Re: PRR Vari-mu
« Reply #140 on: September 07, 2010, 01:46:53 PM »
Hi

Does anybody have a stereo pcb for sale, or know if the are available somewhere? This project seems to be a perfect first time tube project.
If not maybe is a perfect time to try etching.

Thanks
Best


Matthew Jacobs

Re: PRR Vari-mu
« Reply #141 on: September 08, 2010, 05:57:24 PM »
Hi

Does anybody have a stereo pcb for sale, or know if the are available somewhere? This project seems to be a perfect first time tube project.
If not maybe is a perfect time to try etching.

Thanks
Best

If I where you, I'd point-to-point and vero-board it. The tubes, transformers and pots on P2P and the sidechain and output on vero-board

helterbelter

Re: PRR Vari-mu
« Reply #142 on: September 08, 2010, 06:04:55 PM »
Hi

Does anybody have a stereo pcb for sale, or know if the are available somewhere? This project seems to be a perfect first time tube project.
If not maybe is a perfect time to try etching.

Thanks
Best

As Matthew says, it'd be easily done on Veroboard and P2P, but I think Dinesh has got a few boards left. http://www.groupdiy.com/index.php?topic=28107.msg437657#msg437657
Send him an email or PM.

Re: PRR Vari-mu
« Reply #143 on: September 08, 2010, 06:21:39 PM »
Hi

Does anybody have a stereo pcb for sale, or know if the are available somewhere? This project seems to be a perfect first time tube project.
If not maybe is a perfect time to try etching.

Thanks
Best

As Matthew says, it'd be easily done on Veroboard and P2P, but I think Dinesh has got a few boards left. http://www.groupdiy.com/index.php?topic=28107.msg437657#msg437657
Send him an email or PM.

Thats a great idea, didnt think of that. Have a couple og vera-boards laying, and its a great way of learning.
Thanks!

PRR

Re: PRR Vari-mu
« Reply #144 on: September 10, 2010, 12:07:32 AM »
> gain reduction of course reduces the output and if I'm using heavy reduction the gain loss has to be made up somewhere else.  Input attenuation is not really necessary though it might be a good addition.

No no no. You are mixed up.

Leave the threshold mid-point. It will output up to 2V, which is Reference in some studios and fully digestable in +4dBu studios.

This assumes a fairly short <30mS or <30K attack. If you are doing long attacks it is all about how the un-limited transients upset later stages.

SLAM the INput to get your desired moosh. Slam lightly to take the peaks off an untrained singer, slam HARD to steam-roller and cross-modulate your grungy heavy thrash band.

A PC or iPod won't give heavy input slam.

Any source rated to cruise at +4dBu can peak over 6V which ought to be pretty damm slammed.

I expected this to go between a main console and a recorder. (Yes I still own a recorder.) The console can output -10dBu for light trim, +10dBu for moosh.

If you have various sources, you may want 10dB-20dB gain to bring a weak source up to heavy slam. And of course a gain control so strong sources aren't sonically damaged(?) before they hit the tube.

surfkat

Re: PRR Vari-mu
« Reply #145 on: June 11, 2012, 03:03:07 PM »
Re-opening an old topic here. it seems that the links for the layout of this project have are no longer working. I would appreciate anyone posting a copy or pointing me to a working link of the layout. Many thanks in advance.
Ben Franklin never patented his inventions; in his autobiography he wrote, "... as we enjoy great advantages from the inventions of others, we should be glad of an opportunity to serve others by any invention of ours; and this we should do freely and generously."

Re: PRR Vari-mu
« Reply #146 on: July 17, 2012, 03:01:53 PM »
Re-opening an old topic here. it seems that the links for the layout of this project have are no longer working. I would appreciate anyone posting a copy or pointing me to a working link of the layout. Many thanks in advance.
just had to dig this up myself via the wayback machine.  link to pdf still works too.
http://web.archive.org/web/20090309105526/http://www.conditionedresponse.com/DIY/C5/index.html
There's nothing like the right tool for the job.
And -usually- that's what I end up using...
..nothing like the right tool for the job!

bernatvm

Re: PRR Vari-mu
« Reply #147 on: November 03, 2020, 09:24:42 AM »
Just finished my compressor and, though it passes audio and compresses it, i have a band pass filter problem. My transformers are car isolators ones, with center tap. I tried feeding the sidechain in the center tap and I get the same result as I would with the 3k3 r4 and r33 resistors. I attach a screenshot of the frequency response. Note pink is the compressor (Left channel) and blue is the transformer alone using aligator clips from my interface and back to it.

I imagine there's some kind of impedance problem with my transformers but i don't know where to start looking. Thanks!

gyraf

Re: PRR Vari-mu
« Reply #148 on: November 04, 2020, 03:05:08 AM »
Is there perhaps overloading going on - i.e. is the curve the same at 20dB lower levels?
..note to self: don't let Harman run your company..

bernatvm

Re: PRR Vari-mu
« Reply #149 on: November 04, 2020, 03:14:06 AM »
Yes, it is the same curve. Does it mean just not good enough transformers?


Script

Re: PRR Vari-mu
« Reply #150 on: November 04, 2020, 03:56:18 AM »
I had a similar-looking curve several years ago with too cheap transformers., including automotive ones.

Problem was solved with halfway decent ones. In keeping with the spirit of the project for lowest cost I used Edcors.

bernatvm

Re: PRR Vari-mu
« Reply #151 on: November 04, 2020, 04:23:35 AM »
It makes sense, but why do I get flat response when I messure the transformers with aligator clips? They don't respond the same way while inserted in this circuit...

gyraf

Re: PRR Vari-mu
« Reply #152 on: November 04, 2020, 04:52:57 AM »
..because source impedances are higher in circuit then..
..note to self: don't let Harman run your company..

bernatvm

Re: PRR Vari-mu
« Reply #153 on: November 04, 2020, 05:30:20 AM »
If done further mesuring and find out that if I do the transfer function with the signal from the 5532 +IN I get a very extended top end reading (minus the gain obiously). Could it be a bad 5532? Output is pink, 5532 is blue.

bernatvm

Re: PRR Vari-mu
« Reply #154 on: November 10, 2020, 05:00:38 AM »
I decided trying to swap the 5532. The only dual opamp I had laying arroud was a tl072. Whit the swap, the frequency response is now flat in the top end, no more LPF. Is this a bad 5532? Can the differences in this two chips (suposing they both good) have this impact in the frecuency response?

I'm buying some OEP transformers anyway, because the ones I'm using now don't go lower than 125Hz, but I would like to know what's the problem here. Thanks!

EDIT: It was a bad 5532. I build a buffer circuit for it in a protoboard and one of the two opamps in the packet shows this LPF behaviour.
« Last Edit: November 10, 2020, 05:09:54 AM by bernatvm »

gyraf

Re: PRR Vari-mu
« Reply #155 on: November 10, 2020, 07:04:10 AM »
Aah, that's a freak accident then.. Rare, fortunately, but can be really hard to spot in experiments and prototypes..

/Jakob E.
..note to self: don't let Harman run your company..

bernatvm

Re: PRR Vari-mu
« Reply #156 on: November 12, 2020, 05:05:54 AM »
They should work..

Use the 150-Ohms type as input transformer and the 600-ohms type as output transformer.

Connect both primary and secondary windings in series to acheive maximum inductance (to retain low-end)

Be sure to connect internal interwinding shield to 0V/gnd. This to ensure correct CMRR/output balance

Jakob E.

The datasheet of the 150R one says "N.B. Do not pass DC through windings". Doesn't DC from sidechaing go into the windings of the transformer? http://www.farnell.com/datasheets/1872255.pdf here's the datasheet

gyraf

Re: PRR Vari-mu
« Reply #157 on: November 12, 2020, 05:27:46 AM »
voltage, yes, current no. You apply the same voltage to both sides of the transformer, no current flows :-)

/Jakob E.
..note to self: don't let Harman run your company..

bernatvm

Re: PRR Vari-mu New
« Reply #158 on: November 19, 2020, 04:31:29 AM »
Just installed the OEPs and the frequency response is now more than acceptable, giving me -3db at 31Hz, which could be reffered as "rounded low end".

I'm trying to implement some mods, just for the sake of experimenting and learning some easy circuits with opamps. I have a board with switchable Active MS output matrix (and passive one with the input transformers). I also balanced the output using 5532 (i've read about the tascam problem but, as I said, i wanted to experiment with the 5532 designing my own circuits).

The problem is that whenever I power this routing/balancing board, the +-V suplies lower to +-8V or so and the output saturates because the opamps try to amplify past that region. They are fed from the original psu, but with a 1,5A (30VA) power transformer there should be more than enough power to drive 4 extra opamps and 4 relays, right?

Also my original idea was to fed the relays from the heater suply but, when they are active the GR meter slams to the right I should probably not use that rail, but why?

« Last Edit: November 20, 2020, 05:33:51 AM by bernatvm »


 

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