I just received my kit, and I have a couple questions regarding possible customization.
First, I intend to use this amp to power mids/highs of actively crossed speakers. Therefore, no need for bass below 100Hz or so. In fact, if it improves the handling of the upper freq's and allows me to safely use lower impedance midrange speakers, I would prefer to filter lows at the amp's input. Can I adjust the DC blocking filter C1/R1 to raise the cutoff without harming the rest of the amp? Could I use this filter to eliminate that portion of the active xover altogether? Is it 6dB/octave? In that case, I'd want a -3dB corner of about 150Hz.
Second, can the gain be adjusted to match the amp I'll be using for the bass speakers, or is the Rev C's gain fixed?
Peace,
Tom E
First, I intend to use this amp to power mids/highs of actively crossed speakers. Therefore, no need for bass below 100Hz or so. In fact, if it improves the handling of the upper freq's and allows me to safely use lower impedance midrange speakers, I would prefer to filter lows at the amp's input. Can I adjust the DC blocking filter C1/R1 to raise the cutoff without harming the rest of the amp? Could I use this filter to eliminate that portion of the active xover altogether? Is it 6dB/octave? In that case, I'd want a -3dB corner of about 150Hz.
Second, can the gain be adjusted to match the amp I'll be using for the bass speakers, or is the Rev C's gain fixed?
Peace,
Tom E
Peter or Uriah:
There are two notes written on the PCB itself: one at R42 and one at R2 concerning the values of these resistors. I don't understand their significance, and I wonder how you arrived at the values you supplied in the kit. What is the effect of varying these component values? I am not second guessing you; I just would like to know how you chose these values.
Peace,
Tom E
There are two notes written on the PCB itself: one at R42 and one at R2 concerning the values of these resistors. I don't understand their significance, and I wonder how you arrived at the values you supplied in the kit. What is the effect of varying these component values? I am not second guessing you; I just would like to know how you chose these values.
Peace,
Tom E
The board is exactly the last board layout produced by TP including all the writing on the silk layer. The values of all components are exactly according to the last BOM produced by TP. This includesmadisonears said:
that bypass caps were changed from 100nF to 220nF. These are C7/17/18/19/20/21. The silk say 100nF the contents of your parts bag have 220nF for these.
Peter
I'm just thinking about things while I'm bored at work...
I got my kits yesterday but didn't have much time to really look things over yet, but I'm wondering if there are any capacitor locations where it would be worth it to use some boutique caps?
Reason I ask is I have some muse and silmic II caps along with a fair sized collection of Russian PIO caps, K42-Y, K40-Y, and FT-1 teflons. I will probably build it using the standard components first to use as a baseline, but I'm just wondering which caps would be good to bypass or replace if I do some tweaking in the future
I got my kits yesterday but didn't have much time to really look things over yet, but I'm wondering if there are any capacitor locations where it would be worth it to use some boutique caps?
Reason I ask is I have some muse and silmic II caps along with a fair sized collection of Russian PIO caps, K42-Y, K40-Y, and FT-1 teflons. I will probably build it using the standard components first to use as a baseline, but I'm just wondering which caps would be good to bypass or replace if I do some tweaking in the future
I got 220uf FM's in my kit, not FC's, for C1, C2, C9 and C14. Nice!
Please note that 100nf bypass C7, C17, C18, C19, C20 and C21 have all been changed to 220nf. The silk screen says 100nf, but that's where the AVX 220nf's go now. I would consider upgrading those, at least at C21.
I don't recognize coupling C13 brand. BOM says Kemet MKP, but label on cap says AV. That's probably where you'll get the best return with upgrade. There is plenty of room there and different hole spacing for a variety of cap types.
Peace,
Tom E
Please note that 100nf bypass C7, C17, C18, C19, C20 and C21 have all been changed to 220nf. The silk screen says 100nf, but that's where the AVX 220nf's go now. I would consider upgrading those, at least at C21.
I don't recognize coupling C13 brand. BOM says Kemet MKP, but label on cap says AV. That's probably where you'll get the best return with upgrade. There is plenty of room there and different hole spacing for a variety of cap types.
Peace,
Tom E
For C13 I've selected Evox-Rifa PHE426, that according to Humblehomemadehifi 's caps test, should be pretty good; it will be bypassed by a Vishay MKP1837 as well.
I have a bunch of 100nf and 220nf k42y-2 russian pio caps, however they are 160v and probably a bit too bulky to use more than 1 or 2 of them. I also have a little stockpile of ero-roderstein mkp caps, and some 100nf wima mks4, I'll have to dig through my box of caps and see what values I have. This should be fun to play around with 
It is Kemet from the R46 series: http://capacitoredge.kemet.com/capedge2/intellispec.jsp?pn=46KN410000N2Mmadisonears said:
peter
Thanks, Peter. I was confused by the label on the cap itself. BOM is clear.
Clave, and anyone else investigating coupling caps:
The test at HumbleHomemade was for caps used in speaker crossovers, and had nothing to do with coupling/DC filtering. Be careful how you interpret his findings, as the qualities he describes might not apply to other applications.
I would also be careful when reading reviews of coupling caps that their descriptions might not translate directly to crossover applications.
One thing I have noticed in all the cap reviews I've seen for either xover or coupling duty, is that Mundorf Silver/Oil is always ranked among the highest performers. The descriptions of their sound invariably uses words such as "liquid midrange" and "inner detail" and other similar terms. Of course, the VH Audio caps are always ranked higher, but not by a lot, and not for every application. Teflon caps might not be a good match with this amp. I understand it's a little lean and could probably use some fleshing out with the Mundorf's SIO.
Peace,
Tom E
Clave, and anyone else investigating coupling caps:
The test at HumbleHomemade was for caps used in speaker crossovers, and had nothing to do with coupling/DC filtering. Be careful how you interpret his findings, as the qualities he describes might not apply to other applications.
I would also be careful when reading reviews of coupling caps that their descriptions might not translate directly to crossover applications.
One thing I have noticed in all the cap reviews I've seen for either xover or coupling duty, is that Mundorf Silver/Oil is always ranked among the highest performers. The descriptions of their sound invariably uses words such as "liquid midrange" and "inner detail" and other similar terms. Of course, the VH Audio caps are always ranked higher, but not by a lot, and not for every application. Teflon caps might not be a good match with this amp. I understand it's a little lean and could probably use some fleshing out with the Mundorf's SIO.
Peace,
Tom E
Well, up to a point. A company like Kemet sells a whole bunch of brands under their name. In those brands you have all manner of individual product lines. Without detailed reference to product line, for example, you just can't say much as I discovered. For example, these caps are induction free (well, presumably too low to measure since there is no such thing...), and have a reasonably low dissipation factor of 0.1%. There are caps that go way below that dissipation factor. Whether that can be justified by their prices can only be revealed by tests.madisonears said:
If people try tests I would strongly counsel to change one of the two boards, listen to a mono test, and have someone else determine which one you listen to without you knowing. Else the comparisons are meaningless. For subtle differences there is way too much psychology involved for anything useful to come out unless you do a blind comparison. Nothing wrong with subjective comparison, but you gotta do it blind.
Just my 2 c.
In any case, plenty of opportunity here to mess around.
peter
madisonears said:
Tom, I agree that caps reviews on high voltage application vs. low voltage application doesn't apply directly and that the same cap could have different effects on low or high voltage signals.
I've discovered Humblehomadehifi while upgrading the crossovers of my Infinity speakers and I must say that I agree with Tony Gee findings.
After that I've tried MKP1837 as a bypass cap of output coupling caps in three CD/DVD players and found consistently that has the same wonderful effect that has in crossover apps.
I'm confident that PHE426 will be a nice cap also in signal coupling but I couldn't be sure until I've tried it.
Obviously I consider Humblehomemade only as a hint for some possible nice sounding caps... if a cap is awful in high voltage it is unlikely that could be good in low voltage
I was visiting with Steve of ApexJR this morning. He actually happens to have these caps at 10uF!!! They are 3$ each. Sweet! They are also bigger than what fits on the board, but since they are the first thing in the signal path onto the board it should be easy to accommodate them off the board and just jump right over that on the board.ClaveFremen said:
I guess this is another good reminder that Steve has a nice set of all the little stuff that one needs to make a complete amp: binding posts, input connectors, IEC receptacle, on/off switch, fuse holder, beautiful Teflon wire, and some pretty magnificent heatsinks! Also toroids (I picked up a couple more of the 2x25V 100VA toroids; for some folks this may be underpowered; I found them to be more than sufficient; YMMV). As you can probably tell by now I am a happy customer! I am using all this stuff for my own revC build.
peter
schro20 said:
The PHE426 1uF is exactly the size needed:
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I've payed them 0,87 Eurocents ea (Min. Q.ty 10) from RS Components.
Some other alternatives to be tried:
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From left to right:
Takman REY 1/4W 1%
Takman REX 1/2W 2%
Evox-Rifa PHE426 100nF 250V 5%
Evox-Rifa PHE426 250uf 250V 5%
Vishay CMF55 1/4W 0,1% guaranteed non-magnetic
Vishay MKP1837 10nF 100V 1%
Wima MKP2 1nF 100V 5%
Nichicon KW 220uF 63V
Wima FKP2 1nF 100V 5%
Elna Silmic II 100uF 35V
Wima FKP2 220pF 100V 5%
Elna Silmic II 220uF 35V
Wima FKP2 150pF 100V 2,5%
Wima MKP4 100nf 250V 5%
With this one I've had good results as output coupling cap in my SACD Player
An externally hosted image should be here but it was not working when we last tested it.
But in 1uF-2,2uF they're 15mm and in this field size matters...
Look at that prototyping! That's great!ClaveFremen said:
Now, 1uF?! Come on! Just imagine how much lower you can push the phase shift at the bottom end if you go with a 10uF coupling cap!
Size does matter!
Yep 10uF or bust!!!peter
PS: I see your package went on the plane last night...