Originally Posted by James55
Thinking of trading in my marshall 100 watt combo amp on a crate 120 watt half stack with 4 12" speakers.
Not familliar with your particular models but, I hope they aren't 'hybrids'. It's important to have both gain and power tube stages. For the power stage, 6550's are more robust and cleaner. EL34's are both 'sweeter and funkier'. If you know what you're doing, you can mod your amp to run on either but you need to watch the plate voltage if you mod a 6550 to run on EL34's.
If the pre and power stages are 'pure tube' then it's just a matter of taste.
About preamp tubes. Most preamp gain stages are based around the mighty 12ax7(a) with a 12at7 phase spliter to drive the output tubes. I highly recommend the Yugo (EI) "large plate" as it is a damn good Mullard clone. Mullard was a British company who made some of the most renowned audio tubes ever! In fact, the Yugo plant bought the old Mullard 12ax7 equipment.
I've A-B'd the Yugos against vintage Mullards and can state the sound is 100% true. The only prob is quality controll. If you need 2, buy 4

Fortunately they are relatively cheap.
More about tubes later.
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