then ask for custom wound with 20-21Vac secondaries
but - be careful during power up/biasing procedure , when drain resistance of Jfets and load on PSU is minimal , to avoid gray smoke from input Jfets
if you're using Cviller's board - mount cascodes for input Jfets , then you don't need to worry
but - be careful during power up/biasing procedure , when drain resistance of Jfets and load on PSU is minimal , to avoid gray smoke from input Jfets
if you're using Cviller's board - mount cascodes for input Jfets , then you don't need to worry
I think it's advisable to place the resistors between the caps as Pass scheme.
This is the ripple in my F5 at the board input without and with resistors.
(quality picture is low due to no camera tripod)
I enjoyed a marked sound quality improvement with R installed.
Attachments
Even better is a CLC
To get a very good idea of CRC and CLC I use Duncan's PSU Designer II
With only a cap of 66mF you get about 600mV of ripple
With a CRC of 33mF-0.12ohm-33mF you get about 200mV of ripple
with a CLC of 33mF-5mH-33mF you get about 10mV of ripple, that's 20 times less compared to a CRC !
To get a very good idea of CRC and CLC I use Duncan's PSU Designer II
With only a cap of 66mF you get about 600mV of ripple
With a CRC of 33mF-0.12ohm-33mF you get about 200mV of ripple
with a CLC of 33mF-5mH-33mF you get about 10mV of ripple, that's 20 times less compared to a CRC !
I had tried it with resistors at one point but thought I didn't notice anything significant sound-wise. That was a while ago, but I'll try again.
Thanks. So maybe the Antek 20V transformers would be better for the F5 since the the no load voltage is lower than the Plitron.
Hey labjr,
Is the no load voltage truly lower? The Plitron in this case had a primary voltage of 124.5V applied whereas the Antek only had 122V applied to its primaries. I think you will get close to the same output voltage on the Antek if you raised the primary voltage to 124.5V
Steve
I shot scope pictures some time ago when I was aware that one of my treble monoblocks (I built four in biamplification) was clearly harsher than the other treble channel. I forgot to insert the R. After adding the resistance (from C-C-C to C-R-C-C) both treble channels started to sound similar and the modified one lost the harshness I noticed before.
Another 0.16R (C-R-C-R-C) limited and smoothed ripple to around 10mV, but I didn't notice any clear sound improvement.
Guys, usually most of the loaded PS voltage drop comes from rectifier and ESR of the filter capacitors. Measure loaded and unloaded AC voltage on secondaries and note the difference. After that measure the loaded and unloaded DC voltage on filter caps and you'll see that difference is disproportional to AC voltage drop. If not, then you have very good filter caps.
If you don't have very powerfull resistors you can use 10R/10W to load the PSU (or combine few of them) but measure it quickly (up to 5 sec.) and disconnect to avoid flames
If you don't have very powerfull resistors you can use 10R/10W to load the PSU (or combine few of them) but measure it quickly (up to 5 sec.) and disconnect to avoid flames
Antek's spec sheet for the 4218 says the no load voltage is 18.9v with 120V. If I'm calculating properly, comes out to 19.6v at 124.5v input. Still a little low. The Antek 4220 comes out to about 21.47 which is a little high.
I wonder if the Antek spec sheet is accurate? Did Jon actually check these himself with a variac set to exactly 120V? I'd still rather come out a volt over than under by a couple of volts in the end.
I wonder if the Antek spec sheet is accurate? Did Jon actually check these himself with a variac set to exactly 120V? I'd still rather come out a volt over than under by a couple of volts in the end.
We already had one run some time back on transformers that also bordered on Antek bashing. I for one, prefer not to see it again.
How about moving this to a separate thread just for transformers? I think there is enough discussion about how it is the entire design of the power supply that really matters.
How about moving this to a separate thread just for transformers? I think there is enough discussion about how it is the entire design of the power supply that really matters.
Wondering which Antek transformer is best suitable for the F5. I don't see any bashing there. I think my questions are relevant to the voltage required to get the most out of the F5. Kind of difficult to make up for lack of voltage with power supply design.
Thus, I fail to see where your comments are relevant to this thread.
Hey labjr,
I haven't completed the F5 project yet. So, I can't coment from experience. But, I did purchased the 18V Antek for my F5.
However, I did build an Aleph J with two 18V Avel transformers and the rails run at 22V to 23V or so. I think that if I had to do it over that I would go with 20V secondaries and experiment. You could always go CRCRC to drop some more voltage if it comes in too high. And, although I have never done it, you could cascode the front end so that the high voltage wouldn't be an issue there.
Just my thoughts,
Steve
I haven't completed the F5 project yet. So, I can't coment from experience. But, I did purchased the 18V Antek for my F5.
However, I did build an Aleph J with two 18V Avel transformers and the rails run at 22V to 23V or so. I think that if I had to do it over that I would go with 20V secondaries and experiment. You could always go CRCRC to drop some more voltage if it comes in too high. And, although I have never done it, you could cascode the front end so that the high voltage wouldn't be an issue there.
Just my thoughts,
Steve