k66 in a mark IV
- Thread starter CWMW
- Start date
Help Support The Boogie Board:
Boogiebabies
Well-known member
Yes, you will draw way over the reccomended bias in the outer sockets.
I tested a #6 GT KT66HP in one of my IIC's and the inner sockets drew 35ma and the out frew 73ma. At 73ma they would probably last 2 minutes before blowing up. They were fine in the inner sockets.
I tested a #6 GT KT66HP in one of my IIC's and the inner sockets drew 35ma and the out frew 73ma. At 73ma they would probably last 2 minutes before blowing up. They were fine in the inner sockets.
Boogiebabies
Well-known member
The Tung Sol should sound good, and is a true 30 watt tube. A real 5881 is a 25 watt tube and may bias too hot in a boogie. The GT KT 66HP is supposed to be run as a 25 watt tube as well. Otherwise the plates glow if you bias it like a 30 watt. You have to find a tube with a natural plate current that will draw a safe bias for both the inner and outer piar. With the 5881 it should be able to handle the bias. Find a vendor who knows a bit about Boogies. I actually like the outer pair to run hotter. It smooths out the tone a bit, but I also prefer to use EL-34's in the Simul-Sockets.
www.dougstubes.com
A very knowledgable tube guy. Tell him your running -45 on the outer sockets and -56 on the inner. He may want to send you a bit cooler tube for the outers to keep the MPD low enough. Most of the time a matched quad will work just fine, but like the KT-66 it did not handle the -46 very well.
www.dougstubes.com
A very knowledgable tube guy. Tell him your running -45 on the outer sockets and -56 on the inner. He may want to send you a bit cooler tube for the outers to keep the MPD low enough. Most of the time a matched quad will work just fine, but like the KT-66 it did not handle the -46 very well.
RussB
Well-known member
Ed, where'd you get the info that the new Russian TS-5881 tube is rated at 30 watts?
And I think that the KT66's would work out OK. They draw 1.27 amps of heater current compared to the 6L6's .9 amps and the EL34's 1.5 amps (numbers are from the Duncan Amps tube data site)
The MKIV can safely run a EL34's and 6L6's for a total heater current draw of 4.8 amps. 4 KT66's will draw 5.08 amps.
NOW, I don't know if the KT66's will physically fit...they are some big tubes! The one on the left just barely clears the power tranny. I doubt if they'll fit the Mesa...
Here's a pair in my Vibro-Clone. That's a JJ GZ34 rectifier next to them.
And I think that the KT66's would work out OK. They draw 1.27 amps of heater current compared to the 6L6's .9 amps and the EL34's 1.5 amps (numbers are from the Duncan Amps tube data site)
The MKIV can safely run a EL34's and 6L6's for a total heater current draw of 4.8 amps. 4 KT66's will draw 5.08 amps.
NOW, I don't know if the KT66's will physically fit...they are some big tubes! The one on the left just barely clears the power tranny. I doubt if they'll fit the Mesa...
Here's a pair in my Vibro-Clone. That's a JJ GZ34 rectifier next to them.
Boogiebabies
Well-known member
The KT66's fit just fine in a combo. Take my word on this, the bias at - 57 was 35ma and 78 at -39. Can you say orange glow. You dont think the russians would make a true 5881 at 25 watts? Mike Matthews is more worried about returns than remaking a true Tung-Sol.
Yes, I am sure they would work, but a #6 GT was way too hot. I have them in my Soldano and Myles Rose and I had a good talk about the KT66HP.
He really rated them as a 25 watt tube. At 75% MPD on the Soldano they would start to glow within two minutes. Biasing them as a 25 watt tube has led to no issues and superb tone.
If no one wants to take my word for it, then let er' rip in the Simul sockets.
478 Plate volts at -39 ran them at - 78 on my Bias King double socket meter.
Yes, I am sure they would work, but a #6 GT was way too hot. I have them in my Soldano and Myles Rose and I had a good talk about the KT66HP.
He really rated them as a 25 watt tube. At 75% MPD on the Soldano they would start to glow within two minutes. Biasing them as a 25 watt tube has led to no issues and superb tone.
If no one wants to take my word for it, then let er' rip in the Simul sockets.
478 Plate volts at -39 ran them at - 78 on my Bias King double socket meter.
RussB
Well-known member
Interesting info about the GT KT66...I see that tube data does call the KT66 a 25 watt tube.
That said, I have the Shuguang/Valve Arts KT66's, and I have them biased HOT for a 30 watt tube! (45mA @ 460v) No red-plating, great tone.
I do notice that they require a LOT of bias voltage, mine are at about -59v
That said, I have the Shuguang/Valve Arts KT66's, and I have them biased HOT for a 30 watt tube! (45mA @ 460v) No red-plating, great tone.
I do notice that they require a LOT of bias voltage, mine are at about -59v
RussB
Well-known member
Here's an email I got from New Sensor in regards to the new Tung-Sol 5881...
OK, so I take it that the TS 5881 is a 23 watt tube, but is rated at 500pv vs. the 400pv of the original 5881
OK, so I take it that the TS 5881 is a 23 watt tube, but is rated at 500pv vs. the 400pv of the original 5881
Boogiebabies
Well-known member
I have some gulf coast property for sale in Amarillo.
I dont believe them.
I dont believe them.
