Another 500 Series mic preamp - DIY kits!!!

[EisenAudio]

Introducing the DIY500 from Eisen Audio!

Build your own discrete, transformer-balanced microphone preamplifier, which fits all 500 Series lunchboxes and racks!



Choose from over 20 discrete op amps, more than 50 input transformers, and at least 12 different output transformers. Pick your own combination for a limitless variety of tonal colors!

A complete kit, as well as finished units, will be available in the near future when we've finished our design. In the meantime, you can design/clone your own with our http://www.eisenaudio.com/diy500/kit...mal/index.html or have us build a custom module specifically for your application. Questions/comments are welcome!

[jebjerome]

About time. Cool.

[thenoiseflower]

This is cool, I will probobaly start compiling parts for a pair of realy grimey/gooey/thick ones

a resource of what combination of I/O formers & op amps would do what type of sounds we coulds expect would be awsome, Im definetly interested!

more flavor in the 500 series , i think i need another 10 space rack

[EisenAudio]

Originally Posted by thenoiseflower

a resource of what combination of I/O formers & op amps would do what type of sounds we coulds expect would be awsome

This is much harder to do than listing specs, but I'm working on it... slowly! If you have something in mind you can e-mail me for recommendations, or look around on the Group DIY forums for transformer (aka trafo, tranny, xfmr) and discrete op amp (aka DOA) discussions.

[EDIT] Response moved to FAQ section.

[thenoiseflower]

Thanks man, for the extensive reply, Ill do a bit of research.


And thanks for quoting my awful chickenspell

[FunkFaker]

this is a very promising product. seems like the idea of creating DIY eqs will be in the works, as well??

makes the idea of custom 500 series consoles a little more of a reality.

what price point are we looking at?

[subatomic]

nice!

[not_so_new]

Very cool concept for sure, I am interested.

Originally Posted by FunkFaker

this is a very promising product. seems like the idea of creating DIY eqs will be in the works, as well??

makes the idea of custom 500 series consoles a little more of a reality.

Yes I was wondering the above as well. I think there is a big market for a DIY 500 series mic pre but I think there is an even bigger market for an EQ. EQ would be my first call anyway, any chance of that happening?


Thanks, great concept.

[John Peacock]

Originally Posted by not_so_new

I think there is a big market for a DIY 500 series mic pre but I think there is an even bigger market for an EQ. EQ would be my first call anyway, any chance of that happening?

Yes, I thought the same things when I first saw these on the Group DIY.

But I guess one thing at a time. The pre's look very nice.

-Jp

[Tibbon]

Ok, who's gonna compare against SCA first?

[Brad McGowan]

I already have built two of these kits using Cinemag iron and a Hardy 990C opamp. It was a breeze to put together and I was able to get all the help I needed from groupdiy.com and from Eisen Audio. The preamps worked perfectly the first time I plugged them in and they sound great. I built each of mine slightly different and am hoping to compare the differences between the two and tweak it to sound even better. I just need to finish up some mixing and free up my schedule. I bought my transformers as part of a group buy so I saved some money there...but I think my cost was about $250/channel. I got in on the initial batch so I think there might have been a special price offering.

I highly recommend this kit.

I really hope Eisen Audio releases a DIY EQ kit in the future.

Brad

[EisenAudio]

Thanks all, for the kind words! To answer your questions...

Originally Posted by FunkFaker

what price point are we looking at?

Eisen Audio prices are discussed here. I quote custom modules upon request. If building your own, one or two at a time, the total parts cost per channel can vary quite a bit. New discrete op amps range from $45 to $85 USD each, new input transformers from $20 to $75, and new output transformers, if you use one (you can run the output unbalanced instead), from $15 to $70 USD. In any case the cost of accompanying passive components (resistors and capacitors) shouldn't exceed $5 per channel. Brad McGowan's average of $250 per channel sounds about right when you factor in the minimal kit and shipping costs from various vendors.

Originally Posted by not_so_new

I think there is a big market for a DIY 500 series mic pre but I think there is an even bigger market for an EQ. EQ would be my first call anyway, any chance of that happening?

I admit, I started working on this project a year ago and am a little late to the table. I felt it was becoming trivial to try and differentiate, commercially, between so many 500 mic pres all (except for the biz and the buzz) sharing essentially the same design. This particular circuit is so simple (only one op amp!), why not just offer a universal template to be completed any way you please?

Equalizers, on the other hand, have the potential to be much more complicated (and expensive!), containing up to 6 active stages and the plethora of passive components that follow. Granted, I think I'd have a difficult time trying to offer an open-ended DIY EQ, especially something as easily accessible.

However, designing a 500 Series EQ is part of my long-term agenda and I'd love to hear your specific suggestions. I suppose once a concrete design was settled on, it would not be difficult to offer complete, user-assembled kits. Is this what you're all asking for? In the mean time, I need to finish my discrete op amp and transformer designs so that Eisen can offer complete mic pre kits.

[seaneldon]

Eisen Audio is located about 4 blocks from our studio, so I'm gonna be checking these out very soon (and I'm quite excited) and will report back when I put them through their paces.

[andre tchmil]

My problem with all those DIY and clone versions is the price.

How much is it for the real deal (512c )?

by the time you've collected all the parts for your clone, I say you're close.

[Wiggy Neve Slut]

If you could do a simple LF and HF 'passive' eq with an opamp deisgn on the i/o coupled with a transformer im sure it would kik ass.

I had a pair od small electrodyne modules that would have been able to been put onto a 500 series type card and they sounded sweet as!

for freqs, i would like

60,80,110,200
5K, 8K, 10k, 12k

nice and simple but GOOD sounding

Cheers
Wiggy

[Brad McGowan]

I totally agree with Wiggy!

Something that just has High and Low Filters. I would be cool with just shelves, but if it was possible to make it selectable between bell and shelf that would be great. If you kept it a shelf you could actually get away with a passive design that just used capacitors only and no inductors. This would keep the cost low for sure.

Brad

[subspace]

You can keep it affordable and still go class A discrete with inductor-based bell and shelf curves on the high band. This one's 4k, 5k, 6k, 7.3k bell curves or a 10k shelf.

[not_so_new]

Originally Posted by Wiggy Neve Slut

If you could do a simple LF and HF 'passive' eq with an opamp deisgn on the i/o coupled with a transformer im sure it would kik ass.

I had a pair od small electrodyne modules that would have been able to been put onto a 500 series type card and they sounded sweet as!

for freqs, i would like

60,80,110,200
5K, 8K, 10k, 12k

nice and simple but GOOD sounding

Cheers
Wiggy

[not_so_new]

Originally Posted by subspace

You can keep it affordable and still go class A discrete with inductor-based bell and shelf curves on the high band. This one's 4k, 5k, 6k, 7.3k bell curves or a 10k shelf.

as well.

[Brad McGowan]

That's the TapeOp EQ! I made that too. Although mine is more like 3k, 5k, 10k, with a 5k shelf and a 16k shelf. Actually I have no clue what the frequencies really are but it sounds pretty good. I modified the design a bit and used some Orange Drop and Mullard capacitors from some various amp projects.

I'm curious how you wired up your caps to your selector switch. Mine looks way messier. If you have time, I'd really appreciate a pic of the back of that rotary switch to see how you did it.

Is that the Paia Rack, by the way?

thanks,
Brad

[subspace]

Yeah, it's a FracRak. Works as a 500 series if you don't mind pig-taiing the 15 pin edge card connectors. I posted a description of the switch wiring for someone here:
TapeOpCon '06 "build your own eq" question..

[NathanEldred]

Originally Posted by Wiggy Neve Slut

If you could do a simple LF and HF 'passive' eq with an opamp deisgn on the i/o coupled with a transformer im sure it would kik ass.

I had a pair od small electrodyne modules that would have been able to been put onto a 500 series type card and they sounded sweet as!

for freqs, i would like

60,80,110,200
5K, 8K, 10k, 12k

nice and simple but GOOD sounding

Cheers
Wiggy

And out of curiousity, how much would you expect this to be street price if it was made by a manufacturer ready to go (specify if AU dollars)?

[Wiggy Neve Slut]

Originally Posted by NathanEldred

And out of curiousity, how much would you expect this to be street price if it was made by a manufacturer ready to go (specify if AU dollars)?

no idea to be honest.. lol

Im just putting an idea out there?

But im prolly gona say ballpark $800-1000 USD?

If it was to be made u would want decent parts in them.

The thing that excites me about this whole 500 series phenomina is tha fact that the architecture opens itself upto a lot of cross pollination of components so it seems.

Perhaps a basic template could be worked out for a simple 2 shelf/bell passive eq that could have transformers/opamps swapped in and out etc.

But i think that would make it more expensive and there is a fine line between the juncture of both Art and commerce, which im sure you would agree with me about.

I know i got a steal for my old electrodynes and now another Slut is the proud and happy owner.

Anyone keen to step upto the plate??

Cheers
Wiggy

[EisenAudio]

Originally Posted by Wiggy Neve Slut

Anyone keen to step upto the plate?

Short answer, yes. Long answer, tomorrow. Thanks all for your valuable input!

[Wiggy Neve Slut]

Here is a pic of the EQ's im talking of..

They utilised the small AM-10 type opamp that was the main one that the Q8 and electrodyne used AFAIK..

somthing like this would be cool!

Mix buss compressor

cheers
Wiggy

[Improv]

"A . . Lunchbox" Funny!

[seaneldon]

Visited Jens and company over at the shop today, and now I've got 4 Eisen pres in the studio, 3 different flavors/combinations of op amps and trannies. I've also got 2 Purple Audio Biz pres. I'll be doing some rock and roll recording over the next few days using only these preamps, at which point I'll post the song and a long-winded review of the whole experience with them. Definitely excited. You should be, too. I make great music.

[not_so_new]

Originally Posted by NathanEldred

And out of curiousity, how much would you expect this to be street price if it was made by a manufacturer ready to go (specify if AU dollars)?

Originally Posted by Wiggy Neve Slut

Im just putting an idea out there?

But im prolly gona say ballpark $800-1000 USD?

If it was to be made u would want decent parts in them.

I would hope that it would be a little less than that if for no other reason than I can occasionally find real API EQ's used for this price…. well the top end of this price anyway but you get the idea.

If we are talking a simple shelving Eq with fixed freqs I would hope it would go for less than that as a finished product and even less as a DIY. I would think more in the $600 to $700 range US for the finished unit, for that price I would start buying today… seriously…. Above that and I might just hang around and see if I could snag a older API of some sort with more freq's and options.

As far as DIY, I don't really know but $250 to $400 maybe as a complete kit.. talking out my butt really but that is what I would find attractive, no idea if it could be done…...

[not_so_new]

Originally Posted by EisenAudio

I admit, I started working on this project a year ago and am a little late to the table. I felt it was becoming trivial to try and differentiate, commercially, between so many 500 mic pres all (except for the biz and the buzz) sharing essentially the same design. This particular circuit is so simple (only one op amp!), why not just offer a universal template to be completed any way you please?

Equalizers, on the other hand, have the potential to be much more complicated (and expensive!), containing up to 6 active stages and the plethora of passive components that follow. Granted, I think I'd have a difficult time trying to offer an open-ended DIY EQ, especially something as easily accessible.

However, designing a 500 Series EQ is part of my long-term agenda and I'd love to hear your specific suggestions. I suppose once a concrete design was settled on, it would not be difficult to offer complete, user-assembled kits. Is this what you're all asking for? In the mean time, I need to finish my discrete op amp and transformer designs so that Eisen can offer complete mic pre kits.

As to the question "is this what I am asking for?"

In a word…..

YES



At least for me anyway.

I don't speak for everyone obviously but I personally don't need any more mic pres and in my eyes the market is flooded with 500 series preamps.

Your idea for a build kit for the 500 stuff is GREAT so I think you have a good corner going here and all the other 500 series preamps are cool because it makes the whole 500 frame really very attractive… but where are the compressors and EQ's? For mic preamps there are probably 20 to choose from but for EQ and comps… not so much.

[not_so_new]

I would like to see a good shelving EQ with fixed high and low freqs (I agree with Wiggy here lows 60, 80, 110, 200 highs
5K, 8K, 10k *maybe 10.5 instead*, 12k), simple sweepable freq / fixed Q parametric for the mids and an output tranny.

THAT would rock my world.

If you (or someone else) made that as an affordable and good sounding DIY kit I am 100% positive that I would end up buying 11 to fit a whole OSA rack. 100% positive as long as it had the features above and it sounded good, no question in my mind.

As a matter of fact if you offered that as a product I would buy my first this afternoon.

And as a matter of fact I have such a strong feeling that this would be such a hit that I would be willing to talk to you about becoming a financial / business partner to get this solution off the ground.... honestly I think it would be that popular.