question about change this demeter DI box to 220v

[paulster]

The likely problems are your power transformer isn't as happy as it was before, after the overheating episode or thatthe filter caps have suffered a bit, but you've measured the capacitance and they seem to check out okay.

Before you were running the DI on 100Vac, rather than the 120Vac that it's designed for, so your basis was with really low voltages.

Now you're operating it at closer to regular voltages then you'd expect it to sound different, but whether it'll sound better or worse to you is all down to interpretation.

As I've said before, without a voltage chart it's impossible to say whether the DI is working properly, as Demeter intended it.

[kwm488]

in fact, i think this DI box sound better than boss one. more fat, warm and natual. the only one is that i sure the output volume weak than before. sound quality is same with connect wrong wire before.

so can you guess what possible problem of this unit output lower than before?

if OT hurt or demage, will result of the volume low? van you teach me how to test the ot. the rest is just ot and cap

i sure the PT is no problem, because the voltage is correct.

because the voltage accross the cap is over before, will the cap get weak and output volume get lower. will the resistor change value

all resistor are work perfect, i have tested it.

i just need to make sure the PT and OT no problem, so i just need to change all resistor and cap. that more easy

[kwm488]

hi

i have changed all filter cap. result is the same. and i have tested all resistor, value correct. i will change all film cap.

do you mind to teach me how to change the OT.


http://www.jensen-transformers.com/db.html" onclick="window.open(this.href);return false;
model is JT-DB-E

[paulster]

You can actually use your box as a passive DI (I think) if you don't power connect the mains and plug the guitar into the output jack instead of the input and use the XLR as the output.

From what I can see that will connect the guitar straight to the input to the transformer, so it will act as a passive DI.

Give it a try and see whether it works and how the transformer sounds on its own. I can't verify 100% that it'll work without a schematic but it looks like it should.

If you really want to replace the transformer then all you need to do is to get the same Jensen part and then just make sure that you connect the same colour wires to the same points on the board and on the jacks. It should be an easy change.

[kwm488]

i have tried it. if i don't power on the di box and connect in and out. i just hear very very weak(almost no volume) bass sound.

is it mean a transformer is dead?

please let me know more detail about how to check transformer. i need to make sure it is dead before i buy it

[kwm488]

sorry
few more question

if i use the output jack with the unit is powered, is the signal though the OT? the OT function just for XR output?

as the film cap, if it show the correct uf in my tester, is it mean it is 100% work?

[paulster]

i have tried it. if i don't power on the di box and connect in and out. i just hear very very weak(almost no volume) bass sound.

is it mean a transformer is dead?

Not necessarily. It depends how the unit is wired. My assumption is that the primary of the Jensen is connected to the output jack.

please let me know more detail about how to check transformer. i need to make sure it is dead before i buy it

If you look at the schematic on this page:
http://www.jensen-transformers.com/datashts/dbe.pdf" onclick="window.open(this.href);return false;
You can see how to make it a passive DI temporarily. Just look at the yellow and orange wires and connect them to a 1/4" jack temporarily and use that for your guitar input to see whether the transformer is working as expected when you take an output from the XLR socket. It should be 22dB quieter than when plugged in directly, so if you plug your guitar straight into your M-Audio and set a level for 0dB then when using the passive DI it should be around -22dB. That would be normal behaviour.

if i use the output jack with the unit is powered, is the signal though the OT? the OT function just for XR output?

It wouldn't normally go through the transformer but it is possible.

as the film cap, if it show the correct uf in my tester, is it mean it is 100% work?

Usually. When they fail they tend to fail open circuit or closed circuit, so they wouldn't show a capacitance figure in either of these cases.

[kwm488]

i have replaced all film cap, sound seem same.

now, just OT i guess a problem.

but i think maybe this unit no problem.
my m audio have balance input, i try to plug the bass direct to it, sound very weak and aweful.
if i use this DI or plug direct to m audio instrument in, sound better much. i think this di is design for person which audio interface haven't instrument in. right?

and direct plug to balance input and use this di xlr out is hugh different. so is it mean this unit do his duty? so it is no problem?

now, i just need to make sure the OT no problem. is OT have problem, i should hear any sound ,right?

[kwm488]

thank so much. really really thank. i think this unit is ok or fine. i am happy that you do your best to help me

THank

[kwm488]

but last, i hope to know what happen if the DI OT is dead or hurt? can i still hear sound ?
i check the voltage , the OT input is connect to the signal wire. it is no voltage. so even my PT give double voltage, this is no hurt and releate to the OT, right?

if OT is no problem, i can 100% sure this unit no problem

[paulster]

As I've said before the only way the Jensen transformer could have been damaged was if a DC voltage had got onto its primary by a failed coupling cap, and the DC voltage had then damaged its primary.

Since you've measured no DC voltage on the output jack, which is where the transformer primary would be, and all your coupling caps measure fine, I don't think this has happened.

If you had got DC on the primary it would have been in the region of 100-200V depending on whether the particular triode in the 12AX7 was configured as a plate-load or cathode follower, but regardless this kind of voltage would likely have burned out the primary of your Jensen.

I believe it is completely fine.

[Hendo]

but last, i hope to know what happen if the DI OT is dead or hurt? can i still hear sound ?
i check the voltage , the OT input is connect to the signal wire. it is no voltage. so even my PT give double voltage, this is no hurt and releate to the OT, right?

if OT is no problem, i can 100% sure this unit no problem

Hi kwm488

This thread has been very helpful as I also had an Active DI that needed to be converted from 110v to 220v

I would now like to build a Tube DI like your one for use with an acoustic guitar with a piezo pickup

Are you able to provide information on the components & layout used?

So far it looks like:

1/4 Jack in
1/4 jack out
Balanced XLR out
Jensen DBE OT
220v PT providing 6V & 150V AC (heater & cathode)
12AX7 tube
3,300uf and 47uf filter caps
Bridge rectification for 16v & 150v
Ground switch
boost switch

Can you provide information on how the power tube section & boost is configured, values etc?

Cheers

Hendo