Some swear on them, even in this board. I for myself do not have any experience with SS relays in amplifier outputs.
Best regards!
Best regards!
2stageEF high performance class AB power amp / 200W8R / 400W4R
- Thread starter astx
- Start date
... low ohmic Rds-on MOSFETs (< 10mOhm) are expensive. You need 2 of them and some extra parts like special optocoupler with a photovoltaic cell inside to provide the gate voltage. Maybe you need some sort of extra protection for electrostatic safety too...
I like the silent "click"-sound when the speaker relays are contacting ... 😉
I like the silent "click"-sound when the speaker relays are contacting ... 😉
Have you ever measured an SS relay? If so, what devices was it using?
I'm very confident that a custom SS relay made with back-to-back ultra-low rDS MOSFETs would have distortion far lower than the amplifier itself. Benefits of SS relay are numerous:
- Much faster acting
- Much better at interrupting a DC fault
- No ageing (SS relay in 20 years will behave as it does now, whilst a mechanical relay's contacts can get pitted and/or tarnished over time).
He he, you know the other road to the Rome, may be you walk on this road in the future.😉
Dear Harry,
No!
Maybe worth someday to do some testing especially in the sensitive 1W power range. If one can recommend a diy audiophile speaker SSR ...
BR, Toni
it is very easy to wire a couple of mosFETs back to back and insert them into an AC circuit.
Then measure the AC Vdrop across the mosFETS to get some idea of the impedance they have added to the AC circuit.
One slight disadvantage to the SS relay based on dual back to back mosFETs is the small capacitance from In to Out when OFF.
This limits the HF attenuation when active.
I have Bonsai's NX with it's SS relays on the PSU and that minimal capacitance when OFF is not an issue.
Then measure the AC Vdrop across the mosFETS to get some idea of the impedance they have added to the AC circuit.
One slight disadvantage to the SS relay based on dual back to back mosFETs is the small capacitance from In to Out when OFF.
This limits the HF attenuation when active.
I have Bonsai's NX with it's SS relays on the PSU and that minimal capacitance when OFF is not an issue.
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SSR in the rail voltages? Or on speaker outputs?
Both 😉
No !
The Bonsai NX PSU SS relays are in the speaker circuit.
They are not in the supply rail circuit/s.
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Our version of speaker relay uses IPB025N-10N3 mosfets and ASSR-V622-302E Optos to control them. The opto contains a fast off circuit and gate protection to make a complete SS mosfet relay circuit. These parts do add up in cost quickly but I think are money well spent.
I can send you some sample boards if you would like to measure them (You likely have better test equipment than I do).
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Thx for offer! I only need some MOSFETs and the photovoltaic optocoupler for testing. Maybe I will buy some parts for testing in summer if I find the spare time.
On a future todo list: designing a mini pcb to be able to replace the JJM1 relays.
Have fun,
Toni
On a future todo list: designing a mini pcb to be able to replace the JJM1 relays.
Have fun,
Toni
I did run into an anomaly with one SS relay design in a very compact layout that was showing some distortion. I'm not sure of the cause but it was located very close to a control transformer and may have been picking up some EMF in the gates of the mosfets? I'm waiting to get better test equipment to investigate farther.
Did you measure distortion between mosfet's input and out to compare?
Unfortunately i have many many parts missing to try by myself.
I measured distortion at the output of the mosfets and at the amp output with the mosfets disconnected from the circuit. The distortion analyzer I was using is and hours drive from me so I don't use it often.
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My sound card on my test bench computer isn't good enough. Noise floor is higher than the amplifiers.