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
tomcy6's avatar
tomcy6
2,545 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.
georgehifi's avatar
georgehifi
10,312 posts
 
The benefit of balanced interconnects (XLR) is that they reject noise better than single ended (RCA) interconnects.
Only over very long distance >5mts, and if in a studio where there's wires on top of wires.
Cheers George
cshadow OP
21 posts
 
"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."

Great suggestion.

Called Doug and he told me that the 1 Kohm is just not the case.  It says so on the Coda site, however he said this was in production for a short time and if fact it is actually 10 kohm and should be fine for any decent tube pre if that is the issue.

In addition he told me a lot about noise floor and a lot more that was just over my head.  

Hope this helps
tomcy6's avatar
tomcy6
2,545 posts
 
Thanks cshadow.  10k ohms, although that's still low, makes more sense.  Doug could do himself a favor if he would update his webpage.  It's so out of date and has enough errors, like the impedance, that it's not much help.

As I said, I had a BHK tube preamp connected to the balanced inputs and couldn't hear any negative effects.  Pass Labs used to have a 10k ohm input impedance on at least some of their amps and finally upped it.  I guess they got tired of questions about it.

You should keep the output impedance of any DAC or preamp you hook up to the Coda below 1k ohms.  Any solid state preamp and most tube preamps should be OK.  I'm not familiar with  the output impedance of DACs.

As far as preamp recommendations go, the Coda 07x FET Preamplifier is said to have good synergy with the No. 8.
georgehifi's avatar
georgehifi
10,312 posts
 
Thanks cshadow. 10k ohms, although that’s still low
Correct too low for passive pre’s and most tube preamps.
And you need to make sure the output coupling cap on each of the tube preamp channels if using one, is 3.3uF or bigger which will be -3db at 5hz. Any smaller than 3.3uF and you’ll hear the low bass being rolled off.

Cheers George
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