h*e#li^os mic pre

[Andrew]

Hey Guys,

Well i've finished the h#el@ios mic pre now. its only the mic pre stage and not the eq as I haven't sourced the inductors yet and still to decide on the labelling of the front case.

Just a few observations while using it with md421:
-It sounds great!
-makes hard vocals sound nice which generally sound harsh on standard op-amp type pre's...think wackie
-I've not heard an original so no idea if this sounds anything like it
-Its got a ton of gain which makes me think one of the two gain stages might actually be a different design?

Gonna try it with a 58 next...

Hey Barney have you had a chance to try out diy h#eli@os stuff yet?

[Barney Loveland]

Hey Andrew,
Haven't started that project yet! Did you do your own pcb layout? I have all the schematics and also photocopys of the boards that i was going to trace if you need them? I believe Sowter is making the inductors for the reissues, maybe they will be able to help.

Show us some pics please.

regards, BL

[Andrew]

Hey Barney,

No I'll have to try pcb later, I just did point to point on a blank circuit board working back from the schem's that I've got. Sort of a prototype to see if I could get it working, see how hot it gets and to see if anything blows up (hopefully not). I'd love to have a look at the copies of the boards. I got the mic input transformers from sowter but would like to get the eq section going soon so I might give them another call since they are really helpful.

I'm not really good with getting photo's on the net so I'll get my friend to help me do it soon.

I heard the mixer guys in the old days used to drive these pre's hard to get the sound and keep the fader low so I'd want to run it hot soon and see how it responds. It also oscilates when gain is to high...just like the original?

[Andrew]

Hey guys,

Well a few details. The first picture of the front case is split in half. The left is an attempt at a p!ul^tec (transistor output) right is the He#l(ios mic pre. I've only got the gain & 20db cut on the front panel until I get the eq done later on.

If you have a look at the second picture the left and right is the two line cards (pre & line buffer) with a joiner card in the middle to connect into the eq later on. The transfer is has two inputs so the 20db cut is from the transformer as well.

This is a kindofa 'try it to see if it works' so the layout is direct from the schems with sockets for the transistors so I could swap them around. Its been interesting learning about this circuit. I would like to try it with different transistors later on, maybe germ#anium but for now I'm just going to use it heaps and try and finish the eq & front panel.