Randall RD20H Bias

  • Thread starter Thread starter dennyps4
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dennyps4

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Hello ALL,

Just as a friendly service, I am posting my findings with the Randall rd20h. Simply because there is NO info on these anywhere, as far as bias/specs.

So... the amp came to me with 2x Ruby 6v6GTSTR and Ruby 12ax7ac5 x 4, in the the phase inverter and preamp etc...

Plate Voltage on V5 measured 313V. I have not touched the amp since I received it, so this info is how it came to me.

Bias for V5 = 23.9ma
Bias for V6 = 20.6ma

I have had this amp pretty much at the second of release. I have been freaking for something from Mike Fortin, since I first heard the Bones head, and this amp delivers for sure, and the price point is killer. I am not a amp tech genius, I just hope this can be of use to someone who has one of these. I do not hold on to amps for very long. but this one is a keeper!

I also just installed new JJ 6v6S and biased them @ 25.0ma, we'll see how she sound with these. And Mike if you happen to see this post, tell me If I did anything wrong, lol. Cheers to all that care!
 
All I have to say after the tube swap is, Whoa! Big Open and Phat! Sounds like a 6l6 for sure, with that nice tight, and effing mean, gain. This amp responds much better with the JJ 6v6s. I also swapped v1 for a Mullard reissue, and added to the overall joy. Judging by the number of views etc.. Nobody here really gives a crap, but is good for reference for someone. If I can ever find the power cable to my camera, I'll shoot a video. Peace!
 
Yeah Im interested too with the RD45.....I liked JJs in my 5150 back in the day, gonna maybe in the future try them in the RD, btw Dickola try putting an EQ in the loop of the 45, sounds great through the amp....I use s Boss GE7...good investment
 
Hey Dickola the rd45 obviously uses 6l6, so maybe give Tung-sol or the Mullard Reissues a shot. I picked the JJ's (6v6) because they are known for taking a beating. 6l6's are a different beast, I have used JJ 6l6 in the past and were a bit dark, but the rd45 may dig em. Tung-sol and Mullard new production 12ax7's are pretty decent also, for the preamp, all made by New-Sensor, but decent none the less, hope that helps. I highly recommend the Valve Queen for a supplier, valvequeen.com, burns in and tests all her tubes and great customer service.
 
dennyps4 said:
All I have to say after the tube swap is, Whoa! Big Open and Phat! Sounds like a 6l6 for sure, with that nice tight, and effing mean, gain. This amp responds much better with the JJ 6v6s. I also swapped v1 for a Mullard reissue, and added to the overall joy. Judging by the number of views etc.. Nobody here really gives a crap, but is good for reference for someone. If I can ever find the power cable to my camera, I'll shoot a video. Peace!
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Thank you I know this is old but I just bought my rd20h and it had the amm lil bastard mod. They took out the ruby power tubes and put in JJ 6V6S And I think I have a bias issue should both of them be biased to 25 milliamp. I was told by the owner of the tubes were never changed which I found to be a lie because the Ruby power tubes were gone and the preamp tubes which were all ruby 12AX7 AC5 or whatever the number is. Somebody had put a Millard in the clean channel stage... I just purchased a TS I'm hoping to arrives for the one and V2 I ordered a soap tech LPS for the phase inverter currently I move the mullard that was in there over to the PI slot because that tube was long plate which is weird. I think something's up with the bias though because the amp doesn't have the tone you're describing and I've got a 5153 and I've had many two amps so I know what it should sound like lol. Thanks for the info I'm going to check the bias and make sure everything's good Plus it was shipped from California so the tubes may need to be reseated
 
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