Eckmiller TS10 + HS10 -- impedance issues

[wholefoods]

Hello all,

I am racking a couple of Eckmiller TS10 + HS10 hi-lo filters to be integrated into a modern studio. These units are 200/200Ω. I am aware the impedance of these units has been discussed before. I gathered that many people strap resistors across the output to bring the output impedance closer to 600Ω. However, I am still having trouble getting a frequency response that is usable. I am curious if other people have the same experience or if I'm doing something wrong. I am a monkey when it comes to electronics (my background is software - different breed, different way of thinking) so any and all help is greatly appreciated.



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Ultimately, I would like these to play nice with the Burl Mothership converters (BAD8 and BDA8 cards). I don't have specs for impedance of the converters but I imagine it is a typical range for modern bridging gear.

Upon first sound tests, I could tell immediately they were dumping a bunch of lo-end while in ‘bypass' (the “<>” symbol). I tried several value resistors strapped across the output but none of them seem to give me a flat response without losing a ton of level.

I am using FuzzMeasure to get the frequency response of the units.




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Here is a frequency sweep of the unit in BYPASS. First, I just did a loop with the converters to get a base measurement (red line at top). I then did sweeps using different value resistors across the outputs. You can see the level drop as I reduce the value of the resistor. At 150Ω, the response is looking good but I’m now -12dB from unity.

BURGUNDY = interface loop, control
PURPLE = no resistor across outputs
CYAN = 680Ω
MAGENTA = 220Ω
GREEN = 150Ω






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Here is a frequency sweep of the unit with 113Hz HPF and 8kHZ LPF. This is where **** gets crazy - and certainly unusable.

BURGUNDY = interface loop, control
ORANGE = no resistor across outputs
GREEN = 680Ω
RED = 220Ω
YELLOW = 150Ω



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The 220Ω and 150Ω resistors across the output seem to be giving the best response. But the level drop is too severe. My next guess was to try a 200:600Ω transformer to try to change the output impedance without losing level. I wonder if the Burl converters are not providing the proper source or load impedance for my use case. Do I need to place the units between 600Ω impedance matching gear to get a proper response? Like an 1176 for example.

Any and all comments are welcome. If anyone is willing to lend a helping hand - and get me up and running - I would gladly send you a PayPal for beer money as a token of gratitude.

 

[Michael Tibes]

While some connections of the units are a bit of a mystery to me, I believe they have to be connected with pin 1 and 2 of the TS10 as input, pin 7 and 8 of the TS10 go to pin 1 and 2 of the HS10. Pin 7 and 8 of the HS10 should be the output, which has to be loaded with 200R. That would be the input impedance of the following device (typically 10kish nowadys) in parallel with a possible additional load resistor. The value should not be too critical, so a 200 - 210R resistor across the output should be fine with a 10k input, 300R for a 600R input. The insertion loss should be about 2 dB.

What the purpose of the circuit points going to pin 3 and 4 of both units is, is unclear to me.

A 200 R load is on the low side for some modern equipment, but that should rather cause distortion than a warbled frequency response, that's why I wonder if the units are connected correctly?

 

[ruffrecords]

IF this EQ is meant to be 200 ohm in and out then to work properly it needs to be fed from a source impedance of 200 ohms and the output leeds to be loaded with 200 ohms. You need to get both ends right for the correct response. If this is a passive filter then, connected as above, the insertion loss will be 6dB when controls are set to flat. That's how they were meant to work.

Cheers

Ian

 

[C.B. - Boudio]

Weren't they supposed to be driven from a 20 ohm source, like a V72?

 

[Michael Tibes]

The manual states an insertion loss of less than 2 dB (Einschaltdämpfung <= 2dB) while the frequency response chart shows 0dB loss, a 'generator resistance' of 200R 'for real' (Generatorwiderstand = 200 Ohm reell) and an output load of 200R 'for real' (Belastung am Ausgang des Geräteabschlusses = 200R reell). It also states 'Z-Wert am Ein- und Ausgang im Mittel = 200R', which I would translate into 'impedance at in- and output on average 200R'.

I am a bit puzzled how it all comes together and how to put that into practice? 200 R as generator means 100R in each leg in case of a near zero output impedance of the generator and the output of the HS10 has to be loaded with 200 R in total, input impedance of the receiver in parallel with a possible load resistor? This should result in a 6 dB insertion loss, as Ian said. Not the less than 2 dB stated in the manual.

And what are the connections on pin 3 and 4 of each unit good for?

 

[ruffrecords]

I suspect the insertion less they quote in the spec is over and above the 6dB loss you get with 200 ohm source and load. The frequency response is relative to 1KHz not an absolute values(rel. Dampfung).

Cheers

Ian

 

[Michael Tibes]

The frequency response is relative to 1KHz not an absolute values(rel. Dampfung).

Good catch, praised are those who can read

 

[wholefoods]

While some connections of the units are a bit of a mystery to me, I believe they have to be connected with pin 1 and 2 of the TS10 as input, pin 7 and 8 of the TS10 go to pin 1 and 2 of the HS10. Pin 7 and 8 of the HS10 should be the output, which has to be loaded with 200R.

A 200 R load is on the low side for some modern equipment, but that should rather cause distortion than a warbled frequency response, that's why I wonder if the units are connected correctly?

Hi Michael, thanks for your input. I have both the TS10 and HS10 units hooked up as follows. First in the chain is TS10, followed by HS10.

IN + (1)
IN - (2)
IN GRND (6)

OUT GRND (6)
OUT + (7)
OUT - (8)


Pins 3-5 are unused. Various resistors (shunt) tested across the output of the HS10 (pins 7 & 8).