New Member/New Build/New (maybe) Choke Questions?

[The Ballzz]

This is my first post (except for introducing myself in the appropriate sub-forum) and please allow me to apologize for the crudeness of my drawings, as I've not yet gotten into DIYLC. I have a MAC and want to make drawings/build amps, not monkey with work arounds.

Here are the drawings for what I'm endeavoring to build. It is an incestuous marriage of a Fender 5E8-A Low Power Twin preamp and a 5E3 Deluxe power section. My main question surrounds which choke to use for my intended purposes. Yes,I now the choke is in an odd location, but that's the way Fender did it on the 5E8-A. My concern is the current draw vs the current ratings of various chokes.

Thanks Folks,
Gene

[sluckey]

100mA should work.

[The Ballzz]

100mA should work.

Hey Steve,
When using this calculator (even though it doesn't support my 315-0-315 PT) it gives me 117mA for 325-0-325 with an 8K OT and 109mA for a 300-0-300 PT. I'm extrapolating about 112mA of total current draw? Understand that my goal here with this build is to have the magic character and response of a 5E8-A in a lower wattage package. I'm certainly not striving to squeeze every ounce of power out of the amp! I'm also very pleased with the behavior of the power section of the stock 5E3, even with all its warts and stray hairs!  It should be a very happy combination? But you'd likely know better than me. It really seems that much of the real Tweed magic came from certain components be stressed to and sometimes even past their rated capacities. It seems that over speccing the power supply can lead to a sterile sounding amplifier. I'd love your thoughts on this perspective? At 65, I don't really have the time to build and try multiple amps to find my favorite. I wish I had started building years ago!

Thanks,
Gene

[Latole]

Hammond suggest a 40 ma choke for a 5E3;
Power Transformer secondary ;115 ma

https://www.hammfg.com/electronics/transformers/guitar/deluxe-5e3

Same from Triode Electronics

 http://www.triodeelectronics.com/22707.html

[tubeswell]

Hammond suggest a 40 ma choke for a 5E3;
Power Transformer secondary ;115 ma

https://www.hammfg.com/electronics/transformers/guitar/deluxe-5e3

Same from Triode Electronics

 http://www.triodeelectronics.com/22707.html

The OP is wanting a 'whole-of-supply' choke (which includes max plate current)

[Latole]

Those one ?

[tubeswell]

100mA should work.

When using this calculator (even though it doesn't support my 315-0-315 PT) it gives me 117mA for 325-0-325 with an 8K OT and 109mA for a 300-0-300 PT.

A single cathode-biased 6V6 at 360 volts on the plate idling at 12W gets to about 38mA. Under full signal in Class A, its about 1.2X as high, so that's 45.6mA (92mA for two, plus four 12AX7 triodes @ 1mA each = 96mA). In Class AB, slightly less, (because the B load sees one of the output tubes cut-off for part of the cycle)


I recall a reference somewhere showing PT spec for the 5C3, 5D3 - 325-0-325 @ 80mA. In truth, different runs were probably a bit all over the place

[92Volts]

Hammond's website states that:

Inductances measured at rated D.C. current.
...
Units will exhibit less inductance at slightly higher currents or more inductance at lower currents.

http://www.hammondmfg.com/153.htm

Which suggests these won't immediately melt if you go over their rated current. A push-pull amp only draws max current when playing at max volume, if that only slightly exceeds the choke's rating (but idle current draw is lower) it should probably be OK.

[The Ballzz]

Thanks folks for all the input! That one looks pretty darned close, but I think I might go for the actual Hammond unit below, though it may in fact be the same unit, without labeling? I don't want the current capability to be too high and stiffen the supply too harshly. I think the lower mA ratings you folks are getting may not factor in the 8K OT primary, if using this calculator:

https://thesubjectmatter.com/calcptcurrent.html

This 90mA one may be pretty OK, depending on what the actual current draw is:

https://www.tubesandmore.com/products/c ... howman-etc

Although if willing to drop the Henrys to 3.5 or even 3, I get a choice of 150mA or 100 mA, respectively here:

https://www.tubesandmore.com/products/f ... en-bracket

And if willing to bump up to 5 Henrys, I get 120mA here:

http://www.classictone.net/40-18032.html

All the DCR ratings are faily similar around 105, except for the 3 Henry unit at 85 DCR!

With all that said, I think my current plan i to go ahead and build the amp, "without" the choke, get all my voltages into the ballpark that I'm shooting for and then actually measure the current draw with a loop cranked through the amp and see where I end up. Of course, the amp may sound just the way I want without the choke anyway!

We Shall See What We Shall See?
Gene

[shooter]

actually measure the current draw

good to know, also consider Imax and Time, so 3hr gig, 20% at max, 30% at min, avg for gig 62.7% of Imax.
really want wonky, add in thermal dissipation of iron over time 

 

[The Ballzz]

Well Folks,
I'm just waiting on a few parts and I guess I'll just consider this the "build" thread for my TWI-Luxe! I've got the chassis stripped from it's old life of a 2203 preamp with 6AQ5 power section. I moved the power tube sockets down one hole, using up the hole for a can cap (now mounted to the side wall) and fashioned a pretty nice little octal to noval adapter plate. Pics to follow.

I'm now at the quandary of how to lay out my inputs. I'm only going to use two input jacks. One will feed both triodes of one channel and the other will parallel both complete channels, for four triodes in parallel but with a separate volume control for each pair. Here are few questions that I would love to hear opinions on:

A - Wondering if my "one channel" should be the bright or the normal?
B - Then comes the question of wiring. You'll need to look at the schematic to understand whats going on. There are no grid stoppers, but instead each individual triode gets a separate 1MΩ to ground "grid leak" so that one channel, either by my plan or by plugging into the #1 input, gets an effective-ish 500KΩ "grid leak." This means that with the two channels paralleled, the nominal grid stop will be 250KΩ. I will be using Belden 9451 shielded plenum cable to send the signal to the triodes. Should I put all the grid leaks at the jacks or should I put them at the tube grid pins?
C - Another way would be to mount a 500K at each jack and simply send both channels' inputs to pins 2 & 7 of each of the two dual triodes, paralleled at the tube socket. I'm looking for the solution that minimizes the most noise potential.

Just Curious?
Gene