It's Here! and it is Beastly

[Doc B]

It would be very impressive to see 26 Amps of plate current through an EML tube. I think you probably mean 26 watts.

For what it's worth, after all of this discussion I put my EMLs in my Kaiju and ended up going back to EHs. Thought the EMLs were not as open sounding in my system. YMMV, TANSTAAFL, WYSIWYG.

 

[Paul Birkeland]

So - EML Mesh draws 1.4 amps so, 5.25 volts on 1.2 amps (sovtek tube) would be more like 5 volts on the EML. Does the DC regulator (not yet installed) provide 5V independent of current? if so I that is perfect for the EML. Spec is 5v +/- 4%

You might see something like 5.2V on the EML's, PJ would probably have a more educated guess, but in any case, you can just plug them in.  I could have sworn a few months ago that the EML spec was +/- 4%, this is getting pretty tedious to keep up with.

It would be better to have it at 24, recommended is 22.  But it all looks workable with no modification. However, if I wanted to bring it down, what would be the best option?

Western Electric specs 36 watts as the maximum plate dissipation for the 300B, with some suggestions in application notes that you can go as high as 40.  The ultimate question here is why a manufacturer would call a tube a 300B when it can only dissipate 22 Watts.  There are many amps commercially available that have been manufactured over the last 20 years that run at over 30 Watts of dissipation, so this seems pretty unusual.

Are you running the 300B mesh?  The operating point that you measured and posted is one that is recommended on the EML website for the 300B mesh, so I wouldn't adjust it at all.

That leads me to a follow up question - I might be moving in with my GF  .  House voltage there is 119, mine is 125. How much does a difference in AC voltage affect the output voltage of the transformer? Might be just right if it reduces the voltage a bit.

You'll still be on the correct transformer tap.  You might see something like 4.95V instead of 5.25V, and there would also be a slight reduction in plate dissipation. 

 

[drewh1]

Great! Thanks Paul - I don't have the Mesh Plates yet, should have them by the end of the week.  I am measuring everything with Sovtek's.  Gonna plug them in and listen when I get them.

I am learning a lot from this project and really appreciate the detailed answers.  Also, really loving the Kaiju - you guys do a great job in design and support.

drew.

 

[drewh1]

Just installed the DC regulator.  Dead quiet, can't hear anything with ears right upmto speakers.  Now have 4,91v on the filaments.

 

[drewh1]

It looks like I will be out of spec on the filament voltage with the .51 resistors and the DC regulator.

So based on the specs of the EML drawing 1.4 amps, I calculate I need .45 ohm resisters to bring the voltage up to 5V spec.

6.3 - 5 = 1.3  1.3/1.4 = .92  .92/2 = .46   

correct?

 

[ebag4]

Just installed the DC regulator.  Dead quiet, can't hear anything with ears right upmto speakers.  Now have 4,91v on the filaments.

Hey Drew, anxious to learn if you perceive any difference in the music vs AC other than the lower noise floor.  Please post a pic as well, I would like to see what it involves.

Thanks,
Ed

 

[drewh1]

I got the DC heater even though I have terribly inefficient (92db) speakers  . Paul suggested it because EML recommends using it on their tubes. For my budget, these tubes are expensive, so I am being very careful about getting things right.  I did a lot of research on the debate about sound. Like many things in audio there is little agreement.

Here is a quote from the Emissions Lab site on providing power to EML tubes  "Use DC filament heating. AC heating will not sound better, because these will hum, and there is nothing better sounding about that." 

I did some critical listening late last night and could not hear any differences. The hum was noticeable even on my speakers so I think it is a good call.

Bottom line, it is an easy build: very simple circuit board and a couple of wires, and it is not very expensive for what you get. I would recommend it.  Sorry I don't have a picture. If you send me your email by PM, i'll send you a copy of the manual.

drew.

 

[fullheadofnothing]

Could you quantify "noticable"? I.e. do you mean if you put your ear up to the speaker, you can hear a little hum in a quiet room, or do you mean that it is audible from the listening position. Also, what were you seeing on the hum balance measurement?

Please do not offer distribute manuals (or any portion) without permission. A large portion of kit cost is the time and effort of writing these manuals; they are the property of Bottlehead, and we do not take that lightly.

 

[drewh1]

Hi Josh. Apologies about offering the manual. I wouldn't have except that Ed is already a kaiju customer .  at any rate it did not happen

The hum was apparent with ear to speaker and barely audible in a dead quiet room. I listen nearfield at 9ft away. Hum pots were at 4 to 8
mv if I remember correctly. Speakers are dead quiet now.

 

[Paul Joppa]

It looks like I will be out of spec on the filament voltage with the .51 resistors and the DC regulator.

So based on the specs of the EML drawing 1.4 amps, I calculate I need .45 ohm resisters to bring the voltage up to 5V spec.

6.3 - 5 = 1.3  1.3/1.4 = .92  .92/2 = .46   

correct?

More precisely, you should include the 0.1A through the hum pot. Assuming the EI tube is drawing exactly 1.2 amps (it's probably close but not exact), that's 1.3 amps total. Adding the resistor drop to the measured 4.91 volts, I get 6.236 volts from the filament supply as seen at the tube - the 0.064v difference from the target 6.30v is probably lost in the wires. Using 1.5 amps for the EML plus hum pot, I get a target of 0.412 ohms each. This can be done by paralleling the 0.51 ohm resistors with 2.14 ohms each. 2.2 ohms is close enough and readily available. A half watt rating is adequate, though I'd spring for 1-watt resistors. Might as well get some 2.0 ohm and some 2.4 ohm resistors at the same time in case you want to adjust further.

 

[Doc B]

I hate to always be the pragmatist here, but we are dealing with such low resistances that the resistance of the solder joints can influence the readings. Because of that I think picking an exact value may always be a matter of cut and try.

 

[drewh1]

Thanks Paul and Doc  I'll get an assortment of values per Paul's suggestion.  And Paul, I really appreciate the details you provide as I am learning a lot with this project and your information is always a bit help. 

Problem is I don't want to stop listening

 

[drewh1]

finally complete with tubes and all modifications in place, well except I have some Mudorf Silver/Oil 10uf's on the way. But that is the LAST thing I am doing, really. 

 

[ebag4]

Looks great Drew!  Anxious to read your thought on the EMLs.

Best,
Ed

 

[drewh1]

Thanks Ed - Don't know if you saw my other post, but I went through the ringer to get these tubes so I hope they work out. They look awesome and are very well made apparently, feel very solid anyway.

I'll will give them a week or so to break in and provide some feedback on them.  So far they sound pretty darn sweet though.

drew.

 

[ebag4]

Thanks Ed - Don't know if you saw my other post, but I went through the ringer to get these tubes so I hope they work out. They look awesome and are very well made apparently, feel very solid anyway.

I'll will give them a week or so to break in and provide some feedback on them.  So far they sound pretty darn sweet though.

drew.

Wow Drew, just read the thread, that sucks.  I didn't read if you were able to get it rectified or if you had to fork out more $$, hopefully not the later.

Hope they are worth the effort.

Best,
Ed

 

[drewh1]

I put up posters in the hood advertising a reward. Sure enough someone contacted me, so I did fork out a bit more money, but at least not to TubesUSA!

I am thinking of adding these transformer covers over the chokes. I think I like the clean look and the driver tubes stand out more against them. They need to be modified slightly to fit just right.

 

[ebag4]

I like them, I was looking at some aluminum covers on eBay.  I'm still undecided at this point.

Best,
Ed

 

[drewh1]

Mundorf's are in!  As soon as I get a new driver tube, I can start listening again.

 

[drewh1]

Back up and running again. New driver
tubes and caps, ouch.  I bit painful at first but after ten hours I am starting to hear some promising sounds!  I think I'll run it continuously for the next couple of days and get this break in thing done.