Super Hard-On as a Mic Pre

[T1bbles]

Hey guys, I've built a few ZVex Super Hard-On clones, and remember reading somewhere that it's based on the input of an old mixing desk? As an aside; I've been toiling with finding a rack unit of 8 straight forward preamps preferably with phantom power. And so we arrive at our project!

The main questions at the moment are these,

Is there something in the Super Hard-On which voices it specifically for guitar? Or can I just go ahead and plug a mic into it?

Secondly, how do I step 9v up to 48v for phantom power? Or rather, how do I go about powering the thing? Or do I just not bother and buy a few in-line phantom power supplies?

In it's stripboard pot-mounted state the super hard-on is tiny; you can fit 3 or more into 1 stompbox, so 8 into a 1u rack case would be a cakewalk, the prospect of this excites me

[Hides-His-Eyes]

There are some 555 projects I've seen that will give you 48v from 9V, but if you're rackmounting just get a 2*24v mains transformer and jet your 48v there!

[T1bbles]

Ok scratch that, I found this!

http://www.simplypowersupply.com/Open-Frame-Power-Supply/PS-05-48-Meanwell-48Vdc-011A-Open-Frame-Power-Supply.aspx

So that's 48v sorted, just need 9v from that! How do I go about stepping it down?

[Hides-His-Eyes]

For such a low current application a 9V regulator would be fine, but get one of the heatsunk ones for such a voltage disparity

[Processaurus]

Common microphones are meant for a 600 ohm input impedance.  These kind of MOSFET boosters are about a thousand times that (5 Meg).  Won't make that good of a mic preamp, it'll probably would be noisier than any pre with the right impedance.

[Processaurus]

There are some chips that the THAT corporation makes that are specially made for the front end of a mic preamp.  They have a good looking app notes section if you're interested in going that route for your bank of pre's.

[PRR]

> remember reading somewhere that it's based on the input of an old mixing desk?

No.

> Is there something in the Super Hard-On which voices it specifically for guitar?

No.

> Or can I just go ahead and plug a mic into it?

Yes.

However: input is unbalanced, mike level signals may be more contaminated with hum/buzz, which is why we like balanced mike inputs.

MOSFET hiss is typically high, perhaps annoyingly high against typical mike signals.

The unbalanced input does not offer any easy or safe way to apply Phantom power, needed for many modern popular mikes.

(The high input impedance is not a serious "flaw".)

No, an all-around-good mike preamp either needs a costly transformer or a whole LOT of parts (or a special chip). The transformerless ones may not be a lot of money, until you add in frills like jacks, pots, Phantom, and a case.

> 8 into a 1u rack case .... this excites me

You can't put that together once as cheap as asian factories churn them out by the crate-load.

Suggestion: Nady PRA-8 Mic Preamp $129.99

[G. Hoffman]

> 8 into a 1u rack case .... this excites me

You can't put that together once as cheap as asian factories churn them out by the crate-load.

Suggestion: Nady PRA-8 Mic Preamp $129.99

What on earth does that have to do with anything we talk about on this board?  Money is never the point for this stuff here.


But if you are really looking to make a mic pre, look HERE for the $5 mic pre.  (Sorry for the pop ups - the original link appears to be gone.)  Its based on a Burr-Brown op amp (now made by TI, of course), the INA217, that is designed as a mic pre, and its a very fine one.  But if you read the article, one of the reasons the cheap one scored so well is using batteries as a PS, so if you want that kind of performance you'll need to get pretty careful with your PS.


Gabriel

[wormfooduk]

The $5 mic pre seems to have disappeared? can't find the schematic anywhere, all the old links are 404 

[slacker]

It's in the link Gabriel gave above. As explained there, it's just the datasheet schematic with some bits removed.

[Johan]

> 8 into a 1u rack case .... this excites me
You can't put that together once as cheap as asian factories churn them out by the crate-load.
Suggestion: Nady PRA-8 Mic Preamp $129.99

What on earth does that have to do with anything we talk about on this board?  Money is never the point for this stuff here.

without puting words in His mouth. what I think PRR means is. If you build one or two, to learn/becouse you like the collour/just for fun..no problem.thats what we're all here for...
If you build 8, to put in a rack and use for recording, you probably hope to get performance comparable to at least the cheapest storebought units.. you probably want something that feels solid enough to bring to the recording site. you probably want something you can use on the majority of your tracks
8 SHO's in a rack case most likely wont do that. the case and powersupply alone would probably cost more than an asian made 8pre rackunit. and the performance of the SHO probably isnt what you want on all your recorded tracks
if you want decent performance for low cost, the 5$-micpre, as suggested, is good. althou, when you count the case, the connectors, the psu, the gain pots and knobs, you've spent a lot more than 5$/channel
J

[T1bbles]

> remember reading somewhere that it's based on the input of an old mixing desk?

No.

Yes

You can't tell me what I have and haven't heard before;

http://www.noiseguide.com/product_info/zvex_effects_super_hardon

http://acapella.harmony-central.com/archive/index.php/t-2279696.html

One quote in particular; 'zach's own website used to say that he derived the circuit from an old mixing desk preamp design. he doesn't say that any more'

I'm assuming the place I read it previously was actually on the ZVex website, before that was edited out.

...or were you expecting me to take your word for it?

[puretube]

Or here???

[T1bbles]

Or here???

From the man himself, tyvm

[MikeH]

Ive tried the SHO as a mic pre using an impedance  matching transformer, and to be honest it's not the greatest sounding thing... there are some opamp based DIY mic pres around, they might be a better way to go.

[simplypowersupply]

Ok scratch that, I found this!

http://www.simplypowersupply.com/Open-Frame-Power-Supply/PS-05-48-Meanwell-48Vdc-011A-Open-Frame-Power-Supply.aspx

So that's 48v sorted, just need 9v from that! How do I go about stepping it down?

I have had a few visitors on my site from this forum so thought I would pop along and see why....I have notices this post and assume this is where the interest is coming from.

If you want to get more information on power supplies then I am sure I can help - I don't know too much about Stomp Boxes but do know lots about power supplies. So if you have any technical questions just click through to our site and leave a message - we normally get back to you in a few hours (as long as it is during business hours).

The unit which you are linking too will indeed give you 48Vdc - if you also need 9Vdc then it is possible to set a 12Vdc unit down to almost 9Vdc.

Thanks for your interest and feel free to ask any questions or pass on our details to anyone else needing power supply advice

[candidate]

Rupert used a MOSFET?