I have all numbers --- this isn't the place for showing all. It is nearly the same at any freq as I said etc. Only small change -- like the 8 ohm load showed at 20Khz and 1Khz -- all the way down to 2 Ohms.
No osc at clipping.
THx-RNMarsh
Last edited:
Lot's of good stuff here, wooo whooo. (RE: Posts around 981xx and up.)
It's all inter-related too. Imagine my surprise with speaker design guy wanting me to ensure that when I put the Accuton tweeters into the speaker cabinets he designed and built that I make sure that I wire in series with them a 20uF capacitor.
He went on to explain, that even in the mastering studios, the engineer would do something stupid, or someone would, or a power surge would happen.
He continued to describe the sound that these high-end tweeters made, like a glass Christmas ornament breaking, that slight tinkle twinkel tinkle sound and knowing that it would cost $300 - $800 to replace.
They had the Accuton Midranges also... and without protection...I guess he had to replace too many drivers and the company didn't survive.
Kappa 9s?
Options are to find the low impedance portion of the speaker and cross over or under if possible. If not, make an impedance smoothing device. If not, advertise how great they are until you get sued? And, take the money and run then go belly up?
Just wondering...what ever happened?
It's all inter-related too. Imagine my surprise with speaker design guy wanting me to ensure that when I put the Accuton tweeters into the speaker cabinets he designed and built that I make sure that I wire in series with them a 20uF capacitor.
He went on to explain, that even in the mastering studios, the engineer would do something stupid, or someone would, or a power surge would happen.
He continued to describe the sound that these high-end tweeters made, like a glass Christmas ornament breaking, that slight tinkle twinkel tinkle sound and knowing that it would cost $300 - $800 to replace.
They had the Accuton Midranges also... and without protection...I guess he had to replace too many drivers and the company didn't survive.
Kappa 9s?
Options are to find the low impedance portion of the speaker and cross over or under if possible. If not, make an impedance smoothing device. If not, advertise how great they are until you get sued? And, take the money and run then go belly up?
Just wondering...what ever happened?
Last edited:
Strange answer. An important part of commercial design is designing for maintainability and reliability. But then, someone mentioned that 0.5% returns in 3 years was a good figure, that would be crap in many industry segments.
Thanks very much for the information; i´ll try to find the Aug. 1994 issue.
Online i was only able to find an article about the Angelus Spica loudspeaker test:
Spica Angelus loudspeaker Angelus blind test 1993 | Stereophile.com
Tech question -
Can I measure in-circuit (parasitic) capacitances with an ordinairy cap meter? Anything special to watch out for?
Like with the Keysight U1701B?
Jan
Can I measure in-circuit (parasitic) capacitances with an ordinairy cap meter? Anything special to watch out for?
Like with the Keysight U1701B?
Jan
PN junctions and the magnitude of the applied signal. A full bridge would have an adjustable DC bias and a setting for low excitation. Sometimes a large series C helps if you disturb things with the direct connection of the meter. In circuit can be tricky in any case.
.... is the circuit under test powered on or off?
will be very different between the two modes... on-off.
But just pcb parasitics ---> http://www.ti.com/lit/an/sboa094/sboa094.pdf
-RNM
Last edited:
The circuit is powered off. I try to measure the parasitics of a high-impedance Drain node of a Vas driven in common gate, using a cheap handheld C-meter I measure initially 43pF; I calculated max 50pF so looked good. But then when I attach anything like a supply lead it jumps to 200pF. When I remove the supply lead it stays at 200pF. Discharging any supply caps doesn't make a difference. Disconnecting and re-connecting the C-meter resets it to 43pF.
Doing a freq response with the circuit powered it seems that the 200pF is there.
Hate to say, but I haven't a clue.
Jan
Doing a freq response with the circuit powered it seems that the 200pF is there.
Hate to say, but I haven't a clue.
Jan
Hi Jan,
Using the HP 4263A, I can measure the input strays and capacitance, but I have to drop the test voltage and even at 50 mV (lowest setting), it's overdriving the circuit. That may not matter a great deal for that measurement. You just have to make sure your test voltage is not turning junctions on or off.
I don't know what the test voltage is for that meter, but for sure you want to get it well below the level to turn junctions on or off. Something Scott pointed out. You can try this with a good series capacitor and calculate the true value. Obviously the better the equipment, the closer to reality your answer will be. The handheld meter gives you much better isolation from strays to the mains and ground system.
-Chris
Using the HP 4263A, I can measure the input strays and capacitance, but I have to drop the test voltage and even at 50 mV (lowest setting), it's overdriving the circuit. That may not matter a great deal for that measurement. You just have to make sure your test voltage is not turning junctions on or off.
I don't know what the test voltage is for that meter, but for sure you want to get it well below the level to turn junctions on or off. Something Scott pointed out. You can try this with a good series capacitor and calculate the true value. Obviously the better the equipment, the closer to reality your answer will be. The handheld meter gives you much better isolation from strays to the mains and ground system.
-Chris
I would like to talk about something seemingly lost here about what makes for a good audio design.
A great deal of emphasis and energy is put into NUMBERS, or how low the thd can be in a specific design. Is it really that important? What is really audible when listening to differences between amplifiers and preamplifiers? What combination of design compromises gives a historically important design? Can we learn from the past, noting what characteristics are present in world acknowledged extremely successful designs that now probably are collectors items, and almost impossible to get at any reasonable price? For example, the Marantz 9 power amp comes to mind as an early piece that set a listening standard more than 50 years ago. What are its salient characteristics that we should copy in order to make a similar quality solid state power amp? More later.
A great deal of emphasis and energy is put into NUMBERS, or how low the thd can be in a specific design. Is it really that important? What is really audible when listening to differences between amplifiers and preamplifiers? What combination of design compromises gives a historically important design? Can we learn from the past, noting what characteristics are present in world acknowledged extremely successful designs that now probably are collectors items, and almost impossible to get at any reasonable price? For example, the Marantz 9 power amp comes to mind as an early piece that set a listening standard more than 50 years ago. What are its salient characteristics that we should copy in order to make a similar quality solid state power amp? More later.
Those ain't no smug sunglasses, Jan. New test equipment are the best toys!
I know. I have a couple of modern digital scopes, 6.5digit DMMs, that stuff. But also a whole slew of Tek TM500 modules in racks. My very first job, at Philips in Eindhoven, they casually hand me a Tek trolley with a scope (451?), a signal generator and a power supply. I would have worked there for free!
Jan
You lucky bar stewardthey casually hand me a Tek trolley with a scope (451?), a signal generator and a power supply. I would have worked there for free!
Jan
Some people are easy. I would have held out for a 7704 if my chronology is right. Where I started we had a brace of 547s and 1 7704 with the pushbutton attenuator plugins. The 7704 was like something from the far future.You lucky bar steward
what makes for a good audio design?
good parts
good layout
good circuit design
good power supply
good heatsinking
good chassis design & module placement
Some of the above just possibly might require painstaking trial and error, to discover which of N experimental test units, has the greatest amount of audio goodness. Passive parts vendor selection perhaps. Some people might be tempted to say that hand-matching transistor pairs is an example of painstaking trial and error.
_
good parts
good layout
good circuit design
good power supply
good heatsinking
good chassis design & module placement
Some of the above just possibly might require painstaking trial and error, to discover which of N experimental test units, has the greatest amount of audio goodness. Passive parts vendor selection perhaps. Some people might be tempted to say that hand-matching transistor pairs is an example of painstaking trial and error.
_
Last edited:
I have the same problem with an amplifier that has lots of parallel common source
input FETs, so the capacitance plays a big role. Most of Cgs is removed by the
feedback into the source and Cgd is removed by bootstrapping the drain via the
cascode transistors. Gate, source and drain move more or less unison, voltage-wise,
which is kinda weird. It works for small signals, but I cannot dim down the 4274A
bridge to a level that does not kill the proper feedback during capacitance measurement.
It seems I can circumvent that by using the vector network analyzer, using 1 Hz
bandwidth and attenuating the level during S11 measurement to -50 dBm or so.
The VNA starts at 300 KHz only, with uncalibrated under range to 150 KHz.
But S-parameters love 50 Ohms and are not really precise in a hi-resistance
environment.
Looks like I need an impedance analyzer.
\Gerhard
- Status
- Not open for further replies.