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-   -   KT88 and 6SN7 tube spacing and aligment (https://www.diyaudio.com/forums/tubes-valves/322628-kt88-6sn7-tube-spacing-aligment.html)

Mission720 14th May 2018 10:29 AM

KT88 and 6SN7 tube spacing and aligment
 
Hi - I've a question regarding physical layout of KT88 and 6SN7-G valves/tubes.

Reading a KT88 data sheet it mentions that KT88 centres should be not less than 100mm (4 inches) apart, plus that pins 4 and 8 should be aligned for each valve.

For 6SN7-G, there should be no less than 5mm between glass but I can find no other comments about base centre spacing or pin alignment.

Any comments or further guidance would be appreciated. Thanks in advance.

JonSnell Electronic 14th May 2018 10:42 AM

The sole reason for KT88s to be 4" apart is air flow. Alignment of the pins makes it easier to wire and keeps the valves the same way around.
6SN/L7 need 1/2" for air flow and it is usual practice to align the pins for aesthetics.
Always wire the heavy heaters first to minimise voltage drop. Running the 6SN/L7 heaters at raised DC voltages is not requires nor is a DC heater supply.

Burnedfingers 14th May 2018 10:52 AM

It depends on the manufacturer.... some equipment will align pins so everything looks pretty and others will set up socket orientation so that heater wiring is maximized. It would seem that English equipment favors the pin alignment from what I have seen.

Mission720 14th May 2018 11:30 AM

Guys - thanks for the quick response and contents noted...

Should I also look at seperating KT88 and 6SN7 by 100mm (4 inches) as well? I have the PSVANE-UK versions which are full coke-bottle shape.

So for my PP amp I would have a valve base centre square of 100mm x 100mm. This is a PCB based design with a single PCB per channel so two indetical PCBs for stereo.

kodabmx 14th May 2018 01:30 PM

The KT88 pins are aligned so that the coolest side of the bulbs face each other, and the hottest away from each other.

The KT88 is taller than the 6SN7, and most of the heat goes "over the top" of the 6SN7. I have then about 1 inch from the KT88 (KT120) in my build. Here's the GEC datasheet with the supplementary: https://frank.pocnet.net/sheets/084/k/KT88_GEC.pdf

Kay Pirinha 14th May 2018 02:52 PM

Doesn't physical alignment of some tubes, KT88's in this case, only apply to horizontal mounting? The purpose of it is that the long axis of the internal system comes perpendicular, due to avoid unwanted bends of the grid wires.

Best regards!

Mission720 14th May 2018 03:06 PM

Quote:

Originally Posted by kodabmx (https://www.diyaudio.com/forums/tubes-valves/322628-kt88-6sn7-tube-spacing-aligment-post5433082.html#post5433082)
The KT88 pins are aligned so that the coolest side of the bulbs face each other, and the hottest away from each other.

The KT88 is taller than the 6SN7, and most of the heat goes "over the top" of the 6SN7. I have then about 1 inch from the KT88 (KT120) in my build. Here's the GEC datasheet with the supplementary: https://frank.pocnet.net/sheets/084/k/KT88_GEC.pdf

Hi Kodabmx - yes, the datsheet confirms spacing and pin alignment. I suspect you have GT versions of 6SN7. I have PSVANE-UK versions which are 9.8cm height (without pins).

kodabmx 14th May 2018 03:12 PM

I'm using 6N8S actually, but yes, they're T10 tubular.


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