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Old 26th February 2009, 02:23 AM   #1
jonnoh is offline jonnoh  Australia
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Default Volume pot/buffer/optical control

Hello there,

I have just recently made an AKSA 55. I have to say I am surprised by the sound; I would not have thought that the design of the electronics could have made such a difference; at least compared to the analogue things like microphones, speakers.

Anyway, I was thinking of getting rid of my old preamp and using either a) a simple potentiometer, or b) via Greg Ball (Of SKA) his volume buffer or his optical control.

Alternatively a Pass Labs buffer. I dont need all the inputs on my preamp, probably only using either a cd player and DVD player.

Does anyone have an opinion whether a pot will do the job, or do people from experience find the other more complicated buffers/controls sound better?

Thanks in advance.
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Old 18th February 2010, 01:45 AM   #2
udailey is offline udailey  United States
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You might first ask Mr AKSA himself if you will be needing a buffer. A buffer can change the sound. Some of it better like the bass and some of it not as great like flattening the depth of the soundstage. Passives are awesome if the right cdp and amp are used. Its good to have a cdp with low output impedance. Mine apparently puts out 2V of signal and I dont have problems driving any pot so far. Have not tried something with a .9V output or similar. Might be fine, but like I said AKSA is the first guy to ask and he is frequently on this forum.
Uriah
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Old 18th February 2010, 02:22 AM   #3
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I'm using one of these amps also, with a recently completed DCB1 from the group buy. I built an optical attenuator using Uriah's LDR's. Still burning in, but I think this a big step up from the cheap 10k alps "passive pre" I had before. The AKSA needs only 650 mV for full output, and has 47k input impedance. I think it's a good candidate for a quality buffer like the B1. My AKSA is stock except for some boutique caps at the input (forms part of my passive line level crossover). I configured mine to have the ability to easily bypass the buffer completely, and use only the LDR attenutor. I plan to experiment with this myself, it's nice to have options. This is one of the many aspects I enjoy about diy. I think Hugh recommends a cermet pot law-faked with a resistor? Can't remember for sure on this, it's been a long time since I got the amp together.
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Old 18th February 2010, 05:31 AM   #4
rabbitz is offline rabbitz  Australia
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I found a buffer with a very low output impedance has worked the best with all my AKSAs. The B1 wasn't a very good match but the Burson was great.

I have a CD player with an output less than 50R and still benefited from the use of a buffer instead of a passive pre.

I've tried several DIY pre / buffers like the B1, GK-1, P88, SKPre, op amp based, etc but in the end I went with a commercial pre amp.
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Old 18th February 2010, 12:45 PM   #5
udailey is offline udailey  United States
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Well, the good thing is that you have a lot of options. If you want to try buffers there are 3 variants of B1 around right now. The original, the DCB1 and the BF862 B1 by either Juma or EUVL, forget which.
There are several tube buffers on Ebay, none of which I have heard wonderful things about but have heard that they are nice, just not special.
In the Lightspeed thread, however negative the poor thread has turned out, George shows a circuit for a simple tube buffer that would work well with the Lightspeed which I do sell LDRs for but please understand I am just giving advice, not running a commercial here. The Lightspeed is absolutely incredible sounding and I prefer it with no buffer on my 47k input gainclone. If you use a buffer, which still sounds good, there is the tube buffer george recommends and then there is also a buffer design Nelson Pass recommends for the Lightspeed in the same thread. I dont have links for each of those.
Anyway, as I was saying its nice to have options and most of them are easy to build and a good place to start learning about DIY. Also a good and cheap area to start learning about how different resistors/caps/wire sound different without spending to much money to do so.
Uriah
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Old 10th April 2010, 01:37 PM   #6
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Hi,

This thread is getting a bit old now but I thought you might like to know that Greg Ball has designed a simple little no capacitor 2 FET buffer with 100K input impedance that is a good match for his Optivol. It is called, of course, "A simple FET Buffer." and you can read about it at this URL SKA sponsored Audio Forum - A Simple FET Buffer

Joe.
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