Easy Tube Preamp to Front LM3875 GC?

[CarlosT]

Can the words tube and easy be in the same sentence?

The McTubeII caught my eye but are there other easy (I know...there I go again) single tube preamps/preamp kits/preamp schematics to front an LM3875 GC amp?

I'm thinking about a simple bass amp...


Thanks!

[Jarno]

Hello Carlos,

I was thinking of building the real mctube as an overdrive function in a bass preamp. During the search for opinions on this unit I came across quite a few people that weren't very pleased.
For a bass preamp I suggest the alembic F2b schematic or the Mesa Bass 400 preamp. I built and liked both, and made a hybrid version. It's a Alembic preamp with bass - and treble shift functions.

I have the schematics somewhere, but can't seem to find them right now. I think I have them on another computer. I got them from the internet, so, Google is your friend!


Best regards,

Jarno.

[Minion]

I"ve starting useing Sub Mini Tubes with pretty good success...They run off of Low Voltages and low Currents and are extremely small and easy to implement.....

Just a Thought if you want to do something small and easy without haveing to spend a Fortune on parts and High voltage Transformers.....

I am working on a simple Preamp useing Two 6418 sub mini Power amp pentode tubes that will be Powered useing a simple DC adapter.... I"m thinking of putting it in a Small enclosure and useing it as a Guitar/Bass Preamp Pedal....They don"t have a Lot of Power output but it can be suplememnted by useing a couple Fets or transistors or even a cheap Opamp.....

these Particular Tubes are only about 1 inch tall and 1/5 inch Wide and use a Fillament Voltage of 1.25v and a Plate Voltage of between 15v and 30v so they are very easy to use and add a real tooby sound ......

Just a Thought....

[davidlzimmer]

Someone submitted this awhile back.

[CarlosT]

Thanks, guys...hey Minion you always got interesting solutions. I mean...yeah...all I want outta tubes are the tube "inaccuracies" and warmth...no need for super high voltages or huge BLING transformers. The LM3875 or paralleled LM1875s can take it from there.

Tell me more about these low voltage tubes. I'm assuming that they still need a separate warming circuit...

[Jarno]

Hello Carlos,
If expensive transformers keep you from using plain old (and good sounding) 12AX7's why not use two transformers back to back? I got the idea from one of the projects by Gyraf (which they took offline sadly). Does anyone have the schematic?
You can use the low voltage in between the transformers for the heaters.
I built the PSU for my bass preamp like this and it works just fine.

Best regards,

Jarno.

[CarlosT]

I'm afraid of high voltage

[Jarno]

A very sensible anxiety indeed!

I wish I was too, the psu from my preamp is still a bunch of components with exposed soldering joints, 1000uF of capacitance at about 300volts, no bleeder resistor and no fuse. I haven't been zapped yet, but I will have to get around to putting it in a box with a proper fuse (and on/off switch).

Regards,

Jarno.

[CarlosT]

You're never as alive as when you're close to death. Keep up the good work

[culture]

I found this a while ago.. cant remember where..