I want to express my gratitude to Chris Hornbeck for his kind comment on the DIY Audio forum site. If more individuals offered constructive feedback as pleasantly as Chris does, the DIY amplifier forum communities would be much more enjoyable.

Cool, seems to make a lot of sense to go with a fixed bias here. That cathode resistor would have serious dissipation. I think you are on the right track here now! Best of luck with this one.

Здравствуйте, рекомендую использовать комбинированное смещение выходных ламп авто-фиксированное ! Удачи в ваших проектах !

I guess a positive for putting that low amount of voltage on the plate will result in a long lasting tube, you’ll likely never have to replace them. The extra cost of that transformer is well worth it, especially because it can easily be used in another build. Another reason to wait for a BOM…lol. I’ll still wait til all your measurements are done just in case. Cool way to switch between the plate and heaters. The Tavish phono pre I bought has the same two switches which do a similar thing, and it really doesn’t matter which one you switch on first. Yes, there’s always a kind way to say something, rather than looking like an a-hole, especially when a comment doesn’t have the inflection. I have no doubt your finished design will be intelligently done and well thought out. Thanks, Stephe!

Well done Stephe. The worthwhile journey has ups and downs. Love your style. (From Down Under)

Incorporating a time delay relay tube would add a cool feature to the warmup design. I remember one of your videos mentioned this type of tube. A 180-second delay would be compatible with the 6C33C. Current specifications would need to be checked.

Awesome video, glad you caught error in time. Can't wait until the next video 👍

I really, really appreciate that you always try to integrate international DIY-Follower. Thanx for that Cheers Stefan

Why not implement Dave Gillespie's EFB biasing scheme (enhanced fixed-bias, AKA tracking bias). As a somewhat inherently unstable tube, the 6C33C seems ideally suited to the use of EFB to prevent runaways, particularly since you are working from a cathode bias schematic. As the B+ rises, the negative bias voltage will increase proportionately, and vice versa, so that the operating point can always remain in the optimal design center of the tube's parameters, via a solid state bias regulation network (consisting of no more than two resistors, one small capacitor, a potentiometer, and an LM337 adjustable negative voltage regulator). The bias current is not drawn from a separate supply, but is derived from the B+ of the tube itself, thus ensuring tracking, and stability. I will let Dave's own words lay out some of the other benefits... 1. maintains the minimum distortion operating point under all conditions of use... 2. provides exacting, fixed bias operation at the cathodes, and solves the problems attributed to the original cathode bias... 3. (prevents) under-biased tubes at quiescent conditions, which (shorten) their life, and, over-biased tubes... 4. (provides) greater power output, (while) doing so with at least 20% less dissipation under quiescent conditions.

Another thing I will add is that it seems like the modern sockets for these tubes are not up to the task. Most of the old forum threads I have looked at recommended the Soviet Military surplus ceramic sockets, and taking extra precautions to space them from the chassis with Teflon standoffs.

Hi Stephe. May I suggest an alternative power transformer that might make construction easier for you? Please check out AnTek’s AS-2T200, 200VA toroidal transformer, reasonably priced in the U.S. ($52.00 minus the optional cover) This model covers all of your power transformer requirements for a single channel. It’s also not “insanely” large and runs cool and quiet. This item features (2) 115v primary windings, (2) 200v secondaries which will provide up to 320mA when paralleled, and (2) 6.3v heater windings rated at 4A each. One winding could conceivably run one half of a 6C33B heater and the other heater winding for your driver tube with plenty of current to spare. You will need to switch out the H.V. supply for warmup, but that shouldn’t be a problem if you put a switch on the 200v A.C. side (I suggest a DPDT for the full winding). Find specificatons on the flash drive I sent you. (PDF Files => Catalogs => Transformers => AnTek => AS-2T200) I’m sold on toroidal power transformers for tube audio. Try this one out for your future builds.

very nice project im jus wait see this beutiful in the finish he speak

If you use a bridge rectifier on the 250V AC, I don't think you can use the 50V to generate a raw bias supply. (with half way rectifying you could) I could be wrong, didn't put effort in thinking it over.

I thought the filament should be hot before the plate voltage is applied to avoid cathode stripping, so the switching order would be important? Although this seems a controversial issue. Also I thought slowing the switch on current surge on the filament was a good idea, but some say they are designed for that, so not to worry. What do you think is the advantage of having separate plate and filament switches, is it just a stand by setting?

Hi, parallel chokes for th driver tub can caus motorboating, I got that in my 2 stag 845 amp, had to conect in serie to get away from the problem Br Svante

Call for random advice: I tried some gold lions and tung sol tubes in my yaqin MC100B to replace the stock shuguang. I can’t hear any difference. Should i persevere or give up? I wish I could hear something different or better…

Or simply go straight OTL with this

Дайте мне вашу почту и я вам отправлю проверенный проект с идеальным драйверным каскадом