Author Topic: Randall RT 503 power tubes question  (Read 5925 times)

Offline tacklebox455

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Randall RT 503 power tubes question
« on: July 09, 2012, 04:37:47 AM »
I was curious to know if the RT503 can use KT66,KT77,KT88 tube types? I know i can use EL34,6550,6L6,6CA7,5881

I'm just not sure if the trannys can handle some of the KT tubes


Oh and hello everyone i'm new to the forum
Electric Wizard,Weedeater,High on Fire thats my play list

Offline Wookieslayer

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Re: Randall RT 503 power tubes question
« Reply #1 on: July 09, 2012, 11:40:25 PM »
Welcome man.  I believe it can handle KT77s and KT66s... I know someone on another forum who runs the KT77s with EL34s on the other side... Unsure about Kt88s though.
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Offline tacklebox455

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Re: Randall RT 503 power tubes question
« Reply #2 on: July 09, 2012, 11:50:10 PM »
Welcome man.  I believe it can handle KT77s and KT66s... I know someone on another forum who runs the KT77s with EL34s on the other side... Unsure about Kt88s though.

I liek KT66's hope it can handle them to me there like a mix between 5881's and EL34's

I tried some 5881's and 6550's in there tonight both sounded good but not quite what i'm wanting with this amp
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Offline tacklebox455

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Re: Randall RT 503 power tubes question
« Reply #3 on: July 11, 2012, 08:29:46 PM »
Ok just now got the word the amp can use the KT66,KT77 ans so on but KT88 is a no go

I am waiting to hear back to see if the trannys will be ok with the reissue tung-sol 5881 since its a 23 watt tube with max plate of 400Vdc
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Offline tacklebox455

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Re: Randall RT 503 power tubes question
« Reply #4 on: July 11, 2012, 08:38:14 PM »
So far i have used the stock Ruby 6L6GC-STR's they sound good idle bias 41.1

Sovtek 5881 WXT's nice midrange lacks in the bottom end thou idle bias 40.0

Svetlanna 6L6GC's nice lows midrange was very responsive and treble side wasnt to harsh all in all to me better tube than the Ruby 6L6-STR idle bias 44.7

NOS Sylvania 6550's great all around nice attack as well downside they did not work well with the OD2 added way to much bottom end idle bias 48.9

I tried different bias settings on all tubes and have posted what to my ears gave the best tone and range



I have on order now the Tung-sol EL34's reissue we'll see how they go
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Offline Parisstorm

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Re: Randall RT 503 power tubes question
« Reply #5 on: February 16, 2015, 07:45:22 AM »
if anyone puts a set of KT-66 or 77's in their RT503 please share the outcome with us fellow thrashmasters, sounds like something that may pronounce the mid-range without weakening the low-end too much?