Another vari-mu: Chiswik Reach Compressor

[djn111]

Hi,

I think the only thing missing on the boards is the heater supply of the tubes, I have pictures of both versions, and it is clearly show, easy fix with some wire twisted together.

DJN

 

[mikeyB]

thanks for the tips guys - sorted on the heater wiring - it's more to do with biasing of the valves/meter set up and trimmer settings -
still on it!! Might soon get the chance of getting my hands on the real thing!! - that would help immensley!!

 

[tommypiper]

Did he try to add stuff/features/mods and messed that up? Should be easy to fix if purusha would tell people what he "modified."

ALSO, have you tried posting at purusha's forum? People keep posting here, but fixing this board would be better handled at HIS forum. He should own up to his mistake and devote some time to fixing it.
www.diy-racked.com/

There you can ask him directly what he modified so you know which part of the board needs correcting and can focus you efforts there. good luck, it sucks to have so much $$ sunk in a non-working project...

AFAIK, Purusha got an early version of this PCB which was reverse engineered and put together by someone else and some bugs may have still been in the PCB at that time.  It was a two layer board, and Purusha sold it as a one layer board, omitting the heater traces.  He otherwise did not make any mods AFAIK.  I believe Purusha would love to offer fixes, but does not know what they would be, because the original PCB designer and he have had a major spat over the incident.  Silent Arts has a long thread here discussing this situation and I don't think it needs to be revisited.  For those who missed the drama, that should explain the situation for you.  Because of this drama, those who may have figured out solutions to the PCB are reluctant to post them or even share them via email or PM (as I have tried in private discussions)...

The Chiswick schematic that is being circulated along with Purusha's PCB appears to be authentic, and should work on its own, AFAIK.  I'd love to hear some confirmations on that, as I am building it....

Purusha's PCB appears to be the same as the Chiswick schematic, with a couple minor value changes which should be easy to spot, AFAIK...

The big problem in this situation is that we feel our hands our tied in discussing the Chiswick schematic... which shouldn't be the case.

I feel very sorry the dispute (between Purusha and others) happened.  I hope the parties can find a way to move on.  It puts innocent buyers who trusted the forum and offerings from its members into a compromised situation without any support.  This is unfair to innocent forum members who had no knowledge of the dispute or its background and got caught in the middle of other people quarreling.

Guys, life is too short. 

 

[syn]

Why someone doesn't  just rent the real thing, we split the cost and the schemo? What is the point in talking about it every-now-and-then? Why don't we just do it and let  the past go by. The thing is not biased properly- it works- but it has problems. Why don't we just forget about what was before, and start a new build? Even those who have parts will not loose much, maybe not even PCB- it can be edited (traces). I think fix is simple- like proper biasing.
Please.

 

[tv]

>>>> i only wanted to show this poor guy that diy is not all about money.

http://www.youtube.com/watch?v=dqiOpePmnl0

 

[kazper]

If you read from the beginning of this thread the hole deal was based off a member here who had got a deal on one and posted many internal pictures of it. That started the whole ball rolling and it's where the reverse engineered schematic came from and eventually a pcb you all know the rest of the now so called folk story...

It's generally seen as unfair that the project became a hush hush, but life itself is not fair. I do feel for those who paid for a bummer PCB and kit, I was even offered it myself. In all it is what it is.

 

[gary o]

Wow that Zappa guy has some mustash !!!! I bet he could be modded.......shave that off & he would get more HF response from his vocal chords...

Anyway heres my little baby mono version of this compressor as I say its an on going experiment so dont laugh she made out of junk but sounds sweet Psu & in/out transformers live in other boxes

 

[mushy]

Any shots of the guts, Gary?

 

[djn111]

Hi Gary,

Looks good, many of my tube amps start out like that, but if you don't mind me asking you used the schematic of P-you now who ?

I like your workbench as well

DJN

 

[gary o]

Mushy il take a shot of the underside tho il prob have the safety police on my ass.....lots of hazards there.......DJN, I used the schematic from the beginning of this thread , I think its gone now but it & another slightly different schematic and some other info are here on page 4 I believe, as I said I not been following the PCB story staying out of that I just wanted to see how this thing sounded , mine is different in the following ways ...I used my own simple external PSU provides 295VDC 12.6VDC & 6.3 ACV ....my input tran is Sowter 1:4 a higher ratio and a 25K attenuator dual ladder type, that lead me to changing the side chain resistor values so I had better threshold control, I have the balance pot fitted ......as in what I guess is the revised schematic, I tried the extra capacitors from the revised schematic but dont seem to make audible difference, maybe some1 can tell me what they do ....Im goin to disconnect the feedback resistors to see if I get dirtyer sound and maybe have a switch there.....so really this thing is just a Altec 436C with a few tweaks emi tweaks I read somewhere .....I was going to make a 436 for fun, do you think It would sound much different than this maybe with the original input tube??????...... not that I dont like this thing....Iv read bad things about the 436 but then wonderful things when emi ed ......call be a pervert but I think I want some filthy distortion.......

 

[penguin]

il prob have the safety police on my ass.....

we will protect you  ;D wont we guys 8)

 

[gary o]

Cool thats better now I feel unsafe again....

Its a little rats nest very small maybe even a threws nest

 

[mushy]

I didn't see nuttin out of the ordinary in dare... 

 

[mitsos]

Hey Gary, um wow, I thought my wiring was messy! 

would you mind posting the schemo you used? It'd be interesting to compare to the other one.

cheers

 

[mulletchuck]

Is this compressor a DIY version of

???   

Total noob here trying to learn what a vari-mu compressor is, and that was the first link returned in google.

 

[skal1]

loooks good gary o ,

hey  gary o  have you a circuit of your 295v psu what tx did you use current / va.

i built 1 changed e**85 4 p**85 works a treats. what did you set the  grid bias to on the vm tube.


skal1

 

[gary o]

Mushy you would if you put yr fingers in there

Mitsos this is kinda neat for me ....I might post areal mess for you to laugh at......The schematics I used are in a link in this thread on page 3 Im not sure if they are the best ones out there, you may already have better ones, as I said this thing is basically a Altec 436 isnt it .......I changed a couple a things to suit the parts I had to hand, if you read my last few posts youl see i changed couple a things.....I dont really no what Im doing so i learn by doing

Ska1 not sure about grid bias can you elaborate for me as I say Im a little green on electronics theory .

Mullet that is a vari mu limiter but not the one we on about.....check the meta for lots info on vari mu limiters

 

[Tubefreak]

I'm about to start building one of those VariMu's from Purusha. As far as I can tell the PCB's were fine, there's an additional document explaining how you need to place the tube heater wiring yourself. Then it should work just fine. Do any of you truely know of another fault in the PCB?

kind regards,
Maarten

 

[stitch-o]

I have heard from a very reputable source that this build/layout
(and he made 3 of these comps) gave only about 2dB of compression...

I was seriously thinking of doing one of those Purusha special boards but instead, I think
I'll (like Gary, cheers for the pic!) build a pair of 436s in a box, make them
stereo linkable and tweak them out a bit. Or maybe a modified PRR?

Unless, that is, the VK1 gets fixed with confirmation.

 

[skal1]

I have heard from a very reputable source that this build/layout
(and he made 3 of these comps) gave only about 2dB of compression...

duppy know who fee frighten


skal1