REDDI DI

[theokbird]

i'm having trouble finding the correct power transformer for this project.  has anyone in the US found one that can work?  i can't seem to find one that has a 200V/0.1A and 9V/1A dual secondaries.

thanks!

 

[abbey road d enfer]

would this transformer work?
https://www.edcorusa.com/mx12cs

Yes.
But.

it's copper shielding is crucial, and i should use high quality shielded cable for the connections, i assume. 

Not copper shielding. Copper shielding is good against electrostatic disturbances, which you should not fear if your layout is reasonable (not the input leads dressed with the mains leads ) and the circuit is in a metal enclosure.
You need good old mumetal shielding  for protection against magnetic disturbances. Or two separated layers of 1.5mm steel. Box in a box. Very DIY.

should i be worried about it's position in the case?

Very much. Don't assume you can properly predict the best position. Magnetic flux is very stubborn at taking its own unpredictable path. You'll have to experiment by moving and rotating the xfmr. Most often, you'll find that putting the lid on the unit changes the flux orientation. And then you will be faced with the presence of  magnetic interference externally generated by the other equipment in the rack.

 

[mutterd]

i'm having trouble finding the correct power transformer for this project.  has anyone in the US found one that can work?  i can't seem to find one that has a 200V/0.1A and 9V/1A dual secondaries.

thanks!

I built mine with one of these:
https://www.tubesandmore.com/products/P-T261G6

and a custom output transformer wound by our very own CJ…

I built mine with 2 gain stages with pots after the 1st stage and on the output so i can drive it a bit but control the gain on the way out...

sounds amazing… I'm not much for "swiss army knife" products in the studio - but i love the way this sounds on bass, amplified cello, contrabass and violin - so i kind of like the idea of putting XLR's in and using it as some sort of mic tube preamp stage….

 

[fazer]

mutterd?

I built mine with 2 gain stages with pots after the 1st stage and on the output so i can drive it a bit but control the gain on the way out...

Did you add a tube or just split the 6n1P (meaning 1/2 section drives transformer rather than parallel sections)? 

 

[mutterd]

I did 2 tubes - 2 gain stages…

if you look back for irfrench's posts - he inspired the 2 stage topology…

 

[fazer]

So thats a Dual SRPP design.  that is basically a mic preamp if you add an input transformer.  Cleaner and with ECC88  type Tube I'm guessing like irfrench's.  Also the transformer would then be connected via Capacitor to plate with plate resistor and not be a direct to plate  like Redd DI.  Very Cool.  I'm going to play with the tube pre first before committing to a single 6n1p.    I also got a transformer from CJ. 

 

[theokbird]

would this transformer work?
https://www.edcorusa.com/mx12cs

Yes.
But.

it's copper shielding is crucial, and i should use high quality shielded cable for the connections, i assume. 

Not copper shielding. Copper shielding is good against electrostatic disturbances, which you should not fear if your layout is reasonable (not the input leads dressed with the mains leads ) and the circuit is in a metal enclosure.
You need good old mumetal shielding  for protection against magnetic disturbances. Or two separated layers of 1.5mm steel. Box in a box. Very DIY.

should i be worried about it's position in the case?

Very much. Don't assume you can properly predict the best position. Magnetic flux is very stubborn at taking its own unpredictable path. You'll have to experiment by moving and rotating the xfmr. Most often, you'll find that putting the lid on the unit changes the flux orientation. And then you will be faced with the presence of  magnetic interference externally generated by the other equipment in the rack.

thanks for the tips! i'll be sure to take these factors into account when building.  sounds tricky but doable!

 

[theokbird]

i'm having trouble finding the correct power transformer for this project.  has anyone in the US found one that can work?  i can't seem to find one that has a 200V/0.1A and 9V/1A dual secondaries.

thanks!

I built mine with one of these:
https://www.tubesandmore.com/products/P-T261G6

and a custom output transformer wound by our very own CJ…

I built mine with 2 gain stages with pots after the 1st stage and on the output so i can drive it a bit but control the gain on the way out...

sounds amazing… I'm not much for "swiss army knife" products in the studio - but i love the way this sounds on bass, amplified cello, contrabass and violin - so i kind of like the idea of putting XLR's in and using it as some sort of mic tube preamp stage….

very cool, i saw your design earlier in the thread, i was certainly intrigued!  even though we seem to be using two different beasts i'll let you know how adding the balanced input works out, or maybe vice versa if you get it up and running before me 

 

[MicDaddy]

A question for the iron experts;

Aside from the cost of electronic lamination, what would make chosing a larger core size, than the suggested EI100, a bad decision?  Or would it be even a bad one?  Inside real estate not an issue.

Iron is cheaper than copper, and we have lots of old school lamination all ready for cannibalization.  This saves from purchasing new (and also contribute to the green initiative).

Could then the windings be designed to compensate?  My gut says yes but this is all black magic to me.

 

[Winetree]

1. Do i use the 2K or 5K trim? How do I calibrate? What points and what is the voltage read to calibrate.
2. ERROR    B.O.M. reads R8=39K,  R9-R11= 2K.      P.S.B. reads R7, R8-R10.
So is R7 on on the P.S.B. R8 on the BOM and R8-R10, R9-R11 on the BOM?

 

[MicDaddy]

;D ok so I read through the thread again and to answer my own question above, Cj shows us a few times winding a transformer of different core sizes for the same circuit  : derp derp

...now how do I get this copper pallet strap off of the core... is this welded  ???

 

[CJ]

what size lams?

that copper wrapper should be soldered together somewhere, or maybe tucked into the lams,

get a heat gun and heat up the transformer so you can de-laminate,

don't worry about bending the lams a little as this circuit uses a gapped core so perm does not matter that much,

if you post the dimensions of the transformer you are going to get the lams from then we can adjust the turns needed accordingly,

 

[MicDaddy]

what size lams?

that copper wrapper should be soldered together somewhere, or maybe tucked into the lams,

get a heat gun and heat up the transformer so you can de-laminate,

don't worry about bending the lams a little as this circuit uses a gapped core so perm does not matter that much,

if you post the dimensions of the transformer you are going to get the lams from then we can adjust the turns needed accordingly,

The dimensions of the lams are 2.8" x 1.3"  (71mm x 33mm)

Was able to find a bead of solder and removed the copper wrap.  What is the purpose of this copper?

First attempt at removing lams not going so well, perhaps the hot air rework station doesn't have the ooomph... next I will try the paint stripper \m/ 

Thanks by the way CJ!

edit: magmet dimensions for lamination type EI100 are 3" (height of E & I) x 2.5" (length of E flag + I width)

seems my laminates are a bit smaller

Thinking I'm going to have to hack out the bobbin and wire.  Just don't see another way to remove laminates save perhaps either soaking in a heavy handed solvent or bending laws of physics.

 

[theokbird]

1. Do i use the 2K or 5K trim? How do I calibrate? What points and what is the voltage read to calibrate.
2. ERROR    B.O.M. reads R8=39K,  R9-R11= 2K.      P.S.B. reads R7, R8-R10.
So is R7 on on the P.S.B. R8 on the BOM and R8-R10, R9-R11 on the BOM?

i assume you are using the Garash Labs board?  if so then here's what i realized from my build:

1- I used a 5k trim pot, although i had to turn it many times before finding the sweet spot, so perhaps the 2k is better to use...(with 5k pot turn the trim to the right, board oriented so the heat sink is above the trim pot.  i had to turn it about 6 full rotations before getting a decrease in heater voltage.)
2-the BOM has an error for sure! i traced the board, relative to the schematic listed on page 6 of this thread, (DirtyGary, if you're reading please correct this!) and found that R7 = 39k, R8-R10 = 2K (all 1% tolerance, 2W for 2K, 3W for 39K).  i actually used a 5% tolerance for R7-39k/3W, and it didnt seem to matter, i ended up with proper voltages.
There is no R11 on the board or schematic, its just a mislabeling in the BOM.  the test point is between pin 4 and pin 5 of the tube socket, just put the dmm between those points, and turn the trim pot until it reads 6.3VDC.
3-answered in #2

I'll be posting pictures of my build(s) very soon, with a mic input tranformer mod and all(which actually turns out to be somewhat useful, despite previous trepidation!), just as soon as i get these blasted cases drilled!  I tried to fit it all in Dandeurloo's PSU case, turning the board on its side and mounting it on 'L' brackets, but i believe the power TX is still too close a proximity to the output TX- although i havent given up hope: i'm getting a mumetal strip to go around it, maybe that'll knock back the magnetic flux enough?!  we'll see, not holding my breath...

 

[Winetree]

Thanks for the reply.
Also having trouble trying to figure out layout in Dan's Mike P.S. case. Board on side, tube hits O.P. trans, etc.
E-mailed Dan asking if I could buy 2 of his Extra wide & long cases he uses for his D.I. Didn't get a reply.
Yes, using Garash Labs board and transformer. I don't have the power transformer yet.
Which one do you have? Thinking about the Edcor.

https://edcorusa.com/xpwr191

 

[theokbird]

Thanks for the reply.
Also having trouble trying to figure out layout in Dan's Mike P.S. case. Board on side, tube hits O.P. trans, etc.
E-mailed Dan asking if I could buy 2 of his Extra wide & long cases he uses for his D.I. Didn't get a reply.
Yes, using Garash Labs board and transformer. I don't have the power transformer yet.
Which one do you have? Thinking about the Edcor.

https://edcorusa.com/xpwr191

yeah, i had to mount the pcb on a couple 4" zinc L brackets, with the bottom trimmed to about 1" long and drilled to fit along the left wall, if you were looking at the xlr side of the psu case.  i can fit everything inside in this configuration, all neat and tidy  8).  are you using the Garash Labs output tx?

It all fits, however i have a hum. and the thing is, it's not even that bad, but enough for me to want to do something about it.

the hum subsides when taking the power transformer a few centimeters outside the case.  so that's my problem with the CC psu case.  i'm using this power tx: http://www.toroidal-transformer.com/shop/high-end-audio/power-transformers/314/2n465-powertransformer-for-tube-amps---44va-.html#.VGwPbVfF95U
kind of pricey, but it was the only off-the-shelf toroidal tx i could find that matched the specs of the circuit perfectly.  in retrospect i probably would have looked a bit harder for something comparable, or tried a similarly spec'd, but not perfect, toroidal tx.  the reason why i went with a toroidal power tx is that they give off less magnetic flux, making them perform better in closer proximity to the audio circuit, output tx.  in retrospect i might have tried a power tx like the edcor you mention, maybe some mumetal shielding for it, and the hammond 1402FV or hammond 518-0910 case.  unless mumetal shielding stops my hum in the Collective Cases enclosure, i'll be moving it to a hammond 1402fv, which will give me plenty of extra space, but in a similarly portable enclosure.  i bought both cases at the same time, as i anticipated this dilemma and wanted a speedy workaround.  i just think the CC case is very nice looking    but i dont want to sacrifice noise for aesthetic, so if i cant stop da hum, i'm moving on.

ultimately you just have to try it out, as Abbey suggested earlier in the thread.  i always think that going with the best bet for low noise(thus my toroid) would be the way to go, but it depends on the enclosure and how tight and tidy your wiring is and the exact position of both transformers and the pcb.  totally guesswork, to a point, unless you have a way to measure gauss   but easily figured out with minimal parts exchanges. 

i'll let you know how the shield for my toroid improves(or not) the hum, it might be worth the extra $ to have such a small and nice looking enclosure(or not depending on if you mind ;D)

 

[dirty1_1garry]

Hello!

I created a separate thread about my predict pcb Check it out!)
http://groupdiy.com/index.php?topic=57889.0

 

[CJ]

you could put in a 100 ohm hum balance pot, 3 watt wire wound is best but you can use a regular allen bradley and maybe a 1K instead of 100 for less heat,

 

[theokbird]

you could put in a 100 ohm hum balance pot, 3 watt wire wound is best but you can use a regular allen bradley and maybe a 1K instead of 100 for less heat,

Thanks CJ,

can i just strap the pot across the heater pins of the tube socket, like this(terrible picture, left pin is 4, right is 5):

i have heaters running DC, fyi, in case that makes a difference where i place the pot. 

should the wiper reference something other than leg 1 of the pot?
am i totally getting this wrong  ;D?

 

[dirty1_1garry]

you could put in a 100 ohm hum balance pot, 3 watt wire wound is best but you can use a regular allen bradley and maybe a 1K instead of 100 for less heat,

Thanks CJ,

can i just strap the pot across the heater pins of the tube socket, like this(terrible picture, left pin is 4, right is 5):

i have heaters running DC, fyi, in case that makes a difference where i place the pot. 

should the wiper reference something other than leg 1 of the pot?
am i totally getting this wrong  ;D?

What is the purpose of this pot?)