Mic Pre Front-End PCB

[Rochey]

Updated graphics...
http://www.tendolla.com/designgallery/main.php?g2_itemId=14

Work still to do:

- Update PAD circuit.
- Allow space for user selectable high pass caps etc.

Controller Board:
http://www.tendolla.com/designgallery/main.php?g2_itemId=24

 

[Rochey]

It's been upgraded - The pad circuit has been improved, and the high pass filter has been given 2 options - 2.5mm or 5mm capps (WIMA style).

http://www.tendolla.com/designgallery/


Most of the circuit is optional - you can populate it based on your needs. Once the board is complete, I will provide a pdf with details on how to bypass various parts of the circuit - so, one board, mutliple stuff options

Please post feedback or interest here

/R

 

[clintrubber]

[quote author="Rochey"]
6 - Phase.

The Schematic can be found at: http://www.tendolla.com/design/micfrontendpcb/micfrontendschem.png

Feedback please? [/quote]
Nice initiative ! Since you asked for feedback let's make this all time fav. little nitpick remark again (I don't think anybody mentioned it yet):
let's use polarity i.s.o. phase. Everybody knows what is meant with phase, but why not use the correct term ?

Bye,

Peter

 

[Rochey]

okay.. that's more than doable

anything else?

 

[Rochey]

Peter,

It's now done. Please see:
http://www.tendolla.com/designgallery/main.php/v/frontend/

Any other changes you'd like to see?

While we're discussing it. I've also updated the switches. There are now 2 boards that will fit in a 1U case.
1) 3 switches + 5V regulation
2) 2 switches only.

PTownkid spotted that I actually need 4 switches for the unit to work. Having 3 in a line doesn't really aid that
The boards with only two switches allow them to be mounted next to each other or on top of one another.

http://www.tendolla.com/designgallery/main.php

 

[clintrubber]

[quote author="Rochey"]Any other changes you'd like to see?

[/quote]
Sure ! 'phasecontrol' --> 'pol(arity)ctrl'

Must say that I hate it that my 'contribution' was of the not really useful kind. Hope you don't regard is as nitpicking, since it wasn't intended that way.
I don't have anything else to add, looks good.

Enjoy,

Peter

 

[mnats]

This is getting exciting! One request - don't think it has been mentioned specifically in the thread, but I see you are using Combo jacks. Would it be possible to add some pads so that an inserted 1/4" plug can feed an instrument input (looks like switching might get hairy...) instead of the mic input? Also, did Samuel's suggestion for the phantom RC filter get implemented (don't see it on the schematic)? I see clintrubber beat me to the punch on the PHASECTRL pad...

Oh yeah, how about nested footprints for alternate size relays (like the G5V-2 someone has a lot of lying around...)?

 

[Rochey]

Would it be possible to add some pads so that an inserted 1/4" plug can feed an instrument input (looks like switching might get hairy...) instead of the mic input? Also, did Samuel's suggestion for the phantom RC filter get implemented (don't see it on the schematic)? I see clintrubber beat me to the punch on the PHASECTRL pad...

Oh yeah, how about nested footprints for alternate size relays (like the G5V-2 someone has a lot of lying around...)?

1 - PHASECTRL - done.
2 - MIC INPUT - Done, 2 pin headers offer the ability to link the instrument jack to the mic input, or feed off to a DI circuit.
3 - PHANTOM RC / Intelligent Phantom on switch - Nope... if anyone has a schematic for this, i can look into adding it. (isn't is just a huge cap that charges up slowly?). As things are, I don't want to add too much extra size to the board.
4 - ADDITIONAL RELAY FOOTPRINT - Not without relaying the whole board, no. However, I think these relays should be usable with just about any DIP relay.

 

[mnats]

[quote author="Rochey"]2 - MIC INPUT - Done, 2 pin headers offer the ability to link the instrument jack to the mic input, or feed off to a DI circuit.[/quote]
Perfect, thanks!
[quote author="Rochey"]3 - PHANTOM RC / Intelligent Phantom on switch - Nope... if anyone has a schematic for this, i can look into adding it. (isn't is just a huge cap that charges up slowly?). As things are, I don't want to add too much extra size to the board.[/quote]
Check this document from Jensen:
http://jensentransformers.com/as/as016.pdf
[quote author="Rochey"]4 - ADDITIONAL RELAY FOOTPRINT - Not without relaying the whole board, no. However, I think these relays should be usable with just about any DIP relay.[/quote]
If you take a look at a few datasheets from Omron you'll see that they have many DIP relays with very different footprints. But I can live with your choice and will just buy new relays. I like the small size.

Very nice work.

 

[guavatone]

I'm having a hard time seeing what's so exciting about this... :wink:

 

[Rochey]

:shock:

This board allows all the routing of audio in front end (phantom, polarity, pad, high-pass) from a low voltage remote source.

It's not a product all of it's own - used with some basic cmos logic (NAND Gates etc) you could very easily control the system with buttons rather than big ol' switches.

Another advantage would be to control the front end from a midi source or any microprocessor.

Again, this is just a module to be used as part of a bigger picture.

/R

 

[guavatone]

I was just joking Roachey

-I guess you missed the boards that I had fabbed. Less sophisticated Utility PCBs

 

[mnats]

I really hope that this design is still going ahead. It seems like it was well on its way to becoming the best universal microphone preamp input board seen on this forum...

 

[Ptownkid]

It is still happening. Last time I talked to him he was about to order proto boards.

 

[Rochey]

yes, it's still going!

I've just moved house though, AND been travelling with business for the last 2 weeks.

Just a little overloaded

It'd be nice to see how many people are interested in this thread - how many would you be in for? I can then start to work pricing and kitting with ptownkid.

Thanks for the support.

/R

 

[mnats]

How did those prototypes work out?

 

[Rochey]

If there's still interest, I can have them made soon.
PCB is complete (for a while now...) just not manufactured.

/R

 

[flaheu]

Rochey,

These stuff are exactly what I need.
I would like to make them myself, would you mind sharing the eagle files ?

I was to the point to start drawing things like that, but It would save me a lot of time if you just can share the files

I know I should do it myself, but I'm f***** too slow with eagle

Thanks for your work.

Cheers

 

[mnats]

[quote author="Rochey"]If there's still interest, I can have them made soon.[/quote]
Reading from this interest other than my own - I think it's hard for people to commit to buying boards when there isn't an indication of how much they might cost (with shipping) and when. $5? $10? $20? Next week? A month from now? A year?

 

[Rochey]

At this point, the boards would be sub $10 -- however, I need to hear back from the pcb shop.

I'm also having a design review in the next few days to make sure everything is good before I go to production.

- I'll start a different thread in the Brewery once I have photographs of hte pcb's.

/R