#26 pre amp

[12B4A]

The mesh is 100x100 brass wire cloth from McMaster-Carr.

[merlin el mago]

More work in progress: suspended plate with a sandwich aluminium, mu-metal (permalloy) & still-point, of course will be connected to chassis earth.

[amandarae]

Originally Posted by merlin el mago

More work in progress: suspended plate with a sandwich aluminium, mu-metal (permalloy) & still-point, of course will be connected to chassis earth.

Merlin,

What are those rubber dampers called?

Thanks!

Abe

[Wavebourn]

Originally Posted by 12B4A

Thanks! They are just tube frames from vt4c that I lined with fine brass mesh to complete the shielding.

Where did you get that nice cans for covers? Who makes them?

[12B4A]

Originally Posted by Wavebourn

Where did you get that nice cans for covers? Who makes them?

The tube frames are sold by VT4C and the item # is CH-FM-50. The cover over the transformers in the back is just a 7" aluminum cheesecake pan with the bottom replaced by the screen.

[massimo]

Originally Posted by amandarae

Merlin,

What are those rubber dampers called?

Thanks!

Abe

McMaster Carr pn 9311K141 with nylon insert (I don't remember pn)

[Wavebourn]

Originally Posted by 12B4A

The tube frames are sold by VT4C and the item # is CH-FM-50. The cover over the transformers in the back is just a 7" aluminum cheesecake pan with the bottom replaced by the screen.

Thank you!

Looks like round extrusion with fins, machined windows, then cut on peaces, then cut threads for flanges.

May be I can find somebody to make something similar for my tubes.

[amandarae]

Originally Posted by massimo

McMaster Carr pn 9311K141 with nylon insert (I don't remember pn)

Thank you!

[andyjevans]

I built another version of the 26 line stage as shown in the schematic, and this is my current favourite. I swing between this and the 4P1L and for now I've gone back to the 26 because it's followed by two stages of 4P1L in my PSE 4P1L amp. I think 3 stages of 4P1L is too much - the particular sonic characteristics get exaggerated. This is working very nicely indeed. Really enjoying listening. Previously I used it in Alt S 4:4.5 but the other way round makes more sense and I still have enough gain in my 3 stage setup. As usual I have choke input filament supply (Hammond 2 x 159ZC) and a 220v PSU CLCLC with AZ1 mesh rectifier and all polypropylene caps. First cap is usually quite small - not over 4uF.

[mogliaa]

Great Andy, that is practically the same operating point I'm using in my 26 amp:26 DHT pre-amplifier (Gen2) | Bartola Valves

A mix of 26 and 4P1L is better for the sound. The warm of the 26 adds something special that a 100% 4P1L may not provide. Surprisingly I'm not using 4P1L now, I have 26 preamp and then 7193 into the 45 SE. This is why I enjoyed so much the sound of the 4P1L as a line stage before and why I want to rebuild my Siberian preamp!
Perhaps we should learn not to abuse of the 4P1L :-)...
Cheers
Ale