Amp4 Mod Round-up – Input wire, power caps and high capacitance speaker cable

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Hey all,

I’m coming to the last stages of my Amp4 project, where I’m deciding on some of the perhaps more trivial parts. I’ve already sorted out the input caps (Jensen 2.2uf PIO), output caps (Wima MKP2) and torioid inductors (Metglas Cores). However, there are just a few bits I’m undecided on, and would appreciate any feedback available.

Firstly, the electrolytic caps. While many claim Blackgate are the undisputed champion here, they are indeed a considerable amount of money (that said, I did get Jensen PIO for the input :wink:) and more importantly, I trust Michael Mardis’s word when he says they aren’t really suited for this amp. Therefore, after considerable searching, I’m left with generally two choices that seem good for most caps. Firstly, the Elna Cerafine. From what I’ve read about them they offer a good compromise between the ‘naturalness’ of the Silmic II, and the ‘directness’ of the Blackgates, and I’m assuming they’re suited to this application. My second choice is the Panasonic FM series. While rather less impressive, they’re still meant to be ideal for this situation, and are rather cheap too. The various capacitor situations and my thoughts on it are as follows:

2x 10000uF 50V – These caps I do not need to consider, as they’re for AC smoothing, which is unneeded with my battery source.

1x 10uF 10v , 1x 1000uF 10v, 2x 330uF 35V – These caps can all be Elna Cerafine quite easily. There are several places that sell this size range of them but Audio-cube (although they’re currently on holiday) have the best range.

2x 1500uF 35V – These power supply caps are rather important. However, I’ve found it quite hard to find Cerafines in a suitable voltage/size. Audiocube doesn’t stock them, and while the PDF they link to on that site doesn’t say that Elna do anything that large (might be old) I’ve seen several 10KuF caps and some 63V ones on ebay in the past, so they must have been made sometime. Anyone any ideas on where I might be able to source these? If all else fails, I could quite happily go for the Panasonics here, probably to be sourced from Farnell UK.


Next issue, is the input hook-up wire. I’ve been convinced using shielded wire is the way forward, as I have a particular noise issue in my amp’s to-be home (PC, and various other noise makers). However, there’s still quite a list that I have to choose from. If you’d like to express any opinions on your preferred it would be great.

Weisd - Belden 8442 $1.02 / foot
DIY Audio Store- Oyaide Pa-02 $35 AUS /metre ($27.57USD) (A bit pricey...)
DIY Audio Store- Mogami W2893 $4.25 AUS/metre ($3.35USD) – AWG26
Percy Audio - Mogami 2534 - Four conductor (24ga) 6mm D shielded microphone cable OFC Neglex copper $1.15 per foot AWG24
Percy Audio - MUSIC METRE IV A quasi solid core design comprised of four insulated strands, 3x28ga & 1x34ga per + & -, utilizing a high purity Teflon insulated OF copper, foil shield (40pF foot shielded), 7mm D… $7.50 mono foot
Percy Audio - Canare Star Quad: The L4E6S four conductor (21ga) 6mm D microphone cable 44, 57pF/foot, black 6mm D… 95¢


Next, I’m considering making myself some new Cat5e speaker cable, specifically VHaudio’s DIY project. However, the site does state that they will be of high capacitance, and that this could prove a problem for some amps. Even though I’m not going to be using lengths any long than say 2.5m (and there are Zobel caps in the amp4 design), would this be the case with Tripath amps? If so, what would you advise?

Lastly, I’ve already chosen my attenuator from the bargain one on diyfidelity, but I’m still undecided as to which resistance is best. I remember someone telling me Scott Endler said 10Kohm was preferred, while Vinnie of Red Wine Audio fame prefers 20kohm. I’m not really sure how to judge this.

Oh, and on a side note – banana plugs…what are your favourite?

If anyone can offer any advice to help me finish off this project, it would be greatly appreciated. :D

Thanks to all who post,
Peter
 
xenob said:
And, one of the most important questions: What gain will you set for your amplifier?

Good question.

I have 2 sources that I will be using with this amp - firstly, an ipod, which I believe has an output voltage of about 1V RMS and secondly, my M-Audio 2496 Audiophile sound card, which seems to have an output of 2V RMS, but this I shall measure myself to check.

With a desired input into the amp of 4V P2P, This edited diagram explains what I've done best:

An externally hosted image should be here but it was not working when we last tested it.


Unfortunately, I'm not sure what effect this has on the input impedance of the amp, or exactly (and this bit is crucial) where the attenuator goes :eek:, probably between the input cap and the source selector.

Thanks for the post! :)
 
Hi

If you want to uprade the eletrolytics, you could also think of useing bypass caps of foil type. (see many posts on snubbers eg.)

My AMP4 is finnaly working beautifully and I think I prefer it over the AMP6.

I did not do much changes exept the input caps were replaced for Mundorf 2,2 µF Polypropylene caps.

an5ut4y692l4l0y00.jpg


Here you see my first experimental case.

Finnaly the amp went into a nice fisher aluminium case together with a dantimax relay stepped attenuator

an5v05xqceucnqazk.jpg
 
whitelabrat said:
Any thoughts on Nichicon Muse KZ's?

I've just about got all the SMT doodads mounted on my amp4 and should start thinking about upgrading some of the other bits. I'd like to know how things go for you. Good luck!


I also posted this thread on Audiocircle here, and after discussion on there, concluded that the Panasonic FMs were the most suited to most places. More info can be found there :) .
 
I've ordered a set of Nichicon KZ's with values 1x 10uF 10v , 1x 1000uF 10v, 2x 330uF 35V. Voltages may vary though. I was buying some for a phono amp and figured, why not. I'm not sure how to compare these to the Panasonic FM's. I looked over the specs for both. I guess only time will tell.
 
Ah, hi Reverie :) really, the capacitance of a speakercable will be in the range of pF or nF max. especially at 2.5 meters...:cool:

An ESL produces a capacitive load far beyond that value...I think most amps can handle Cat5e as in 'not break down'...only down sides can be filtering effects...(highpass=loss of bass....)
 
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