Maximum Vout on SSLV1.1
Apologies if this question has already been asked. I have the SSLV1.1 boards and the user’s guide states that the maximum Vout is 45 volts. I would like to use the positive regulator at 50 volts out. What is the limiting factor and what would need to be changed on the positive regulator to operate it at 50v output?
Thanks in advance.
Apologies if this question has already been asked. I have the SSLV1.1 boards and the user’s guide states that the maximum Vout is 45 volts. I would like to use the positive regulator at 50 volts out. What is the limiting factor and what would need to be changed on the positive regulator to operate it at 50v output?
Thanks in advance.
The leds tail jfet max. Its spec is 50V. To get 50 out you need at least 55 in and all it separates that from the jfet is 3-4 leds drop. You get the picture. Marginal. If you will not luck out on edge and it goes, replace it with a 10k 1W resistor standing upright. Less good a CCS but it will survive.
Hi Salas,
Thank you for that excellent explanation. Now I see the problem. 58v in minus the LED Vf 6.3v leaves 51.7v across the JFET. Would it be ok to add a small value resistor in series with the JFET Drain to bring the Vgds below 50v? Alternately would it be worthwhile to look for a JFET with a higher Vgds rating? Thank you for the 10k resistor solution as a backup.
Thank you for that excellent explanation. Now I see the problem. 58v in minus the LED Vf 6.3v leaves 51.7v across the JFET. Would it be ok to add a small value resistor in series with the JFET Drain to bring the Vgds below 50v? Alternately would it be worthwhile to look for a JFET with a higher Vgds rating? Thank you for the 10k resistor solution as a backup.
Not easy to find any low noise and relatively low capacitance jfet at even higher Vds easily available. But if you do, watch the dissipation also. That will be its voltage across times IDSS. IDSS is controlled by the associate R108 resistor to can be moderated though. Don't get it lower than 3mA for the LEDS to work adequately. A small resistor in series with the drain would be a botch job and it will compromise it a bit but it can be a solution.
SSLV1.1 Oscillator!
Hi
I have completed two of your supplies. They are set to 15V and will supply my phono preamp. I bench tested them and they were stable at 15V with no remote sensing.
I then installed them into my preamp using 4 core cable for power and remote sensing. Unfortunately I now have approx 11.5V on each output and oscillation. The output/sense cables are 200mm long and the phono board has 0.1uF decoupling caps only. If I reconnect sense wires directly at the reg. I get my 15V back.
Do you have any guidelines for using remote sensing with these supplies? I guess there is too much phase shift on the sense input, and its upsetting the feedback loop. Any suggestions?
Thanks
Hi
I have completed two of your supplies. They are set to 15V and will supply my phono preamp. I bench tested them and they were stable at 15V with no remote sensing.
I then installed them into my preamp using 4 core cable for power and remote sensing. Unfortunately I now have approx 11.5V on each output and oscillation. The output/sense cables are 200mm long and the phono board has 0.1uF decoupling caps only. If I reconnect sense wires directly at the reg. I get my 15V back.
Do you have any guidelines for using remote sensing with these supplies? I guess there is too much phase shift on the sense input, and its upsetting the feedback loop. Any suggestions?
Thanks
I would try 3 experiments. 1. To delete the 0.1uF decouplers on the phono board if they aren't absolutely necessary to its design. 2. To install 100uF locally on the reg across the sense outputs. 3. To buffer the phono +V input with 10R resistors so to turn the capacitive decoupling to an RC filter.
Thanks for your suggestions.
I tried 100uF across the sense terminals and then at the preamp board. Both seemed effective but I am not sure 100%. In a listening test the sound was rather brittle, not what I am used to for this design.
Next week I can check the output properly with a scope. I'll let you know how that goes.
Thanks
Jeremy
I tried 100uF across the sense terminals and then at the preamp board. Both seemed effective but I am not sure 100%. In a listening test the sound was rather brittle, not what I am used to for this design.
Next week I can check the output properly with a scope. I'll let you know how that goes.
Thanks
Jeremy
I use the SSLV to power the BA-2 front end and very good it is too. I found that the sound of the amp was sensitive to how the reg was set up e.g., C104 altered the sound significantly depending on whether it was an electrolytic or a plastic (I preferred the latter, a cheap WIMA). Also the sound was poor (incoherent) until I removed the supply decoupling filter from the BA-2 board. I don't have a scope but it was evident from listening tests that things were not right so small changes will sound significant.
Chris
Chris
Oscillation follow up
Thanks guys for your input.
Just a follow up after having some problems with remote sensing.
I hooked up the scope to my regulator(s) and saw a major oscillation in my setup with remote sensing. A large 142kHz saw tooth wave was present. Both regulators had the same issue.
I tried placing a 100uF electro at 1/ the output pins (with and without C204 connected), 2/ the preamp board and 3/ across the sense pins. The 3rd was the only one which removed all oscillation.
I then removed this cap and connected the sense pins directly at the regulators output, and ran with no load. Even without remote sensing there was 20mV of oscillation at approx 45Mhz. Both regulators had this mild oscillation. I then hooked up the load and any trace of oscillation dissapeared. So I have left it this way, without remote sensing, and my little phono amp is starting to sound very good.
Just to be clear about my parts on the circuit boards. The boards are standard setup as per the BIB guide, running with 180mA CCS. C202 and C204 are both 6.8uF WIMA MKS4 and input caps are 4700uF KG.
I would recommend that anyone running remote sensing get stability checked with a scope. A tell tale sign is any voltage drop at the regulators output after remote sensing is connected. A hard sound is not a characteristic of this regulator and it may indicate a stability problem.
Jeremy
Thanks guys for your input.
Just a follow up after having some problems with remote sensing.
I hooked up the scope to my regulator(s) and saw a major oscillation in my setup with remote sensing. A large 142kHz saw tooth wave was present. Both regulators had the same issue.
I tried placing a 100uF electro at 1/ the output pins (with and without C204 connected), 2/ the preamp board and 3/ across the sense pins. The 3rd was the only one which removed all oscillation.
I then removed this cap and connected the sense pins directly at the regulators output, and ran with no load. Even without remote sensing there was 20mV of oscillation at approx 45Mhz. Both regulators had this mild oscillation. I then hooked up the load and any trace of oscillation dissapeared. So I have left it this way, without remote sensing, and my little phono amp is starting to sound very good.
Just to be clear about my parts on the circuit boards. The boards are standard setup as per the BIB guide, running with 180mA CCS. C202 and C204 are both 6.8uF WIMA MKS4 and input caps are 4700uF KG.
I would recommend that anyone running remote sensing get stability checked with a scope. A tell tale sign is any voltage drop at the regulators output after remote sensing is connected. A hard sound is not a characteristic of this regulator and it may indicate a stability problem.
Jeremy
Are there film caps still on the rails at load's side? If you could have the sense too in your set up without problems it could be an enhancement but if not doing the job cleanly better without indeed. That "tell tale sign is any voltage drop at the regulators output after remote sensing is connected" is correct.
Thanks to Salas for this design, and thanks to Tea-Bag for the SSLV1.1 boards and JFET kits which I recently received.
Some advice, please:
I will be building a +/-13V supply for a TP Legato I/V stage. The Legato should draw approx 170mA +ve and 190mA -ve.
I was thinking to shunt 60mA on each rail, and heatsink to the chassis floor. Is this enough shunt current?
Some advice, please:
I will be building a +/-13V supply for a TP Legato I/V stage. The Legato should draw approx 170mA +ve and 190mA -ve.
I was thinking to shunt 60mA on each rail, and heatsink to the chassis floor. Is this enough shunt current?
I run my Legato with +/-15 V rails, and shunt around 160-200 mA. I feel the Legato sounds better at 15 VDC. You will need more heatsinking if you run higher shunt currents, and how much sinking you need will also depend on how much voltage drop you are running. I found a section of 1/4" thick by 1.5" aluminum angle stock worked great for heat sink, then bolt that down to the chassis floor to further spread the heat. I get it from onlinemetals.com, but it is a pretty standard size-online metals will also cut it to whatever length you want.
I would also experiment with the onboard decoupling caps on the Legato (the 100 uF electrolytics), I changed all of them to .1 uF films (used vishay MKPs from Parts Connexion). I found the farther away I got any elctrolytics from the Legato, the better it sounded.