Tube DIY Asylum Do It Yourself (DIY) paradise for tube and SET project builders.

---

[ Follow Ups ] [ Post Followup ] Thread: [ Display  All  Email ] [ Tube DIY Asylum ]

---

[ Alert Moderator ]

---

RE: Operating SE trans just at limit current...

Posted by mqracing (M) on June 6, 2007 at 20:08:06

In Reply to: RE: Operating SE trans just at limit current... posted by SomeJoe on June 6, 2007 at 13:21:40:

Hi Joris:

:::Here is the inductance vs current graph for the James trans. What do you think of it? I am affraid that the inducatance might fall dramatically with current over 100mA.:::

Sticking with just practical considerations I would share your concern---

It's tempting to go into a more detailed analysis of the chart and what it's ramifications are or are not. But, rather than me Monday morning quarterbacking someone else's work--- my sense is that their own data points toward 100 madc as not being ideal or well suited for this device.

And keep in mind that the above chart was generated with a half of volt rms (which (if I did my math right) would be 5/100ths of one milliwatt power level assuming a 5K primary impedance) at 60 hertz--- none-the-less this is a good test to document the small signal response of the transformer--- but this graph does not show you the large signal response of the trans. If you have both the small signal (for demonstrating incrmental inductance)and the large signal analysis together--- that's even better :=)

Sticking to the wholly practical level--- my advice would be to use it somewhere in the range that they show--- from about 4 mils up to about
68 mils--- and notice that this trans may give it's best performance at about 40 mils (which is firmly situated on the L plateau of this device)--- which is about what a 45 tube wants to see. Other advantage is that the 45 tube is not going to tax this trans so much from an AC flux density point of view--- overall, the lower the total flux(ac and dc combined) the less core losses you will have and generally, keeping the total flux low, will also lead to reduced levels of core generated harmonic distortion.


::::Aside from that, should i decide to build a push-pull, is it possible to design a 10K PP tranny with good performance?::::


much depends on how you are going to define "good performance". within my
purview of what constitutes a "good" transformer--- then, yes, it is entirely possible to build a good quality 10K pp trans. In some ways it will far outshine any conventional single ended airgapped transformer--- for instance, in terms of providing a stable non-reactive impedance for the tube to work into--- also note that parafeed SE outputs generally show marked improvements in this area.

If you evaluate performance say using Peerless' exciting current test\analysis then again most PP and parafeed SE outputs are going to look good compared to most conventional SE airgapped output tranneys.

From a small signal freq response analysis (the most commonly used barometer of quality--- though I don't agree with it being the singular or even most important parameter) I've seen smaller power level PP output tranneys with 12K pp primary impedances that had good FR from sub 20 hertz to greater than 100KHZ at plus or minus 1 db.

As George Harrison said--- "It's all up to what you value"...

hope I've been some help--- bottom line (in just my opinion of course) I'd use your trans with something like the 45 tube--- if my tube were operating at 100 mils I'd look for another tranney or find a different set of operating points for the tube which you have in mind.

Remember that--- even if the tube's plate curves demonstrates an operating point at 100 mils that looks sweet and of low distortion--- the graphical analysis is assuming you do in fact have the resistance load specified across all frequencies and that it is a pure resistance. Once you use a transformer as your load impedance--- those ideals are just simply that--- wholly academic ideals--- real world transformers are reactive devices (even the best of them) and real world transformers have core generated harmonic distortions to add into the analysis--- you want to find a place on the tube's curves where your real world transformer will exhibit it's best behaviour. That might not be the same sport or set of operating points as if this load impedandce were truly purely resistive.

again--- I hope I've been helpful.

MSL

This post is made possible by the generous support of people like you and our sponsors:

Amplified Parts

---

[ Top of Page ] [ Contact Us ] [ Support/Wish List ] [ Copyright © 2024, Audio Asylum, all rights reserved ]

---

[ General ] [ Speakers ] [ Tubes ] [ Vinyl ] [ Digital ] [ Hi-Rez ] [ Video Asylum ] [ Cables ] [ Tweaks/DIY ] [ Music ] [ Films ]

---