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  1. Audioguru

    Back to the Breadboard

    Messy ling wires all over the place on a breadboard cause feedback. I think the gain pot has the gain too high causing crosstalk between the opamp input wires and its output wires.
  2. Audioguru

    Newbie Question 18650 Powerbanks

    Samsung (Korea) and Panasonic (Japan) make high quality 18650 cells and real ones are sold by reputable dealers. Horrible knock-offs are sold by '"sellers" on all the Chinese websites. Frequently the fake one has less weight but looks better than the real one.
  3. Audioguru

    Question long term storage batteries

    Cheap poor quality batteries do not hold a charge for a long time. Measure the voltage in 2 months and if the voltage did not drop then measure the voltage each year.
  4. Audioguru

    Power supplies

    Audio is an alternating voltage that can be positive and negative or simply a positive voltage that varies like from the output of your opamp. Then the output coupling capacitor blocks the DC but passes the audio allowing the audio to be varying positive and negative voltages. A speaker also...
  5. Audioguru

    Question long term storage batteries

    This thread is on and has been answered on 3 or 4 other forums.
  6. Audioguru

    Knightkit 400(A) or Lafayette TE-15 Assembly/Maintenence Manual

    Many years ago I made Eico and Heathkit kits. I remember Knight Kits and Lafayette Kits in ads but never seen one.
  7. Audioguru

    Newbie Question 18650 Powerbanks

    Here is the same brand name last year as 8 years ago, Ultrafire. It is labelled with 3 times the capacity of Name Brand more expensive batteries but it is a lie. It tested at 1163mAh. Another cheap lightweight 18650 Chinese battery was opened 3 years ago and it was almost empty inside. Another...
  8. Audioguru

    Newbie Question 18650 Powerbanks

    Here is an 18650 battery bought from ebay. It is one of many fakes that are sold:
  9. Audioguru

    Back to the Breadboard

    I watched a guy on You Tube showing how he plays the G "Chode on his guitah ", mate!
  10. Audioguru

    Back to the Breadboard

    I listened to Fly by Night by Rush and the D chord at the beginning sounds fairly clean (low distortion). You can adjust the amount of distortion with the gain control or with the intensity of your playing. Play intensely and you produce lots of distortion. Play softly and you produce low...
  11. Audioguru

    Back to the Breadboard

    The voltage divider can use any equal resistor values when the opamp that he always uses has very low input bias current. But Wampler did not see the problem with his input capacitor value being way too high that might cause input overload of the opamp input if the guitar is thumped.
  12. Audioguru

    A really small and cheap audio stereo amplifier 3w/3w from 5V psu

    I remember hearing 8 bits audio many years ago. It sounded awful.
  13. Audioguru

    Studio Active Monitors Speaker/Woofer Damaged buying equivalent one instead of original?

    Since the amplified speaker has no detailed audio specs then nobody knows anything about it. If the amplifier power rating was truthful saying real Watts (maybe 40 real Watts) over a range of frequencies at a low distortion level, then play it for a moment at a loud enough level for you to hear...
  14. Audioguru

    Back to the Breadboard

    Since the original circuit used a TL081 opamp that has Jfet inputs, its maximum input bias current is 200pA which is very close to zero current, then any value for the voltage divider resistors up to 200M ohms are fine. The old 4558 dual opamp maximum input bias current is 0.5uA and the two...
  15. Audioguru

    Studio Active Monitors Speaker/Woofer Damaged buying equivalent one instead of original?

    Decibels are usually used to measure sound levels, not power Watts. Every speaker design has its sensitivity listed in its detailed specs and measured in an anechoic chamber at a distance of 1 meter. Your (cheap?) speakers do not list any detailed specs.
  16. Audioguru

    Studio Active Monitors Speaker/Woofer Damaged buying equivalent one instead of original?

    The cheap woofer burned out (?) because you played it too loud. I have stereo speakers I built with 6.5" woofers in ported enclosures and with dome tweeters. I never play them with more than 20 real Watts each. The Alexis 620 speakers say 100 Whats in the owners manual that might be 100 peak...
  17. Audioguru

    Back to the Breadboard

    My temperature controlled Weller soldering iron is 53 years old and is always at 371 degrees C (700 degrees F. I always use name-brand 63/37 tin/lead rosin-core solder. One solder joint takes 1 second. I have never fried any electronic part. I am glad to hear that you got it to work well.:)
  18. Audioguru

    Back to the Breadboard

    Wire the circuit the same as on the schematic.
  19. Audioguru

    Power supplies

    Swing definition: In your circuit that uses a 9V supply and an old 4558 dual opamp, the maximum opamp output "swing" is +1V to +8V. Then the maximum loudest waveform is 7V peak-to-peak. It idles with no signal with the input and output at +4.5V which is half the supply voltage so it can swing...
  20. Audioguru

    Back to the Breadboard

    I looked through all your threads and posts looking tor the 3.3uF capacitor that I recommended from 220nF and found it in your different thread over 1 year ago. It is C28 to ground which is in series with the 1k R46 at pin 2. 3.3uF passes most audio frequencies. When C28 is 220nF it cuts 727Hz...
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