Tube pre-amp for recording?

[M Fowler]

My friend wants me to build a tube pre-amp for recording with volume and TMB controls.

Anyone have experience in this department? I ordered a small PT for it and Hammond chassis to fit it into. I am looking at using the Alembic Tube Preamp F-2B what do you think?

Mark

[ampgeek]

Scroll down a few clicks here and look for the "Tube Pre-amp in a Pedal Box" project.

http://www.el34world.com/schematics.htm#Mods

This one is designed specifically for recording and clips can be found elsewhere in Hoffmans Library of information.

Cheers,
Dave O.

[guitardude57]

Hi Mark,

I think either the Alembic or the Hoffman would work well.

The one extra point I would consider, would be to have a 3 Band Active EQ (sweep with cut/boost) to help dial in a finer detail to the EQ. Very similar to what a Sound Desk would have, or some of the boutique preamps out there.

That way you could dial in exactly what you need. Plus EQ bypass switch, if no EQ is needed or wanted.

You could always adjust the gains for this. Wire the EQ/out switch for Unity gain, so it won't change the gain structure when off. Transparent.

Shouldn't be too terribly difficult, but different from stock TMB used in guitar amps. I'm sure there are some interesting Schemos out there.

Would be a good learning experience.

[Andy Le Blanc]

thats a -10 tone stack and you can't get a flat response unless its bypassed.

[M Fowler]

Thanks guys I am still looking.

Andy which one are you referring to and what is a 10 tone stack?

[Andy Le Blanc]

That fender TMB, you have a -10 Db insertion loss, It carves pretty deep.

If you have that tone stack calculator, look at the response curve.

[M Fowler]

The site says that Alembic Tube preamp F-2B is a Fender Twin Reverb type?

Also found this one. base on Fender. There is also just a plain one that I could add TMB with lift.

[selloutrr]

Don't cheap on transformers! Utc lundahl jensen are all sweet.

Replace any ceramic caps you might use with orange drops it will help keep your noise floor low.

Make sure you use awesome knobs . Precision pots don't hurt either!

If you make multiple consider an outside power supply that powers them all.

[M Fowler]

What I can't go cheap here

Well its for a good friend that records all day long for a living and like us he is on a budget. That means me.

If it doesn't suit his liking then I will use it my self. Besides good learning curve for me.

[Andy Le Blanc]

that simple one looks good, thats a good place for a couple 12v back to back.
With the digital media's its more about getting the right tone color before
it goes into the digital. have fun swapping caps, I like oil/foil on the input.
But do try NOS ceramic and those molded paper in bakelite.

[guitardude57]

Mark,

Here are a couple of examples of some EQ circuits.

The H&K is very cool....

You want the absolute best grade audio transformers you can get.
Stepped pots are pricey, but worth it!

[M Fowler]

Thanks guys I do have a whole bunch of old parts handy. Wow that H & K reminds of the 42 inch chasis I took out of my Hammond organ loaded with tubes, relays, and something I don't what they are.

[JD0x0]

i think david gilmour uses roger water's old F2B in front of his hiwatts

[Jana]

How much gain do you need? The reason I ask is because if the first gain stage is enough then bringing the output signal off of the cathode on the last tube (no bypass cap) would really lower the output impedance. Like down to 1k instead of the 70K or so coming off the plate.

[M Fowler]

Jana,

He wants it squeaky clean with TMB and volume. No smart ass comments on that either.