EEVBlog #1103 - Omicron Labs Bode 100 Review & Experiments

[Bud]

Mouser and Vishay singing audiophile praise to MELF resistors, with the familiar "no distortion" thingie.
 

High-end audiophiles want their analog-to-digital converters (ADC) and digital-to-analog converters (DAC) and amplifiers to exhibit the lowest noise possible and be ultra-stable. MELFs delight audiophiles because they deliver low noise performance, uniform component design, excellent stability and precision, and best of all, they provide nearly ideal resistor performance – introducing essentially no discernable signal distortion to pass through.

https://www.mouser.com/blog/reating-a-sound-people-cant-resist-melf-resistors

[Kleinstein]

Form the color code those resistor seem the be 5.1 K and 1 K with 0.1% tolerance. They might be used for there low tolerance, maybe in a kind of differential amplifier between the AD834 mixer and the ADC.

Compared to smaller SMD resistors the MILF form factor might offer a slightly better excess noise because more resistive material is used, though I doubt this would be a factor here.

[Bud]

There are 0.1% low thermal PPM SMD resistors, you do not have to use MELF ones .

[voltsandjolts]

"MELF Resistors - The World’s Most Reliable and Predictable, High-Performing Film Resistors"

Long-term  stability results in a superior maximum resistance change (ΔR/R) of 0.05  %  after  8000  h  operation  for  high  precision  MELF resistors.

If MELF does indeed have superior long term stability, maybe that was a deciding factor for them.

[Bud]

Yes i was also thinking about better aging characteristics as a possible reason

[precaud]

Given the target customer for their gear, Omicron was very brave to give this unit for an Eevblog review!

They intimated exactly this in their recent newsletter:
"...And this is the moment when you have to take risks. Risks like sending a Bode 100 to Dave at EEVblog."

[Wolfgang]

The isolation transformer seems to use a regular Hammond type aluminum cast enclosure. Perhaps $8 a piece or something. The main unit seems to use a standard enclosure as well. Nothing against it in terms of performance but I'd think for the selling price something custom could be made to stand out better.

Hi,

now I have the opportunity to test the B-WIT100 and a functionally equivalent homebrew transformer on a Bode 100 and on the sharpest knife of LF VNAs, a Keysight E5061B-3L5 (35k$, 5Hz to 3GHz). A few € wont do the job, but with about 70€ you can homebrew something decent:

https://electronicprojectsforfun.wordpress.com/injection-transformers/

at the bottom.

[Bud]

The VAC T60006-L2030-W514 core appears to be something exotic, $30 Canuck bucks here at Mouser plus shipping, i will probably pass.

[precaud]

I picked up a T60006-L2030-W423 from the Mouse for about 1/3 that much. I want to play around with a 2:1 winding.

[Wolfgang]

The VAC T60006-L2030-W514 core appears to be something exotic, $30 Canuck bucks here at Mouser plus shipping, i will probably pass.

I picked up a T60006-L2030-W423 from the Mouse for about 1/3 that much. I want to play around with a 2:1 winding.

Please tell me about the results. My prediction is:
Als long the coupling inductance is in the range of 200mH and strays are low (less than 1uH) results will be comparable. A look at Omirons SPICE model gives you some idea:

* BWIT 100 WIDEBAND INJECTION TRANSFORMER MODEL
* CREATED BY OMICRON Lab ON APRIL 7, 2011
* VERSION 1.0
*
* CONNECTIONS: PRIMARY SIDE SIGNAL
*     
| PRIMARY SIDE GROUND
*              | | ISOLATED OUTPUT 1
*              | | | ISOLATED OUTPUT 2
*              | | | |
*              | | | |
.SUBCKT BWIT   1 2 3 4
* CAPACITORS
CPRI 1 2 14e-12
CPRISEC 1 3 85e-12
CSEC 3 4 14e-12
*
RESISTORS
RPRI 1 5 0.36
RCORE 6 2 35e3
RSEC 8 3 0.362
* INDUCTANCES
LLEAKPRI 5 6 0.85e-6
LLEAKSEC 7 8 0.85e-6
LMAG 6 2 199e-3
* IDEAL 1TO1 TRANSFORMER
E 9 4 6 2 1
F 6 2 VM 1
VM 9 7
.ENDS BWIT

Probably a lot of similar cores with the same material would do.

[Alextsu]

I realise the Analog Discovery has nowhere near the breadth of capability the Omicron has but it would be interesting to see a few comparisons.

Does the Analog Discovery FRA give comparable results, at least within it's comfort zone?

Could not compare Analog Discovery (=AD) FRA's performance directly against any of those kilo-$ FRAs like Omicron or Venable. It would be interesting to know if anyone has a chance to test it.
But I tried AD to measure Gain-Phase response of a very noisy DIY AC-DC swithcing PSU. The DUT PSU had a high enough conducted EMI level so all my attempts to measure it's frequency responce with USB PC scope-based FRAs failed.   
Surprisingly, AD was the ONLY device among other low-cost FRAs that gave a well-defined FRA responce of DUT PSU.

[rbola35618]

Can you show us some of your plots. I am interested in seeing your results. 
Robert Bolanos

[EEVblog]

The isolation transformer seems to use a regular Hammond type aluminum cast enclosure. Perhaps $8 a piece or something. The main unit seems to use a standard enclosure as well. Nothing against it in terms of performance but I'd think for the selling price something custom could be made to stand out better.

Hi,
now I have the opportunity to test the B-WIT100 and a functionally equivalent homebrew transformer on a Bode 100 and on the sharpest knife of LF VNAs, a Keysight E5061B-3L5 (35k$, 5Hz to 3GHz). A few € wont do the job, but with about 70€ you can homebrew something decent:
https://electronicprojectsforfun.wordpress.com/injection-transformers/
at the bottom.

EEVblog APPROVED! 

[Wolfgang]

Dave, you need to look forward to my "Nude Virgin Current Injector" !

Stay tuned
  Wolfgang

[BFX]

Not nude but injector
Parameters are similar or mostly better like original