Douglas:
thanks, that's helpful.
now if i can just find a brick and mortar bookstore that has one for me to thumb.
Aaaaah well, what's life without a little challenge?
mlloyd1
thanks, that's helpful.
now if i can just find a brick and mortar bookstore that has one for me to thumb.
Aaaaah well, what's life without a little challenge?
mlloyd1
Hi Guys,
I know they still make them and I know earbuds are extremely common and thousands of folks listen to music through them from their phones and ipods, but how many folks sit down to listen to music where they would plug into a headphone amp? How many of you do? I know myself, if I am going to sit down to really enjoy some music, it will be through speakers. Headphones mess with the mix. When you listen to music through speakers, your right ear hears the left speaker as well as the right, and your left ear hears the right as well as the left. That doesn't happen in headphones. Anyway, I just wondered.
Blessings, Terry
I know they still make them and I know earbuds are extremely common and thousands of folks listen to music through them from their phones and ipods, but how many folks sit down to listen to music where they would plug into a headphone amp? How many of you do? I know myself, if I am going to sit down to really enjoy some music, it will be through speakers. Headphones mess with the mix. When you listen to music through speakers, your right ear hears the left speaker as well as the right, and your left ear hears the right as well as the left. That doesn't happen in headphones. Anyway, I just wondered.
Blessings, Terry
Binaural recordings can be great for out of head sounds
with a small apartment in a dense city I don't have a big enough room for a quality speaker setup - I do own ~$3K of headphones
"crossfeed" filters or plugins for music players can help with headphone's "between your ears" "soundstage"
more sophisticated simulators exist too: Dolby Headphone
the Smyth Realizer is very convincing - can capture any room/loudspeakers you can get ~1/2 hr access to
SVS Technology
deep bass still has a "body" component that headphones even with full bass extension lack - I've never owned a "butt kicker" although I suppose the iMax theater I (seldom) go to may have them
with a small apartment in a dense city I don't have a big enough room for a quality speaker setup - I do own ~$3K of headphones
"crossfeed" filters or plugins for music players can help with headphone's "between your ears" "soundstage"
more sophisticated simulators exist too: Dolby Headphone
the Smyth Realizer is very convincing - can capture any room/loudspeakers you can get ~1/2 hr access to
SVS Technology
deep bass still has a "body" component that headphones even with full bass extension lack - I've never owned a "butt kicker" although I suppose the iMax theater I (seldom) go to may have them
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I do own a Smyth Realiser and can vouch for its total convincing sound stage. I have even used it for surround, set up using just one single speaker to capture a fake surround speaker system and my room acoustics.
The Smyth does have a butt kicker output but I haven't worked with that.
Jan
I would appreciate more attention to Input stage RFI rectification sensitivity, as well described here:
http://www.analog.com/library/analogdialogue/archives/39-05/web_ch7_final_j.pdf
This might make different insight to JFET x BJT considerations.
http://www.analog.com/library/analogdialogue/archives/39-05/web_ch7_final_j.pdf
This might make different insight to JFET x BJT considerations.
Yes, it was the phono preamp of a Heathkit AR-15 receiver. Apparently, the 0.001 capacitor from the ground side of the phono input jack to chassis ground was not doing its job. The quasi complimentary power amp went into common mode lockup, there was a loud 120 Hz hum indicating that the load on the power supply was much more than the filter capacitor could handle, and the output blew up 1-2 seconds later.
The trouble might be quite subtle, isn't it? Sound degradation, but not just audible demodulation.
My Blameless (built with 1994 Signal Transfer boards) never suffered from any kind of RFI troubles. It always puzzled me because it has neither RC low-pass filter at the input nor power supply RC decoupling.
??? What was common mode about it?
This sounds like any ordinary hit-the-rails fault, hence the hum. I wouldn't have thought it could be triggered by RFI on a phono preamp input.
I am on holiday at the moment so I can't check, but as I recall all the Signal Transfer power amplifier PCBs have/had both an RC low-pass filter at the input and power supply RC filtering. (on the -ve rail only, as that's where it's needed) However 1994 was very early days so I'm not sure about the RFI filter.
I would emphasise, however, that the series R is only 10 Ohms, and the filtering is in the RF region only. DO NOT put series resistors above 100 Ohm in series with the input as the input currents drawn by a BJT input stage are non-linear and THD will be much increased.
This may be true for JFET inputs also (due to non-linear input capacitances) but I am speculating here.
Here is an advertisement as published at the time in Electronics World + Wireless World from which I purchased the boards as soon as they were available. I also join a photography for more details.
I interpret the lack of RFI detection despite no special protection against it as being due to the fact that the input stage (differential stage with resistive degeneration loaded by a current mirror run at 2*3 mA) is intrinsically very linear and not susceptible to rectify HF signals.
More annoying in the first batch of the boards was the lack of a high value resistor connected to ground at the input side of C1, I added one on the copper side of each of my boards.
I never found necessary to add an RC low pass filter. Of course, would I have done it, R would have been low value, as you recommended it a bit later after your first articles on power amps.
Attachments
Looking at the photo of the PCB, there was indeed no RF filter on the input of the EW PCB
Possibly "common mode lockup" is known by different names in different parts of the world. This is a case where the signal is faster than the output transistors and the second transistor turns on before the first has a chance to turn off. The result is the output transistors become a short across the power supply rails.
My understanding is that quasi complimentary outputs are more susceptible to this lockup condition than full complimentary.
The transistors were house numbered RCA 40411 which have ft = 800 kHz, very slow by any standards today.
I was increasing the volume to maximum with an open input on phono to listen for noise using headphones.
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