[wuwhere]

Quote:

Coax are 75 ohms.

Nope. There are 50 and 75 Ohms coax. Even Agilent makes 50 and 75 Ohms Spectrum Analyzers that I've used for coax application in a coax network like a cable plant. I think there is a difference of 7dBmV. But I could be wrong.

 

[mrarroyo]

Coax as intended for the gear we use for audio is 75 db. The information below is from Wikipedia.
 
 
 
Quote:

Significance of impedance

The best coaxial cable impedances in high-power, high-voltage, and low-attenuation applications were experimentally determined in 1929 at Bell Laboratories to be 30, 60, and 77 Ω respectively. For an air dielectric coaxial cable with a diameter of 10 mm the attenuation is lowest at 77 ohms when calculated for 10 GHz.[1] The curve showing the power handling maxima at 30 ohms can be found here:[2]

CATV systems were one of the first applications for very large quantities of coaxial cable. CATV is typically using such low levels of RF power that power handling and high voltage breakdown characteristics were totally unimportant when compared to attenuation. Moreover, many CATV headends used 300 ohm folded dipole antennas to receive off the air TV signals. 75 ohm coax made a nice 4:1 balun transformer for these antennas as well as presented a nice attenuation specification. But this is a bit of a red herring: when normal dielectrics are added to the equation the best loss impedance drops down to values between 64 and 52 ohms. Details and a graph showing this effect can be found here:[3]^{[citation needed]} 30 Ω cable is more difficult to manufacture due to the much larger center conductor and the stiffness and weight it adds.

The arithmetic mean between 30 ohms and 77 ohms is 53.5; the geometric mean is 48 ohms. The selection of 50 ohms as a compromise between power handling capability and attenuation is generally cited as the reason for the number.

One reference to a paper presented by Bird Electronic Corp as to why 50 ohms was chosen can be found here: [4]

50 Ohms works out well for other reasons, such as that it corresponds very closely to the drive impedance of a half wave dipole antenna in real environments, and provides an acceptable match to the drive impedance of quarter wave monopoles as well. 73 Ω is an exact match for a centre fed dipole aerial/antenna in free space (approximated by very high dipoles without ground reflections).

RG-62 is a 93 ohm coaxial cable, originally used in mainframe computer networks in the 1970s and early 1980s. It was the cable used to connect the terminals (IBM 3270) to the terminal cluster controllers (IBM 3274/3174). Later, some manufacturers of LAN equipment, such as Datapoint for ARCNET, adopted RG-62 as their coaxial cable standard. It has the lowest capacitance per unit length when compared to other coaxial cables of similar size. Capacitance is the enemy of square wave data transmission and is much more important than power handling or attenuation specifications in these environments.

All of the components of a coaxial system should have the same impedance to reduce internal reflections at connections between components. Such reflections increase signal loss and can result in the reflected signal reaching a receiver with a slight delay from the original. In analog video or TV systems this visual effect is commonly referred to as ghosting. (see Impedance matching)

 

[twylight]

Just wanted to say Ibasso serviced my D10 very fast - kudos!

 

[Armaegis]

Phew, my opamp impressions post (p266#3984) is starting to get kinda long. I recently got a bunch more opamps from Ron and have been experimenting. Some quick notes:
 
- the latest topkit (TLE2141/EL8201) feels slightly tubey and airy
- EL8201 as buffers takes everything I like about LMH6643 and does it better (smoother and more relaxed)
- AD8599 as opamp is really bright
- OPA 2227p as opamp just grabbed me right at the start
- LT 3158 as opamp made me feel like I was listening to an AKG through my Shures

 

[HiFlight]

OPA2227 + EL8201 has always been a nice-sounding combination, especially with phones or IEMs that tend to be lighter in the bass octaves.  This combination might, however,  be too dark for bassy-heavy phones. 

 

[Armaegis]

My tastes are definitely leaning towards the dark side of things (I'm sure there's a Star Wars joke in here somewhere). AD4841 and AD8599 were almost unlistenable for me.

 

[Punkfans]

thought I might just post it here, hope it's not off topic
 
I got mine about 2 weeks ago, so far I've experienced some problem when using it as a DAC via USB, I'm using WASAPI and DS for output. From time to time, I heard sizzle when using WASAPI, sometimes with DS as well. It just got worse and worse then eventually stopped working. I had to change to another track or restart foobar.
 
In the worst case, I can saw from the "playback devices" management window that it was occupied, the volume bar was moving up and down, but nothing really was working.  I had to unplug it then replug. 
 
this only happened when using it as a DAC, while connected via AUX, no problem at all.
I'm using windows 7 ultimate 64bit, AMD cpu, 4 gb ram, and yes, I have disable the Aero themes. I hope mine is not defected,  so what am I missing? any ideas?

 

[Armaegis]

Does anyone know if the opamps we use for the D10 are all compatible with the Travagans Red speaker/headphone amp? I've read in headphoneaddict's review of the Travagans that he used the AD743, but how about some others?

 

[HeadphoneAddict]

Quote:

Does anyone know if the opamps we use for the D10 are all compatible with the Travagans Red speaker/headphone amp? I've read in headphoneaddict's review of the Travagans that he used the AD743, but how about some others?

Many of the same opamps will work.  Some that worked in the D10 didn't work in the Travagans Red and I noted them in my Red review.  Remember that the AD743 are two single channel opamps on a 2:1 adapter, and it needs to be a very small 2:1 adapter for the D10 (HiFlight has perfected the size in his opamp kits).  While the OPA627 work very well on a 2:1 adapter in the Travagans Red, the D10 doesn't give them enough power to sound good in that role.

 

[HiFlight]

Quote:

Does anyone know if the opamps we use for the D10 are all compatible with the Travagans Red speaker/headphone amp? I've read in headphoneaddict's review of the Travagans that he used the AD743, but how about some others?

All of the D10 Topkit LR modules can be used in the Travagans Red, but do not use the EL8201, as it cannot tolerate the supply voltage used in the Red. 

 

[Armaegis]

If I look up the opamp specs online, which values should I looking at to determine compatibility?

 

[antyr]

I just ordered some 6,3V 220uF BlackGate caps and found an experienced DIYer near to me who will do the soldering. My question is: Do the BGs HAVE to be bypassed in order to make a big change or is it just another tweak to install them in "bypassed mode"?
 
Do the bypass caps influence the sound signature as much as the BG caps in the signal path themselves? What bypass caps do you suggest if so?
 
And to HiFlights topkit: Would you think that it is a good couple for my Beyerdynamic DT880 250Ohm?
 
Cheers,
 
antyr
 
 
PS: For those who want to order BG caps: THLaudio in Taiwan is selling some for a reasonable price. Just ask at info@thlaudio.com

 

[jamato8]

If Black Gates are bypassed it is better to do it with another BG. They play well with each other but not with others. The 220uf is a nice cap. I would just go with it as there is only so much room and they do good with themselves. The 22uf is good but again, there is only so much room. 

 

[slickooz]

How is the D10 with ultimate ears tf-10?

 

[HeadphoneAddict]

Quote:

How is the D10 with ultimate ears tf-10?

I thought it was a good pairing and works better than my D4 with the TF10 to fill in the mids and keep the highs smooth.