NOSValves

2006 are we having fun around here again....watch out they'll lock the thread 😁😜

Wow Allan great to see you posting! Hope you and yours are doing well! You still styling with the Mac gear?

No trade secret at all! I like Stackpole because they make a nice 2 watter for plates. I also like the green Kiwame (or cheaper and the true manufacturer KOA Spear). The problem with either is they are getting hard to source. I used to buy the 2 watt versions of the Stackpole from Handmade Electronics http://www.hndme.com/ but he has stopped selling them. I purchased a boat load of the common 2 watt values I use from him at clearance. The 1/2 watt versions are readily available I believe Digikey sells them.

All I'm going to add some really good carbon film resistors are available today they sound great and do not drift enough to talk about. I personally do not like metal film resistors in vintage amps.

exactly what I said

Pretty much what I said......of course the guy selling the product begs to differ.

Joe, If you can take some detailed photos top, bottom and I'll take a peak and see if I can figure something out for you. Be patient my available time is very limited these days.. I agree if he did both amps parts would match in both amps

Joe I used Curcio stuff many years ago but my memory is to foggy on it to help you. Contact Joe I'm sure he'll help you out.

John, Yup Heyboer does a nice job on many vintage transformer replacements. Most of the Scott they worked with me to iron out the specs many years ago.

Dave order them from www.tubesandmore.com they do a decent matching with Ampex tube tester.

The Valve Art is a basic Shuguang factory made KT88-98 with Valve Art QC testing. The Ruby KT88-STR is the exact same tube with Ruby QC testing. It is also sold as the Shuguang KT88-98 It is a nice sounding KT88 for reasonable entry cost

Rich, What you describe going from KT88 to EL34 is totally normal. Now when/if switch back realize the reverse is going to be true and you should adjust the controls about 8 full turns counter clockwise before you fire the amps back up with KT88 type tube again. Each output tube type can take a hugely different applied negative voltage applied to the tube to achieve the proper bias current. Realize when you adjust the bias screw your not adjusting the actual voltage you read at the test point you are adjusting a voltage applied to the control grid of the tube that causes the test point voltage to change.

Rich, Not ignoring you I did reply but promptly received a kick back notice of a permanent fatal delivery error. I believe your mail server has my mail server blocked. Here is what I* replied. I also tried to send you a current manual which should/could be the same as the one you have. Rich, XXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXX first line X out because it was personal in nature. Glad you wrote me about bias confusion. Always refer to the manual that came with your amps. The folks mentioning .70 bias setting have some of the amps manufactured in the early to mid-2000’s and have not had them updated. I believe your manual should give you bias setting for EL34’s. If not attached you find one that does. I will caution you that if using modern production EL34’s error to the cool side first than check the large plate structure inside the tube for red glow. Many modern production EL34’s are pretty weak. Also realize I have never had someone report back they preferred EL34’s in a VRD which makes total sense since it runs them too darn hard. You could help things out a little by running them with a 5U4 rectifier tubes which will lower the voltages in the amp a little but in the end the amps are still primarily designed to run the KT88 family of tubes. Thanks Craig Ostby

mix and match pairs? Not sure what you mean?

It will work just fine. Those are re-branded most likely Mullard made tubes. Sylvania never made tubes in England. Either way they should be really good tubes. Do realize the 299B is not a plug and play amplifier when it comes to the output tubes they do require proper biasing when installed and periodically after that.