Kingston

PM670 raspberry shake flavour
« on: November 13, 2010, 02:56:46 PM »
Because when you can't have the stuff you want off the shelf you have to DIY.



years of work in this one. Turning a lofi compressor into a mastering and all-around flexible unit is not an easy task. Besides the PSU and the general gain staging configuration from the PM670 there's not much here from the original plan. Everything is extended and made optional for front panel. I guess if I started it now I would completely redraw everything into a single PCB per channel instead of making it a clusterF*ck like this one. Every switch is actually a relay so signal paths stay reasonably short, and all signal path wires are shielded. It's a brute force way of doing it but there is practically no 50hz hum peak visible on the FFT noise floor graph. Those lundahl transformers also make frequency response flat to about 50khz! I have no other compressor that can do this.



I guess it could be called the mkII or RM670 (richman). The front panel looks much better than these pictures. I'm a bad photographer. Those four purple top layer panels actually have purple-metallic stickers on them with the text (3mm aluminum slabs bolted on to a white powder coated 4mm aluminum panel). The black text on white background is a transparent sticker. I made sure the stickers can take the heat generated by the unit.



Hey look, it's the infamous "Kingston duct". Laugh all you want, it allows me to take power switch to front panel with absolutely no hum coupled to audio circuits.



I designed two additional PCB's for it. There's one for I/O transformers, mid-side, feedback and sidechain highpass. There's another one for time constants and stereo link. The same time constant network works very well for both scamp and plain modes, switched through relays. They sound quite different to each other. There's some plain RC constants in the network, some parallel trickery. Scamp is not in its original form either, of course I had to tweak it, but I still like the plain mode best. It's fast enough for most stuff, and the time constant "shape" is better.

I completely screwed up with the mid-side implementation. Tried to make it like the one in fairchild 670, but with relays. It's currently disabled and I will have to redo it one day. Can't say I've needed it this far but it would be nice to have. The feedback switch is quite subtle and unnecessary, but I had to try it as well.

Couple of other tricks there, let's see. There's the B+ VAC line that cuts out if heaters die (protection relays). Then there's the completely separate 12VDC supply for relays and other utilities so they don't pollute the audio circuits. It's not visible on these pictures but heater regulator has a massive heatsink outside the case.

What a nasty time-waster of a project! I learned lots, but still can't quite get over the initial disappointment of the stock version. It haunts me how bad it sounded and how inflexible it was compared to all the hype surrounding it. For that reason it's very likely the last kit-pcb project I will ever build. I don't want anyone else to blame for bad sound or design other than me.

Mike

[edit]

I almost forgot. Thanks analag, silent-arts and lolo-m for making all this possible in the first place! Thanks to many others who helped on the projects as well, too many to list here.
« Last Edit: November 16, 2010, 03:17:29 PM by Kingston »


kazper

Re: PM670 raspberry shake flavour
« Reply #1 on: November 13, 2010, 03:44:52 PM »
The front panel is killer!
Intentionally left blank

Stagefright13

Re: PM670 raspberry shake flavour
« Reply #2 on: November 13, 2010, 03:49:12 PM »
Yeah I think if I put that in my rack every ones eyes would just wander to it and stop.

Very Very Cool!

John
Amateur experimenter

mulletchuck

Re: PM670 raspberry shake flavour
« Reply #3 on: November 13, 2010, 04:16:00 PM »
soundclips!!!!

I bet if you created an all-inclusive PCB for this, people would buy it as a kit in the white market....
www.youtube.com/mulletchuck for all my recordings

okgb

Re: PM670 raspberry shake flavour
« Reply #4 on: November 13, 2010, 04:19:16 PM »
nice job inside & out
I'm selling my 670 " kit "
because i'm not getting to it but
your pix almost make me want to keep it
GKB Audio / Greg Boboski

baadc0de

Re: PM670 raspberry shake flavour
« Reply #5 on: November 13, 2010, 04:27:47 PM »
soundclips!!!!

I bet if you created an all-inclusive PCB for this, people would buy it as a kit in the white market....

Damn, you've beat me to it.. But still, this hasn't been done yet in this thread:

2 kits for me pls!!

I kid, I kid. Congratulations on a seriously good looking (and, I'm sure, good sounding) build. I concur on sound clips, would really like to hear a mix or vocals/guitars/drums through this.

Cheers and congratulations once more :)

idylldon

Re: PM670 raspberry shake flavour
« Reply #6 on: November 13, 2010, 04:32:09 PM »
Absolutely beautiful work on all aspects.  Congrats!

Cheers,
--
Don

mich

Re: PM670 raspberry shake flavour
« Reply #7 on: November 13, 2010, 04:39:32 PM »

Very Pimped indeed..Good Job!
"Tubes gone - darkness,darkness,darkness no colour ,no contrast." - Joni Mitchell

Re: PM670 raspberry shake flavour
« Reply #8 on: November 13, 2010, 08:08:53 PM »
Looks great, I love it!

canidoit

Re: PM670 raspberry shake flavour
« Reply #9 on: November 13, 2010, 09:02:12 PM »
Great front plate design!

Just curious, how much $ do you think you have put into it?
iva dunit formerly known as canidoit


California Road

Re: PM670 raspberry shake flavour
« Reply #10 on: November 13, 2010, 09:30:38 PM »
Stunning build!!  Would love to hear some clips.

Re: PM670 raspberry shake flavour
« Reply #11 on: November 13, 2010, 11:51:56 PM »
Very pretty!
You really putting the Y in DIY!
 :o

creal

Re: PM670 raspberry shake flavour
« Reply #12 on: November 14, 2010, 04:33:21 AM »
wow very nice comp.
so beauty

ultra-alex

Re: PM670 raspberry shake flavour
« Reply #13 on: November 14, 2010, 05:03:21 AM »
a beauty. indeed.  :o

zebra50

Re: PM670 raspberry shake flavour
« Reply #14 on: November 14, 2010, 05:07:10 AM »
Oh boy, that's a labour of love!

I always like your front panels - lots of fun.

:thumb:
Ribbon microphone services
http://www.xaudia.com
Microphone blog

radiance

Re: PM670 raspberry shake flavour
« Reply #15 on: November 14, 2010, 05:37:51 AM »
Nice one Kingston!

I might go the relay way as well. Did it make a difference "hum wise" compared to rotary switches & unshielded wire?

Duct is also very cool. My power switch is located at the same location but my audio wires are a little further away from it. So far I've had not much hum.
Still...I might go for the duct anyway :-)
"Knowing that you are dreaming, however, does not automatically guarantee full rationality.
Then again, being awake doesn't ensure good thinking, either." -  Lynne Levitan

rrs

Re: PM670 raspberry shake flavour
« Reply #16 on: November 14, 2010, 06:07:57 AM »
Now there's a sugar fix.

I'm sure it doesn't look so good with a hangover though.
David Wilson

Ptownkid

Re: PM670 raspberry shake flavour
« Reply #17 on: November 14, 2010, 08:31:14 AM »
That is one of the best front panels I have seen in a loooong time, wow, excellent work!

Did you happen to notice that you are missing a w on the right hand slow? ;D
« Last Edit: November 14, 2010, 09:02:26 AM by Ptownkid »

Re: PM670 raspberry shake flavour
« Reply #18 on: November 14, 2010, 08:38:41 AM »
That looks sweet man! 

MartyMart

Re: PM670 raspberry shake flavour
« Reply #19 on: November 14, 2010, 09:24:02 AM »
Absolutely gorgeous !!  10/10  :-)

MM.
"Success is the ability to go from one failure to another with no loss of enthusiasm"


 

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