I have always wondered why we can't use back to back zeners as crowbars at the headphone jack? Say 3.2v etc. better than nothing?
Zeners in the signal path ? Bah. Yeah, I know: everybody does it..... Like using 78XX/79XX, electrolytic caps in signal path, no muting relays, electronic source control, toroids etc. etc.
When using micro relays of good quality with paralleled contacts (so one relay per channel) no problems. Simplest form, reliable and not intrusive. No burnt headphones and no switch on/off clicks or DC oomphs.
Select relays for low power draw and good quality contact materials. Don't even bother to think about using cheap low quality stuff. It does not belong in the class of this device. When choosing a standard relay pinout builders still can decide to make the mistake of buying cheap pin compatible stuff. Or add pads for 2 different relays to leave choice.
Wrong design philosophy. Always go for the best solutions for the purpose, evaluate influence on signal integrity of found solutions, make a choice (and then calculate down to second best if absolutely necessary). Using opamps for a HA amp is also better than nothing 😉
When using micro relays of good quality with paralleled contacts (so one relay per channel) no problems. Simplest form, reliable and not intrusive. No burnt headphones and no switch on/off clicks or DC oomphs.
Select relays for low power draw and good quality contact materials. Don't even bother to think about using cheap low quality stuff. It does not belong in the class of this device. When choosing a standard relay pinout builders still can decide to make the mistake of buying cheap pin compatible stuff. Or add pads for 2 different relays to leave choice.
Wrong design philosophy. Always go for the best solutions for the purpose, evaluate influence on signal integrity of found solutions, make a choice (and then calculate down to second best if absolutely necessary). Using opamps for a HA amp is also better than nothing 😉
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My question is more whether or not a Zener can provide protection at all or is it flawed. I use them routinely in the signal path to protect the gate of a MOSFET. I see them routinely in the base of a CCS to set the current. No problems. I think you won't hear them until they activate and by then you wouldn't want to hear the sound of your cans getting 15v rails in any event.
Sadly, I heard this sound of full rails hitting my left channel phones the other day. It sounded like a crunch sound. Then the driver is damaged and now clicks on heavy bass notes. I know I need Headphone protection before I hook up my more expensive phones.
I think the new generation low Rdson MOSFETs also work well as protection "relays".
Sadly, I heard this sound of full rails hitting my left channel phones the other day. It sounded like a crunch sound. Then the driver is damaged and now clicks on heavy bass notes. I know I need Headphone protection before I hook up my more expensive phones.
I think the new generation low Rdson MOSFETs also work well as protection "relays".
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Zeners are the "electrolytic caps" of semis 🙂
Often noisy... better use LEDs for many purposes.
Often noisy... better use LEDs for many purposes.
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Are they noisy when not conducting in reverse breakdown? They are just off right? How would you do it with LEDs? Stack two red LEDs to get 3.2v forward drop? LED can only provide 10 to 20mA current relief. The Zener on the other hand is like 1A current capability.
Relays are quite low noise and linear devices. They are also somewhat digital with either on or off operation 🙂 I would use relays.
Bit of nostalgia too. Good devices always clicked when switched on 😀
Regarding the LEDs, they are not suitable in this application as you already indicated (with respect to current). It could be done with power LEDs but it is a headamp not a flashlight.
That is a pity but a very good learning exercise at the same time that only needs to be experienced once. Devices need non intrusive protection systems to protect the often more expensive equipment. Never needed it in the past (as many think) till some expensive woofers burned when a Graetz bridge had a diode failing. Then I built a kit of an expensive class A amp that had a very slow servo for someone. At night there were a few short power blackouts and the amp was always on in standby mode (class AB). The power going up and down caused the amp to ramp up a few times very very slowly....burning the woofers. Yeah those ultra slow servos that are better for sound quality you know. The woofers did not thank me.
Muting/DC protection relays are a must since then. There is a lot of comment on relays but when wisely chosen they can be nice reliable components.
Bit of nostalgia too. Good devices always clicked when switched on 😀
Regarding the LEDs, they are not suitable in this application as you already indicated (with respect to current). It could be done with power LEDs but it is a headamp not a flashlight.
That is a pity but a very good learning exercise at the same time that only needs to be experienced once. Devices need non intrusive protection systems to protect the often more expensive equipment. Never needed it in the past (as many think) till some expensive woofers burned when a Graetz bridge had a diode failing. Then I built a kit of an expensive class A amp that had a very slow servo for someone. At night there were a few short power blackouts and the amp was always on in standby mode (class AB). The power going up and down caused the amp to ramp up a few times very very slowly....burning the woofers. Yeah those ultra slow servos that are better for sound quality you know. The woofers did not thank me.
Muting/DC protection relays are a must since then. There is a lot of comment on relays but when wisely chosen they can be nice reliable components.
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it's actually a S.Wurcer design.
It's in the low distortion oscillator Thread.
There was a distribution of PCBs last week, but you obviously don't read those Threads.
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upc1237 protect ckt manually calculated for VCC of +15VDC with G6K-2P relay, smd version of the same can also be fitted on the same footprint.
1. 2.5 sec delay
2. +1.24/ -1.07 DC detect threshold as per datasheet
3. Immediate switch off-AC loss
4. Manual reset in case of fault or can be made auto resetting also.
5. with generic led indication ckt from net (pl comment).
I am no expert designer, so comments welcome.
reg
Prasi
1. 2.5 sec delay
2. +1.24/ -1.07 DC detect threshold as per datasheet
3. Immediate switch off-AC loss
4. Manual reset in case of fault or can be made auto resetting also.
5. with generic led indication ckt from net (pl comment).
I am no expert designer, so comments welcome.
reg
Prasi
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Hi Prasi,
Nice work. If this is like post 249, I'll take 2 please.
http://www.diyaudio.com/forums/pass-labs/298369-jumas-head-amp-25.html
BR,
Eric
Nice work. If this is like post 249, I'll take 2 please.
http://www.diyaudio.com/forums/pass-labs/298369-jumas-head-amp-25.html
BR,
Eric
Is 6 to 8 enough?
A pair would make a very good stereo line driver. 2pair would make a very good balanced impedance line driver. That's 6 already !
Then there are the rear channels of a 5.1 system.
5.1 speakers would be driven by an existing receiver. diy 5.1 amp would be a huge cost and time, i am not prepared to invest in foreseeable future.
Whats the opinion around here for following?
Should I go for a quick order (at a slight premium charged by boardhouse) for protect PCB too so that I may ship all PCB's in a single shipment for complete HA/pre/Class-A amp?
BTW here is the PCB size for protect.
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