DIY Tube Preamp

[FBLEAGH]

Ok thanks guys,

Now i've got something to start on

btw do you think this a good design to start with ?

Is this going to be easy to modify and pay with later ?

I was gonna build it using the tubebuilding PTP boards, good idea ?


also where can i find some good info on tube theory ? eg topologies, basic design ideas etc

oooo 1 more thing, how easy will it be to add a decent selector ciruit and possibly some tone controls later ( and where whould the tone controls fit i the circuit )

THanks agian
Fbleagh

[fdegrove]

Hi,

also where can i find some good info on tube theory ? eg topologies, basic design ideas etc

See here amongst others:

Tube Question, what the....?

btw do you think this a good design to start with ?

Other then that you said it to be a preamp I don't know what circuit you picked.
Care to tell us some more?

Is this going to be easy to modify and pay with later ?

Depending on real estate,why not?

I was gonna build it using the tubebuilding PTP boards, good idea ?

You mean these phenolic boards with a row of solder lugs?
Those are easy and give better soundquality then PCB.

oooo 1 more thing, how easy will it be to add a decent selector ciruit and possibly some tone controls later ( and where whould the tone controls fit i the circuit )

Selector switch is no problem but tone controls never interested me.
Can be calculated though.They can be done within a feedbackloop or passively with specially tapered pots.
When passive they can go at the inputs.
Is this for a guitar preamp stage or similar application?

Let us know what you want to do and we'll take a look.

Cheers,

[FBLEAGH]

thanks for your response fdegrove

I am looking a the line preamp design 2
Looks nice and simple.


as for the application i am looking at, it will be used as a preamp for my solidstate power amp.
and i want to add a selector switch ( cd, pc, dvd, tv )
and an extra set of pre amping outputs to goto my headphone amp.


hmm you mentioned that this could be used as a guitar preamp hmm that could be cool, i ve started learning bass and need an for practicing at home

[fdegrove]

Hi,

The circuit on the picture above will work even better than #2
and can be arranged much the same way.

Where it says "stepped" on the picture you put the volume control.
It has a very good sonic reputation as a topology and the 6SN7 is one of the best sounding octal tubes around and still in production.

Moreover it can drive much longer interconnects than the anode follower as proposed in #2.

Gain will be more then ample for all known sources and you have all the required components values for it to work right here.
Might you have more questions,just ask.

At the end of the day it is your call,so I'm only ging advise here.

Cheers,

[FBLEAGH]

Ok so the above design uses both halves of a 6sn7gtb.
i s that right ?

and then i make another circuit the same for the left channel.

cool.

i understand ( basically ) what is going on in the bottom half but what is it doing in the top half , ie what is the second tube half doing ?


BTW thanks for all you help
just finshed reading http://www.eecs.umich.edu/~mmccorq/t...roduction.html -- good intro to tubes, i know feel i ahve at least some understanding of whats going on

[FBLEAGH]

also what are good 6SN7GTB's to look for ?

RCA, GE, Raytheon ??

[TubeHound]

rca 5693 red base (6sn7) Arguably the best! $100-150 for NOS pairs.

[DaveInVA]

Or get some 12SX7's.....


Dave

[fdegrove]

Hi,

No need to shout it from the rooftops.
Seems to me someone is browsing a databook.


Indeed,a very good alternative.

No need to spend big bucks on tubes unless you want to build a very,very good preamp in the first place.
And you all know my recipe for that by now,don't you?


Worthy of consideration as well: *SU7.

There're bound to be others but I need to look them up.

As far as the diagram posted goes it is an SRPP (shunt regulated push-pull) in it simplest form and more than adequate for the task.

The top tube basically replaces the classic anode resistor and isolates the bottom half from the PSU.
Low output impedance and better dynamic range are the result but it is highly dependent on a well regulated PSU.

More about it later,

[FBLEAGH]

As I am fairly new to all of thiswhat would you guys suggest as a good tube to start with preferably easy to get hold of and reasonably cheap, but with some good tuberolling options later.

fdegrove wrote:

No need to spend big bucks on tubes unless you want to build a very,very good preamp in the first place.

would you be so kind as to point to where i can read about this recipe for preamps


Cheers guys, youve been a great help