I can't think of why you have the 11MHz ringing. I may get around to optimizing compensation today.
Do you think that a 100k input impedance would improve the sound? If your source has no DC coupling cap, output offset will be below 10mV, but if you disconnect the source, output offset will go to +200mV. A 50k resistor would mean 100mV.
Do you think that a 100k input impedance would improve the sound? If your source has no DC coupling cap, output offset will be below 10mV, but if you disconnect the source, output offset will go to +200mV. A 50k resistor would mean 100mV.
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I think I figured it out. It appears your cable is resonating in series mode. The oddly shaped overshoot is a giveaway for series resonant overload. So the buffer may not be to blame, but suboptimal termination of the output cable. You can test this by putting a 50R resistor between the buffer and the cable to the scope. Or you could put the buffer next to the scope input and not use the cable.
If I'm right, then the buffer isn't to blame. Any buffer can suffer from these problems.
If I'm right, then the buffer isn't to blame. Any buffer can suffer from these problems.
Pilgham Audio FPS kit
Joachim,
I read the Linear Audio article this past weekend and am interested in building an FPS. I tried getting more info from this thread but it's a very long one with lots of seemingly side discussions so my apologies if I'm asking a question that should have an obvious answer.
My question is if the kit sold by Pilgham Audio still represents what you believe to be a good version of the circuit. I can't quite follow if this thread has been changing the basic design too much so just wanted to check.
Also do you, or anyone know what's going on with Pilgham's website? I don't seem to be able to order anything at the moment and there is a message about a server room fire on the home page. I don't know how long it's been this way as this is my first time to their site in 9 months or so. Should I contact Jan (or perhaps someone else) directly?
Thanks in advance for any info, and Joachim, thanks for sharing your design.
Joachim,
I read the Linear Audio article this past weekend and am interested in building an FPS. I tried getting more info from this thread but it's a very long one with lots of seemingly side discussions so my apologies if I'm asking a question that should have an obvious answer.
My question is if the kit sold by Pilgham Audio still represents what you believe to be a good version of the circuit. I can't quite follow if this thread has been changing the basic design too much so just wanted to check.
Also do you, or anyone know what's going on with Pilgham's website? I don't seem to be able to order anything at the moment and there is a message about a server room fire on the home page. I don't know how long it's been this way as this is my first time to their site in 9 months or so. Should I contact Jan (or perhaps someone else) directly?
Thanks in advance for any info, and Joachim, thanks for sharing your design.
Sorry for the lag, but I FINALLY got to test out my compensation scheme on the buffer. I used a trimmer for R9 here and was able to dial in a good corner on the square wave. unfortunately my signal generator keeps dying and I wasn't able to do all the tests I wanted. Still, I saw no overshoot into either 50pF, 270pF or 1nF.
Hi willamp,
just to let you know i built that kit (~3yrs ago or so) and I am a happy listener, its a great sounding phono stage worth every penny.
just my two cents....
Good to hear, can you tell me if you built the high Z or low Z version? I'm a little confused at this point about which one I would want. I need to do more research I guess.
Also, I heard back from Ward Maas at Pilgham and he expects the website problem to clear up by the end of the week and still supplies FSP and PSU kits.
Kean, when you have any new circuit of the buffer i will build it.
Thanks for the tips.
Sadly one channel of your buffer i have build died.
I am looking how to fix that.
I you recommend any changes please tell me and i will implement them.
Thanks for the tips.
Sadly one channel of your buffer i have build died.
I am looking how to fix that.
I you recommend any changes please tell me and i will implement them.
Yes, the FPS is still hard to beat when you want balanced.
I am in contact with Pilgham and will ask what is going on on the website.
I am in contact with Pilgham and will ask what is going on on the website.
Group buy for the Calvin buffer for Paradise is on:
http://www.diyaudio.com/forums/group-buys/239776-calvin-buffer-paradise.html#post3573058
http://www.diyaudio.com/forums/group-buys/239776-calvin-buffer-paradise.html#post3573058
I think that in posts #9381, #9382 and #9384, Kean was probably "mightily hinting" about the tone versus focus parameter adjustment via some compensation fine tuning.
These "kind of" adjustments are indeed quite fatiguing, the finishing touch needs a sure instinct. If it comes to burst-like oscillations (often depending from layout or wiring) it can take some time..
Unfortunately i had no time to explore this buffer any further but i will.
One channel is dead and i have not repaired it.
I know that the same circuit can sound very different dependent on parts choices, layout, PSU, idle current and so on.
One channel is dead and i have not repaired it.
I know that the same circuit can sound very different dependent on parts choices, layout, PSU, idle current and so on.
Hi Joachim. I fell victim again to the inconsistent forum notifications.
I have struggled "mightily" with compensation and while the compensation scheme I provided does very well in terms of not messing with the sound, I find some clarity is always lost. It always seems the best compensation is to not need compensation in the first place, and if so, compensation that decreases loading instead of increasing it. Based on this I have a new design which beats the previous in every way, especially focus. It uses an input snubber, a ferrite bead and a 47R output resistor. The output resistor may be optional, and air-core inductors (~2uH or so) could be used for the beads. Tell me if this seems like a problem.
I have struggled "mightily" with compensation and while the compensation scheme I provided does very well in terms of not messing with the sound, I find some clarity is always lost. It always seems the best compensation is to not need compensation in the first place, and if so, compensation that decreases loading instead of increasing it. Based on this I have a new design which beats the previous in every way, especially focus. It uses an input snubber, a ferrite bead and a 47R output resistor. The output resistor may be optional, and air-core inductors (~2uH or so) could be used for the beads. Tell me if this seems like a problem.
I have ferrite beads and can make air coils.
When you publish the circuit i will build it. I have some time this week.
When you publish the circuit i will build it. I have some time this week.
On Analogplanet they showed a picture of Joachim Gerhard's new phono preamp.
Please give us some details about this commercial phono.
Please give us some details about this commercial phono.
That phono is called " Stille" that is " Silence" in english.
The input stage is floating and works on batteries.
It is not a transconductance design and not a transimpedance design eather.
I call it "Power Transfer Input" because it has an input impedance of ca. 5 Ohm that is similar to the DC impedance of low output moving coils.
It is a modified common base design with base current recycling and what i call a " Hum Bugger". It is not really balanced but the earth pins of the cartridge are not directly connected to audio ground. It suppresses hum nearly as well as a balanced input but without the complication of doubling the circuitry.
The RIAA is two stage, first treble transimpedance and bass active.
The second stage is a class A Opamp design.
The input stage is floating and works on batteries.
It is not a transconductance design and not a transimpedance design eather.
I call it "Power Transfer Input" because it has an input impedance of ca. 5 Ohm that is similar to the DC impedance of low output moving coils.
It is a modified common base design with base current recycling and what i call a " Hum Bugger". It is not really balanced but the earth pins of the cartridge are not directly connected to audio ground. It suppresses hum nearly as well as a balanced input but without the complication of doubling the circuitry.
The RIAA is two stage, first treble transimpedance and bass active.
The second stage is a class A Opamp design.
How long can a 20mA circuit run on say, a 9V battery? And if you use something like a button cell for biasing the base of a BJT or even a Jfet for instance, what kind of battery can stay in service for years without corroding while the current dray is tiny? Can non-rechargeable batteries handle tiny reverse current for extended periods of time?