• WARNING: Tube/Valve amplifiers use potentially LETHAL HIGH VOLTAGES.
    Building, troubleshooting and testing of these amplifiers should only be
    performed by someone who is thoroughly familiar with
    the safety precautions around high voltages.

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I forgot to put here my Preamp... ;)

An externally hosted image should be here but it was not working when we last tested it.

An externally hosted image should be here but it was not working when we last tested it.

An externally hosted image should be here but it was not working when we last tested it.


Please don't look at the volume knob I'm using... the real one is still in the building process :D

An externally hosted image should be here but it was not working when we last tested it.

and this is me... :angel:
 
Tube Linestage/Preamp

This is the first project I ever finished using tubes. I wanted to taste the various valves (because they are all so very different ;-) so I made a linestage with options. You can pick up a measurement of the DC heater suppy and adjust it on the rear of the unit. There is a discharge resistor and momentary switch so you can shut off the unit, discharge the caps and switch the valves without any clicking or popping and minimal risk to the tube. An advanced version may have the sockets entirley switched for non-tube swapping of instant comparison, where all flavours would be plugged into their appropriate sockets and selected via a large selector type rotary? I can't be bothered but a fun idea?



I hope you like it. It is a fun thing to have. Oh yeah, I think I'm going to add an octal socket when I rewire it.

Ja Bless,

Shawn.
 

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Exposed Electrolytics

Hey, one more thing. If you ever have to put an electrolytic on the top side of your "hot" looking chasis, why not strip the plastic off the elctrolytic capacitors, on most you will find "a more pleasing to the eye" aluminium barrel. Perhaps not for everyone.

Cheap and dirty works now just as much as it did back in the day.
 
ddd said:
But I doubt the Elcos could look better w/o thair motley sleeves.

I thought about this for my preamp a couple of posts up, but since I use a voltage doubler, the alluminium can carries 150V... :xeye:

Hello Tomwaits, great preamp! Very good idea that of exchange tubes. But a little remark: I don't think that your totem configuration is best suited to put in evidence the differences. It's intrinsic degeneration tends to null out special tube "flavours": if you have to rewire it, why don't you try the classic grounded cathode -> DC coupling -> cathode follower (the same tube number as now). That will give you strong tube characterization: but I must admit that if I read right in the schematic, you're using one of my favourite dual triodes so... ;)
 
Aside from shielding users from the potentials that may appear on the capacitor cans, the ugly plastic has a couple other advantages:

If you need to replace it, look at it and there the values are in plain text
Some caps are wrapped in such a manner as to contain or direct a large leak / minor explosion so that they do not turn into little bombs
 
Giaime said:

I thought about this for my preamp a couple of posts up, but since I use a voltage doubler, the alluminium can carries 150V... :xeye:

My aluminum cans don't; Rubycon, Jamicon and Mallory have all worked for me without conductivity to the barrel. I have certainly not tried every cap out there and peeling the label can be very destructive depending on the result you require. Like I said cheap and dirty. It is a cheap trick and it has worked for me and it is not for everyone.

Giaime said:

why don't you try the classic grounded cathode -> DC coupling -> cathode follower

Please post this schematic or your favorite version of it, it sounds nice.

Shawn.
 
ddd said:
I like your approach, Tom. Any observations?

Sound? To me?
Nothing to it, it is clean and the circuit leaves very little to the tube to color the stage. Great for a line stage that you require only a little gain from, from time to time. I wasn't looking for "warm" when I decided on building this. I must have studied and downloaded a thousand schematics and I'm not exagerating. I want sterile and clinical on a linestage perhaps you don't.

Try it to see. I did it in a weekend including the case.

Shawn.