I didn't use a PI filter in my build. But I think someone more expert should comment on this. Maybe Andrew, Rudi or Mihai will be kind enough to comment.
I don't remember seeing a Pi-filter in this amp, but I admit not going back to look at the schematic to answer this. A Pi-filter is a C-R-C filter. The R-C forms a low pass filter. If you raise the C value (or the R value), the cutoff frequency will drop. This is a good thing for a power supply. You don't have to recalculate the 0R1 resistor, and it is not inductance related in this case.
You can use an inductor L instead of an R for steeper cutoff, but then you may have an issue with damping that needs to be addressed, as well as magnetic field issues from the inductor. In sum, don't worry about upping the cap value for the given R.
Nice! That is not extremely expensive compared to other cases I've seen, for what you get. The heat sinks that come with it appear to be sufficient for this amp, too. They don't show the inside of the case in the pics, so I don't know what you added to it. I thought you had Conrads. I bought some of those too, which is why I took a special interest. I assume you added the clear aluminum plates to your sinks. That REALLY looks overkill, especially if your heat sinks are the MF35-151.5 models that I bought, which should be more than sufficient in themselves.
Hi Pooge,
Hard to say what the thermal resistance of the included heatsinks with this case is. My Conrad MF35-151.5s run just warm to touch so the stock case heatsinks might be ok. Using the stock case heatsinks would be the easiest option for you I think.
I had already had the Al plates made so I decided to adapt the case to them. Actually at the moment I am using a bunch of M4 washers to emulate bushes ~ 5mm raise the from and back panels so everything fits with the Conrad heatsinks and Al plates. I now have 5mm M4 bushes I got from ebay to replace the washers. Hope all this makes some sense to you! Its a bit hard to describe in words exactly what I have done.
Hard to say what the thermal resistance of the included heatsinks with this case is. My Conrad MF35-151.5s run just warm to touch so the stock case heatsinks might be ok. Using the stock case heatsinks would be the easiest option for you I think.
I had already had the Al plates made so I decided to adapt the case to them. Actually at the moment I am using a bunch of M4 washers to emulate bushes ~ 5mm raise the from and back panels so everything fits with the Conrad heatsinks and Al plates. I now have 5mm M4 bushes I got from ebay to replace the washers. Hope all this makes some sense to you! Its a bit hard to describe in words exactly what I have done.
I found a 150mm high version of this chassis that does ship to UK.NEW DIY full aluminum chassis amplifier Box 4015 big power case -sn | eBay
Does any one know of a source with cheaper postage cost?
Only good european source for me is modushop.biz .They also make some customisation of front panel.
Hi Andrew, given you considerable expertise in this area do you think the stock heatsink will suffice? They say :
Radiator Specifications:
300 W 50 before and after each splice 30 mm thick radiator length of the substrate to 360 mm, length 9 (substrate thickness 10)
Unilateral radiator weight 2.6 kg, less suitable for installation 35W Class A circuit
I can post some photos of the stock heatsinks if this helps?
Hi guys,
I should have been more informative. Rudi mentioned an alternative Filter Network in his BuildersManual - a 1mH coil around a 33Ohm Resistor. There is the origin of my question, but Rudi answered me and send me this link
http://www.diyaudio.com/forums/pass-labs/101993-pi-filter-clc-vs-crc-vs-c.html
which has plenty informations and further links on the Pi-Filter topic. I worried some unsuspected oscillation behaviour if I would keep the coil and the resistor but increasing the caps.
regards
Alex
p.s. great builds here 😉
I should have been more informative. Rudi mentioned an alternative Filter Network in his BuildersManual - a 1mH coil around a 33Ohm Resistor. There is the origin of my question, but Rudi answered me and send me this link
http://www.diyaudio.com/forums/pass-labs/101993-pi-filter-clc-vs-crc-vs-c.html
which has plenty informations and further links on the Pi-Filter topic. I worried some unsuspected oscillation behaviour if I would keep the coil and the resistor but increasing the caps.
regards
Alex
p.s. great builds here 😉
I own that case with a much larger 5 pair OPS running on those heatsinks.
I can run the "snot" out of the amp with paralleled 8R speakers all day
, can't trip my 50C thermal limit.
Normal use they barely even get 35C.
Heatsink material is more of a AL/MG alloy , not quite as good as a HS USA
extrusion. End to end conductivity is not quite to the heatsink USA spec.
OS
Has anyone tried these Russian MBGO's eg 1 uF 630 V STRONG MATCHED RUSSIAN PAPER IN OIL PIO AUDIO CAPACITORS MBGO ????-2 | eBay input caps and as a replacement for the 1839 1uF (I think in Rudis schematic it is called C1)
Personally i use dc coupled with no input cap. Best russian combination in my opinion is k75-10 bypassed with a snall ft-1 teflon (0.018uf in my case).
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Hi atupi,
Hi atupi & WatrixReloader,
Many customers have had destroyed speakers because the preamp developed a DC offset (Krell). This is a fact of life, sometimes parts fail. With many new preamps, muting is achieved with muting transistors. These are special parts designed with high E-B breakdown voltage, and they go bad (but test great!) more often than you want to know. Any of the "plastic" ester family capacitors will sound better than an electrolytic. Use for a combined 10 uF capacitance if you are worried about bass roll-off, but that is not going to happen. Wima makes some excellent products. You do not need anything near even 50 VDC, so there you go.
Shy away from physically large capacitors. They are often microphonic and need to be shock mounted as a result. They will still make noise though. Some are worse than others. You have much larger problems to deal with than your input capacitor.
Hi Pete,
Good to "see" you. Has the fc100 had any changes since I bought my boards a long time ago in the second group buy? The thread has become very long.
-Chris
Now, there is a risk I am unwilling to take. Sooner or later, it could cause you grief!
Hi atupi & WatrixReloader,
Many customers have had destroyed speakers because the preamp developed a DC offset (Krell). This is a fact of life, sometimes parts fail. With many new preamps, muting is achieved with muting transistors. These are special parts designed with high E-B breakdown voltage, and they go bad (but test great!) more often than you want to know. Any of the "plastic" ester family capacitors will sound better than an electrolytic. Use for a combined 10 uF capacitance if you are worried about bass roll-off, but that is not going to happen. Wima makes some excellent products. You do not need anything near even 50 VDC, so there you go.
Shy away from physically large capacitors. They are often microphonic and need to be shock mounted as a result. They will still make noise though. Some are worse than others. You have much larger problems to deal with than your input capacitor.
Hi Pete,
Good to "see" you. Has the fc100 had any changes since I bought my boards a long time ago in the second group buy? The thread has become very long.
-Chris
Hi Pooge,
Ahhhh, I see now. Thank you.
There are some really excellent preamplifiers out there. A strong buffer on your CD or Phono preamp could drive all that properly. I am not a fan of driving cables with a high impedance, although your variac is better than simple resistive pots. I wonder what the response of your variac looks like at various levels and sources. Hmmm.
At least you have DC sources dead. How about the input bias currents from your amplifier? With tubes or J-Fets it is in pA. With bipolar inputs it could run into 100 nA levels. Varying DC resistance would then affect the amplifier.
I know. There is always a problem with everything! 🙂
-Chris
Ahhhh, I see now. Thank you.
There are some really excellent preamplifiers out there. A strong buffer on your CD or Phono preamp could drive all that properly. I am not a fan of driving cables with a high impedance, although your variac is better than simple resistive pots. I wonder what the response of your variac looks like at various levels and sources. Hmmm.
At least you have DC sources dead. How about the input bias currents from your amplifier? With tubes or J-Fets it is in pA. With bipolar inputs it could run into 100 nA levels. Varying DC resistance would then affect the amplifier.
I know. There is always a problem with everything! 🙂
-Chris
The TVC can only transfer AC voltages. In that respect the output of the TVC can only be AC. That leaves the next stage safe drom DC or output offset.
But the TVC will not tolerate DC at all well. The primary will pass DC and this will affect the core. Don't feed any DC, or output offset, into your TVC.
But the TVC will not tolerate DC at all well. The primary will pass DC and this will affect the core. Don't feed any DC, or output offset, into your TVC.
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