Current DIY projects

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evm1024

evm1024

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Just to post a note for the DIY analog folks. I'm almost finished up with 2 channels of Great River MP-2 mic pre. This is the original version not the NV version. Dan Kennedy is a great guy as that he released the artwork and has been helping get many of these pres built.

The other photo is the 12ax7 and 6dj8 tubes that I have been matching and testing for sonics. They have been through a tube tester and will get put into a NY Daves one bottle pre and/or some other mic pre to grade them on their "sweetness". Then the best are for me and the rest off to eBay.

Regards, Ethan
 

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That GR pre board looks great! Nice work on that. Did you design that PCB or is it available for sale somewhere?
I don't see any ICs on it, is it a 100% discreet design?
I might want to build me one of these can you please share some more info on it? :D

Let's see, projects I have are many. Two that are most active right now are renovating my Toa RX-7 and my Synthacon voltage controlled filter.
With the RX-7 I have finally designed new line amplifier modules and whipped up a PCB for them.
Original LA module...
Line-Amp-crop.jpg

PCB layout for my custom replacement...
RX7-LA-01.gif


Just need to save up the dough to have the PCBs fabbed now.

Then the VCF project notes are here:
http://www.somnium7.com/samples/pcbdocs
I did a group-buy with the Synth-DIY community for these to get the PCB price down to $9 per board. Obviously, I plan to use one of these in my synthesizer project but I am making a stompbox version too for guitars and processing loops and stuff. The stompbox is under construction now and it includes an LFO and an envelope follower for modulation sources. I think I'll also add an input for a standard volume pedal for sweeping the cutoff frequency.

So many projects, so little time/money :o
 
Great River MP2

Just head over to prodigy-pro and search on mp2 or great river. You might still be able to buy a few more boards and I think that some new boards are in the works for a group buy. This is not my pcb or design. It is a DOA (Discrete Op amp) which is to say an op amp made of discrete transistors as opposed to a monolythic opamp (such as the Burr Brown).

Regards!

http://www.prodigy-pro.com/forum/viewtopic.php?t=25440&highlight=mp2
 
Hey Ethan,

You wouldn't happen to have an RCA clear-top 12ax7 in all that would you? :)
 
no but...

... I do have a RCA clear top 12au7.

All of those shown are 6dj8 that I am matching and listening to for sweet audio qualities. There is another batch with 12a(XUVT)7 and some others that I've not gotten to yet.

Most of these are from Tektronix spare part kits. That means that they have been burnt in and sorted to weed out the bad/noisy/microphonic ones. They date from the '60s and'70s.

-Ethan
 
cool

BUMP!
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Looks great.
And post update or even better photo of the thing in action when you finish it.
:cool: :cool: :cool:
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btw, just curious, what exactly method you use to 'match' tubes and test them for sonic. ?
I myself have never got into that "area", I mean, beyond Just basic tests and transconductance... . Maybe I should.
 
Somebody expressed an interest in my Thunderchief pedal so I am linking to the pics of it here. This is a design from Runoff Groove that I built and am quite happy with.
Note: the stomp switch hasn't been installed at the time of these pictures...
thunder-01.jpg


The controls are as follows:
Left knob = Gain
Right knob = Level
Top center switch = Lead/Rhythm
Bottom center switch = Brite/Low filter
Top right switch = power full/starve (battery -2V)

The next image is huge...

http://s108.photobucket.com/albums/n13/somnium7/gear/?action=view&current=thunder-02.jpg

Sorry about the blur. Camera phones are hard to hold steady :)
You can see some of the large diodes on the right side. These diodes drop the battery voltage by two volts to starve the circuit and give it the mushy rectifier sound. These diodes are switch in on one position of the power switch and the other position applies full battery voltage.
 
DIY update. New ideas for my Toa RX-7 while I am waiting for the PCBs. I had been trying to decide if I should bother rebuilding the program channels I cannibalized for parts since I only use two of the 8. Here is the new plan - I will rebuild these channels in pairs with different transformers and DOAs so each pair can be used for a different color. I'll turn them into a box of crayons by taking one pair and using 990 DOAs with Jensen OPTs. Then another pair with API 2520 DOAs and Cinemag OPTs and another pair with JLM Hybrids and Edcor OPTs. The possibilities are exciting. :D

While I am having some downtime I am revisiting a very old project which I have been tinkering with for a few years. It is formerly known as the Aztec Processor. I just renamed it to the Quetzalcoatl Quantizer. It's an analog bitcrushing effect - yes analog ...kinda. ;)

It was a design I came up with for my former synthesizer project but I am finding really cool for other stuff like guitar and bass lately. It makes a really cool distortion tone. Here's a preliminary schematic.
https://i108.photobucket.com/albums/n13/somnium7/Aztec%20MkII/AztecMkII_REV3.gif
The circuitry on the far right is all new today. It allows the generation of up to four octaves of multiplication on the fundamental tone. This can be mixed with the variable quantized audio.

Basically what happens in the core is a signal can be dynamically varied from between 1 and 20 bits resolution with any modulation source like a volume pedal or LFO. It will take basic waveforms and turn them into ziggaurat shapes - hence the original name Aztec Processor. Once you hear it on a guitar though you'll agree it takes on more Godly dimensions :D
Heres what it looks like:
Oct29002.jpg


I'll be poking at this some more over the weekend.

BTW does anybody know how to get accepted into the Prodigy Pro forums? I've been trying for months - emails, signing up with different names etc. and can't get in....
 
huh! looks freaky.
were lm3916 /14 s ever been abused (I mean used) in such fashion before? :D
sounds? - would be cool to hear. record something if you get time.
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btw, while we're here in diy moods, and before I forget to mention, look what I've found on eBay:
http://cgi.ebay.com/ws/eBayISAPI.dll?ViewItem&rd=1&item=190189249848
the seller got four of them listed (see other items), and nobody cares (well, except some last sec watchers , maybe :))
get them if you have a few bucks to spend.
 
Wow a VCA that looks like a box of matches! How cool is that!!! :D
Too bad the specs aren't listed.
If I wasn't spending my savings on a dang MD441-U right now I'd buy this just for the sexy 80s lady on the graphics :eek:

Regarding 3914s I have seen them used for frequency analyzers and rudimentary oscilloscopes before. In 2002 I decided to see if they could be made to run at audio frequencies after reading a question about this in the Synth-DIY list and sure enough they can. The big problem with them is a transition overlap from one output to the other. At audio rates this will create little spikes on the edges of the pulses when they are summed with a R2R type DAC like I'm using. It's hard to see them on the scope but when you record the output as digital audio and zoom in really tight on the waveform they appear. Hey it's more free harmonics :D

Samples over the weekend if I can manage it...
 
Somnium7 said:
Samples over the weekend if I can manage it...
Click to expand...
Don't make any promises. :)
I know how it is. it's easy to blah, and pain in the neck to do.
Record something when ever you have it set and feel like doing it.
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ps
you can find a scoop of info about those M-5 Ladies, not much though. I recall I saw some circuit with it. I guess you can 'fire them up' with +/-15VDC, audio in/out, maybe 10K load across input and output coupling electrolytic (10uF?) , I don't really know. Then test/apply some Vc and see how it goes. So much for specs...heh heh :D
 
ok, i know this thread is really old, but i'm looking to diy this great river mp-2. Any way i could get a schematic, it would be much appreciated. Thanks guys!
 
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