JDS Labs C5 portable amplifier appreciation + discussion thread (check 1st post for review) - Page 32

Looking at picking one of these up, Anyone have any problems with the volume controls? Never used a portable amp but it looks like the volume control has a chance of rubbing up against something and getting cranked up to deafening levels(say if i had it loose in a backpack). Is there any type of hold feature or is this a non-issue
 

Quote:

Originally Posted by jonny564 

Looking at picking one of these up, Anyone have any problems with the volume controls? Never used a portable amp but it looks like the volume control has a chance of rubbing up against something and getting cranked up to deafening levels(say if i had it loose in a backpack). Is there any type of hold feature or is this a non-issue
 

Agree with randomkid.  I've only had it for a week.  Wrapping up my 4 flight travel week and haven't had a single instance of an incidental volume change.  I put it in my slacks pocket, my snugger jean pockets, shirt pocket, and laptop bag.  All good!

Quote:

Originally Posted by miceblue 

Also, why did you define rOut and vUnld, and then re-defined them later in the scrypt?

Because it can be calculated in two different ways from the available data, and the results do not agree (that is not necessarily a problem with the specs, because the total open loop output impedance - which also includes internal components of the op amp, the power supply, and the virtual ground, if there is one - is likely non-linear). The first method uses the known unloaded output voltage, and one of the voltages with a load, by solving the equation

v150 = vUnld * 150 / (150 + rOut)

for rOut. This way, the output voltage calculated for the 600 Ω load would be slightly higher than the specified value. Alternatively, the two loaded voltages can be used, and solving these equations

v150 = vUnld * 150 / (150 + rOut)
v600 = vUnld * 600 / (600 + rOut)

for vUnld and rOut gives parameters with which the results are correct for both the 150 and 600 Ω loads, but this time the maximum unloaded voltage does not agree with the specifications (it is 12.8 Vpp instead of 14). The formula for rOut actually simply divides the voltage difference by the current difference. Initially, I chose the first approach, but then added lines 11 and 12 to modify the script to use the second one. With those lines removed, the results are:

 16 ohms: V = 0.509 Vrms, Ipeak = 45.0 mA, P = 16.2 mW
 32 ohms: V = 1.018 Vrms, Ipeak = 45.0 mA, P = 32.4 mW
 50 ohms: V = 1.591 Vrms, Ipeak = 45.0 mA, P = 50.6 mW
 62 ohms: V = 1.973 Vrms, Ipeak = 45.0 mA, P = 62.8 mW
150 ohms: V = 3.337 Vrms, Ipeak = 31.5 mA, P = 74.2 mW
300 ohms: V = 3.986 Vrms, Ipeak = 18.8 mA, P = 53.0 mW
600 ohms: V = 4.416 Vrms, Ipeak = 10.4 mA, P = 32.5 mW

The difference is not major, but with all the low impedance loads, the maximum power is determined by the (not necessarily correct) current limit.

Ultimately, it is only possible to get reliable and accurate values by actually measuring the amplifier with the various loads, especially in the case of the lower impedance ones.

Quote:

Originally Posted by jonny564 

Looking at picking one of these up, Anyone have any problems with the volume controls? Never used a portable amp but it looks like the volume control has a chance of rubbing up against something and getting cranked up to deafening levels(say if i had it loose in a backpack). Is there any type of hold feature or is this a non-issue

I haven't had any problems with the volume control getting too loud. On the contrary though, I often listen at "volume 1", so sometimes I accidentally press volume down and I don't hear anything.

The volume control is almost flush with the metal surface, so the chances of accidentally moving it are pretty slim, and even more so when you have the source/headphone jacks sticking out. The volume level takes 3.5 seconds to go from 0 volume to max, so there shouldn't be a problem about it reaching deafening levels. There's no hold feature.

Quote:

Originally Posted by randomkid 

Plus you used high gain, that might make a difference. With IEMs on volume 1, low gain, it might last longer. Volume one if sufficiently loud for my CIEM

Does a higher gain suck-up more battery life?

I figured volume level was probably the biggest factor, and if the volume level is the same regardless of the gain, then the battery drains at the same rate.

In any case, the higher gain on volume step 4 of 63 should be plenty of volume for louder music instead of the quiet music I was playing (which I found to be the bare minimum volume to use while riding in a noisy public bus with the fairly sensitive V-MODA M-100's).

Quote:

Originally Posted by akash neagi 

anyone tried them with the MDR-1R, SRH840 or XBA3?????

I don't have a SRH840, but I have the SRH940 and it sounds pretty good with the C5 to me. The bass boost also does wonders for that headphone.