ARP thread, part 2!

Ok, so I'm restarting this thread over here, with new and exciting info.

I'm working on putting up a little site for these guys, which is printed on the back of them, and I'll have the schemo and pictures and stuff up there.

Here's the pics of them for those of you that missed the first go round:



Also, here's a simple sound clip for ya - it was recorded very straightforward, with an SM-58 straight into ADA8K, into hammerfall 9652, into Nuendo. It's recorded at a level where the version with the ARP in wouldn't clip, which makes the non-ARP version a bit quiet because of the gain the ARP has. It's me playing the guitar with the mic about 3-4" from the neck joint of the guitar. Please be gentle, I am NOT a guitar player

I used an SM-58, and not a ribbon, because another ARP is installed in the ribbon, and I didn't want to take it out to give you an A/B. Sometime soon I'll get you a clip of the improved fum ribbon, but I want a decent source to put in it first!

http://diy.usedforcomparison.com/arp/media/arp-clip.wav

One of the boards I have is bad. That leaves me with three assembled ARPs, one is installed in my mic, I have two more, and I'd be happy to sell them to a couple of early adopters, which will help me finance the prototype of revision 2, and a production run of both.

revision 1 doesn't have a good mounting solution for the ribbon, but it is perfectly fine for using as an in-line preamp for any mic that's not already phantom powered. Obviously you can't put this in front of a phantom powered mic without adding another phantom power source on its input, because the ARP eats the phantom on the line. Revision 2 is designed to replace the scrap of PCB that lives inside the fum ribbon, has the same mounting holes, and has enough throughholes to make the off-board connections, four holes for the ribbon wires, four for the transformer, four for the XLR jack (quad cable), and all the components on board. The caps are throughhole, and located toward the edge of the board, and the rest of the components are SMD, as the board mounts right on a piece of metal that precludes throughhole components in the center of the board.

I'm toying with the idea of a box with just a 48V PSU, and interconnects with the 6k8 resistors built in, so that you can chain together 5 or 6 of these guys to make a mic preamp. Might be stupid, might be really cool

So guys, first couple people to pm me about the prototypes can buy 'em, and everyone let me know if you're interested in this, and which type of board you'd like. I'll probably do a production run of both types of board, so I want to get an idea how much demand there is for each.

And now I have stuff up on the ARP's own little web page. A good bit of it I lifted verbatim from the post I just made


http://diy.usedforcomparison.com/arp/

I like it. :thumb:
My only question is which is hot,cold and groud on each end of the schemo?

the grounds are the center pins of each header.

The square pins are hot, the opposite pins are cold. Each transistor inverts the signal, so the hot signal going into the left transistor comes out as the cold signal, and the cold signal going into the right transistor comes out as the hot signal. Microphone is attached to the bottom header, J2, and J1 is the preamp side.

looking at it again I see the ground pin. how I missed it the first time...

Nice tmbg, thanks for posting the info. and sound clip. Hopefully I can play around with it soon.

[quote author="JCMaudio"]Nice tmbg, thanks for posting the info. and sound clip. Hopefully I can play around with it soon.[/quote]Same here. Reminds me that I need to start selecting input transistors and get to it!

This is an old thread I know - but I hope there is still life in it yet.

I have read the active ribbon preamp thread with much interest, in particular the preamp that tmbg made. I have two cheap chinese ribbon mics and plan to have a go at building this to make them active and safe against phantom power (it's only a matter of time with me!). I'm more music-man than electronics-man, but have a couple questions regarding the 2N4401 transistor, if anyone can enlighten me.

Firstly, I have had a look at specs on this tranny, and the voltage across the emmiter and collector seem very close to the breakdown voltage. Am I way off base or is there a better alternative?

Secondly, should I try to match the gain of the long tailed pair (manually) or even try to find a suitable monolith device to do the job (any suggestions are welcome - the couple I did come accross [e.g Analog Devices SSM2210P, Mat-02] are verging on obsolescence and quite expensive)?

As I said, the last time I looked at an electronic circuit was at high school, so if I'm burbling nonsense please be kind to a novice. This just seems a great idea to build and I want to do the best job possible.

Thanks,
Terence

ribbons and phantom power? I wouldn't worry.

watch this video.

thanks to fum for doing it.

http://www.shinybox.com/RibbonPhantom.php

pucho812 said:

ribbons and phantom power? I wouldn't worry.

watch this video.

thanks to fum for doing it.

http://www.shinybox.com/RibbonPhantom.php

Click to expand...

Thank you for the link. Actually, the phantom power protection, important or not, is of secondary concern to me. I really would value that initial bit of (hopefully clean, quiet) gain. Other than that, and if this building project appears a dubious notion, I will probably just purchase something like the AEA TRP ribbon preamp, which has up to 84 db of gain and an EIN noise figure of -129db. But it would be nice to save that chunk of cash.

Terence