Power Tube Preamp

[Pim Driessen]

Dear Forum Members,
The plan is to make a tube preamplifier, the amplifier itself is actually already present as far as the schematic is concerned.
But the stabilized power suply is not quite as desired.
Would like to put in a power source to make the zener diodes more stable and thus make the whole power supply more stable.
Since we are talking about 250 volts DC voltage, not many components are eligible, an LR8N has been thought of that can be used up to 450 volts, but can only be used up to 10 mA and then with this IC the difference between in and output are 20 volts.
Using a TL783 might be possible, but I wouldn't know how to fit it myself.
Who has an idea for a power source that is capable of doing its job at high voltage.
Greeting,
Pim

 

[Nigel Goodwin]

Why do you want a stabilized power supply?, the whole point of a valve amp/preamp is to give lower quality, and HT variation is a very big part of that. Stabilizing it will make it sound less like a valve amp.

However, if you really want to?, first thing is to determine what the current requirements are.

 

[Pim Driessen]

Hi Nigel, In the first instance it is about the lowest possible hum level, and that does not seem the most obvious option with a tube rectifier.
That is why I opted for a power supply with transistors.
Now I just got an idea through a forum that actually makes the power source superfluous, here's the schematic.
Greeting,
pim

 

[Nigel Goodwin]

Hi Nigel, In the first instance it is about the lowest possible hum level, and that does not seem the most obvious option with a tube rectifier.
That is why I opted for a power supply with transistors.
Now I just got an idea through a forum that actually makes the power source superfluous, here's the schematic.
Greeting,
pim

It's very similar to what you posted in the first post

But again, why are you wanting the lowest possible hum level? - that's part of what people are looking for with valve amps. If you want low noise and high quality, just build a transistor amp

However, historically (as I said) they didn't stabilise voltage rails, and the preamps were just fed from the main HT via a dropper resistor and smoothing capacitor - this was often done in two stages, so the first dropper feeding the phase splitter etc. then a second dropper from that to the preamp. If it was a multi-stage preamp, then there would probably be another dropper and smoothing capacitor between the stages.

In this highly rated valve preamp, there are actually three stages of dropper - R32/C15, R25/C12, R20/C7

Quad 22 schematic

manualmachine.com

 

[Pim Driessen]

Hi Nigel,
There are also manufacturers of tube amplifiers that use stabilized power supplies, such as Audio Research, here is a schematic of the SP-6C preamplifier.
Greeting,
pim

 

[Nigel Goodwin]

So they can charge you more, and make it sound more like a transistor amp

 

[rjenkinsgb]

As Nigel says - gimmickry to sell to people with more money that sense or technical knowledge.

 

[Pim Driessen]

Dear Nigel, rjenkinsgb,
Thanks for the advice, but I promise that when the tube preamp is finished, the listening experience will be shared by me here.
Greeting,
Pim

 

[rjenkinsgb]

If you want a true valve amp, use valves?

Stabilisation and Smoothing with Thermionic Valves

85A1 voltage stabilisers are also still available.

 

[Pim Driessen]

Thanks for the information.
Greeting,
Pim

 

[audioguru]

I sold my vacuum tubes kit amplifier 58 years ago and have never seen another one since then.
I replaced it with a solid state amplifier that still works today.

 

[crutschow]

when the tube preamp is finished, the listening experience will be shared by me here.

So we can hear why you prefer the sound of music altered by the distortion characteristics of a tube amp?

 

[audioguru]

Some people think that an old tubes AM radio sounds fine. Maybe their hearing (or brain?) muffles the highs and rectifies the waveform creating massive distortion like the radio.