The input filter that attenuates RF is around 100kHz to 200kHz.
An RC of ~1us gives that value.
Change the RC to 0.1µs (=100ns) and you have moved the RF filter up one decade.
If your 1us was made up with a 1k0 and a 1nF then simply adding a temporary resistor in parallel with the 1k to reduce it to 100r will achieve that decade rise in the RF filter.
BTW,
there is a lot of variation in that RF filter.
The resistor can be anywhere in the range from 100r to 10k
The capacitor can be anywhere in the range 47pF to 2n2F
But what matters for your filter is the RC time constant. Multiply the R value by the C value and you end up with a time constant in seconds, or millionths of a second (µs).
Hi Andrew,
Sorry, that all went over my head. I'm sure the other EE's here understand all of your abbreviations but I don't. I do appreciate your willingness to help.
For those curious, I bought the Solen caps here. I'm not sure how they compare to the Auricaps but they fit and sound fine to my ears. Much less expensive too.
I have a question about the SMD. Someone eluded to the part having better thermal properties than a through hole part. Does this mean that the temperature of the actual PCB comes into play? I have to assume that this type of mounting technique results in a warmer running PCB, even with the washers between the top of the transtor and the PCB.
Blessings, Terry
Sorry, that all went over my head. I'm sure the other EE's here understand all of your abbreviations but I don't. I do appreciate your willingness to help.
For those curious, I bought the Solen caps here. I'm not sure how they compare to the Auricaps but they fit and sound fine to my ears. Much less expensive too.
I have a question about the SMD. Someone eluded to the part having better thermal properties than a through hole part. Does this mean that the temperature of the actual PCB comes into play? I have to assume that this type of mounting technique results in a warmer running PCB, even with the washers between the top of the transtor and the PCB.
Blessings, Terry
Thats right, SOT 223 package parts have a heat spreader and your board has a section of copper foil provided to help the dissipation.
A standard T092 version can dissipate around 0.8W but the SOT 223 ZVP2110 can dissipate 2W, soldered to adequate foil.
Temperature rise is quite reasonable with this modest rating and the actual temperature reached in typical use. They are designed
for safe, long life use in this manner. HTTP 301 This page has been moved
A standard T092 version can dissipate around 0.8W but the SOT 223 ZVP2110 can dissipate 2W, soldered to adequate foil.
Temperature rise is quite reasonable with this modest rating and the actual temperature reached in typical use. They are designed
for safe, long life use in this manner. HTTP 301 This page has been moved
It may not be all that helpful in communicating what an RC time constant is, or what RC circuits generally do in audio devices nor how to manipulare them but this is the essential stuff of electronics. It's a basic math expression that relates how long it takes to charge or discharge a capacitor or even a battery.
That can be a slow, all-day event or blindingly fast, since audio circuits charge and discharge at audio frequencies which is a lot harder to follow, either in your head or in real devices. The point is, the time it takes to charge a cap. is called the time constant and and that is defined and conveniently found by multiplying the values of the 2 components that control it - R and C. That's Resistance and Capacitance, nothing abstract or complicated yet.
Before I run into arguments with pedants about other factors that don't really help the discussion, I'll hand over to this article which has some easy diagrams that help visualize what sometimes eludes people in words. It's thorough and goes on with fancy expressions invoving Kirchoff's Law, which you don't need to be concerned with but you only need to look at how the main, highlighted expression, tau = RC is significant to get the gist of it.
OK, so it doesn't say much yet about filters but this term "RC time constant" is exactly what determines the roll-off or bend in the frequency response graph of RC filters. If you want to calculate the parts you need, this is the basis of "how-to". The RC thing keeps turning up, eh?
That can be a slow, all-day event or blindingly fast, since audio circuits charge and discharge at audio frequencies which is a lot harder to follow, either in your head or in real devices. The point is, the time it takes to charge a cap. is called the time constant and and that is defined and conveniently found by multiplying the values of the 2 components that control it - R and C. That's Resistance and Capacitance, nothing abstract or complicated yet.
Before I run into arguments with pedants about other factors that don't really help the discussion, I'll hand over to this article which has some easy diagrams that help visualize what sometimes eludes people in words. It's thorough and goes on with fancy expressions invoving Kirchoff's Law, which you don't need to be concerned with but you only need to look at how the main, highlighted expression, tau = RC is significant to get the gist of it.
OK, so it doesn't say much yet about filters but this term "RC time constant" is exactly what determines the roll-off or bend in the frequency response graph of RC filters. If you want to calculate the parts you need, this is the basis of "how-to". The RC thing keeps turning up, eh?
I can't help but be intrigued by this tiny tweak cap, care to elaborate? I found that there are a wealth of Hugh' tweaks to be found by carefully looking through the various threads, my plan is to try to gather as much info as possible in one place, and so would love to see if this tweak is mentioned elsewhere as well.
Nope, that tiny cap was actually Swordfishy's and appeared in his schematic posted earlier in Lineup's main thread, IIRC. I don't know all that was discussed outside the forum but what's significant is that the cap was there when the Aspen Fetzilla was agreed between them and finalised.
If you consider that mosfet types and bias currents in the VAS had been changed, it would be reasonable to expect a change in compensation.
Yes, quite an intriguing situation, when you think about it.
I can't even find the title of Lineup's long thread at the moment, so I apologise in advance if I goofed somewhere in relating events but they are all explained at length by AKSA in the OP of the Swordfishy/Aspen Fetzilla thread in the Manufacturers forum.
If you consider that mosfet types and bias currents in the VAS had been changed, it would be reasonable to expect a change in compensation.
Yes, quite an intriguing situation, when you think about it.
I can't even find the title of Lineup's long thread at the moment, so I apologise in advance if I goofed somewhere in relating events but they are all explained at length by AKSA in the OP of the Swordfishy/Aspen Fetzilla thread in the Manufacturers forum.
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I have been running mine on just a 15k step attenuator and it sounds lovely so I would think any clean pre would be just fine. The FetZilla seems to have plenty of gain so I bet the B1 pre would work fabulous. I will try it with my B1 Mezmerize this weekend and get back to you. They sell boards for the Mezmerize in the DIY store. It is a nice build.
Blessings, Terry
Blessings, Terry
While i cannot offer up any suggestions based on experience, my plan is to make a DAC/pre combo using a Subbu/J-P DAC v2.6 and one of Chris Daly's LDR preamp kits. It will take some doing, but the long-term plan is to make a nice remote-controlled unit, look out for a thread on this Real Soon Now(tm). I feel it meshes well with Hugh's sentiment that we should try to avoid relays if we can. They constitute a mechanical interface which may not perform as well over time as they do when new. I suspect this could be true of stepped attenuators as well, but i'm merely hypothesising here.
On a sidenote it's so unfair that Terry got his boards already and soldered the thing together in what must have been record time!
Can't wait to get mine, going to really take my time with it.
While i cannot offer up any suggestions based on experience, my plan is to make a DAC/pre combo using a Subbu/J-P DAC v2.6 and one of Chris Daly's LDR preamp kits. It will take some doing, but the long-term plan is to make a nice remote-controlled unit, look out for a thread on this Real Soon Now(tm). I feel it meshes well with Hugh's sentiment that we should try to avoid relays if we can. They constitute a mechanical interface which may not perform as well over time as they do when new. I suspect this could be true of stepped attenuators as well, but i'm merely hypothesising here.
On a sidenote it's so unfair that Terry got his boards already and soldered the thing together in what must have been record time!
In Patrick's defense, I didn't order any extra parts, just the boards and paid for them back in December. I outsourced all of the parts and had them for quite some time before Patrick received the boards. As soon as he reported the he had received them I began bugging him to ship. He had only recently sent me boards for a different GB so we knew the shipping costs and sent him the money for it. You can only take so much time assembling these as they have very few parts compared to most other amps. Remember, I did not use the PS portion of the boards and they fired up first time. Mine are not in cases yet and likely won't be for some time. I have 5 different amps that are assembled and mounted on heatsinks. I need to hit the metal supply so I can build some more cases but I'm not is a hurry. I have lots of other amps I can listen to.
Blessings, Terry
In the interest of completeness, here are the threads of interest to FetZilla builders that i've been able to find so far:
http://www.diyaudio.com/forums/solid-state/186650-jfet-input-mosfet-vas-lateral-output-perfect.html
-- The original thread that started it all, April 2011.
http://www.diyaudio.com/forums/aksa/191053-swordfishy-aspen-fetzilla-power-amp.html
-- The first group buy thread, organised by Hugh in the AKSA forum, June 2011.
http://www.diyaudio.com/forums/aksa/198170-group-buy-2-fetzilla.html
-- The second group buy, also organised by Hugh, October 2011.
http://www.diyaudio.com/forums/aksa/207504-group-buy-3-fetzilla-amp.html
-- The third and final group buy organised by Hugh, February 2012.
http://www.diyaudio.com/forums/aksa/207772-fetzilla-build-documentation.html
-- The first builder's thread, also in the AKSA forum, February 2012.
http://www.diyaudio.com/forums/solid-state/223357-fetzilla-builders-place.html
-- The second builder's thread, November 2012.
http://www.diyaudio.com/forums/group-buys/224424-fetzilla-groupsbuy-4-a.html
-- The fourth group buy, organised by Patrick, November 2012.
http://www.diyaudio.com/forums/group-buys/246149-fetzilla-groupsbuy-5-a.html
-- The fifth group buy, also organised by Patrik, November 2013.
http://www.diyaudio.com/forums/solid-state/247407-building-fetzilla-questions-answers.html
-- The latest builder's thread, December 2013.
Quite a body of information indeed, my next task is to comb through them all and gather the information into an article / wiki entry. Hopefully while listening to sweet music through my Fetzilla sipping on some single malt Scotch.
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In Patrick's defense, I didn't order any extra parts, just the boards and paid for them back in December. I outsourced all of the parts and had them for quite some time before Patrick received the boards. As soon as he reported the he had received them I began bugging him to ship. He had only recently sent me boards for a different GB so we knew the shipping costs and sent him the money for it. You can only take so much time assembling these as they have very few parts compared to most other amps. Remember, I did not use the PS portion of the boards and they fired up first time. Mine are not in cases yet and likely won't be for some time. I have 5 different amps that are assembled and mounted on heatsinks. I need to hit the metal supply so I can build some more cases but I'm not is a hurry. I have lots of other amps I can listen to.
Blessings, Terry
I know, i know, it's what i deduced had happened as well. Whenever i use the term "it's so unfair"(imagine me saying it with a kids voice), i'm being sarcastic. I'm very happy with my current situation, waiting a bit on the boards and parts is going to be worth it without a doubt, and i know Patrick has given considerable time out of his already busy schedule to assist us.
B1 + Fetzilla
Hi Terry,
Did you had any chance to listen the B1 with your Fetzilla?
If yes, How do they fit together?
thanks in advance
Theodore
Hi Terry,
Did you had any chance to listen the B1 with your Fetzilla?
If yes, How do they fit together?
thanks in advance
Theodore
Hi Theodore,
Sorry it has been so long. I have been busy with other amps. This morning, while discussing the use of an SMPS for the power supply in another thread I got to wondering about the Fetzilla so I hooked it up and played it through my A/B setup and compared it to my SKA GB150D. They were close but the SKA had stronger bass and the Fetzilla had seemingly more definition in the mids and highs. So I disconnected the SMPS and hooked up a Cap-multiplier and Torroid transformer. I had to run through my variac because the PSU puts out +-50V. I dialed it down to +-37V to feed the Fetzilla. Now in the A/B comparison, the two amps are almost indistinguishable from each other. As Patrick stated earlier, the bass has more authority with a standard supply. I am going to go ahead and install the PSU components on the Fetzilla board and buy a transformer. I am convinced that, at least with the SMPS that I have, the conventional PSU is better.
So now for your question. I hooked up the Fetzilla to my DCB1 Mezmerize and it sounds superb. Just the way I would want it to sound. The Fetzilla has plenty of gain so, though I didn't try it, I believe you cant get it pretty close to clipping, which is louder than I would ever choose to listen to it.
I'll let you know more when I get the PSU portion built.
Blessings, Terry
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