3Khz to 12Khz 80% nickel output transformer.

[dave slagle]

The goal is to load a tube with an Rp of 1K with 50ma of DC with a 20:1 (15R driver) output transformer. A line level crossover will control the rolloff points which will be at ~3000hz and ~12,000hz. The original spec was for 5hy @ 50ma but the possibility for slightly higher current was requested.

Below are the measured results of the first attempt.

More to come.

dave

[dave slagle]

did a revision to get some more top end. -1dB point is now 155K and -3 is 211K.

dave

[dave slagle]

Lets say you have this transformer gapped with the red spacer for 7.7hy and you want to change it to the blue spacer for 4.4hy. The pic below should tell you everything you need to know and also clue you in on how to change bobbins.

dave

[Romy The Cat]

The goal is to load a tube with an Rp of 1K with 50ma of DC with a 20:1 (15R driver) output transformer. A line level crossover will control the rolloff points which will be at ~3000hz and ~12,000hz. The original spec was for 5hy @ 50ma but the possibility for slightly higher current was requested.

More to come.

[dave slagle]

Hey,

I really like the parallel socket idea, I plan on using that in my next strain gauge design. I had a chance to briefly listen to the 6E6P's you sent (many thanks!) and they sound nice!

I am not a big fan of that 1.75K dropping resistor in the PS. what is the source of the 400V?? Does it need to be that high in order to feed other frequency ranges?

dave

[Romy The Cat]

I am not a big fan of that 1.75K dropping resistor in the PS. what is the source of the 400V?? Does it need to be that high in order to feed other frequency ranges?

I have 200V and 400V in this chasses I do not what to bring new voltage. To drive it from 400V is too much. The source of the 400V is LCRC with 15000uF in the last cap the drives 6 driver stages. The high capacitance sound “hard” and I would like MF channel do not “see” it. So, I think that large PS impedance is irrelevant in my case as my channel will not care any LF at all. A high resistor will in fact do some good duty: decouple the “stiff” PS from the tube and the tube will have a local cap grounded locally right to cathode ground. So, the MF will be pretty much totally isolated circuit: the impedance of 100uF cap will be let say 1R and impedance of return to main PS will be 1.7K. My two concerns in this circuit to see if I will be able with one cathode resistor to driver both tubes (in worth case I can switch in for 2A3 another parallel cathode resistor) and to try to use the SAME filaments droppers for 1A/4V on YO186 and 2.5A/2.5V on 2A3. As you see the 1R and .75R are VERY close and it will be an elegant fun to combine them. I do not know it is good idea to drive the 2A3 type of tubes with under voltage on heaters… If yes then I would put in there .95R resistor and have very simple life..

The Cat

[dave slagle]

A new version was requested. The goal was to load a 2A3 with 6K and a 45/yo186 with 9K. The other design change was max dc is now 50ma in place of 70ma.

Given the 50ma max i was able to rework it a bit and the 6K setting is -1dB @ 215khz and -3@ 246Khz when moving to 9K and upping the source to 1800 ohms -1@196Khz and -3@220Khz.

I let my mind get the best of me and I gave them a listen and I was shocked how clear they were. The bass was a bit lacking but man, everything else was beautiful. This was in direct comparison to a large 49% nickel output with 6X the inductance and -1dB@ about 60khz. The resistances of the two transformers were 75 ohms for yours and 200 ohms for my full range units.

I fully expected to ship today, but I needed to listen a bit and try a few things to clear some things in my mind. I swapped the 80% nickel core out for 49% and much of the new found magic went away. Going back to the full range OT brought back the bass but the middle magic still did not show up. (shines if you are listening, I see big 80% in our future

dave

[Romy The Cat]

Thanks, David. Very good to hear that you like how it turning out. Will I need to change the gap gasket with new coil?

Minor corrections:

The objectives were not to use the 45 tube but to have 9K load for my 4V tubes (RE604/KL71403/YO186). They are 1200R that is different from 800W of 2A3 that still will be loading to 6K. I reality I think the numbers are much high as I drive my tubes very gently and at 38mA I presume that I have pate impedance twice higher.Sure, to have 9K load would make the operation of 45 tube with its 1800 plate impedance is much more possible and friendly.

The second major objective of the new coil was an option of switching the 6K and 9K load “on fly” by remapping the multiple sections of secondaries just with one switch.

Rgs, Romy the Cat

[shinebox]

Allo

Dave - Indeed I am listening, with great interest... Did you notice the lams singing along at all? That was a minor issue I had with my Sowter 80% opts (smaller core, different lams, different winder), yet the sound was much as you described.

Romy - very much looking forward to your reports on this. If you like what you hear, then you too may catch the big nickel fever.

Cheers
shines

PS Dave - I think Coco-san mentioned I was going to listen to his Io tomorrow... I will report back. My expectation is that it is the 80% sound writ large.

[dave slagle]

Romy,

Thanks for the correction.

Shines,

I didn't notice any signing but i didn't use a dummy load so the noise (um music) from the speaker might have swamped it out.

dave

[shinebox]

Hi Dave,
My lams were singing noticeably with music playing. But such glorious music...
Cheers