[L0rdGwyn]

So I realized I actually had the terminals I needed to make the resistor change in the DarkVoice, derp. Still need my Mouser order for the power supply changes but figured I'd go ahead and swap out the resistors.

Here is my solution to the hot resistor problem. Had to reroute the output wiring, the ground bus. Got rid of the aluminum-housed resistors, put some solder lug terminals on the standoffs instead, and used three 3.9K 12W NOS Mills non-inductive wirewounds in parallel. 1.3K cathode resistance with the 36W of rated power dissipation and they are no longer attached to the chassis by metal contact.



I have been running the amp for a little over an hour now. With the old setup, top plate was hitting around 40C and the interior of the chassis 48-50C.

Top plate still comes to around 36-37C, but floating my thermocouple on the interior of the chassis, air temperature only hits around 37-38C, that's a 12C improvement. I'll take it.



Sounds really good too with a National Union 6SN7GT and Western Electric 421A.

 

[Tjj226 Angel]

Kinda spitballin' some thoughts on this E55L spud...

I like the idea of using spare parts. If I were to parafeed it and use a CCS load rather than a choke, I have a transformer perfect for the job, old Sowter custom job from version 1 of my 45 parafeed amplifier.



Has a healthy B+ winding rated for ~100mA DC (perfect), and three 6.3VAC windings, two with high current ratings as they were originally intended for the 45. I also have some Tent Labs DC heater regulators which I could put to use on the E55L (pictured).

Using the CCS would simplify the power supply as well given it's PSRR, so could go passive. For soft start, could use a hybrid SS diode-tube full-wave bridge for swag, plus could use a higher Vdrop rectifier to knock off some excess voltage and save the CCS some heat.

Since I have plenty of 6.3VAC to go around and the E55L only needs perhaps -6V on the grid, could potentially use one winding for a negative bias supply and go fixed bias. Would probably go with a 1:2 SUT as well.

The last question then becomes the output transformers. I think I would go with a multi-tap parafeed from Electra-Print. Have swapped emails with Jack a few times, want to try out his stuff. If I went for a 8-32-120-300 secondary setup, would be in good shape for a flea-watt speaker amp and gobs of power for headphones.

I'm avoiding starting anything else new until I have cleared the queue, but I like this as a future project, high on the "potential projects" list.

Would this be just for headphones? Or for headphones and speakers?

 

[L0rdGwyn]

Would this be just for headphones? Or for headphones and speakers?

Both in theory, could do about 2W into 8ohms. Figure if I get multitap parafeed transformers, might as well include an 8ohm tap.

But I am trying to pump the breaks on all of my ideas and be more picky. No more simultaneous projects for me LOL one at a time from now on, it's too much work and money. The fact that I have a mains transformer ready to go for this one makes it very appealing. I did buy some nice NOS ceramic magnoval sockets though, just in case

 

[L0rdGwyn]

I tracked down a copy of a book I have been keeping an eye out for, Designing Power Supplies for Tube Amplifiers by Merlin Blencowe. I really like his preamp design book, became my leisure reading on a vacation last year LOL so I need a new one for this year. Obviously this information is available in many places and it will be a lot of review, but it's nice reading a text where everything is in the context of tube circuits. I can read about series / shunt regulators anywhere, but very few contemporary books written on TUBE series / shunt regulators anyway, I was happy to find it. Sort of highly sought-after in the DIY world, this book is out of print, typically listed on auction sites for insane prices.

 

[Tjj226 Angel]

I tracked down a copy of a book I have been keeping an eye out for, Designing Power Supplies for Tube Amplifiers by Merlin Blencowe. I really like his preamp design book, became my leisure reading on a vacation last year LOL so I need a new one for this year. Obviously this information is available in many places and it will be a lot of review, but it's nice reading a text where everything is in the context of tube circuits. I can read about series / shunt regulators anywhere, but very few contemporary books written on TUBE series / shunt regulators anyway, I was happy to find it. Sort of highly sought-after in the DIY world, this book is out of print, typically listed on auction sites for insane prices.

I have seen this book from time to time. I have read a lot of Merlin's stuff on the forums, websites, and so on, so I am not too sure what this book really has to offer. If you feel like this book divulges some secrets that you can't find on the internet, please let me know. I am sort of tied up with family issues at the moment, so I am taking this time to research and read up.

I actually just finished my first pass of "High Quality Horn Loudspeaker Systems" (which is nothing short of a kick arse book) and I am waiting for my new book to get here.

https://www.amazon.com/Transformers-Tube-Amplifiers-INTERSTAGE-TRANSFORMERS/dp/0980622387

 

[L0rdGwyn]

I have seen this book from time to time. I have read a lot of Merlin's stuff on the forums, websites, and so on, so I am not too sure what this book really has to offer. If you feel like this book divulges some secrets that you can't find on the internet, please let me know. I am sort of tied up with family issues at the moment, so I am taking this time to research and read up.

I actually just finished my first pass of "High Quality Horn Loudspeaker Systems" (which is nothing short of a kick arse book) and I am waiting for my new book to get here.

https://www.amazon.com/Transformers-Tube-Amplifiers-INTERSTAGE-TRANSFORMERS/dp/0980622387

It goes deeper into topics he touches on on his site and has all the typical power supply type stuff, but also explores topics that I have not seen him get into elsewhere, particularly power supply regulation. Of course you can find that info other places, but it's nice to have it in one book in the context of tube circuits. Not sure there are any secrets, but I think it's a good read!

That book you linked is terrifying, Pandora's box, I will avert my eyes.

 

[Galapac]

I thought this was funny and wanted to share with y'all...you might relate to a few of these if not more.

You might be a tubeneck...
http://www.netads.com/~meo/Guitar/Tubes/tn.pl

 

[bcowen]

I used/build these sockets in an amplifier.
And replaced them within a week.
They grip the pins so hard it’s impossible to get any tube in or out. A tube rollers nightmare. And well, i like tube rolling. These were too much stress on the base/pins for me.
I like this design for my B4/5 and UX4 tubes.
With only 4/5 pins they are perfect. Also with 1920’s “not the best aligned” pins.

Sockets came in today, and they must have heard about your death grip experience. The contacts in these were so loose the tube would probably have fallen out if I'd turned it upside down. Sigh. The teflon body is nicely machined, but the contacts are terrible. They are made differently than the ones in the ceramic sockets, and those I've really liked -- firm contact even after many tube swaps and no death grip. Fortunately I ordered a pair of the ceramic body ones too, and ended up swapping the contacts between them. Now I have a nice teflon body with good contacts. Obviously pretty ridiculous to have to go to these lengths, and I'm certainly not recommending the teflon versions to anyone going forward (but I do still like the ceramic ones).

Teflon on left....with the ceramic body contacts swapped. I re-tensioned the teflon contacts before putting them in the ceramic body(s) so they have a nice grip now....but not sure if they will stay that way or loosen back up in short order.

 

[Paladin79]

oh crap, some are heading my way too lol

 

[bcowen]

oh crap, some are heading my way too lol

Uh-oh. Well, @Tom-s 's were way too tight and mine were way too loose....maybe you'll get some Goldilocks ones that are just right.

 

[whirlwind]

Sockets came in today, and they must have heard about your death grip experience. The contacts in these were so loose the tube would probably have fallen out if I'd turned it upside down. Sigh. The teflon body is nicely machined, but the contacts are terrible. They are made differently than the ones in the ceramic sockets, and those I've really liked -- firm contact even after many tube swaps and no death grip. Fortunately I ordered a pair of the ceramic body ones too, and ended up swapping the contacts between them. Now I have a nice teflon body with good contacts. Obviously pretty ridiculous to have to go to these lengths, and I'm certainly not recommending the teflon versions to anyone going forward (but I do still like the ceramic ones).

Teflon on left....with the ceramic body contacts swapped. I re-tensioned the teflon contacts before putting them in the ceramic body(s) so they have a nice grip now....but not sure if they will stay that way or loosen back up in short order.

That is a shame because they look like some quality sockets.
If I get another amp I think I would splurge for Yamamoto sockets , if the amp would use multiple tubes for rolling.
May need to get rid of a kidney, but there is no denying the quality of these sockets....probably not necessary though.

 

[bcowen]

That is a shame because they look like some quality sockets.
If I get another amp I think I would splurge for Yamamoto sockets , if the amp would use multiple tubes for rolling.
May need to get rid of a kidney, but there is no denying the quality of these sockets....probably not necessary though.

If I was replacing sockets or building a really nice amp, I might splurge for the Yamamotos. Kind of overkill in the Darkvoice though.

 

[whirlwind]

If I was replacing sockets or building a really nice amp, I might splurge for the Yamamotos. Kind of overkill in the Darkvoice though.

Yes,absolutely and understood

 

[Zachik]

If I was replacing sockets or building a really nice amp, I might splurge for the Yamamotos. Kind of overkill in the Darkvoice though.

Did GE ever made tube sockets?

 

[therremans]

Why not stick with Belton? I have little experience with sockets but the Beltons were a great upgrade from the Chinese ceramic and Russian plastic.