would 6.3v be too low for c9? im thinking about blackgate nx... price is not an issue for me, availability is 🙁
You can have them too, I've buyed from ASE-Audiotuning.
This one is also suitable, Suburra uses them.
Both FKs and NXs are quite better than standard, more refined and transparent with bigger and deeper soundstage.
The difference between FKs and NXs is more subtle.
Race update and some news
He will kindly make some measurements to verify if the problem is present so than we can, eventually, fix it. 😎
This will obviously lead to a one week/ten days delay (I would have ordered next Monday) but I'm sure that all partecipants will be happier this way. 😉
Any comment is welcome. 🙂
- BMCBob
- SoIL4x4
- Lehmanhill
- b.veneri
- billo44
- arthur
- StefanoSan73
- Suburra
- KSTR (ongoing)
- Randytsuch
- diymax62
He will kindly make some measurements to verify if the problem is present so than we can, eventually, fix it. 😎
This will obviously lead to a one week/ten days delay (I would have ordered next Monday) but I'm sure that all partecipants will be happier this way. 😉
Any comment is welcome. 🙂
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Leakage current in the timing cap can be a problem.
Recently, I went back to a pre-amp with a delay relay on board. It had been unused for ~1yr.
It would not switch on (unmute).
The timing cap had gone short circuit. !!!? Much worse than just increased leakage.
I replaced the cap and then tried to reform the faulty cap. It remained short circuit. It was OK when it was last used.
Some electrolytic caps go faulty. If you can get the delay circuit to work with a film cap, then reliability will be improved. That will require a redesign of the relay drive circuit.
Recently, I went back to a pre-amp with a delay relay on board. It had been unused for ~1yr.
It would not switch on (unmute).
The timing cap had gone short circuit. !!!? Much worse than just increased leakage.
I replaced the cap and then tried to reform the faulty cap. It remained short circuit. It was OK when it was last used.
Some electrolytic caps go faulty. If you can get the delay circuit to work with a film cap, then reliability will be improved. That will require a redesign of the relay drive circuit.
thanks dario. the price is better than i expected. i am hesistant about the new value, though. i know its been advocated in the past but not sure if maruo condoned it or not.
i think it alters the bass response? i'm going to have to do some backlog reading before the purchase.
i think it alters the bass response? i'm going to have to do some backlog reading before the purchase.
Hi Andrew,
😱
Was it a good quality cap?
It's a nice idea but it's a bit over my knowledge, maybe. 🙁
You're proposing to mod the RC network R19/C15 or also C16?
😱
Was it a good quality cap?
It's a nice idea but it's a bit over my knowledge, maybe. 🙁
You're proposing to mod the RC network R19/C15 or also C16?
This seems a very interesting approach:
(image from A DC Fault Protection Circuit for Audio Amplifiers)
But sadly it miss the needed initial delay.
(image from A DC Fault Protection Circuit for Audio Amplifiers)
But sadly it miss the needed initial delay.
which post is the schematic in? I have found C16 in post1. That is the time delay capacitor. Note, it has 2*Vbe across it.
The old cap was a 16V 470uF holding just 1.4Vdc. It was a Rubycon CE W M541 and no reason to think it was low quality control.
The replacement is a Nichicon VR(M) 25V 470uF.
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That's the one I found.
R19 C15 is the output offset detect.
R21 C16 is the time delay. R20 is not required.
If you want a sensible time delay then change C16 to 1uF (MKT and MKS is compact and cheap and does not affect sound quality). Remove R20.
The RC becomes 220k*0.0001=22seconds. Seems long enough but the charge only rises to 1.2V to start to trigger the relay. That is only 1.4/24 of the RC charge assumption. A bit too short.
Increase R to 1M0 and you get 1s.
Now insert a Zener or a couple of LEDs between the two transistors and you can stretch the time to a bigger proportion of the RC. Needs a bit of development (change R22), but possible with very few changes to the PCB.
R19 C15 is the output offset detect.
R21 C16 is the time delay. R20 is not required.
If you want a sensible time delay then change C16 to 1uF (MKT and MKS is compact and cheap and does not affect sound quality). Remove R20.
The RC becomes 220k*0.0001=22seconds. Seems long enough but the charge only rises to 1.2V to start to trigger the relay. That is only 1.4/24 of the RC charge assumption. A bit too short.
Increase R to 1M0 and you get 1s.
Now insert a Zener or a couple of LEDs between the two transistors and you can stretch the time to a bigger proportion of the RC. Needs a bit of development (change R22), but possible with very few changes to the PCB.
Thanks Andrew, instructive post. 🙂
But my comment on the needed delay was referred to the MOSFET circuit I've posted, the delay in My_Ref's protection circuit is OK as is.
I was asking if you think both or only one of the elcos should be replaced with film caps.
Are you still referring to the amp in the thread title?
Are you still referring to the "problem" as in posts 656/7?
Are you still referring to the "problem" as in posts 656/7?
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Post673 has me confused. That's why I had to ask if you were in some other place.
Could you repeat your post673 enquiry?
Could you repeat your post673 enquiry?
No problem 😉
If I understood correctly you were suggesting to modify the protection circuitry (to improve reliability) to use film caps in place of elcos.
I was asking if you were referring to both C15 and C16 or only one of the two.
I am specifically referring to the time delay cap C16.
I am not so sure that the DC detect can get away with a cap around the 1uF value and achieve the sensitivity required and importantly only require tiny changes in the PCB.
It is perfectly possible to use a film cap here that can achieve usable time delays, with just very minor changes to the PCB.
I am not so sure that the DC detect can get away with a cap around the 1uF value and achieve the sensitivity required and importantly only require tiny changes in the PCB.
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Fine 🙂
Maybe we should rely on Mauro's circuitry another time... In the end most of us never had a problem with it.
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