Bass DI zod / Reddi ?

[Spencerleehorton]

Yep thats sorted it, into Line input and sounds great! 5 string bass comes alive now!!!!
If anything could do with a bit more gain!!

just got to get it all into a case now and hope it doesnt hum!!!

 

[CJ]

Good deal!

It ain't gonna hum.

What is pri ac and sec ac voltages at 100 hz?

(Voltage ratio)

 

[Spencerleehorton]

For some reason my tube gen only goes down to 122hz today!!
Pri - 795mv
Sec - 1.35v

 

[Spencerleehorton]

 

[Gus]

View attachment 108198

If the heater transformer has enough current you can try a voltage doubler for the heater rectifier section.

 

[Spencerleehorton]

I think I’m only getting 5.5db of gain so this transformer must be way off!!

Will wind another with the second suggestion gauge from CJ.
0.101mm on primary and 0.12mm on secondary.
Want to get about 930ohms on primary and 132 ohm on secondary

 

[Spencerleehorton]

Will check again my voltages and I think I’ve worked out if primary was 0.75v and secondary was 6v this would be about 24db of gain? Is that right?

 

[CJ]

You might have it hooked up backwards,

Primary should have 5 or 10 volts ac. Divide that by about 4 on the output.

 

[Spencerleehorton]

I’ve got the high ohms (680 ohms) connected to B+ and low ohms (38ohm) connected to 300ohm resistors.
As far as I was aware it was a step down transformer?

 

[CJ]

Sounds right.

Yes. It is a step downtown.
Like Leroy Brown.

 

[Spencerleehorton]

I think I’m having some problems with my frequency generator and my tube gen needs some TLC, I do have another but not sure it works will test.
Will test again the primary and see what voltage is across it with my fluke MM as that seems to be the most reliable one.
I will also wind another txf and split the primary (2x2250 turns) so I can measure inductance or at least try with my inductance meter as it only measures up to 20H.
I’m assuming if I get the turns on there and I get close with the resistance I should be close with the inductance? Or does it not work like that?

 

[Spencerleehorton]

It’s all connected in the case but had to have another play with the resistors on B+ as it shot up to 198v?
Settled on 3 x 1.5k and now at 173vdc B+
I’ve measured ac across primary and goes from 7.9v ac to 27.3v ac
From high to low with pot.
Generator is putting in 5.2v at 24hz.
At 100hz it goes from 13vac to 53vac.

 

[Spencerleehorton]

Wound second txf:

Wind 1 - sec - 710T - 0.14mm
Wind 2 - pri - 2250T - 0.1mm 5.5H @ 100hz
Wind 3 - pri - 2250T - 0.1mm 5.5H @ 100hz
Wind 4 - sec - 710T - 0.14mm

Pri - 1000 ohms
Sec - 170 ohms 2H @ 100hz

Txf works much better, used wax paper for gap (grease proof paper)
No hum, more punchy

 

[Spencerleehorton]

On a second test my output level is very low? So I’m questioning whether I’ve hooked this up right and when I then boost the signal it does introduce noise?

I’ve got some new testing equipment coming end of the month so should be able to test inductance up to 200H and getting a new digital scope rather than the dodgy hantek module with laptop(Ubuntu only seems to run it!!)

What level should I expect out?

 

[Spencerleehorton]

When I hook up the xlr output to my line in on my Apollo 16, I get very low level output and when I boost up I get noise.
When I put xlr output into Neve preamp I get nice level out and no noise?

 

[Spencerleehorton]

So it seems that with 220R and the 470uf. On the cathode im only getting 1.2v which as Ian put is only 5mA and I need 1.8v at nearly 9mA.
Shall I try 100R in replace if 220R? Or what cathode resistor?

 

[Spencerleehorton]

Checked voltages today and everything is way off!! Going to try a different tube as I suspect a dodgy tube has been my problem all along!!

 

[Spencerleehorton]

for some unknown reason i had lost my gnd on the cathode? i've also changed the cathode resistor from 220R to 300R and get 3.1v, i then changed to 150R and get 2.1v, 2 x 220R gets me 110R and 1.73v
so probably 120R is the best to use here.

 

[Spencerleehorton]

also thought it was my patchbay playing up but when i use the other jack for an dry output for either bass amp or into interface it cuts the signal by at least half and kills all the low end?

 

[Spencerleehorton]

have also tried powering the heaters from AC rather than DC and within this case it doesn't work, too much noise, also did a CT using 2x100R and was slightly better but still not as good as the DC version. The DC version was still a little noisey.
Will go back to DC heaters and might try a bit of steel in there or some mumetal and see if shielding the txf helps?