Ok thanks a lot this is great news! I have looked at mouser and cannot find an equivalent
I have used search filters 50K Audio Dual gang and No switch, but there are no audio tap ones... can I achieve the same functionality without the tap?
I have used search filters 50K Audio Dual gang and No switch, but there are no audio tap ones... can I achieve the same functionality without the tap?
20€ + shippping for the european sources, and 3€ from aliexpress but to be delivered between january and end of february... all of those are chinese sources, I bet there must be some equivalents from european vendors
I'm not against buying in china but now in Belgium they are appplying a 15.50 import tax which ruins everything, and don't ask me why but I'm not confident buying old stock from aliexpress...
Is the tap for the bass boost critical or can I connect it to the center leg of the potentiometer?
I'm not against buying in china but now in Belgium they are appplying a 15.50 import tax which ruins everything, and don't ask me why but I'm not confident buying old stock from aliexpress...
Is the tap for the bass boost critical or can I connect it to the center leg of the potentiometer?
No, the tap is important. Here's one in Australia:
1Pcs potentiometer 50K log alps audio amp volume control pot stereo w lo.cf | eBay
1Pcs potentiometer 50K log alps audio amp volume control pot stereo w lo.cf | eBay
final update on this topic I guess,
I have received the ALPS potentiometer and have installed it with the new RC values for loudness
Hiss is lower now but there is still some I guess due to the balance pot which is still a 250K, however it is very satisfactory to have something better and this is not annoying anymore
Thanks a lot for your help, I now have a great amplifier 🙂
I have received the ALPS potentiometer and have installed it with the new RC values for loudness
Hiss is lower now but there is still some I guess due to the balance pot which is still a 250K, however it is very satisfactory to have something better and this is not annoying anymore
Thanks a lot for your help, I now have a great amplifier 🙂
That's a good result.
I don't think the balance control is implicated as a source of hiss. Although the control at 250kΩ is a high value, at the centre position the output wiper is connected directly to the input for each channel respectively, so the 250kΩ of the control is in parallel with the impedance of the connected source (as well as being in parallel with the load impedance i.e. the volume control) - the source impedance should be quite low. The Johnson noise (hiss) is determined by the equivalent resistance of all of these impedances in parallel, and the high balance control Z is swamped by the lower Zs on either side.
It's a bit tricky to try to diagnose the noise source without having the unit on the bench in front. This amplifier is a vintage design with a fairly modest specification even for its day. It's possible that transistor noise is now dominant. If you have some freezer spray you could try chilling each transistor in turn and see if one or more are contributing to the noise floor. If the noise reduces slightly when a transistor is chilled, then that transistor is implicated. The T201-4 2SA666 transistors could be replaced with BC560, but be careful to check the pin connections which are in a different order. The noise figure (NF) for the 2SA666 is 16dB max, compare to the BC560's 4dB max, a huge improvement.
I don't think the balance control is implicated as a source of hiss. Although the control at 250kΩ is a high value, at the centre position the output wiper is connected directly to the input for each channel respectively, so the 250kΩ of the control is in parallel with the impedance of the connected source (as well as being in parallel with the load impedance i.e. the volume control) - the source impedance should be quite low. The Johnson noise (hiss) is determined by the equivalent resistance of all of these impedances in parallel, and the high balance control Z is swamped by the lower Zs on either side.
It's a bit tricky to try to diagnose the noise source without having the unit on the bench in front. This amplifier is a vintage design with a fairly modest specification even for its day. It's possible that transistor noise is now dominant. If you have some freezer spray you could try chilling each transistor in turn and see if one or more are contributing to the noise floor. If the noise reduces slightly when a transistor is chilled, then that transistor is implicated. The T201-4 2SA666 transistors could be replaced with BC560, but be careful to check the pin connections which are in a different order. The noise figure (NF) for the 2SA666 is 16dB max, compare to the BC560's 4dB max, a huge improvement.
This is now far less annoying even with a headset...
I have plenty of modern 2SA from old marantz equipment so I guess if I would need to replace transistors it would be easy to keep the same pinout...
However if I would like better specification I may have to start thinking about making an amplifier from scratch... I have plenty of components at hand and it would be easy to make something from Nelson Pass or another, I have a few dozen TO3 and plenty of stuff in my drawers
I have plenty of modern 2SA from old marantz equipment so I guess if I would need to replace transistors it would be easy to keep the same pinout...
However if I would like better specification I may have to start thinking about making an amplifier from scratch... I have plenty of components at hand and it would be easy to make something from Nelson Pass or another, I have a few dozen TO3 and plenty of stuff in my drawers
Some years have passed and since my latest thread about the dead channel I have progressed quite far
Had to change the voltage regulator transistors from the phono and main preamps because they were doing a lot of noise... this improved the situation to quite silent. There was still some noise when going full volume, and I solved this by changing the first transistor device of all preamps, and the high value resistors as well - they were all conveniently marked with a red dot.
So far so good, I have a near silent amplifier now!
I put it back where it was sitting and hiss and cracks, noise from the wifi or TV supply, I don't know, but this is very frustrating... this is not from the cables picking noise but the preamplifier itself as when I mute or ground the power amp input, it stops immediately...
How would one deal with this situation efficiently?
Had to change the voltage regulator transistors from the phono and main preamps because they were doing a lot of noise... this improved the situation to quite silent. There was still some noise when going full volume, and I solved this by changing the first transistor device of all preamps, and the high value resistors as well - they were all conveniently marked with a red dot.
So far so good, I have a near silent amplifier now!
I put it back where it was sitting and hiss and cracks, noise from the wifi or TV supply, I don't know, but this is very frustrating... this is not from the cables picking noise but the preamplifier itself as when I mute or ground the power amp input, it stops immediately...
How would one deal with this situation efficiently?