Hoffman Amplifiers Tube Amplifier Forum

Amp Stuff => Tube Amp Building - Tweaks - Repairs => Topic started by: hiegdk on July 01, 2024, 12:18:51 pm

Title: 6550s for Sunn 300T
Post by: hiegdk on July 01, 2024, 12:18:51 pm

I'm in the process of fixing up a Sunn 300T and was wondering if anyone could recommend a good 6550 for this amp - gonna need 6 of them so I want something reliable. The schematic shows B+ at 742V.

https://el34world.com/charts/Schematics/files/Sunn/Sunn_300t_service_manual.pdf (https://el34world.com/charts/Schematics/files/Sunn/Sunn_300t_service_manual.pdf)

Title: Re: 6550s for Sunn 300T
Post by: mresistor on July 01, 2024, 01:22:31 pm

https://sonoboom.com/best-6550-tube/ (https://sonoboom.com/best-6550-tube/)


The Sovteks are $372 for an Apex matched sextet at Antique Electronic Supply  ( Tubes and More )

Title: Re: 6550s for Sunn 300T
Post by: Latole on July 01, 2024, 01:26:45 pm

I use JJ 6L6GC on a Univox amp with 700 volts at plates
6550 JJ's look a very good tubes too

Title: Re: 6550s for Sunn 300T
Post by: cfortner on July 02, 2024, 04:47:32 am

6550 normally have an absolute plate voltage limit of 600V or 650V.

In your case I would prefer KT88 instead, 740V might kill the 6550.

Title: Re: 6550s for Sunn 300T
Post by: Latole on July 02, 2024, 04:51:50 am

Quote from: cfortner on July 02, 2024, 04:47:32 am

6550 normally have an absolute plate voltage limit of 600V or 650V.

In your case I would prefer KT88 instead, 740V might kill the 6550.

Like the 6L6GC with 500 volts limits  I use at 700 volts ; answer #3
Screen grid voltage are low, so tubes are safe

Title: Re: 6550s for Sunn 300T
Post by: tubeswell on July 15, 2024, 07:45:29 pm

^What Latole said^


Ampeg SVT-CL runs 6550 plates at 660 with screens at 345