Sorry for the intrusion. I recently got a couple of LC VSSA. I run them with 36+36 volts. The ps are for use in CNC and I got two of 350watt each but I connected for two rails.
The questions are: Need a Zobel? Which value? Does need a coil in the output? The sound is a little ringer with my lowther of 15ohm. I want to connect in balanced input. Can I?
Best Regards
The questions are: Need a Zobel? Which value? Does need a coil in the output? The sound is a little ringer with my lowther of 15ohm. I want to connect in balanced input. Can I?
Best Regards
Do you have the manual from LC else find it here with other good stuff for the GB, LINK: http://www.diyaudio.com/forums/vend...lateral-mosfet-amplifier-254.html#post3653117.
You don't need a Zobel filter at amp end of speaker cable, it's build in at PCB in form of R21/R22/C23/C24. You free to put Zobel filter other end of speaker cable (speaker terminals) to linearize the driver impedance but it's another story.
Does need a coil in the output? Don't think so, only if using exotic speaker cable. See page 4 manual and attached picture.
Your Lowther's impedance 15ohm is relative high, in principle VSSA then needs max voltage from PSU which is +/- 45V. But i don't think it's a problem because at same full rangers can't take much power and they are quite effective at lower power.
Balanced inut? See the manual from your balanced source, most have schematic suggestions for converting balanced to single ended.
PS Just a suggestion. About PSU if your goal is this amp is only to be used for the Lowthers and you want +/-45V, cheap 59,99§ SMPS connex SMPS300R from here Power supplies, use 2x times for stereo. Else if feeding other speakers and need more current use 2x SMPS500R instead.
Attachments
Hi. I removed all liitle blue caps, put OUTPUT GND wire to amp GND tab, made one grounding point, put very short wire from output to speaker.But it is still quite noisy. Maybe it is littlebit quieter. Also i haven't got scope (yet), but i think i gonna buy it in this week. Also I tried to put little coil (18 turn on 6mm drill bit in two layers) in to output, but it didn't change nothing.
My speakers dont have tweeter, i have broadband speakers
, but i still can hear this noise.
My speakers dont have tweeter, i have broadband speakers
, but i still can hear this noise.
Hi again. After some testing i discovered that when I put 47nF (type is K73-9) cap in intput, amp get silent. But, when i let it there, it gonna "eat" hight frequencies? But, we dont need higer frequencies than 20kHz
Hehe good humor. Yes in principle 20KHz is maybe enough for simple sinus (use 2n3055 output devices)
. LC constructed GB VSSA for 100KHz square wave reprodution if i remember and in lab he had it higher, to benefit this keep input as delivered.Recommend oscilloscope and LC guide, but if not available now and you have time and patience here suggestions to try:
Concentrate on only one module getting up running perfect, and thereafter the other based on knowledge from first if succeeded.
Dismantle the module, inspect visual for errors and especial see if INPUT pair and VAS pair should by accident be turned around.
Pre calibrate TR1/TR2/TR3 by this guide http://www.diyaudio.com/forums/vend...lateral-mosfet-amplifier-157.html#post3532755.
Short input by soldering little wire, and don't take this off before amp first is calibrated and later running with speaker connected and no noice at all in speaker.
Many had little smoke from R21/R22 belonging to Zobel filter and then resistence go off spec so with DMM in ohm mode measure them they should be 20ohm.
Mount PCB again and if possible isolate screws for two VAS devices with isolated washers of some kind. But do only this if shure heatsink always have ground potential through box or wire.
Now calibrate as in manual + the amend for calibration that can be found here http://www.diyaudio.com/forums/vend...lateral-mosfet-amplifier-254.html#post3653117.
If now still sea sound noice try desolder C4/C5, those oversize green 10uF MKT's you used, amp can run without. If no good try another simple PSU for trials.
Good weekend.
Last edited:
Haa... Those 3055/2955 are probably the worst output devices i know, not sure if the slowest.
Try 100k resistor... feedback resistor value?
Power supply GND connection to frame? The input cables should be islolated, So far I havent found anything better than well shielded 50R cable.
Biased to class A?
Try 100k resistor... feedback resistor value?
Power supply GND connection to frame? The input cables should be islolated, So far I havent found anything better than well shielded 50R cable.
Biased to class A?
No the slowest is Elektrohoolik's VSSA when using 47nF at input filter ...
....You free. Not a LC module anymore, there some error elsewhere at Elektrohoolik's VSSA think better to find that.
See point 6 here (LC recommended grounding connections for VSSA) http://www.diyaudio.com/forums/vend...lateral-mosfet-amplifier-254.html#post3653117.
When calibrated right it do automated class A at low power and AB at higher power as i understand.
Last edited:
Try to sync the waveform to be still on the scope's screen. Don't forget to record the X,Y values.
For a little higher price and size you'll get much greater performance from a ready made and well tested First One amplifier.
