I just questioned if you have deduced Vout from V0 in your calculation and you said you already have. I don't see it very clearly, and your 2 calculations differed by more than 2 %. So I wasn't modify it, just that after deduction it's closer to your earlier calculation. I presume you're correct!
Last edited:
No, I was only ever saying that the expression for the efficiency should be (Pi/4) * Vout/V0. That other formula I wrote down was my attempt to interpret what I thought you were suggesting, and I then went on to argue that it couldn't be right because it didn't have the right limit in the "maximal" case where Vout=V0.
Sorry if I misunderstood what you weer saying.
Chris
Sorry if I misunderstood what you weer saying.
Chris
Well, I still yet have to fully experience it. As this time I have the sim for cathode and voltage follower based on your M60.
For the moment I would ask as if voltage follower gives more power than cathode follower in your experience. Cathode follower has lot of feedback (if not NFB) whilst voltage follower has more gain and therefore more efficient, so if you convert M60 amp to voltage follower will that give you more power and efficiency.
Actually there's no real difference in gain if the tubes are used in a Circlotron. No difference in output impedance either. We used to build the original MA-2s as "voltage follower" outputs, but other than phase inversion, there was no measurable difference between that and driving the load with the cathodes. But building the amp was a lot easier if the load is cathode driven!
Average current = 2.5A * 0.636 = 1.59A, according to Amplifier Efficiency.
If 1.59A, then 150*1.59=238.5-25=213.5*2=427W dissp, which one is correct?
0.8A or 1.59A?
.You're correct at least agreed with this lecture. Vout is the peak voltage of the output, which is 20V-p in our case. eff=78.5*20/150=10.47%, or 238W dissp. is a little higher compared to the other calculation (214W). Thank you.
I'm just back from Berlin and I brought 3 "non-magnetic" bolts in my carry-on luggage. There was a small problem with security but the German police eventually OKed them for boarding. I had tested them in the bolt suppliers with a magnetic clasp on my belt and they showed no magnetism but when I used a more powerful magnet on arrival home, I found them to be about 10% as magnetic as ordinary mild steel bolts. I reckon that 10% magnetic will still fit the bill, so one of them will be used to secure the two larger concentrically mounted transformers.
Spray paint.
All holes are now drilled and I'm ready to spray the chassis satin black. I have noticed in the past that ordinary cheap spray paint from the hardware store is just not durable. Can anyone suggest a good brand?
All holes are now drilled and I'm ready to spray the chassis satin black. I have noticed in the past that ordinary cheap spray paint from the hardware store is just not durable. Can anyone suggest a good brand?
Attachments
Why not use aluminum furnace powder coating, such services are popular. The paint would be scratched proof and not expensive. Usually it's difficult to paint aluminum, you have to scratch the surface or it would stick properly, the coating service should be able to do surface treatment if necessary.
Last edited:
Thanks for that tip. I can mount above or below. I'm just about to install them now, so I'll size the outside option first and see if the tubes stand lower than the transformer cover. It would help wiring, testing and maintenance if they are lower, as the the 3 transformers are so heavy that the amp can stand inverted on the transformer box without any extra support.
i am mounting my sockets below the chassis, with a gap pf 8 to 10mm...
i will use copper strip sinks on filament socket pins to hopefully get rid of some heat...i may even use active cooling....
Assembly
The assembly is almost done. All that remains are the 3 transformers, 2 fuse-holders and the 2 meters. I have a fuse in each of the 2 supplies for both the left and right channels, 4 in all. There is a fuse in the left and right loudspeaker outputs as well as a mains fuse, 7 fuses in total; overkill some might say but I have read all the posts on the two Mellows OTL threads and decided to be on the cautious side, particularly in the light of all that cnpope had to say about catastrophic failures.
The two long strings of capacitors for HT2 and HT4 have been combined into just two Panasonic 4,300 uF 250 Volt units (part number ECE-P2EA432HA) and all other psu capacitors are mounted on two sub plates. All connections to the tube-socket terminals will be taken to two rows of tag-strips and any associated components will be mounted there. The 4 trim-pots for the bias are accessible from the top of the chassis, so during operation there will be no need to remove the bottom cover.
Due to the weight of the two largest transformers, I had to strengthen the base underside with a 3mm alum plate and spine because of a considerable sag. Wiring will commence in the next day or so.
The assembly is almost done. All that remains are the 3 transformers, 2 fuse-holders and the 2 meters. I have a fuse in each of the 2 supplies for both the left and right channels, 4 in all. There is a fuse in the left and right loudspeaker outputs as well as a mains fuse, 7 fuses in total; overkill some might say but I have read all the posts on the two Mellows OTL threads and decided to be on the cautious side, particularly in the light of all that cnpope had to say about catastrophic failures.
The two long strings of capacitors for HT2 and HT4 have been combined into just two Panasonic 4,300 uF 250 Volt units (part number ECE-P2EA432HA) and all other psu capacitors are mounted on two sub plates. All connections to the tube-socket terminals will be taken to two rows of tag-strips and any associated components will be mounted there. The 4 trim-pots for the bias are accessible from the top of the chassis, so during operation there will be no need to remove the bottom cover.
Due to the weight of the two largest transformers, I had to strengthen the base underside with a 3mm alum plate and spine because of a considerable sag. Wiring will commence in the next day or so.
