[cfisher835]

I'm considering trying out KT150s in place of 6550s in an old Jolida JD801a that I have sitting around. I want to make the tube change in order to try and drive a pair of RAAL-requisite SR1a headphones. Would I get the added wattage of the KT150 without making any modifications to the amp? Anyone tried something like this? Did it sound good? Did you burn your house down? Thanks.

[Meicheng]

Why don't you call Jolida/Black Ice in Maryland and ask them?  They usually answer the phone.  Not all tube amps can take the KT150 tubes. 

[cfisher835]

I emailed them but didn't hear back. I will try to call today. I saw something at Underwood that the company had changed their name, so I was thinking they may not be responsive.

[cfisher835]

Jolida got back to me today with the following: "yes you can with the 120, 150. Not sure on the 170s since we have not tested them. You might get a bit of a bump in the wattage but not much."

[FullRangeMan]

Jolida got back to me today with the following: "yes you can with the 120, 150. Not sure on the 170s since we have not tested them. You might get a bit of a bump in the wattage but not much."

Well these seems goods news, keeps us posted on your sound impressions with the KT150.

[cfisher835]

Well these seems goods news, keeps us posted on your sound impressions with the KT150.

Yeah, I wish I understood what was involved in getting the full increase in wattage. I would happily make the mod if it were reasonable. Still, I probably will give it a shot if I can get my hands on the headphone/amp interface from RAAL. I have nice 6SN7s and 12AX7s laying around, so it seems like a fun experiment.

[jjss49]

going from traditional kt88 6550 to kt120 kt150 etc require the amp to be able to deliver the proper biasing current, and of course the rest of the circuitry and componentry (esp. output and power transformers) need to be sized and designed to handle the additional output and bandwidth the bigger stronger tubes are capable of...  an amp 'can' run those tubes but it does not mean it takes full and proper advantage of what they are able to do if optimized  -- best not to conflate a vs b...

[FullRangeMan]

Yeah, I wish I understood what was involved in getting the full increase in wattage. I would happily make the mod if it were reasonable. Still, I probably will give it a shot if I can get my hands on the headphone/amp interface from RAAL. I have nice 6SN7s and 12AX7s laying around, so it seems like a fun experiment.

To get more watts you will need more Bias and more B+.
Do you have tried more sensitive speakers as 100dB?

[cfisher835]

To get more watts you will need more Bias and more B+.
Do you have tried more sensitive speakers as 100dB?

Jolida provided some info on setting the bias higher but still said that it would not get the full power out of the KT150. I'm planning on using the amp with RAAL-requisite SR1a headphones.

[FullRangeMan]

Jolida provided some info on setting the bias higher but still said that it would not get the full power out of the KT150. I'm planning on using the amp with RAAL-requisite SR1a headphones.

Conservative use always better to extend the tube life.