110 Style

[JustinS]

Hi all, all of this bashing of 5534 bashers has inspired me to build a couple of ISA110 style pre's, only used a 110 a couple of times before but they did sound good, not too hard, not too soft... and it does seem an easy and cheap build.

There are plenty of circuits on the web for the pre, but does anyone have a circuit of the eq?? In fact what the hell is in the eq at all?? Is it inductor based or an active thing... or what? Hmm, could be a good build too!

Justin

 

[gyraf]

The EQ is also 5534-based, state variable sections. Nice, but not easily diy'ed. If you've had one open, you will know that there is a LOT of stuff going on in there.

You may want to ask Thomas Kristianson (user Tekay) for a GroupDIY password for the

http://www.vintagedesign.halmstad.net/ - there may be something you could use.

Jakob E.

 

[JustinS]

Thanks Gyraf... will do!

Justin

 

[Category 5]

Justin,

If you get to the stage where you are making a circuit board myself (and I'm sure plenty of others here) would be glad o chip in on having a quantity run. The pre section from the ISA110 is fantastic. i would love to build one. You could also do the pre and eq seperately. As stated the EQ is plenty complicated, but there's nothing stopping you from pairing the pre with a different design.

Shane

 

[Kev]

[quote author="Category 5"]
If you get to the stage where you are making a circuit board ...[/quote]

:roll:

Peter C. already did ... and I think it may have had the Lundahl/OEP input option ... look to the Group DIY General Mic-Pre page.
I've always wanted to try an LM833 and then use the second side of the opamp for a Hi-Pass filter section ... one day it may happen.

??? :?

 

[Category 5]

Sorry for the bother but could you direct me to where I can find it? Are you referring to the green pre? I thought that was based on the 9098.

Shane

 

[JustinS]

Hey Shane,

Check out the link here...

http://recording.org/users/kev/mic_pre_general.htm

There's a schematic & an untested layout

Joe Malone has 2 different schematics here (as well as some other cool stuff)

http://www.jlmaudio.com/Schematic.htm

Though I'm sure Peter's layout is cool... I though I might give it a go myself... just for the fun of it... will keep everyone posted.

Justin!

 

[peterc]

My 110 layout works, but was never studio tested. I tried it on my bench only.

As far as I remember, I laid out PCB's for the OEP/Lundahl & Neutrik transformers.

Peter

 

[rafafredd]

what would be a nice turns ratio for a mic/5534 transformer? 1:2 or 1:4?

 

[owel]

[quote author="rafafredd"]what would be a nice turns ratio for a mic/5534 transformer? 1:2 or 1:4?[/quote]

The Sony console preamps used a Jensen JE-115K-E for their NE5534 preamps.

 

[cuelist]

[quote author="rafafredd"]what would be a nice turns ratio for a mic/5534 transformer? 1:2 or 1:4?[/quote]

If you are interested in the lowest possible noise, you need to find a transformer who's turns ratio squared multiplied by the source resistance best matches the optimum source resistance of the opamp.

In my experience, something in the region of 1:5 or 1:7 works best with the 553x opamps. Let's say 200 ohm source x 7 x 7 = 10k.

I've built a few such preamps with Sowters 3195 transformer. Unbelievable value for money in my opinion. Sounds real nice too! I used two cascaded 5534's to share the gain (but with a common single track pot) and to keep the feedback reasonable at high gains.

 

[Kev]

[quote author="cuelist"]Unbelievable value for money in my opinion. Sounds real nice too! I used two cascaded 5534's to share the gain (but with a common single track pot) and to keep the feedback reasonable at high gains.[/quote]

yes,
thats why this was going to be part of the Group DIY Mic-pres. It would have given us at least one of each type of Mic-pre as a DIY project. This one being the Transformer + opamp type.
Changing to a Dual Op-amp like the 5532 or LM833 would give the option of either the shared gain or the HiPass filter.

Mats,
If you have something you are proud of and want to share ... you know I have a new site under construction with some of the old and a little of the new. It would be excellent to have something from you I may even talk Pete into a re-think of the above PCB. Drop me an email if you're interested.

 

[cuelist]

[quote author="Kev"][quote author="cuelist"]Mats, If you have something you are proud of and want to share ... you know I have a new site under construction with some of the old and a little of the new. It would be excellent to have something from you I may even talk Pete into a re-think of the above PCB. Drop me an email if you're interested. [/quote]

It's been ages since I worked on this but I have the schematic and the PCB layout filed away somewhere. I'll dig it up. It was used in a portable broadcast console I designed in the early 1980's.

 

[omeiko]

I've done a preamp based on the i.s.a 430 mic-amp section wich I believe is the same as in 110. In my experience the orange toroidal output tx with tertiary feedback winding is a big part of the isa-sound.
It was also quite expensive (70 euros each from carnhill) but sounds amazing.

I have a working layout but don't have a website where I could put it.

cheers!

Okko

 

[Kev]

[quote author="omeiko"]I have a working layout but don't have a website where I could put it. [/quote]
send the info to me ... :thumb:

oh ... and welcome to omeiko

 

[omeiko]

Ok. Thanks Kev. This might take a while since I don't have a net connection at home. I'll try to send them to you on monday.

Okko

 

[JustinS]

Hey Kev,

Looking at your schems and Peter's layout is the gain switch a 2 pole 12 way ala the ELMA part 422-277 from the Farnell catalogue?? And the variable resistor on his layout where is that hooked up... in series with R21 on your schem?? (Sorry, a newbie having trouble followingPete's checkplot) :wink:

Justin.

 

[Kev]

:?

Im a little confused too as I haven't look at this for a while.
The rotary switch is a dual layer 12 position and if I can find my Farnell catalogue I'll check that number.

The variable resistor R30 in my schematic is a trim. The main gain is set by the rotary switch even though in some positions the gain is fixed and the other layer becomes an attenuator post trafo.
Hope that made sense.

The Trim should give +/- 6dB and on Pete's PCB layout it is VR1

:shock:

I'm looking at the papers now and can't work it out ... there seems to be two R26's.
... and I can't find C9 ...

Have you made a PCB ??
I think it is about time I made one and took a closer look at all this.

 

[gyraf]

Original mic input section:

http://img.photobucket.com/albums/v172/gyraf/ISA110_mic_input.gif

Jakob E.

 

[Kev]

yep :thumb:
... and all we did was add the 5534 balanced drive section ... much like the ouput of the SSL clone. ( sub the LM833 for fun )

I don't remember who suggested the 6dB trim ... Joe perhaps ??