Quick question, if I buy a 5k/8 ohm opt. With my panels, they be 4062k. But if I buy a 6k6/8 ojm, it will be 5362. Which do feel would be the better choice? To hit close to 5k number, I would need a 6k/8. Can't find that.
Your speakers impedance is not the same as it's DC resistance.
In reality the impedance varies widely over its operating frequency range.
You only get one tap, so use the tap that corresponds with your speakers stated impedance number and realize that the plate load is going to also vary as a result, but your tubes can compensate for this if you load them about in the center of the range they will be happy and so will your ears.
In reality the impedance varies widely over its operating frequency range.
You only get one tap, so use the tap that corresponds with your speakers stated impedance number and realize that the plate load is going to also vary as a result, but your tubes can compensate for this if you load them about in the center of the range they will be happy and so will your ears.
Well my diy planar magnetic panels are 6.5 ohm impedance across the the frequency band from 10hz, to around 10k, then rise slightly to around 7.5ohm. Out to 20+. And that is measured impedance. Just want to try to match everything up. It is really amazing how flat planar magnetic impedance curves are.
But I'm leaning towards the 6.6k/8, for the actual 5360. Am I wrong to assume better to error on the high side?
Somewhat unrelated to my original post, just did a deep dive into the schematic for the organ these came from. 48 tubes!, wow. Lol. So shouldn't have any trouble with a pair of el34. But also scored some 6550s so looking at those?
As yet said before, no issue regarding heater current with th given PT. Anyway, why? For higher output power you'd better replace the rectifier tube by a pair of 1N4007's, but watch the filter capacitors' voltage ratings. And you need to chose the OT according to the power tubes.
Best regards!
Best regards!
Yes indeed, already ordered a pair of OTs. And have the diodes already. Just looking at thermistor to limit in rush current a bit. Also debating using cathode bias, or fixed bias. Thinking about fixed bias for each el34, just to balance them more accurately.
The 270K on the 6sn7 gain stage needs to go to b+. You want to apply the GFB to the cathode of the 6sn7 just to not mess with the input impedance. It may just mean you need to ground the positive side of the output transformer and take GFB from the negative side. Or flip the power tube control grids.
Also this will not have as much gain and make need 5V for full output once you have appropriate negative feedback. Organ amps used a lower gain approach to keep hum levels low in many cases.
Also this will not have as much gain and make need 5V for full output once you have appropriate negative feedback. Organ amps used a lower gain approach to keep hum levels low in many cases.
Thank you so much for your help. I thought about using a different driver stage, but my preamp puts out quite a bit of voltage . (Carver C1) and I already built " color preamp" Skunkie design. I may mod. It put be a higher output preamp for these.
And should the 270k on the 6sn7 first plate go to the 400v with out the 43k. Wouldn't that make the voltages on the plate higher? 310 ? No first voltage drop?
