Hi Shaan, what is the best BIAS configuration to obtain maximum fidelity from this amplifier and the best sound quality?
Hi Cejas.
200mA output stage, 10mA VAS.
Use standard LR network at output for best stability. 10 turns of 1mm enameled wire wound on a 10ohm 2watt resistor will be sufficient.
200mA output stage, 10mA VAS.
Use standard LR network at output for best stability. 10 turns of 1mm enameled wire wound on a 10ohm 2watt resistor will be sufficient.
Whether it is influenced by any differences in build or not, I cannot say. But I ofcourse started out at the standard spec. but was not entirely happy, on my four monoblock builds each supplied by Samy's 600w SMPS's and with Exicon's in the output stage.
I have other Latmos based amps and they are all running higher bias, something that Shaan specifically set out to avoid the necessity off.
Still, raising the bias to 2½-3 times the specified, I cannot remember the actual bias value, but total power consumption is now around 65w/Ch.
Improvements were mainly 3D imaging and spatial resolution and the low end performance, not as lean.
A friend borrowed the 2x2 amp's with std. bias and raised bias and also highlighted the improvements. He didn't want to return them 🤣
I've used them also with my smaller Apogees and it was magic.
But you should just try it out yourself - given that you have sufficient cooling, it's just a matter of dialing it back if you don't like it.
Check the biasing sections in the setup guide. It's all detailed in there. Shared in post #1.
No, but if I remember right the std. bias yielded about 27w consumption at idle.
In reality I biased it as you do a classic Threshold power amp, be it SA/1-SA/3 or S200-S500, stable temperature = ensuring fairly stable thermal conditions also at load. aiming for the 45-50C range.
Use that for a guidance rather than the specific bias current!
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A friendly note, anyone looking for assembled V4H amp modules and PSU modules?. Please see in Swap Meet. Excuse my typo error in Title " VH4 " should be V4H. Discounted price, good deal I think.
Thanks,
MM
Thanks,
MM
Hi shaan or other V4H builders,
Powered up my psu's for the V4H using a 24VAC secondary and everything went well. No smoke, led's lit, psu output with 120V mains is +/- 34VDC. I am going to mount the V4H amp boards on heatsink and I have a quick question:
" Is a nylon shoulder washer needed to insert into the MFet mounting hole on the pcb top, or, is metal bolt to metal plate OK" ? I looked at a lot of pics and could not determine clearly.
Thanks for the help,
MM
Powered up my psu's for the V4H using a 24VAC secondary and everything went well. No smoke, led's lit, psu output with 120V mains is +/- 34VDC. I am going to mount the V4H amp boards on heatsink and I have a quick question:
" Is a nylon shoulder washer needed to insert into the MFet mounting hole on the pcb top, or, is metal bolt to metal plate OK" ? I looked at a lot of pics and could not determine clearly.
Thanks for the help,
MM
No shoulder washer are needed, you do need some isolation/insulation between the transistors and the heatsink. No legs should short to the heatsink, always check this before applying any power.
So, after testing psu and further wiring to perform the amp test:
I have mounted the amp module on a heatsink. The 4 MFets are mounted on mica pads w/ grease on both sides, and the 2 smaller transistors are mounted on sil pads. I have connected a ground wire from the heatsink to one of the 5 grounds on the psu. I have also connected a wire from SGND to PGND and from PGND to another of the 5 psu grounds.
I performed a continuity test with DMM from the amp output tab to the heatsink and I get a constant beep. I also performed a continuity test from the Drain's of the 4 MFets to the heatsink and they all beep. I have looked at the MFet/pads underneath the pcb and all looks good.
Before I attach pics, " is the only way" to have continuity between the amp output or the MFet drains and the heatsink is from the metal parts of the transistors contacting the heatsink.
Thanks for the help,
MM
I have mounted the amp module on a heatsink. The 4 MFets are mounted on mica pads w/ grease on both sides, and the 2 smaller transistors are mounted on sil pads. I have connected a ground wire from the heatsink to one of the 5 grounds on the psu. I have also connected a wire from SGND to PGND and from PGND to another of the 5 psu grounds.
I performed a continuity test with DMM from the amp output tab to the heatsink and I get a constant beep. I also performed a continuity test from the Drain's of the 4 MFets to the heatsink and they all beep. I have looked at the MFet/pads underneath the pcb and all looks good.
Before I attach pics, " is the only way" to have continuity between the amp output or the MFet drains and the heatsink is from the metal parts of the transistors contacting the heatsink.
Thanks for the help,
MM
Something is wrong, you should not have continuity to the Output tab and heatsink, check in resistance mode on your DMM to see if it’s a dead short (0.0-0.5 ohms) or just low like 10-ohms.
Same goes for the legs of the mosfets and drivers, none of the legs should have continuity with the heatsink. I typically just use the mounting bolt and each leg to test.
Same as above, check actual resistance too so you know what kind of short.
Take your time, could be as simple as a solder bridge, or mixed up wiring. But double check those mica pads, can easily get cracked and only cause issue when you tighten down the mounting bolt.
Same goes for the legs of the mosfets and drivers, none of the legs should have continuity with the heatsink. I typically just use the mounting bolt and each leg to test.
Same as above, check actual resistance too so you know what kind of short.
Take your time, could be as simple as a solder bridge, or mixed up wiring. But double check those mica pads, can easily get cracked and only cause issue when you tighten down the mounting bolt.
