Bass DI zod / Reddi ?

[Spencerleehorton]

Hi all,

I’m now looking to build or use what I’ve got for a killer bass di.
At the moment I’m Di’ing the bass and mixing the bass amp and getting some nice sounds with minimal compression and EQ.
I’m using a passive DI box to split the signal and using either Neve 1290 pres or API-312 pre amps.
I have a dbx mini pre which I haven’t tried yet to di the bass, will feedback my results.
I’m micing the bass amp with a t bone RB500 ribbon mic which can take 146db.

Thinking about building a reddi tube di or if possible the zod tube di.

Wanted to know any thoughts on this.

 

[Spencerleehorton]

I've given the DBX mini-pre a go and its too noisey, the LA-2A which i have works well with a API-312 preamp, bit of EQ and compression and sounds great.
More intrieged to build the REDDI DI now to compare.

 

[Newmarket]

What is the dbx pre ?

 

[ruffrecords]

I am not familiar with the Zod DI. Is there a schematic of it?

Cheers

ian

 

[dmp]

Thinking about building a reddi tube di or if possible the zod tube di.

There was a great thread here figuring out a tube DI like the REDDI using a 6N1P
I built a pair using CJ wound transformers (8k:600, EI100 I think) and they are fantastic.
Simple build on turret board.

 

[Spencerleehorton]

The missing piece of the puzzle now is to get a power transformer for the 2x170vac @ 9mA and 8vac @ 600mA.
Or I could wind my own!!!

 

[Spencerleehorton]

No schematic that I know of yet for this one, it’s pretty pricey £800!!!

https://zodaudio.com/id-di/

 

[Spencerleehorton]

CJ has very kindly given me the output txf winding specs so I’ll wind one up and start making the turret boards.
Still need to either get 2x170vac @ 10mA txf and a 8vac @ 600mA txf, or wind my own.
Winding my own I need to know wire gauge and turns per wind, will try and work out but if anyone could chip in so I can verify would be helpful!!!

 

[CJ]

random wound works fine,

look up wire AWG gauges and convert to metric by x 25.4.

 

[Spencerleehorton]

I’ve found a mains txf on eBay which gives 170v and 6.3v so after diode bridge should be able to tweak down from 240vdc by dropping 70v with 3 x 2.2k resistors.
6.3v is made for 700mA so should cope fine.

 

[Spencerleehorton]

I’ve wound my first test output txf and I upped the gauge wire as I didn’t have the small wire here yet. Kept the same turns and kept the same ratio in gauge difference.
Pri test at 2H inductance @ 100hz and my inductance tester won’t register the secondary as it’s beyond the 20H it can measure so I will need to measure with my scope, resistances are well below what they should be and I’ve kept the turns the same and my core is 25mm2 (1”) so it should be 75H upwards by my preliminary calculations.

 

[CJ]

You have a signal generator?

 

[Spencerleehorton]

Yes but it’s a digital laptop one, got a nice old valve frequency generator which has ohm output and 600ohm output?

 

[Spencerleehorton]

Ok, I have a valve frequency generator 20hz-50khz has 5ohm and 600ohm output and I have a laptop with a hantek 6022be scope.

I have set the generator to 600ohm output at 20khz.
I then adjust for output to 1v p2p @ 20khz.
Then put the txf winding in parallel and see the voltage drop.
I then adjust frequency on generator to show 500mv and write down frequency

L = 4.57 / f = henries

L = 4.57 / 253 = 0.0180

But this equation is for a 50ohm output on a generator?

Could someone point me in the right direction please?

 

[volker]

Could someone point me in the right direction please?

Your measurements are a bit pointless because the transformer is used with DC in the circuit. So unless you supply the appropriate DC current as well it's not much use. You did include a gap, right?

 

[Spencerleehorton]

I didn’t put a piece of paper in there as I read that CJ didn’t have anything in there?
I just wanted to know if inductance is close.
It says 3-5mil gap?

 

[Spencerleehorton]

so I need 8mA and gapped with something that’s 3-5mil?
5mil = 0.127mm

Paper is 0.05 - 0.1mm thick

 

[CJ]

ok so use 20 Hz, not 20 Kilo Hz.

the steel is not fast enough for 20 k hz so it drops out of the equation.

600 ohm output is fine, that is what i use,

set sig gen for max level, i get 20 volta rms out of mine,

insert ac ammeter in series, do you have ac ammeter?

measure current

divide voltage by current, (ohms law, of course)

this is your inductive reactance which is directly proportional to inductance

so all you have to do is divide the reactance by 2 * pi (6.28)

then divide by frequency and you are done

since i use 20 hz all the time and 2 pi all the time, i use the constant

6.28 * 20 = 125.6.

so inductance will be V/(125.6 * I) bam.

 

[Spencerleehorton]

That’s great stuff, I have a multimeter I can use as ammeter.
Once I finish my night shift and have a rest I’ll plug it all in and see what I get!!
Thanks again CJ.

 

[Spencerleehorton]

When I connect my multimeter set in uA AC mode in series I get 9.3.
Generator set to 24hz lowest it goes and probe in series.
Out generator 600ohm into probe, gnd of probe to uA on MM, com of MM to gnd on generator.
Scope says 10.2v at 24.420hz
MM is 9.3

V = 10.2 / 9.3 = 1.096

1.096 / 6.28 = 0.1746

0.1746 / 24.420 = 0.00715

?