MC input and TX Zobel Networks

little eddy · Post by **little eddy** » Thu Dec 29, 2011 1:47 pm

I stumbled upon a passage in MJ, (pages 560/1) where he talks about a large input shunt capacitance, a square wave test and concludes "very disappointing" without explaining how/why.

How might this be disappointing (I'm assuming that the large capacitance will make the response to the squarewave overdamped)?

Is this an 'engineering' suboptimal situation or will it have a sonic influence?

Ca-g for the ECC83 is 1.7pF and with an AV of 100 gives 170pF per valve so 340pF altogether compared to MJ's theoretical 64pF or measured 189pF for the single EC8010, so should I do anything without a scope and squarewave generator?

My cartridge is 6R so this would suggest 1nF and I assume a series 2k4 resistor a la MJ. Have I anything to loose?

Max N · Post by **Max N** » Thu Dec 29, 2011 5:38 pm

What step-up transformers are you using?

I think MJ is talking about ringing when testing with a square wave input. The zobel would be tweaked to give best square wave response. I have heard people say that the zobel measures better but subjectively the sound is better without. If you don't have a scope I might be inclined to not fit a zobel.

Andrew · Post by **Andrew** » Thu Dec 29, 2011 10:31 pm

little eddy wrote: so should I do anything without a scope and squarewave generator?

Yes, to be blunt, buy a scope....how can you improve what your are doing if you cannot see, please don't be offended but right now you are driving blind

http://www.rapidonline.com/Tools-Equipm ... pes-400399

PC and a sound card and Audacity can be your square wave generator...or buy Audio Tester or there's a few freebies that can do the same thing. Or, if you want proper test gear try this.

http://www.rapidonline.com/Tools-Equipm ... ator-71558

or pick up a sig gen from ebay.

Honestly, it will move you to the next level.

Neal · Post by **Neal** » Thu Dec 29, 2011 10:41 pm

Max N wrote:What step-up transformers are you using?

I think MJ is talking about ringing when testing with a square wave input. The zobel would be tweaked to give best square wave response. I have heard people say that the zobel measures better but subjectively the sound is better without. If you don't have a scope I might be inclined to not fit a zobel.

I tried it some time ago and exactly as Max said, it measured fine but sounded worse...

Max N · Post by **Max N** » Fri Dec 30, 2011 1:00 pm

That scope that Andrew linked to - under £200 for a digital storage scope with FFT. I wish that kind of value had been around when I bought my secondhand CRT scope. I paid more than that I think.

I'm seriously thinking about getting one of these - I'll start a new thread.

Post by **Nick** » Fri Dec 30, 2011 1:09 pm

I have one of those. Can't recomposed them enough (when they get them back in stock). Its taken me some time to get my head round to what digital scopes do better and worst than analog, but would probably miss it if I went back to a older scope. Apart fro anything else, being able to save traces to USB stick makes it worth it. It means you can actually compare to see if a change has made a measurable difference, rather than trying to remember.

I loved the old Tek scope I used, but the workshop is a bit damp (especially at this time of year), and eventually the EHT section of CRT scopes break down. I have three analog scopes that have done that, so I thought it was time to go to one that was LCD based so no EHT in there.

Paul Barker · Post by **Paul Barker** » Fri Dec 30, 2011 2:47 pm

Yes I have had the same problem as you with all my CRT scopes, my top floor is also cold and damp.

after seeing yours at work at Eggborough I bought a used 150mhz one on eBay. Very pleased.

Also treated self to a cheap chinease function generator. It is flawless unlike all the old signal generators I have ever owned where the waveform is never perfect and varies across the range, the modern chip based chinease ones have a perfect waveform which is rock steady through the full range.

Not that I ever connect these things to my circuits.

for me an MC transformer which has a good square wave response sounds artificial. One which is imperfect sounds analogue yet quirky. I prefer quirky analogue to sinthetic. Boils down to personal preference.

little eddy · Post by **little eddy** » Fri Dec 30, 2011 5:14 pm

Max N wrote:What step-up transformers are you using?

I'm pretty sure they are from here: http://www.precision-windings.fsnet.co.uk/

Max N · Post by **Max N** » Fri Dec 30, 2011 9:19 pm

little eddy wrote:
Max N wrote:What step-up transformers are you using?
I'm pretty sure they are from here: http://www.precision-windings.fsnet.co.uk/

OK, so nothing available in the way of performance specs or suggested loading?

little eddy · Post by **little eddy** » Fri Dec 30, 2011 10:34 pm

No and that's why I was tempted by Colin's Silk SUTs he had for sale recently.

audio-talk

MC input and TX Zobel Networks

#1 MC input and TX Zobel Networks

#2

#3 Re: MC input and TX Zobel Networks

#4

#5

#6

#7

#8

#9

#10