Seventh Circle Audio

Hi Tim.... and Hi to everybody who frequents this site !!!!

I'm new here and maybe Tim or somebody will be kind enough to drop me a line and answer my question !!!

Some peolpe say that what I will say is very subjective, but I'm pretty convinced that preamps with large bandwith sound more OPEN and three dimentional !!!

I would like to have a preamp with the largest bandwith I could have....so now here's my question:

In order to get... lets say 20 to 100 Khz of bandwith out of a J99 will I have to just change a few componentes or have a new design from scratch?

Thanks again !!!!

Lincoln

10 Hz to 75Khz isn't enough for you?

Hi Tele...thanks for replying to me !!!

10 to 75 Khz is the actual frequency response of the J99 ???

If thats the case...yeah baby...i willl be more than satisfied !!!!!!!

Just one more newbie question...

Is the J99 a class A preamp ?????

Thanks a lot !!!!!

Lincoln

10 - 75Khz is the freq. resp. in the specs for the J99. A very (very very very) similar device, the John Hardy Jensen Twin Servo, has a published spec of very flat 20-20Khz, 3db down at .4hz and 140Khz.
The Hardy and the J99 are based on the same design. These are very precise, very broad bandwidth amplifiers.

As for Class A? I don't know - I've got the schematic for the 990C op amp, but can't at a glance tell how it's got the output transistors biased.

Bottom line: these are incredible preamps.

Hey tele !!!

Thanks again for the reply !!!!

Since it seems that you know a ton more than I do about electronics and the anatomy of a preamp...if you don't mind I'd like to ask a few more questions.

I don't understand why the frequency response is quoted two times on the specifications....first you have 20-20Khz...than 10-75Khz -3db....this is probably very lame for you guys but for me it's rocket science.

Second...I have NO DOUBT that the preamp sounds amazing...but for my kind of voice it seems that class A preamps work better...maybe it has something to do with the fact that they capture transients with more acuracy or something.....

Third and last question...Why do they call this kind of preamp HIGH VOLTAGE...and say that you can kill yourself building one of them ???? As far as I can tell they take 110 AC and output 27 DC...maybe I'm being stupid but....where is the catch...where is the high current ??!!!!

Thanks again,

Lincoln

Frequency response. Well, amplifiers tend to fall off at the high and low end, so specs sometimes show the linearity in the relevant audio band, and then show the -3db points. While it wouldn't really be a straight line, you could still approximate, for instance, how it will behave at 50Khz if you know it's only down 3db at 75Khz (or whatever).

Frankly, I think should forget what you think you know about the way your voice sounds through Class A amps, but I expect these are Class A push-pull op amps.

Tim - are 990's biased for Class A?

You could certainly get a lethal shock if you mishandle the 120vac lines, and you might get an uncomfortable shock if you mishandle the DC voltages. Caution is advised.

Hey Tele...thanks for the answers !!!

I don't know if i grasped everything but.....

about the high voltage..I will assume that you are talking about those things (I forgot the name) that have the particularity of storing charges from a 120 source than liberating everything at higher voltage (and at once)...anyways, I will be careful.

About frequency response....well.....maybe my original question should be wether or not I could change the J99 so it would have 10-75Khz at 0 db...right ?????

Now about what I think my voice sounds like on a class A preamp......hehehhehe....man I still remember being at the now defunct MARS...remember MARS ????? And flipping over the mackies...ARTs and all those preamps without anything new...then.....suddely I heard my voice so clear... SO OPEN...like I'd never heard it before.....only to realise I was singing through a focusrite green....no EQ, nothing, just the preamp !!! Man...I will never forget !!!

I sing through a behringer preamp now...lame huh ???? but as soon as I can I will build a class A preamp.....and maybe revive that experince I had with the green I could never afford !!!

Thanks a million !!!

Lincoln

Think of it this way.... the closest thing I could find to the GREEN preamp is the "Focusrite TrakMaster Pro Channel Strip" which has one channel, but aslo has compression and eq and costs about $300. Ok... lets leave off $100 for the compressor -- that's about $200 for the one channel and is the cheapest pre I could find from them in a quick search.

Now... assuming your berringer has 16 channels ... at $200 per channel, it would have cost you $3,200 for the mixer right? No?

Though I have no personal experience with Focusrite, what you were hearing was a much higher quality preamp than what you were using through the mixers. To keep costs down, the pres used in the type of mixers you mentioned are not nearly as high quality as the separate pres you buy from Focusrite, someone else, or here at SCA. They are made with less expensive components etc, which is generally fine for a live setting, but in the studio, a higher quality setup is more desireable.

Class A -- if I understand correctly, is just how the circuit is layed out and doesn't necessarily mean a "better" preamp or a better "sound".

These preamps Tim sells are outstanding (though I havent presonally tried the J99 yet) and i would venture to bet that they will do even better than the Focusrite you heard regardless of whether they are "Class A" design or not.

Focusrite is not straight class A. It is class AB. What you were hearing when you fell in love with that sound probably wasn't the class of operation, but rather the sound of a good transformer.

IMO the best of all the focurites was the original RN designed ISA110 (class AB design) which the newer stuff is likely based on (with budget minded shortcuts).

The J99 will mop the floor with the ISA110 IMO. they are both great, but for bandwidth lovers the J99 is where its at.

That doesn't mean the API and Neve designs are any less incredible...even though by comparison they might look bandwidth challenged.

Forget everything you are thinking right now though. The SCA preamps (all of them) are probably so far beyong what you've heard you'll be blown away when you hear them. Any of them. They are the real deal.

I doubt anything you've ever heard at MARS or Sam Ash could compare realistically (with the exception of maybe Manley, Vintech, API if they carry those now).

The designs are pretty much where they need to be. Just from your questions I can tell you won't have the technical know-how to improve upon Tim's designs. Honestly...a rack of SCAs will not leave you wanting.

Shane

Thanks for waking the board up Cat.......

Cat 5 is right basically...except for a few caveats...

The ISA and Red ranges from Focusrite are indeed Class A - but the Platinum and (now defunct for years) Green Range were/are not. The original ISA 110 module (and the 130 comp module) built for the Lyndhurst Neve were from a similar design and were Class A as well....the 110 and 130 mods have been combined into the 430 (of which I have two - old and new) and the 220 (with a few different freq choices) - and the 428 which is the pres only with impedance choices. The original 430 is still the best bass recording channel I have ever heard, even though the instrument input is transformerless (the new 430 uses the transformer on the instrument input, but I don't like it as much for bass, go figure...)

The Cat is right about one thing though - these freaking SCA pres are NOT something to sniff about. They sound freaking GREAT! They stack up to everything you can throw at them. You will not be unhappy with a set of them. Period.

Right arm, as they say....


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