210, miss-type, I meant no caps inside the circuit of an op-amp, only external.
Yes, it does seem like FETS are the preferred input devices of those folks here that have direct experience building amps. I take that as sound advice.
Contemplating several schematics, the majority are not very different in macro concept, but of course, the details are everything. ( Vastly different implementation of feedback poles etc)
These are obviously really basic questions:
Input is usually an LTP. Sometimes "improved", sometimes fed by a CCS. Two questions from this. Most amps do not use it as a phase splitter but implement that in the second stage. Second, one amp has it upside down from all the rest. Any particular reason?
In the LTP, I have seen comments on them not needing to be matched inherently, to needing to be matched, to needing to be isolated, to a one-die matched pair. What is the thinking?
Second stage being the VGS. Frequently more than one stage. Is this because a gain of 30 or so is a bit much for a single stage?
Then the outputs. Within the same (under 50W) range, I see it about split if single output pairs or multiples. As this is well within the range of single devices, is there a noise/impedance or any other obvious reason?
Is there a general rule of thumb on the amount of class A range in an AB amp, or is that a matter of how much heat sink you are willing to buy? Making the assumption most music is below 5 or 6 Watts, that seems like a reasonable target.
Besides fiber not picking up RF, it is totally immune from ground loops or ground potential problems blowing up inputs when equipment is powered from different sub-panels.
I once had a tweeter blown by a yahoo in a pickup truck with a 1000W CB amp. Picked up in the speaker cables, detected in the feedback. I "solved" the problem.
There was a power transformer down the street that wiped out FM around 100Mhz for a couple of years within 100 yards. I complained to the power company and to the FCC and got totally rebuffed in spite of the clear law. Eventually it blew up and the new transformer did not have the faulty connection causing the problem. Ya try to help some people.....
Yes, it does seem like FETS are the preferred input devices of those folks here that have direct experience building amps. I take that as sound advice.
Contemplating several schematics, the majority are not very different in macro concept, but of course, the details are everything. ( Vastly different implementation of feedback poles etc)
These are obviously really basic questions:
Input is usually an LTP. Sometimes "improved", sometimes fed by a CCS. Two questions from this. Most amps do not use it as a phase splitter but implement that in the second stage. Second, one amp has it upside down from all the rest. Any particular reason?
In the LTP, I have seen comments on them not needing to be matched inherently, to needing to be matched, to needing to be isolated, to a one-die matched pair. What is the thinking?
Second stage being the VGS. Frequently more than one stage. Is this because a gain of 30 or so is a bit much for a single stage?
Then the outputs. Within the same (under 50W) range, I see it about split if single output pairs or multiples. As this is well within the range of single devices, is there a noise/impedance or any other obvious reason?
Is there a general rule of thumb on the amount of class A range in an AB amp, or is that a matter of how much heat sink you are willing to buy? Making the assumption most music is below 5 or 6 Watts, that seems like a reasonable target.
Besides fiber not picking up RF, it is totally immune from ground loops or ground potential problems blowing up inputs when equipment is powered from different sub-panels.
I once had a tweeter blown by a yahoo in a pickup truck with a 1000W CB amp. Picked up in the speaker cables, detected in the feedback. I "solved" the problem.
There was a power transformer down the street that wiped out FM around 100Mhz for a couple of years within 100 yards. I complained to the power company and to the FCC and got totally rebuffed in spite of the clear law. Eventually it blew up and the new transformer did not have the faulty connection causing the problem. Ya try to help some people.....
They go with 100 meter optical cables. Box of electronics has digital optical outs, internal DAW on a flash drive, and +4 dB balanced analog outs.
However, no sinatras/armstrongs were recorded by such mikes, so it would be hard to convince modern singers to sing in something invisible and unknown.
That is a wonderful little recording they have on their website. Choral stuff hard to do well.
If Tony Bennett or Willy Nelson heard it they'd be all over it like white on rice wanting to give the mic a try.
Jan
"If you want to decouple 'good sound' and 'purchase decision', I am all in agreement, because in actual real life they are only loosely coupled at best. Even a very cursory view of the market will confirm that."
My naive view is the amp should not "sound" at all. What I have been asking all along is why some sound "bad". If I wanted to make the signal sound different, I would call that a signal processor, i.e. those who insist on a tube buffer between their CD and preamp to intentionally change the sound.
Purchase decisions we can agree are totally another topic!
"If you want to decouple 'good sound' and 'purchase decision', I am all in agreement, because in actual real life they are only loosely coupled at best. Even a very cursory view of the market will confirm that."
My naive view is the amp should not "sound" at all. What I have been asking all along is why some sound "bad". If I wanted to make the signal sound different, I would call that a signal processor, i.e. those who insist on a tube buffer between their CD and preamp to intentionally change the sound.
Purchase decisions we can agree are totally another topic!
Perfection isn't all it's cracked up to be.
Yea, I once worked for someone I could say was a perfect idiot, but no one is perfect.
You meant the feetback cap, right ?
Is reducing the hf-gain by using a cap in parallel
to the feetback resistor common and will be seen by experts there, or just if needed ?
Measured less Overshot and settling time correlates
with the more precise/detailed sound I hear when using the Fet-input.
The measured harmonics are neglectible low at normal hearing levels when using bipolar or Fet-input.
Probably anyone thinks (slightly) different what's appropriate.
Transformer coupled Coax-SPDIF is usuable
when the possible drawbacks are acceptable
compared to Toslink and when it's properly done
(no connection to ground and not grounded to earth).
CB-amp with 1kW? America.
A solution is good.
Just working on the concept. In this case, it is just the output of my old Hp 206.
Comments on the unexpected lack of phase?
Avoiding errors introduced by earth loop currents.
When I measure the electrical response of a passive crossover I do so via a small wide bandwidth microphone transformer, except in this case I have it wired for step down, which gives me around 15-20dB of voltage "attenuation", just right to step the voltage output of a 100w amplifier down to a level that a line level sound card input can handle.
If I use a resistive L-Pad to do the step down instead I find that the signal earth loop current between the PC, amplifier, speaker and back to PC again causes errors in the response at low levels - for example if I measure a high pass filter the response rolls off as expected at first but around 20-30dB down it starts rising again, which is due to the out of phase earth return current in the negative speaker lead. With the isolation transformer there is no such effect.
The isolation transformer also prevents hum loops, so I get a much greater SNR than using a direct connection via an L-Pad.
As a bonus I can measure any part of the crossover, series or parallel in any polarity as needed without having to make the measurement with reference to earth.
When measuring speaker current I do what Wavebourn suggested - reverse the transformer to step up mode and shunt its input with a very low value resistor, both placed in series with the speaker.
As long as the transformer has low distortion and a flat frequency response I find I get a lot better measurements at speaker terminals or on passive crossovers through the transformer than any type of direct connection such as an L-Pad with a common earth.
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Appreciate the hint! For people like me who firmly believe that the major obstacle in sound reproduction (given the paradigm of stereo) is the source material, this is far from OT!
The specs on this thing are horrible. 1% THD at 84dB is that a mis-print? The noise is worse than one of those $1 Panasonic capsules, the frequency response is not great, the Max SPL is only 114dB.
EDIT - I see these are mainly medical devices to go into MRI's, CAT scans, etc.
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