What preamp should I build?

[OzMikeH]

I've never built a tube project before, I do maintain some simple tube equipment (although it does pull several amps at 6kV). I'm an experienced electronics tech so I'm not afraid of a complex design.

I'm looking for a preamp design or kit, I'd prefer something that can be done point-point because I'm not set up for making PCBs. I will consider kits as well.
I have a faulty Tektronix 545B CRO I can salvage a power supply and sockets from, maybe even tubes.

My requirements:
Some gain, 6dB is plenty.
volume control.
one unbalanced line in, one line out.
Very high sound quality, high resolution, not muddy or overly warm.

Nice to have:
Balanced line out.
no really obscure parts.
an output topology suited to coupling direct to my active crossover without buffers.

Can anyone point me to a few threads or sites? There's plenty of preamps out there, many with boutique parts, but I have no way of knowing which of them actually sound good.

[arnoldc]

26!!!

[KP11520]

Hi Mike,

The other day, I saw someone asking for a decent Tube Phono Stage schematic to build a stage as his first project.

One guy recommended a kit to make it easier for the "First" project and pointed to this site. They make Preamp/Linestages and Amps too. The site looked interesting but I can't vouch for where they sit in the pecking order. Take a look: http://www.bottlehead.com/et/et.html

Oh, like he said, Eileen is not included with any of the products!

You might ask the forum what they think!

Regards//Keith

[staggerlee]

Here's a nice thread for you to digest This pre sounds great and can be as simple or complicated as you like: 12b4

[cerrem]

Just my 2 cents....
There are some key things to note....
I would say the power supply is the most critical section of the pre-amp..... ALthough having good PSRR is nice, I still like using very low impedance power supplies.... I usually like to use a triple Darlington arrangement for the pass element...
Most important is to protect your V_reference, whatever you use protect it...for example if you use a Zener string for your reference, make sure to feed it with a PNP constant current source for example....
If you ever add a phono-stage....you will see how critical the power supply can be...
Typically when you say you want high resolution, to me that means a high gm tube....this tends to make the little things jump out more....
As for the output of the pre-amp....the norm is to use the resistor loaded cathode follower....also a high gm tube is good for lower output Z..... The resistor loaded follower is not all that linear for large signal analysis....so a current sink is typically used in the cathode to maintain a constant current, this will greatly help linearize the follower .....

Chris

[Poindexter]

Try this.

I've made a lot of line amps, and this is the daddy so far.



If interested, let me know, and I'll show you the power supply and stuff.

Hau'oli Makahiki Hou,

Poinz

[planet10]

Originally posted by Poindexter
If interested, let me know, and I'll show you the power supply and stuff.

I'm interested in anything you do Poinz

dave

[Poindexter]

Thazz why you my idol, Dave.

You want the whole circuit? I'm working up a page about it, but it'll take a little time. I do have various working schems, though.

Best,

Poinz

[zacster]

The Aikido at Tubecad.com is an easy build, but it is board only. You need parts (There may be a kit available) and a power supply, chassis, jacks etc... But you're a tech, so this shouldn't be too hard. Bottlehead is good too. I've built both a BH and an Aikido, and my vote goes to the Aikido on sound, but BH on ease of build, mostly because it is a complete kit.

[planet10]

Originally posted by Poindexter
Thazz why you my idol, Dave.

You want the whole circuit? I'm working up a page about it, but it'll take a little time. I do have various working schems, though.

Take your time... can't rush the cook...

dave