15Vac is too low for a CCS Shunt Regulator set to 15Vdc output.
When the CCS Vdrop has gone down due to insufficient supply voltage then it is wrong to lower the CCS resistor to try to get the output current you need. The Vdrop across the CCS will keep dropping as you lower that resistor.
There is simply not enough supply voltage.
Sort the supply.
When the CCS Vdrop has gone down due to insufficient supply voltage then it is wrong to lower the CCS resistor to try to get the output current you need. The Vdrop across the CCS will keep dropping as you lower that resistor.
There is simply not enough supply voltage.
Sort the supply.
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Good Call...
Andrew. I did not even notice his Transformer.
For the Legato regs I am using a 2x17.5 VAC transformer (52 VA), which, under the load, actually outputs around 18.2 VAC with 117VAC input (US voltages).
Merlin: I would recommend a 2x18 VAC transformer, and it would not hurt to get a bigger one, 50 VA or so, for sonic purposes.
Andrew. I did not even notice his Transformer.
For the Legato regs I am using a 2x17.5 VAC transformer (52 VA), which, under the load, actually outputs around 18.2 VAC with 117VAC input (US voltages).
Merlin: I would recommend a 2x18 VAC transformer, and it would not hurt to get a bigger one, 50 VA or so, for sonic purposes.
So you also reduced to 2R2 the negative rail, I don't have on hand 2R2 I used 1R5 & get 433mA.
I'm using the Bal/SE converter, can be enough positive rail 379mA & negative rail 433mA?
About negative voltage could you remember me tha exact value because I don't remember the exact value 13V or 13.5V, etc?
Thanks for help Barrows
I used the tx bought to TP for it's regs. I know it's a little small 2x15 VAC 30VA but to adjust the reg & test the Legato is enough, if OK I will buy R-Core 2x18VAC 80VA.
Thanks,
I have been jotting down some reference voltages for a future blog.
I've got two Legato one's written down now.
If anyone else has some reference parts for specific voltages, PM and I can get it together quicker.
About negative voltage could you remember me the exact value for Legato because I don't remember the exact value -13V or -13.5V, etc?
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Legato 3 is fine with +/-15V rails. It is only on (modified?) Legato 2 where some say running the negative rail at -13.5V is better.
Cheers,
Nic
About the transformer... I'll have to agree with these guys that you really want 18x2 secondaries, rather than 15x2, for +/-15V rails on the Legato (or whatever). Puts the rectified/ filtered DC in the "Goldilocks" zone, just right...
Legato 3 meant for 15 symmetric rails, Legato 2 some guys running slightly lower negative rail. My own L2 +14.9/-13.9 to put it in the "sweet spot" (VCC/2)-1. My Legato is mostly stock, but I changed the I/V resistors to 180r from 150r.
Legato 3 meant for 15 symmetric rails, Legato 2 some guys running slightly lower negative rail. My own L2 +14.9/-13.9 to put it in the "sweet spot" (VCC/2)-1. My Legato is mostly stock, but I changed the I/V resistors to 180r from 150r.
Thank you, William.
Will there be any problem going with 2x20 instead? And is the current rating important?
I would really stick with an 18x2 if I had a choice. Plenty of headroom already for the regulator to work as designed. 20x2 just more dissipation and unnecessary. I have a 40VA rated transformer on the Legato, with ~.62A total draw.... runs barely warm and is certainly "enough", but I normally err on the higher side with transformer sizing.
Successfully done 2x3.3V with these board. Now I am doing one for my t-amp. I need some comment here:
The equipment list:
-R301 is 1ohm and current set is about 0.96A.
-Using a 80VA toroidal trans with 14-0-14Vac (use 1 side only).
-the other are as in BOM
With a small speaker, the setup is solid, can turn to full volume and the supply voltage stay steady at 13.0V. But when I put it in my main system powering a pair of Castle Eden bookshelf, ithe voltage jumping up and down. I think is a sign of lack of current.
I try with a 200VA 24-0-24 trans but the heat produce is too much, the diode is burning hot also. I am using an Phoenix Gold old amplifier chassis as heat sink (pic attach), it is whole piece of aluminium block. I try with reducing R301 to 0.5ohm, and change back to 80VA 14-0-14 trans, but the voltage is fluctuating even connect to small speaker, I think it is asking too much CCS from the 80VA trans. Tomorrow I will try with maybe 0.8ohm. Has anyone has a better experience?
The equipment list:
-R301 is 1ohm and current set is about 0.96A.
-Using a 80VA toroidal trans with 14-0-14Vac (use 1 side only).
-the other are as in BOM
With a small speaker, the setup is solid, can turn to full volume and the supply voltage stay steady at 13.0V. But when I put it in my main system powering a pair of Castle Eden bookshelf, ithe voltage jumping up and down. I think is a sign of lack of current.
I try with a 200VA 24-0-24 trans but the heat produce is too much, the diode is burning hot also. I am using an Phoenix Gold old amplifier chassis as heat sink (pic attach), it is whole piece of aluminium block. I try with reducing R301 to 0.5ohm, and change back to 80VA 14-0-14 trans, but the voltage is fluctuating even connect to small speaker, I think it is asking too much CCS from the 80VA trans. Tomorrow I will try with maybe 0.8ohm. Has anyone has a better experience?
Attachments
On small T-Amp 13V rail I remember 1.5A plus was needed on over 90dB 8 inch quarter wave speaker (8 Ohm), if this gives you an idea. The 9610 is not that capable if you need go near 2A with your speakers. Maybe 9620 then. That one is also tamer for Vgs, i.e. will give more CCS for same resistor. Keep the drop over the reg logical ~6-7V to avoid additional heat. To do the job properly, you need measure top consumption from previous supply when playing the big speakers. A DVM in series mode (Ampere scale) passing the rail through it, will tell. Then you need top that for CCS set.
P.S. Read http://www.diyaudio.com/forums/power-supplies/153484-using-hypnotize-general-shunt-reg-pcb-2.html#post1995942 for an app on 13V T-Amp. From post#20 to #28.