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Welcome to the Graham Slee Audio Products Owners Forum  Open to all owners plus those contemplating the purchase of a Graham Slee HiFi System Components audio product and wishing to use this forum's loaner program: join here (Rules on posting can be found here) This website along with trade marks Graham Slee and HiFi System Components are owned by Cadman Enterprises Ltd |
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Graham Slee 
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Retired Joined: 11 Jan 2008 Location: South Yorkshire Status: Offline Points: 16314 |
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 Posted: 14 May 2008 at 8:52am |
So right that people reach for their cheque books, spending £15,000 in one go I'm told. Yes the man with the beard - he probably had spectacles and a false nose too, but my friend didn't notice... Tell me Dave, what is the time period used to determine the peak current? I'd be very interested to know. I think I've got some math somewhere to work that out - something like dX/dY... "If you go down to Willow Farm........... " |
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That none should be able to park up and enjoy the view without a smartphone and the knowledge in how to use apps
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stuxter
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Joined: 26 Mar 2008 Status: Offline Points: 140 |
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Posted: 14 May 2008 at 9:23am |
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........."to look for butterflies, flutterbyes, gutterflies
Open your eyes, it's full of surprise, everyone lies" |
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Graham Slee
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Retired Joined: 11 Jan 2008 Location: South Yorkshire Status: Offline Points: 16314 |
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Posted: 14 May 2008 at 6:15pm |
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...."like the fox on the rocks" (the cinema [Roxy] or TV news [Fox/Pathe...])
...."and the musical box" (the radio) |
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That none should be able to park up and enjoy the view without a smartphone and the knowledge in how to use apps
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stuxter
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Joined: 26 Mar 2008 Status: Offline Points: 140 |
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Posted: 14 May 2008 at 9:09pm |
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Touch`e Mr Slee
you know the old saying....
"As Sure As Eggs Is Eggs"
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dvv
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Joined: 12 Jan 2008 Location: Belgrade, Serbi Status: Offline Points: 95 |
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Posted: 14 May 2008 at 10:53pm |
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Blimey, I just noticed this thread ...
Graham, since you asked the question, we can argue and argue, but the simple fact is that if I use my Sennheiser HD595, or my Sony 270, or my Grado cans on a headphone amp which has an output impedance of approximately 1 Ohm, the bass above all sounds tighter and better defined than when I use the same cans on amps with an IEC recommended outpit impedance of 120 Ohms.
If I use my AD826AN based headphone amp which has current boosting transistors, namely a BC 546B driving an MJ15030 and a BC 556B driving an MJ15031, AND which has an LF411 based DC Servo circuit, I get an overall clearer sound.
I believe, or if you prefer I choose to believe that this is no freak accident, no great stroke of luck, and no God's little finger pointing at me, but rather the fact that I do possess a reasonable damping factor of 15:1 into 30 Ohm cans, and the fact that there are no nasty capacitors to muck around with frequency and phase response.
Now, you can choose to consider all this pure drivel and hence disregard it altogether, or you may choose to investigate. If you do choose to investigate, then by all means do try a balance knob as well, you could find it well worth the effort and the extra expense. And if you want to hog it, try a L+R switch as well, it's a wee little thing, but it does so much.
In a few days, I'll be turning 55 and I no longer have much of a stomach for theorizing, I turn more and more towards hard practice - implement it and see what you get, you'll do the maths later. As if anybody gives a damn about maths, which can become far too abstract far too fast, the customers are especially keen on the maths.
Speaking of maths, have you ever in your life experienced the mathematical rule that a minus multiplied by another minus will produce a plus? I haven't, and in hard fact, it is my experience that if anyone does someone one wrong, he will be paid back by a far greater wrong sometime, somewhere, somehow. Quite the opposite of math, don't you think?
Not being belligerent here, simply avoiding what I feel is an essentially useless argument, in which you will hit me with a lot of formulas, and I will slug you by constantly saying "Been there, done that, it sucks". No future in it.
Case in point - I just got back from a demo. I DEMONSTRATED to a hard core tube fellow what a simple, text book unity gain buffer based on an AD826AN can do for his beloved tube sound; he took it like a man.
 A very nice fellow, actually, or I wouldn't be wasting my time. Tubes and op amps? How pervrese can you be? Next to me, Marquis de Sade is still in the kindergarten.  |
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Graham Slee
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Retired Joined: 11 Jan 2008 Location: South Yorkshire Status: Offline Points: 16314 |
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Posted: 17 Jun 2008 at 2:21am |
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The trouble with the AD826 is that it cannot drive the capacitive load of even the tiniest driver transistor. It can do 186pF on a 7.5V peak excursion, anything heavier than that and it will bandwidth limit which means heavy input filtering or a spike in the HF response which the much slower transistors won't like, unless you opt for ultra high distortion by excluding them from the NFB loop like I see one of my competitors does (and with a different op-amp). The suggested output transistors (or anything similar) would not give sufficient Hfe for the small current demands of headphones for the 546/556 to be operated at low enough current to keep their input (base-emitter) capacitance down, and values between 1nF and 10nF can be expected - more that the 826's 186pF. This is partly why we stopped using it in headphone circuits. It is however good in some of our phono stages because the EQ network slugs the peak. I recently repented from my anti-spice model stance and I learned quite a bit about what I'd calculated on paper in a new light. Somehow we get more high fidelity the further we distance ourselves from hi-fi. Maybe one day folk will realise...?
However, the MJE15032's would make a very good 20W amp for loudspeakers given a good discrete voltage amp and pre-drivers. I think we'll be working on that next. Edited by Graham Slee - 17 Jun 2008 at 2:28am |
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That none should be able to park up and enjoy the view without a smartphone and the knowledge in how to use apps
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Graham Slee
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Retired Joined: 11 Jan 2008 Location: South Yorkshire Status: Offline Points: 16314 |
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Posted: 17 Jun 2008 at 2:29am |
You mean X=X as not in X=Y which many would have it in HI-FI-FO-FUM... Edited by Graham Slee - 17 Jun 2008 at 2:30am |
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That none should be able to park up and enjoy the view without a smartphone and the knowledge in how to use apps
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