SKA GB150D now public domain...

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weskoki

weskoki

Member
Joined 2009
still4given said:
Hi PinPing,

I just finished my Ovation nx amp today. I took some time to make comparisons of about 5 amps including the nx, SKA, VSSA, DX Super A, & Honey Badger just because they were all handy. I have an A/B setup utilizing a dual pot arrangement and a speaker switch. The two pots allow me to equalize the volume of the two amps and the speaker switch allow both amps to share the same pair of speakers which gives me instant switchablity. I'm using a pair of JBL 4412 speakers for the test. I would love to have someone who thinks they could tell the difference between amps to come have a listen. They are all so close that one click on a pot, up or down could fool anyone. The SKA is oh so slightly less detailed than the others. That is a good thing on a lot of music. Especially now a days when the engineers think they need to add "air" to all the vocals. The SKA tends to tame that a little. Nothing is missing, just tamer. Perhaps that is why it gets compared to valve amps. If you are looking for someone to tell you one amp is superior to another, it won't be me. Ever since I built the A/B setup, I have realized that once you get amps to the level of the Blameless, Leach, VSSA, SKA.......well, they are so clean and full, it is just all but impossible to tell them apart. The SKA GB150 is a really good sounding amp. It doesn't require any unobtainium parts or even expensive ones. It is a fun build and fits in a small case with average size heatsinks. What's not to like? I say build it. If you don't love it, give it to someone that will and build something else. You wouldn't be here if you don't want to build and learn. Certainly you could just buy a nice amp on ebay if all you need is an amp.

Blessings, Terry
Click to expand...



Hi Terry

Could you spare some time describing the VSSA vs Ska?
I wonder if i should build one.
 
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PJN

Member
Joined 2004
I have had a GB150 SKA for several years that I got as a kit from Greg Ball. It is a great sounding amp, and I found Greg to be a very helpful and nice guy when I needed advice. My SKA has been rock solid and can hold it's own with other amps that I have (F5, AlephJ, Honey Badger).

PJN
 
still4given

still4given

Member
Joined 2004
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PingPing

Banned
Joined 2014
Hi AndrewT, thanks and can you explain/show what a buffered pot is and what would be suitable in this case?

Can you also explain why a 10k log pot with an output impedance maximum of 2k5 would just about suit a 27k input? Also, how do you workout the output impedance of a log pot?

thanks:)
 
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AndrewT

R.I.P.
Joined 2004
Most will recommend that the receiver impedance be at least 5 times the transmit impedance and many agree that a 10:1 ratio is good enough.

I tend towards 20:1, even though I know that 10:1 works.

A 10k vol pot with a 20:1 ratio requires a source with an output impedance ~ 500ohms.
Many reasonable quality Sources get below 500r.

The 10k vol pot with a maximum output impedance of 2500ohms would require at least 12k for the receiver and preferably >25k.
Your receiver falls into this bracket.

But a 2k5 source impedance is very susceptible to losing treble due to cable and receiver capacitance. You need to keep the connection capacitances very low for good treble performance.

A buffered vol pot is simply a vol pot with a buffer on it's output.

The vol pot can be any value that suits all your Sources, typically 10k to 500k.
The buffer should be designed to drive any domestic style interconnect. The output impedance of the buffer can be anywhere from 1ohm to 200ohms. Some will even have an added resistor to ensure it is capable of driving any capacitance without damage/oscillation.

A buffered vol pot can drive a long cable and thus be placed in any convenient position that makes adjustment easy.

I mount my amplifiers behind my speakers.
I don't want to have to fiddle around behind the speakers each time I adjust the volume.

I have used Hyp, Mez and Perander's, all work well and drive 3m of star quad interconnect.
I will shortly experiment with Calvin's which can double as a headphone driver.
 
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