My Next Build Journal: Soursound 5E3 and 5F1

[gabasa]

So is the mojo 50246 the same as sours 1839? And what I’m gathering is the 1839 is not really seen in the 5e3s ?

Yes, they're based on the same vintage design. 1839 = 50246. Have you had a chance to read this info already:

Tweed Deluxe Transformer SET

Soursound Tweed Deluxe Transformer Set

soursound.com

Are Mojo's and Soursound's really the same? I bet you know the answer to that already.

I'm trying to finish up a 5E3 build today, which will have an SST1839 and a Jensen BB40 speaker. I'll let you know how it sounds when it's done. FWIW, this Champ I just finished is fantastic, it's like milk and honey on my ears. I'm going to borrow a friend's Champ soon to do some more side-by-side comparisons, but this one seems to have a luxuriously silky sound to it compared to previous builds. The Soursound 265 (8 Ohm) OT is really good in this circuit!

 

[Jasonpatrick]

No I know they don’t sound the same! I was just trying to figure out the numbering systems and how he was going about it. Looking at different years online from 57-59 it looks like most of the 1957s had the 50246 then 1958 was mostly the 108 and even though he says 1960 was the 125a1a it seems to show up a lot in the 59s .. only 1839 I saw was in a Pro.

 

[gabasa]

I think a lot of confusion could be avoided if Bryan just changed the part number for that output transformer to SST50246. Maybe I’ll suggest it to him.

 

[gabasa]

I just fired up the 5E3 and my numbers look interesting:

B+: 369V
Plate voltages: 355V and 356V
Cathode resistor: 248r
Cathode resistor voltage: 22.1V
Plate current per tube: 42.1mA
Plate dissipation: 100% exactly

How safe do you think these numbers look? 100% is supposed to be safe in cathode bias, but when you're at 100%, it's a little scary. Here's a pic, all I have left to do is bolt it to the cabinet. I'm wondering if I should up the value of my cathode resistor to 270r or 300r, or if I should just leave it alone and let it run the way it's meant to run.

 

[CirrusBand]

Leave it be I reckon, Those look like good numbers. I can understand people wanting to cool them down when the plate voltage heads up towards 380v+, but your numbers look like basically where the original ones land, there's nothing crazy going on there.

Mind you, I am coming from the world of AC30s, where I recently cooled one down from 130% to 110% and thought I was being very conservative.

 

[2L man]

I just fired up the 5E3 and my numbers look interesting:

B+: 369V
Plate voltages: 355V and 356V
Cathode resistor: 248r
Cathode resistor voltage: 22.1V
Plate current per tube: 42.1mA
Plate dissipation: 100% exactly

How safe do you think these numbers look? 100% is supposed to be safe in cathode bias, but when you're at 100%, it's a little scary. Here's a pic, all I have left to do is bolt it to the cabinet. I'm wondering if I should up the value of my cathode resistor to 270r or 300r, or if I should just leave it alone and let it run the way it's meant to run.

Most likely power tubes run hotter when you don't play and playing quiet. When you play loud tubes mostly conduct current alternating and when loadline stay close slightly above the 12W line power dissipation decrease. This attachment green "headroom" where operation meet g1=0V grid line is well below 12W and other tube does not transfer current at all.

Screen voltage has effect to all pentode operation but to me it looks 6V6 effect is stronger when screen current is often limited using series resistors to extend tube operation life. Here I did use 330V because thats what it might be to achieve your cathode voltage.

 

[cobaltu]

Those voltages look pretty standard to me.

The thing that puzzles me - I thought that the Soursound power transformer was suposed to replicate vintage B+ with regular 120V wall voltages. I thought that it might be a modern 5y3 rectifier, but it looks like you're using a vintage one in the photo.

EDIT:
From the Soursound website:
"SST6452E: Our Tweed Deluxe “Vintage Voltage” spec power transformer is designed to give you the same power supply voltages you’d find in your amp if you plugged it in to the wall back in the 50’s, yet powered by today’s 120VAC. Additionally we’ve gone to great lengths to recreate the dynamics and feel of an original Tweed Deluxe by matching the original DC resistance of the high voltage winding and consequently the sag and compression in the original circuit. In a standard 5E3 circuit the first node in the power supply will sit around 368VDC plugged in to 120VAC at idle."

 

[cobaltu]

Also I wouldn't worry about running at 100% dissipation. My 5e3 was running at ~102% for a couple years and I never had any problems. And that was with modern TAD tubes.

I changed to a set of JAN Sylvania 6V6GTs And now I get ~98% dissipation and that - for reference - is at 319V on the plates.

 

[gabasa]

Thanks everyone for the responses.

I haven't had a chance to play this Deluxe loudly, but with the Soursound transformers and the Jensen Blackbird 40, it definitely sounds great. There's no honky, boxy midrange, it's very balanced. I've literally only played it quietly for a minute, so I need to get to know it better.

I noticed thought that the TOCOS pots ramp up nicely. I always found with CTS that the sound kicked in all of the sudden, but the sound actually tapers in with these. That's a good thing in a 5E3. PEC pots also were good in this way, but they cost more.

 

[gabasa]

Here’s the completed 5E3. The grill cloth needs to be redone, but the rest is great.

 

[cobaltu]

Are those 10uF caps at the input?!

 

[gabasa]

Are those 10uF caps at the input?

The little red electrolytic bypass cap is 25uf, the first two film caps are 0.1uf. Why?

 

[Brendan]

Wow, I had no idea that's what Brian Sours is doing these days. He was known locally as an amazing amp techncian and I stopped by his shop around 15 years ago. I wouldn't doubt that's top shelf product.

 

[gabasa]

Wow, I had no idea that's what Brian Sours is doing these days. He was known locally as an amazing amp techncian and I stopped by his shop around 15 years ago. I wouldn't doubt that's top shelf product.

Bryan’s level of knowledge is amazing, and it shows in his products!

 

[Jasonpatrick]

I just fired up the 5E3 and my numbers look interesting:

B+: 369V
Plate voltages: 355V and 356V
Cathode resistor: 248r
Cathode resistor voltage: 22.1V
Plate current per tube: 42.1mA
Plate dissipation: 100% exactly

How safe do you think these numbers look? 100% is supposed to be safe in cathode bias, but when you're at 100%, it's a little scary. Here's a pic, all I have left to do is bolt it to the cabinet. I'm wondering if I should up the value of my cathode resistor to 270r or 300r, or if I should just leave it alone and let it run the way it's meant to run.

View attachment 1069063

My voltages are about the same as yours. I got 350v on the plates. B+ is 385v … What is your B2 voltage? I look at Robrobs and his B2 is super low relative to mine.. Like 318v while mine is 342..

 

[Jasonpatrick]

The little red electrolytic bypass cap is 25uf, the first two film caps are 0.1uf. Why?

They look huge compared to the other set of film .1s!

 

[cobaltu]

The little red electrolytic bypass cap is 25uf, the first two film caps are 0.1uf. Why?

That makes sense. It looks like "10" rather than ".10".

 

[gabasa]

I can't remember the B+2 exactly, but I can measure it when I open up the amp again. Mine is higher because it has a choke.
By memory, I swear it was 353V, just a hair under my plate voltages.

Those caps are copper foil paper in oil. They're large but they do have their own sound, which I really like.

 

[gabasa]

That makes sense. It looks like "10" rather than ".10".

I just took a look at the pic, I can see how it looks like a 10. There actually is a little dot in front.

 

[NTC]

Thanks everyone for the responses.

I haven't had a chance to play this Deluxe loudly, but with the Soursound transformers and the Jensen Blackbird 40, it definitely sounds great. There's no honky, boxy midrange, it's very balanced. I've literally only played it quietly for a minute, so I need to get to know it better.

Any updates? How does this compare to your other 5E3 builds sound-wise?