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stereo coffee

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Everything posted by stereo coffee

  1. Hi Andy As many inputs as needed, one at a time can be accommodated. How this is done is arranging the series LDR current to a pole of a switch, then in your needed case 8 contacts, each diverting one at a time to a series LDR pair anodes. The method I would use is to arrange a trimpot of 2k value between the anodes of each, and then achieve minor LR alignment at the same time. In their OFF state, referring to the cell side ( where signal is connected ) the series LDR acts as a contact-less switch , but in their ON state as a variable contact-less attenuator. The entire circuit only needs one shunt pair, which are continuously powered, but requires a series pair for each desired input. The result is then as many inputs as needed, can be achieved . If we said 24 inputs were needed, you would simply pass the last of the prior contacts on the first switch to the pole of a subsequent switch, where its contacts in turn would deliver to the anodes of next bank of LDR's Image shows my own 6 input built into a Quad 33 case Here I am using 6 contacts of 12 which are available, and each contact can be seen wired to the anodes of each LDR pair.
  2. Although covered earlier, a recurring question is about having volume zero at minimum volume position, and setting the start volume position. The circuit which enables this, is located on the series LDr pair cathodes, it is best done with a bandgap regulator, where Vin is attached to the series LDR cathodes ( normally volume UP attaching to the attenuator ) and a resistance from that devices adjustment terminal which outputs 10ma of current, is then coupled to a higher voltage potential than the voltage measured at any time on the series anodes. In operation it cancels any possibility of audio occurring at lowest volume setting, the figure of resistance established on the LDR cell side is higher than multimeters will read, so is extremely effective in creating silence just when silence is needed. Volume can then commence exactly where it is needed. The start position can be set anywhere across the volume adjustment range . Volume commencing at 7am is usually desirable in most audio systems
  3. High time to head in the needed direction for software, if you are not there already, namely: https://www.fsf.org/ "Free software developers guarantee everyone equal rights to their programs; any user can study the source code, modify it, and share the program. By contrast, most software carries fine print that denies users these basic rights, leaving them susceptible to the whims of its owners and vulnerable to surveillance"
  4. Similar to the circuit shape of a T pad, https://en.wikipedia.org/wiki/T_pad a third pair of LDR's shown as R3 in the diagram at the Wikipedia page could couple on the LDR cell side, from the source component to the normal L pad output. It would remain a passive circuit, however would couple a adjusting user set curve level, that could provide added signal if this was needed, over and above the attenuation of the plain L pad. It would need though to tie in with the ability of silence at zero volume, and as such have current against its cathodes when the L pad section was steered toward the shunt pair. The output would be passive but coupling closer ( user curve set ) to the output impedance of the source, and therefore beneficial. Like the old saying having your cake and eating it too, it would avoid any change away, from the simplicity and purity of signal LDR's are capable of.
  5. Thanks for that, I watched the first concert, it was great. Really nice playing very professional musicians who love what they do. I had only seen photo's of the Village Vanguard, but great to see it & hear some very good jazz there, as happened last weekend
  6. Hope this helps you, maybe the headset needs charging, the information here: https://en-us.sennheiser.com/wireless-headphones-home-audio-rs-175 maximum time is 18 hours, also the Frequently asked questions informs: " What do I do if my Assistive Listening System suddenly stopped working? In a situation where a unit that has been functioning correctly has suddenly stopped functioning for no apparent reason the issue is likely an internal electronics glitch caused by a power surge. To resolve this issue an internal electronics reset is required. Disconnect the transmitter (base station) from both the audio source and the power source and at the same time remove the batteries from the headset. Leave the system disconnected from power and the batteries out of the headset for 15 minutes. This gives the internal electronics unit a chance to reset back to factory settings. After the reset period reconnect the system to power and put the batteries back in the headset and test the system.
  7. Unfortunately there are no schematics at hifi engine for me to assist you, for your product. but I would check sections of the circuit that may have relays, or possibly a PTC thermistor that is sensing excessive heat and disconnecting circuitry and reconnecting. Also valve sockets should be checked. The product should have sufficient regulation to work with a wide range of voltages, the manufacturer cannot blame the grid etc, as there is no excuse for not regulating a circuit sufficiently. I would book it in straight away for service under the products warranty.
  8. A Quad 306 power amp has fixed resistance loading of 22k and offers the following specification " Power output: 50 watts per channel into 8Ω (stereo) Frequency response: 13Hz to 40kHz Total harmonic distortion: 0.03% Input sensitivity: 0.375V Signal to noise ratio: 105dB https://www.hifiengine.com/manual_library/quad/306.shtml
  9. Tackle the subject, not the player. Do you consider there is a audible difference in a audio circuit using a 78xx , lets say its a 7805 , that measures 5v , vs a LM317 also exactly with output of 5v ? The objective outlook would say that there is no difference as each measure the same, whereas the subjective outlook easily finds audible difference between the two. The post by @muon* found subjective difference, which I praised as having wisdom.
  10. But quite inaccurate as there was no agenda being pushed. If you can take the time read the post. It was saying there is wisdom in making subjective assessments.
  11. It means you have exceeded the sensitivity of the input stages, and possibly also its output stages of your integrated amplifier, to pass audio without clipping. You should instead reduce your DAC so its output is minus 7db if it has a graduation scale, and leave it there. Your available volume is then from your integrated amplifier. Whilst setting to 0db is tempting it is a sad fact of digital recording that it cannot handle peaks. As with everything there are exceptions, namely where companding equipment is used, that would allow you to use greater levels.
  12. The error for any audio use, with 78xx and 79xx regs is the shunt resistor they have internally from output to ground. The resistor programs the regulator to be continuously processing current. Historically it was there more for the reason of offering a device that could be used without a output capacitor, and therefore would work without said capacitor, but with dire consequences for audio. See the page 2 schematic, and spot the resistor from output to ground http://users.ece.utexas.edu/~valvano/Datasheets/LM7805C.pdf Subjectively they add a gritty presentation., fine for washing machines but not your audio system.
  13. What do you consider is the reason for one regulator sounding better than another ? Its an interesting example of the shortcomings of approaching audio with a objective view, The objective mindset would say each are adherence to a voltage and current, and therefore there cannot be any difference, however the subjective outlook has as we can see, far more wisdom.
  14. Sorry you did not understand it, have a read of this https://en.wikipedia.org/wiki/Bandgap_voltage_reference
  15. Which DC regulators in our hypothetical amplifier would view as Vin to V out differential, and merrily keep on regulating, regardless to properly supply each part of the circuit with needed voltage and current. The LM317 HV as example can tolerate a 60v Vin to Vout differential and can regulate supplies to 700v as long as the input to output differential is not exceeded, https://www.ti.com/lit/ds/symlink/lm317hv.pdf The transformer in our hypothetical amplifier could then have a soft start circuit, and a PTC thermistor to protect against in rush current. Each section is then catered for, rather than being challenged by the ups and downs of a transformer.
  16. Given this is hypothetical, with no schematic thus far, a good design of amplifier would not be loading down the rest of the amplifier supply with its provision for heater current. Rather a good amplifier would offer voltage regulation for all stages ensuring each of the valves needed parameters were adhered to, and would indeed separate the heater function with a separate transformer running a DC supply rather than a AC 6.3v winding off the main transformer, that has potential to couple into other sections. Some schematics are shown here: http://education.lenardaudio.com/en/14_valve_amps_6.html for traditional and improved designs.
  17. Not if a separate toroidal is used, like a 20VA MT2084 from Jaycar, the other secondaries are then enabled away from the heaters
  18. Then again its not hard to regulate the heater supply itself, http://www.pmillett.com/DC_filament_supply.htm
  19. Setting the correct voltage value is important, but more so the current used by each device. The humble fuse, is one such device, and offers modest protection. Better is to deploy a fuse in the primary winding, followed by a circuit breaker after the devices switch. The circuit breaker will disconnect the circuit at exactly its current rating which should reflect proper operation of the device up to where it requires to be disconnected , vs a fuse which is less precise. With lessening alternating currents, voltage value, a isolation transformer, is still subject to line fluctuations, it will though reduce the voltage value of said fluctuations. A better arrangement would see resistance being used to also properly reduce current, and better still, regulation of that current, so your equipment is powered at its correct voltage and current. To extend the use of your valve equipment consider a soft start circuit, and power with a PTC thermistor that senses temperature and offers a manner of regulation for in rush currents. https://en.wikipedia.org/wiki/Thermistor
  20. Sonar's Tranceportation 2 is due for release Friday this week. It is the second installment of a recording that took place in April / May this year in Switzerland https://www.rarenoiserecords.com/2020/06/01/new-release-june-2020-sonar-w-david-torn-present-tranceportation-volume-2/
  21. Given a straight wire also requires shielding and represents little resistance, what attenuation method, did you use ?
  22. Companding has been a major feature of almost every recording since the mid 1960's It is celebrated by recording engineers as being able to properly preserve the actual dynamic range present in recordings. The earlier post by @Ittaku sought to allow and replace with artifice, what is already in recordings, which I expressed as a backward step. I was standing up for what is in the recording, pointing out, few have heard what is actually there.
  23. Until heard without coloration. Regarding interaction of electronic components noting your preference for objective measurements, let your ears instead be your guide is my recommendation. A good place to easily begin that discovery is to do some op amp rolling. Your CD player will need to have DIP sized components, as SOIC is tricky where wave soldering is present. Try to hear the distinct differences between say a opa2107 and a opa 2604 dual op amp.
  24. Your post reveals a trap that readers need to be very aware of, namely power amp sensitivity then dictating without your choice, how attenuation is achieved. Quad the UK audio manufacturer have for the last 53 years made every power amp have its full output achieved with signal below 1 v, typically 1/2 a volt ( 500mv ) for most models. It remains one of THE most important figures to check, enabling you - rather than the manufacturer, choosing for you, other partnering equipment.
  25. ,Funny how you missed the bits about companding, about adding artifice unnecessarily, about the importance of timing, and preservation of the recording.
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