New tweed overdrive build

[daveyajd]

Hey everyone,
I have loved my TOS so much that I want to build another one as a gift for someone. In mine I used a Hammond 290DX PT and a 1760 OT. If I want to use something to get a little less wattage overall so maybe I can use 6V6 or something what would be a good choice of transformers?

Aaron

[tubenit]

I recommend a 300-0-300 PT with at least 150 ma.

300 X 1.1 5Y3 = 330   6K6 (maybe?),  6V6, 6L6 or 5881

300 X 1.2 5V4 = 360   6V6, 6L6 or 5881

300 x 1.3  GZ34 = 390  6V6, 6L6 or 5881

300 x 1.4  solid state rectifier  =   420    6V6, 6L6 or 5881

IF you used a 275-0-275  150 ma that could be a reasonable choice also.  And you could build an adapter like I did that allowed a 6BM8 to plug into an 8 pin socket while using a 5Y3GT for 300 v on the plate of the 6BM8.

With respect, Tubenit

[daveyajd]

Thank you. Would I need to change the OT as well? Also, I guess I could use the same PT I used because I have around 400v with a 5V4.

Aaron

[HotBluePlates]

Also, I guess I could use the same PT I used because I have around 400v with a 5V4.

Plate voltage with 6V6's will run higher than your amp with 6L6's because less current is being drawn from the power supply.

Would I need to change the OT as well?

Use an OT with 6.6kΩ - 8kΩ primary impedance. It seems you like Hammond, so something like a 1750/1760 E or H seems appropriate. Hammond's 290PAZ seems to have fitting voltage/current ratings, but double-check the filament current of that transformer compared to your proposed circuit.

[daveyajd]

So I've been hunting around and looking at transformer specs for a few days. I like the idea of using a smaller OT like the Deluxe but I can not find a PT that has the specs 300-0-300 and at least 150 mA. I've looked at Hammond, Heyboer, Magnetic Components. Anything I could. It seems that most are in the 660 volt or higher range or they are lower in the mA rating. Where am I not looking? Also, with my budget I need to be in the $160 range for both so I can't spend what Mercury Magnetics cost. Or the dual primary Hammonds.


Aaron

[HotBluePlates]

... It seems you like Hammond ... Hammond's 290PAZ seems to have fitting voltage/current ratings ...

Hammond 290PAZ

Yeah, 290-0-290 @ 140mA. Close enough, call it a day.

[daveyajd]

Yeah I have looked at that. It does fit very closely. I have wondered about 2A on the 5V. But I guess that would only really eliminate a 5U4 type rect. Also I just found the Hammond 200 series. The 272Fx looks good. It is a vertical mount style. How does that work for orienting transformer stacks? Just turn one?


Aaron

[John]

Just turn one?

Yup. Distance helps too.


OTOH, I've had to cram them right up beside each other with zero hum. I think some OT's just pick it up more than others?

[tubenit]

On scratch builds,  I only use stand up PT's.   I have the Hammond 272FX on both my D'Mars and my Tweed BluezMeister.

I like how the stand up PT's give me more room inside the chassis & they seem to make for a quiet amp.

With respect, Tubenit

[daveyajd]

Ok. I am putting together an order for a 272fx PT, and a 1760H OT. Do I also need to use the smaller 50mA choke or can I use the same 90mA I used in the first one? This should be sweet sounding, lower volume tone machine!

Aaron

[tubenit]

I'd use the larger choke, so you can use either 6V6 or 6L6/5881.

With respect, Tubenit

[daveyajd]

Awesome. Thanks. Will I still be able to set this up to use and handle EL34s?

[DummyLoad]

So I've been hunting around and looking at transformer specs for a few days. I like the idea of using a smaller OT like the Deluxe but I can not find a PT that has the specs 300-0-300 and at least 150 mA. I've looked at Hammond, Heyboer, Magnetic Components. Anything I could. It seems that most are in the 660 volt or higher range or they are lower in the mA rating. Where am I not looking? Also, with my budget I need to be in the $160 range for both so I can't spend what Mercury Magnetics cost. Or the dual primary Hammonds.


Aaron

http://www.hammondmfg.com/pdf/EDB272DX.pdf

http://www.hammondmfg.com/pdf/EDB272FX.pdf

the 272FX is overkill. 71 bux and change from uncle mouser. i'm sure someone knows where to get one cheaper and will chime in...

http://www.mouser.com/ProductDetail/Hammond-Manufacturing/272DX/?qs=3TG34Bgp1HAJrQyw8RI4qw%3D%3D

--pete

[daveyajd]

What do you mean by overkill? To big for this version of the amp? AES has the 272DX for $65.

Aaron

[DummyLoad]

What do you mean by overkill? To big for this version of the amp? AES has the 272DX for $65.

Aaron

meaning for a 6V6 output stage the 272FX is larger PT than you need. tubenit uses the 272FX so that he can use 5881/6L6GB. if you don't plan to use 5881 and stick with 6V6, then 272DX will be more than adequate.

--pete

[daveyajd]

Ok, perfect. I like to keep some options open there as well so I will go with the 272FX. Thanks.
Now looking at the OT. What are the benefits of using this option:

https://www.hammfg.com/part/1620A?referer=1047

Over something like this:
https://www.hammfg.com/part/1760H?referer=1025
They look virtually the same except for the shielded case. Is the non shielded  more prone to hum and is it worth an extra $50?

Aaron

[tubenit]

I don't know what the answer is to your question.  Having said that, I have used the 1620 OT on two different amps that turned out very quiet at idle.  One is my current Tweed BluezMeister running 6L6's.  I sometimes use 6V6's with that OT also.

With respect, Tubenit

[HotBluePlates]

Now looking at the OT. What are the benefits of using [1620A]

• ver something like [1750H]?

They look virtually the same except for the shielded case. Is the non shielded  more prone to hum and is it worth an extra $50?

On the spec sheets for both, look at the frequency response. 1750H is 20w, 70Hz-15kHz. 1620A is 20w, 30Hz-30kHz.

The more expensive transformer goes twice as low, twice as high at the same full power. It uses a bigger, heavier core to do that. You could probably push 30-40w through it to land at the same 70Hz-15kHz bandwidth as the 1750H.

Subjectively, bass will be clearer. Some might say the amp sounds "bigger" while others might gripe that it's too "hi-fi" for 20w.

The only way to know for sure is to try and see which you prefer. Or take the advice of those who've built a TOS (I haven't). Or just pick one and go with it...

[daveyajd]

Chassis has arrived and things are moving ahead. I went with the same size chassis I used before (20x8x2.5) but opted for inside tabs for mounting. I will be making a large order of the chassis mount parts soon then the drilling begins.


I have been thinking ahead about what kind of caps to use. In my first build I used Mallorys throughout and have been happy with the sound. But I'm wondering if there are places in the circuit that would benefit from a certain type. Like Mallorys in the clean stage and something else in the overdrive. Or Mallorys in the PI? The choices for me would be between Jupiter, Sozo, OD. What say you all?


Also, I am largely following designs for my previous build for the faceplate, labeling, etc but for those of you that have built this amp is there any features you have discovered or built in that are nice add ins? Things like various switching, tone stack cap switching, bright switch, parallel caps.




Aaron

[tubenit]

I would be inclined to have the Mallory's in the OD section and Orange Drop in the clean section and Xicon in the post LTPI coupling caps.

Doug carries all of those.

With respect, Tubenit

[daveyajd]

How are the Jupiters or the Mojo Dijons? If I was trying to add yet another flavor to the already tasty OD are those good choices? I'll probably build this one with Mallorys, get it sounding good and then try something else but I'm curious.

Aaron

[tubenit]

I've never tried the Jupiters or Mojo Dijons.  Having said that, I hope you're following Willabe's thread on capacitors and tone.  He seems to like the Jupiters when he reviewed them. I might be inclined to try those especially if they are similar to the Orange Drop PS series. 

Maybe do the Jupiters in the clean channel and mostly Mallory's everywhere else?

http://el34world.com/Forum/index.php?topic=19534.0

With respect, Tubenit

[daveyajd]

Yes I saw that thread. Great! I didn't want to even consider Musicaps, but now........

[Willabe]

The yellow Jupiters are very good sounding to me also.

I agree with Tubenit that; different amp circuit, guitar/PUP's, playing style, music style will/would all matter which cap/caps you would like better in a given situation.   

Sorry, I wish there was, but at this point I don't see/hear an ABSOLUTE BEST for EVERYTHING cap.

For me, since I don't play with much distortion, I'm looking for/wanting some coloration from a coupling cap. At least at this point I think I am, I very well might change my mind latter on.     

[shooter]

Mojo Dijons

I used these in my last 2 builds, work very good outta the box(smooth, quiet) , that said, when I want to *change tone*, I change speakers 

[daveyajd]

Ok, it has been a bit but I have found some time to continue my build. I will post some updated pictures very soon.

Right now I have a quick question about my PT wiring. The transformer is a Hammond 272 FX. Instead of the usual two black wires on the primary side it has a white (0v) a black (125v) and a grey (115v). It makes sense that the white would connect to the white from my outlet. Why would I need the option of the black or grey?

The other thing I've run into that's different than my first build is that there are seems to be a center tap wire for the yellow 5v as well as the usual HT and 6.3v. I should just ground these all as usual?

Aaron

[sluckey]

Why would I need the option of the black or grey?

Because your line voltage may be higher than you expect. My line voltage is usually somewhere between 120 and 125v. I would use the 125v winding.

seems to be a center tap wire for the yellow 5v as well as the usual HT and 6.3v. I should just ground these all as usual?

Don't connect the yellow 5v center tap to ground because it will have B+ on it. Just tape it up and tuck away.

[daveyajd]

Thank you sluckey. I will shrink-wrap both of those wires.


Here are some updated photos. I am just doing the wiring for the PT and figuring out how I want to position my heater wires.
Suggestions and observation always welcome. Thanks all.


Aaron

[daveyajd]

Ok, bumping this back up. Just received a final order of parts from Doug so I'm ready to finish this thing up.


I'm trying to wrap my head around the wiring for the relay switching and LEDs. My amp has a toggle switch on the front panel and a cliff jack on the back panel for a foot switch. I also have an LED for the OD on the front panel.


In my first build I used the Weber relay board. So I wired it up like the attached drawing. Then I wired the front panel LED up from the diode on the board.


On this one I have all the same connections but I'm using Doug's relay and PS boards. I also want to add an LED to my footswitch. What does the wiring look like for this? Am I just running wires from the 2 diode turrets on the relay board?


Aaron