Solid State Preamp Project, Which One?

[Vikki]

I know what you mean about bass there always seems masses of it on acoustic and you can't get that nice airy top end. I notice 7 circles do the J99 preamp with a couple of the op amp modules could be along the same lines. The mics i was getting aren't top end stuff, just Condensor AKG C451b and its big brother AKG C414b, they seem the pick of the crop in that price range from what i hear, i don't know how the 414 will work on female vocals though.
Vikki(uk) :grin:

 

[neilium]

Vikki,

You could do a whole lot worse than those AKG's you picked up. I've had really good experiences with both mics, both on acoustic guitar and vocals.

-neil

 

[Vikki]

Soundguy
Them pics of Joes preamp do look tasty, have you tried on acoustic yet?
Neil i was hoping someone would give me a clue with the AKG mics, i've been staring at em for weeks trying to decide which ones to buy, funny thing is tried to order the small one today and no one in the uk has one in stock same with the 414! Should be next couple of weeks though.
Vikki(uk)

 

[Mark Burnley]

Yep,

Ditto on the AKG's. I've had some great acoustic sounds just using a 451! We had the guitar player in a "tent" made of sleeping bags, searching for that "Bowie" acoustic sound. We just had the 451 going into a bog-standard Soundtracs Quartz desk and then the magic seemed to happen in an 1176 and Tube Tech PE1c (note the DIY-able nature of the previous two units )

BTW, have you tried Funky Junk? I know they had a good deal on ex-BBC 414's a while back?

Mark

 

[Vikki]

I'll give Funky a ring and see if they have any left, from their site looks as if thy are all gone. Did think of a pair of Josephson C24's but i don't know if my other gear comes up to par, then there's having them sent from the us and import duty.
Vikki :grin:

 

[Flatpicker]

I've heard lots of respected folks say that Joe's 99V is an incredible sounding op-amp, but I remember Joe saying it was like a Neve on steroids. So, unless he's changed it, it's probably not the sound you want.

Personally, for your application I'd try Peter Simonsen's circuit with a Forssell 992 or JH990 first. (Peter - you drew that with "Electronics Workbench", didn't you? :wink: )

Here's a few mods I would do if I were making my own pc board:

1. Use a 12-position, shorting switch in place of the 10K reverse-log pot. You'll have to calculate the resister values - there was a web site around here somewhere that would do that for you, forgot where it was. Anyone?

2. Use a 5K feed-back resister in series with a 5K pot for a "fine" gain adjust. Use a good quality pot here - conductive plastic or something.

3. Put a small .22uF film cap in parallel with C2 and C5.

4. Use high quality Panasonic or equivalent caps. (Peter may very well be using h.q. caps here, but just though I'd mention it since they're not spec'd on the schematic)

5. Make a "balanced" output using two 49.9 ohm and one 10K resister, shown on the Forssell schematic as R11, 12, & 13 that I linked to earlier.

6. Kludge in some type of LED level meter. Doesn?t have to be anything elaborate ? at least 1 LED to let you know where it clips.

You can use a power supply down to +/-15V, but I?d use +/-24V if at all possible.

 

[Vikki]

Flatpicker
Perhaps a silly question this, do you play guitar and if so what preamps do you use for recording.
Vikki(uk) :grin:

 

[Vikki]

Peters circuit looks pretty simple, i think i could build that one on vero board. Where can i obtain the Chip?
Vikki :grin:

 

[Flatpicker]

[quote author="Vikki"]Flatpicker
Perhaps a silly question this, do you play guitar and if so what preamps do you use for recording...[/quote]Me? I like the Neve clones! :green:

Seriously though, I do like a little color when recording a flatpick guitar style, but you said you didn?t want a colored pre and I agree that the ?pristine? sound is probably better for fingerpicking anyway.

 

[SeventhCircle]

Actually, the A12 minimal kit ($59, available now, send me an email) can be populated to produce a good facsimile of a Hardy M1. Use a 1538XL, a Hardy 990C, and a Jensen JT-11-DMCF on the output. You'd have to recalculate the feedback resistors, but the values for the J99's input attenuator and first gain stage would get you in the ballpark. Plus you'll get dedicated on-board voltage regulators and enough supply bypassing for a small power amp.

I guess the chassis is expensive compared to a plain sheet of 16 gauge steel, but keep in mind that they are entirely custom made, with vents top and bottom, welded seams, black powder coating, and a thicker-than-usual aluminum panel. Also, the internal divider and mu-metal shield have been tested to assure noise-free performance with the power supply mounted in the chassis. Heck, the mu-metal alone costs us $30 per box.

BTW, I am working on a JFET circuit, but it's been delayed by what I'm calling the SC25, a "slightly improved" version of the 2520 discrete op amp. It has better CMRR, much lower input bias current (by two orders of magnitude), and is qualified for +/-24V supplies. It retains the lethargic slew rate (2.5V/uS), beefy output (clips at +19dBu into a 50 ohm load), and sonic character of the original, however. We're going to bundle it with the A12 complete kit for a total price around $299.

 

[rafafredd]

[quote author="SeventhCircle"] We're going to bundle it with the A12 complete kit for a total price around $299.[/quote]

Will you also sell this alone?

 

[JLM Audio]

My reference to Neve on the 99v page is to do with circuit topology and nothing to do with the Class A Neve sound. The 99v is much more defined and tighter in the low & low mids and silker in the high end than a 1073 type mic pre. But a lot depends on the input & output transformers used as to how pure or how coloured the mic pre ends up.

Joe

 

[soundguy]

additionally, the 99v I built (1578 input/2503 output) sits in a completely different place in the mix compared to a 1272. I tracked a bunch of stuff this week with 1272's and the 99v isnt at all competing, it sits on top, way on top of the neve. I personally wouldnt compare these to neve amps (which I generally consider to be kind of poofy on top) at all, similar idea, different sound... This would make one hell of a great all around preamp, if you could only have one...

dave

 

[Vikki]

To Seventh Circle and JLM just to say congratulations on putting together the products you have, it must be down to total dedication to see the product through to a kit or completed unit. Seventh Circle i wasn't having a dig about your chassis, living in the uk we are highly taxed and nothing gets through customs without a knock and someone holding there hand out!
Here's an example Audio Technica AT 4060 valve mic U.S price around 1000 dollars, u.k price around 3000 dollars U.s.
So i'm looking at things from that angle.
So its time for me to sit down and have a ponder now, any more ideas greatly appreciated.
Vikki(uk) its raining as well! :grin:

 

[Peter Simonsen]

Flatpicker,

Thanks...yes I did use EWB ;-).. have been driving these pres as un-bal output pres...with no problems at all for a long..long time...I have 4 of them in one cabinet. (ext powersupply).

Vikky...I´m a guitar player myself and use these pres to record a lot of acc-guitar...The combination off the 990C, and Lundahl X-formers are very good imho. I get a very true, tight sound..very "airy topend" without getting thin at all..tight low mid freq, and bottom.. the upper mid freq area are very detailed..(very good for acc instruments). One of the very best thing about this combination is that I like this preamp with many different mics...and on many different sources..that more than I can say about something like my millennia preamps..(sorry John)

Kind regards

Peter

 

[Vikki]

John
I think i will have a go at building a couple of these, is the circuit the same as in the other thread? Flatpicker mentioned some mods and additions. By the way is there a seller for the 990c?
Thanks
Vikki :grin:

 

[Flatpicker]

[quote author="JLM Audio"]My reference to Neve on the 99v page is to do with circuit topology and nothing to do with the Class A Neve sound...[/quote]Thanks for the clarification, Joe. Believe me, the 99V is on my list of things to have!

 

[Flatpicker]

[quote author="Vikki"]...By the way is there a seller for the 990c?...[/quote]The one and only, John Hardy: http://www.johnhardyco.com/

BTW, the beauty of this circuit is that you can drop in a Forssell 992, a JH990c, a JLM99V, or even a 2520 if you lower the supply down to +/-18V. The latter is a good reason to build your supply using adjustable regulators.

 

[Kev]

Thanks to Tim and thanks to Joe.

Tim,
I look forward to hearing more about your SC25.
Just remember to stay out of Paul's way. :wink:

On that subject there is some info on a similar unit at Group DIY. It is burried very deep so don't ask me to point to it for you. There is even a P .... errr shut up Kev.

 

[mattmoogus]

Just for the record, Ive used the 99V pre (with OEP input and single 99V config) with my Beyer M200 and M130 ribbon mics, and thats now my all time fave male vocals and accoustic guitar path.

Ive only used the single opamp version though, which has less gain, even still I found it fine on vocals and only just a little low on acc guitar.

Oh and I must say it doesnt sound like a Neve - to be honest Ive never used a pre that I could compare it to, sonically.

YMMV or course.


Matt