qmp audio

Re: 24ch API SUMMING MIXER DR-2402
« Reply #60 on: March 14, 2016, 02:58:13 PM »
Jeff also mentioned the BI-pots, that are much cheaper and have a similar feel. However he does not stock the 1k value.

...so, any tips?

I'm planning on making my own front panel,  and using concentric level/pan:
http://capi-gear.com/catalog/product_info.php?cPath=50_131&products_id=445

I don't see a reason why that wouldn't work.

I already got 16 of the pan pots from CAPI,  so I may sell those if anyone needs them (http://capi-gear.com/catalog/product_info.php?cPath=50_131&products_id=308)


Ninuz

Re: 24ch API SUMMING MIXER DR-2402
« Reply #61 on: March 17, 2016, 10:03:30 AM »
It was the only solution I found at the time being.
The Sifam meters did include a mounting set which let the meter frame be mounted with screws and bolts but as the meters are placed near each other its not possible on the panel included in the kit.

I used epoxy glue.
Same for the framing of the Sifam meters I used as the mounting set/bolt and nuts didnt fit.

So you glued the LEDs and the meters directly to the frontpanel? I was thinking about that too...but I'm not giving up trying to find a "nicer" way to mount those ;)

Re: 24ch API SUMMING MIXER DR-2402
« Reply #62 on: March 26, 2016, 06:01:57 AM »
A question regarding the toroid supplied for the PSU:  are the primaries the white and black cables, and secondaries the red/blue? How do you identify the x1-x4?




Also a question about the VU meters: I`m using the one from Hairball, that came with a plastic frame and a set of screws/plastic fasteners to fasten it to the front panel. However, it seems that the needle-adjustment screw on the bottom front of the meter prevents the meter to stand flush with the panel?





« Last Edit: March 26, 2016, 07:07:48 AM by fragletrollet »

buckethead

Re: 24ch API SUMMING MIXER DR-2402
« Reply #63 on: March 26, 2016, 01:21:12 PM »
Hi!

I routed two small pockets to make them fit (sorry, the image quality is really bad, but you'll get the point):



The black and white cables are the primaries.  You can use the secondaries like this:



Have a nice one!

Mathias


buckethead

Re: 24ch API SUMMING MIXER DR-2402
« Reply #64 on: March 26, 2016, 02:25:49 PM »
P.S.:

I made small brass holders to mount the meters, didn't want to glue them to the front with epoxy:




Re: 24ch API SUMMING MIXER DR-2402
« Reply #65 on: March 26, 2016, 02:33:14 PM »
With your custom brass hardware, did you end up mounting the meters a little "into" the unit? Or did you manage to route enough out of the front panel to fit the screw?

I think routing will be the way I`ll go then. Hope I dont screw it up (no pun intended  ;D)

And thanks for the picture of the toroid  8)
« Last Edit: March 26, 2016, 02:38:42 PM by fragletrollet »

buckethead

Re: 24ch API SUMMING MIXER DR-2402
« Reply #66 on: March 26, 2016, 03:47:47 PM »
I made the pocket deep enough for the whole screw to fit in, so the meters are lying flat on the front panel (or rather on the black mounting frames). But it was a real pain to take away that much material, I was shopping for a new front panel in my head while drilling :)

Looks like some of the other guys mounted them a little angled...

Good luck man!

Re: 24ch API SUMMING MIXER DR-2402
« Reply #67 on: March 26, 2016, 05:18:53 PM »
Yes it does not look that "angled" when seen from the front (fitted as is). My local hackerspace has a very nice CNC, might be a mission for it  8) Did you use a hand-drill?

buckethead

Re: 24ch API SUMMING MIXER DR-2402
« Reply #68 on: March 27, 2016, 09:05:32 PM »
Yeah, I used a hand drill with a metal drill bit at first and then some router bit to deepen it. Quick and dirty!

JessJackson

Re: 24ch API SUMMING MIXER DR-2402
« Reply #69 on: March 29, 2016, 02:56:53 PM »
u guys are fast, I'm still building op amps! smh


Re: 24ch API SUMMING MIXER DR-2402
« Reply #70 on: March 30, 2016, 01:58:34 AM »
Yeah I finished 26 opamps a few days ago... I know it gets a little tedious after a while :) Altough I know the gar2520 by heart by now  8)

Now if I only had the money for the last order  :o

Re: 24ch API SUMMING MIXER DR-2402
« Reply #71 on: April 07, 2016, 09:08:57 AM »
Should be fine. Just check diameter and spacing pitch so they fit the PCB.
Did you get the external box for the PSU board? If not I would recommend it as it gets to hot inside the rack case which can cause some problems. Also use shielded cable for as much cabling as possible. 

Ninuz, that`s beautiful! :)

I have a few more questions regarding parts:
1uf electrolytics: BOM calls for "low essr". How low are we speaking here? A link to a suitable cap from Mouser`s  inventory would be appreciated.
The same applies to the "Audio" 470uF electro, again a link to a Mouser cap would be appreciated.

Is this a good choice for the bipolar electro? I see the lifetime rating of bipolars are way lower than ordinary polarized electro`s. Something to think about?
http://no.mouser.com/Search/ProductDetail.aspx?R=UEP1E220MEDvirtualkey64700000virtualkey647-UEP1E220MED

This one good for the 1000uf?
http://no.mouser.com/Search/ProductDetail.aspx?R=EEU-FR1V102virtualkey66720000virtualkey667-EEU-FR1V102


And a question regarding the chassis: the back-panel has 8 xlr-cutouts in addition to the power inlet. So,  send/return (4), main out (2) and... a second set of outputs from the aca/bo?

for the 470uf this was recommended to me:

http://www.mouser.com/Search/ProductDetail.aspx?R=EEU-FC1V471virtualkey66720000virtualkey667-EEU-FC1V471

I plan on getting the same 1000uf but maybe Ninuz has a better recommendation


Argh. I am fretting over the cap choices for this one.

The BOM says the 22uF should be bipolar, but lists "audio" in the rightmost category.
Bipolars on Mouser seem to have pretty short "lifetime" rating, between 1000-2000 hours that seem really short to me. Also, selecting "bipolar" and "audio" are either/or categories, so getting one that is applicable in both categories is not possible.

Help a confused brother out  :o

Re: 24ch API SUMMING MIXER DR-2402
« Reply #72 on: April 07, 2016, 09:11:34 AM »
Also, if someone could clarify abit about the "low essr" comment. What is considered "low essr"? What would be the consequence of using "high" essr caps in this circuit?

I must confess I`ve allready stuffed caps on the lower part of the pcb`s without thinking about "audio caps/low essr caps", as I figured that this is all concerning the LED driver (caps around the TL074) and that the choice of caps wouldn`t affect the unit too much. But when it comes to the audio-part of the pcb... I want to get it right.

I was also recommended to switch out the LM337 to an LM338, and the same for the LM317. I can however not find a suitable replacement for the 317. Any advice? Also wondering on what heatsinks you guys used, all the ones I seem to find are pretty small in size (again was recommended getting a big one) and I`d like one that fits the footprint of the pcb nicely.
« Last Edit: April 07, 2016, 12:04:04 PM by fragletrollet »

Andy Peters

Re: 24ch API SUMMING MIXER DR-2402
« Reply #73 on: April 07, 2016, 03:07:48 PM »
The BOM says the 22uF should be bipolar, but lists "audio" in the rightmost category.
Bipolar on Mouser seem to have pretty short "lifetime" rating, between 1000-2000 hours that seem really short to me.

The lifetime specs is for the capacitor operating at its maximum temperature rating, which is for the cheaper caps 85ºC, for less cheaper caps 105ºC, and for stuff that has to last forever, 125ºC.

The rule of thumb is that a capacitor's lifetime is doubled for every 10ºC decrease in temperature. The cap rated for 1000 hours at 85ºC should last for 32,000 hours at 35ºC.

The operating temperature also needs to include self-heating from ripple current due to cap ESR.
"On the Internet, nobody can hear you mix a band"

Andy Peters

Re: 24ch API SUMMING MIXER DR-2402
« Reply #74 on: April 07, 2016, 03:22:14 PM »
Also, if someone could clarify abit about the "low essr" comment. What is considered "low essr"? What would be the consequence of using "high" ussr caps in this circuit?

I can't find a schematic for this thing, so I don't know how the caps are being used.

That said, "low ESR" is generally considered under an ohm. 

In an audio-path DC blocking circuit, ESR is probably not all that important.

When used for power-supply smoothing (after a rectifier or a switcher), ESR is important because the higher the ESR, the more self-heating in the capacitor, which reduces its lifetime. Also for switch-mode power supplies, the ESR is important because it affects the efficiency of the supply.

With some low-dropout linear regulators, RTFDS because they may specify a minimum ESR. With large-value ceramic capacitors being readily available (replacing tantalums in many applications), the ESR is so low that the LDO may oscillate.


Quote
I was also recommended to switch out the LM337 to an LM338

That would be potentially disastrous, as the LM337 is a negative regulator and the LM338 is a positive regulator.

Quote
and the same for the LM317. I can however not find a suitable replacement for the 317. Any advice?

The replacement for the 317 is the 338. But why? Do you need the current-source capacity of the 338? Does the design draw more than the 1.5 A the LM317 can do in the TO-220 package (with appropriate heat-sinking)?

-a
"On the Internet, nobody can hear you mix a band"

Re: 24ch API SUMMING MIXER DR-2402
« Reply #75 on: April 07, 2016, 04:48:48 PM »
Hey Andy,

thank you so much for your in-depth answer regarding the caps/esr! Makes me able to take a more educated choice.

Ofcourse, I mis-spelled the regulators, and indeed, was intending to swap the 317 for the 338 (and needed something to swap the 337 with to match the 338`s 5a current limit).
I have not built up the mixer yet, so have not measured the actual current draw reqiurements. However, headroom is always nice, and I`m presuming it would produce less heat aswell? The advice came from the tech affiliated with the project, so I take his advice with some seriousness  8) (what can a noob do)
« Last Edit: April 07, 2016, 05:00:06 PM by fragletrollet »

Andy Peters

Re: 24ch API SUMMING MIXER DR-2402
« Reply #76 on: April 07, 2016, 06:01:34 PM »
I have not built up the mixer yet, so have not measured the actual current draw reqiurements. However, headroom is always nice, and I`m presuming it would produce less heat aswell?

Heat dissipation is a function of current draw and voltage drop, which will be the same for either regulator given the same input and output voltages.

You can reduce regulator heat dissipation by using a low-dropout regulator such as LT1963, which has a max dropout voltage of 450 mV at full tilt boogie, compared with about 2.25 V for the LM317. With 1.5 A load, that's 675 mW vs 3.75 W, which is significant.
"On the Internet, nobody can hear you mix a band"

Re: 24ch API SUMMING MIXER DR-2402
« Reply #77 on: April 07, 2016, 06:25:32 PM »
Thanks, but afaik (going from the ds)

Quote
The devices are available in fixed
output voltages of 1.5V, 1.8V, 2.5V, 3.3V

I`m having a hard time that would be sufficient, afaik the mixer runs on +16V? (jn addition to the negative rail)

Anyways, I`m probably overthinking this. I guess all the other peeps in this thread have built it up with the 317/337 combo and have no problems.

Anybody have a (mouser preferrably) link to  suitable heatsinks?

buckethead

Re: 24ch API SUMMING MIXER DR-2402
« Reply #78 on: April 07, 2016, 06:33:54 PM »
I use these heatsinks, they fit perfectly: http://www.mouser.at/Search/ProductDetail.aspx?R=513102B02500Gvirtualkey53210000virtualkey532-513102B25

I'm using 317/337s, will see if they can handle this thing. Hopefully I get this thing running very soon, then I'll measure the current draw and let you know

KasperNyhus

Re: 24ch API SUMMING MIXER DR-2402
« Reply #79 on: April 09, 2016, 09:53:27 PM »
Does anybody have the schematics for this fine build?