2. amps-preamps
  3. 163711-81570

No preamp?

I struggled making this decision to go direct from Dac to amp and here is where I am at:

I gave up my much loved Hegel h360 and replaced it with the Coda TS v2 , direct to exasound dac. The Coda TS is exactly the same animal as the Coda continuum 8 reviewed by Terry London (minus the dials)

This was a very compelling review and I am thrilled that I went this way.

https://hometheaterreview.com/coda-technologies-continuum-no-8-stereo-amplifier/

Although the Hegel is an obviously great performer, it was not quite to my taste.  I respect what it was able to do and clearly there is synergy with my kef reference1's.  Having said that, there isn't a single area were the hegel bested the Coda, except for possibly soundstage. My suspicion is - and this is hugely naive - that the lack of preamp may be the reason for this, however I have no idea.

I believed the Hegel was quite neutral and organic, however it is not. Slightly lean and laid back, with awesome transparency and a "clean presentation", that was a little dynamically challenged. I thought the low midrange on my Kef reference 1's is a weak spot in an otherwise brilliant speaker. This is where I heard the most profound difference.  

The kefs are now "dynamic" and from the mid bass down everything improved and came alive.  It is like a pillow (a very small pillow) was taken away to produce a more open and full sound. Clearly the class A bias in the Coda makes a difference.

Next step is hearing how integrating a pre may possibly improve what is easily the best sounding, and simplest, home system I have every owned.

Would love some preamp suggestions, or general comments. In the above review the microzotl mz2 headphone amp was used with the Coda, so that is an obvious starting point, but I am sure there are other cost considerate suggestions that make sense.

Any thoughts as to a pre, or am I just wasting my time?
cshadow
georgehifi's avatar
georgehifi
10,312 posts
 


cshadow
Any thoughts as to a pre, or am I just wasting my time?

Wasting time/money, if you get "going direct right"



Your Coda TS V2 is a great amp, bi-polar output, no global feedback, just a little local feedback, and has 26db of gain for full output no problem for any source, and it will drive anything, has current output up to 150amps per channel!!!

Going direct from a dac or cd that has volume control is the only way I would go, for the most transparent, dynamic, uncoloured sound.

NB: But you have to do it via the "50kohm unbalanced inputs" as the balanced 1kohm of the Coda is stupid low impedance, too low for a dac’s output stages to push into, suitable for only the "most gutsy of SS preamps" with very low output impedances EG: Krell ect.
Coda Input Impedance
50k Ohms unbalanced /1k balanced.

This from Stereophile: similar for all Coda amps I see.
The voltage gain into 8 ohms was 28.45dB from the unbalanced input, but 1dB lower from the balanced jack. This discrepancy was explained when I looked at the amplifier’s input impedance: a high 47k ohms unbalanced. It was just 1kohm balanced.
This will tax many preamplifiers, which like to see an input impedance of at least 10k ohms. And if you intend to use a capacitor-coupled tube preamp with the Coda, make sure you use an unbalanced connection or the bass will be prematurely rolled off.
The Coda low input impedance in balanced mode mandates that care be taken in choosing a partnering preamplifier. Otherwise, this is a well-engineered design that performs well. Impressive.—John Atkinson
Cheers George
tomcy6's avatar
tomcy6
2,636 posts
 
There is something up with the 1 kohm balanced input impedance.  It just doesn't make sense.  I had a Coda No. 8 here connected to a PS Audio BHK tube preamp with balanced interconnects.  Based on the low input impedance you would expect rolled off lows and generally poor sound, but that wasn't the case.  The Coda No. 8 performed as well as amps with much higher input impedance.

Someone needs to call up Dave (I think that's it) at Coda and get an explanation.
georgehifi's avatar
georgehifi
10,312 posts
 




There is something up with the 1kohm balanced input impedance. I had a Coda No. 8 here connected to a PS Audio BHK tube preamp with balanced interconnects. Based on the low input impedance you would expect rolled off lows and generally poor sound


It will still work, the response won’t change if the coupling cap on the BHK is large enough, and low enough impedance, dynamic/volume will though, like putting on the brakes slightly in a car and accelerating at the same time.
Into the rca inputs though, it should be more dynamic (no brakes this time, same acceleration) with less volume control position needed "maybe" if both were the same gain.

Analogy: (A bit like pouring a drink into a funnel then into a glass, then doing it without the funnel straight into the glass). The booze still get into your glass in the end.

Cheers George
cshadow OP
21 posts
 
When it comes to impedance and these discussions I am way out of my depth.

Is that why the XLR outs sound way better than RCA's?  Or should it be the opposite?  Confused...
Not to get into a ridiculous cable discussion, but using the cardas neutral reference rca's, vs the Kimber hero XLR was a sad result for the Cardas.  

Clearly I have to get a decent preamp and hear what happens.

Having said that, I can not believe now much better this Coda performs vs the Hegel.  Doug makes a rock solid amp.
tomcy6's avatar
tomcy6
2,636 posts
 
What you need to know about impedance is that you want a low output impedance driving a high input impedance, i.e. a preamp (or DAC) with a 500 ohm output impedance connected to an amp with a 47,000 (47k) ohm input impedance.

The rule of thumb is that the input impedance should be at least 10x the output impedance of the component that preceeds it. This applies to DACs and phono stages too.

The benefit of balanced interconnects (XLR) is that they reject noise better than single ended (RCA) interconnects. Some people say that if your interconnects are not that long, there really isn’t a big difference.

You could do us all a favor if you would call Doug and ask him why the balanced input impedance is so low on his amps. I think he may be measuring it differently because a 1 kohm input impedance is ridiculously low and as you’ve stated Doug doesn’t build junk.

If you would find that out, we could go on to a discussion of whether you want a preamp in your system and what cables you might want to try.
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