ohms

With a 10K resistor across a 1K trim pot we get:

909.0909090909091 Ohms

Obviously there is a difference. But are they not just 'balancing' those two pairs? I'm not an expert but I do not think the value is crucial here. The 10 Ohms give you very little range to play with in terms of trimming though... I might pull out the 10K resistors I have a see.

fluxmonkey · Joined: Jun 24, 2005 Posts: 708 Location: cleve

with Romeo's permission, I am considering organizing a short run of PCBs for this project. Go HERE for more information or to register interest.

Note: I am not taking preorders at this time, just gauging interest. All updates will be made via that thread.

thx!
b

vladosh · Posted: Mon Oct 31, 2016 3:31 am Post subject:

here's a sample i just recorded ,sounds like bells still i'm not sure i tuned it right there is little bit more bleedtrough on one input ,thanks for the layout ,used BCM transistors for the matched pairs

buchla ring modulator.mp3

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