Matching as closely as possible and incredible resolution are hardly measurable.
My three cheap multimeters are all 2000 count and all three have a repeatable resolution of 1lsb.
That gives matching to 0.05%. Is that good enough?
My Bench multimeter is 50000 count and it's repeatable resolution varies between 1lsb and 3lsb.
at one lsb matching to 0.002% is possible and at 3lsb matching to 0.006% is possible.
Gentlemen, facts if you want us to listen and believe.
Now the real questions are:
Q1.) which resistors need to be matched?
Q2.) what accuracy of matching is needed for the matched pairs?
Do we need 1% ot 0.1% or 0.01% or something else?
There is absolutely no point in wasting money on buying an absolute accuracy of 0.1% when
We have volunteers that can match better than that.
Put me in the volunteer list if Uriah needs any help.
Okay,
I will get pricing for Obbligatos. Hoping we can command a lower price than they are asking with our quantity.
AndrewT, I can sit down and match them out while watching TV in a night. Its not a problem. But I sincerely appreciate the offer. Thats really kind of you. I had to match a bunch earlier, maybe 4 months ago, for my testing jig for LDRs and it was pretty quick even with 600. I am buying 500 of each value we have to match and I am sure that is overkill, but at least its not to few.
I am sure that .01% is insane and not necessary and I think it will be pretty easy to get .1% matches. The improved howland current pump as written up by Bob Pease does not need the .01% matching like the original howland did, or benefited greatly from anyway. The tighter match apparently reduces noise in an already very quiet circuit. So I think .1% will be my guideline but with that many resistors I am sure most of them will be even better match than that.
Okay we are rolling now
Uriah
I will get pricing for Obbligatos. Hoping we can command a lower price than they are asking with our quantity.
AndrewT, I can sit down and match them out while watching TV in a night. Its not a problem. But I sincerely appreciate the offer. Thats really kind of you. I had to match a bunch earlier, maybe 4 months ago, for my testing jig for LDRs and it was pretty quick even with 600. I am buying 500 of each value we have to match and I am sure that is overkill, but at least its not to few.
I am sure that .01% is insane and not necessary and I think it will be pretty easy to get .1% matches. The improved howland current pump as written up by Bob Pease does not need the .01% matching like the original howland did, or benefited greatly from anyway. The tighter match apparently reduces noise in an already very quiet circuit. So I think .1% will be my guideline but with that many resistors I am sure most of them will be even better match than that.
Okay we are rolling now
Uriah
You're right Tom specs for the input cap are from 1uF, in fact quite all caps I've tested are between 1 to 1.2uF.
It seems that sound is not affected and they reduce/eliminate spikes quite well at least the majority, some (minor) spike pass.
Probably the selection of the varistors could be better done but I didn't found any information on how to select them...
In my sims, the improved Howland pump works fine even when there's a mismatch of up to 10% in the resistor ratios on the positive and negative feedback networks. There's some impact on the output impedance, the sonics and the phase margin, but it still works.
If they're matched to 0.1% by hand, it will be indistinguishable from an exact match. Only the resistors on positive and negative feedback networks around the LM3886 (2 sets of 2 resistors each) need to be matched this closely. Everything else only needs to be at ~5%-10% tolerance - if they're at 1%, that's great.
Thanks for running a simulation. Thats nice information. Yes, the two resistors in the positive and negative feedback, plus the .47R are all part of the current pump and need, at least as I read it in AN1515, to be matched closely but not nearly as important as in the original Howland.
Uriah
Uriah
If BlueGTI is reading he could tell us his impressions on his Silmics MyRef...
I just came across this thread...
Its hard for me to give a impression because I have not listened to any other capacitor in this position. Overall, I'm very pleased with the amp. I'm using it with a Lightspeed pre-amp driving Jim Griffin Jordan/Aurum Cantus speakers.
I've brought the combination to several DIY meets and everyone has been extremely complimentary.
With regard to the input cap... I'm using an Obbligato.
With this model, I think we could step up to 1,5uF. The 1uF costs 8€ and 1,5uF 9€. But for 2uF you have to step up to 12,5€. Just to aim for a bit more lower extension.
Or go with the gold premium ones is there are any audio discernable difference.
I think you need to parallel 2 of these:
Teflon Tin Foil 0.47uF 1000V | Diy HiFi Supply
Totally joking of course!!
But in seriousness, do they not make anything but 600V caps?
PS, I am following the thread because I still have a kit unassembled and may want just the components but haven't see that offered yet.
Teflon Tin Foil 0.47uF 1000V | Diy HiFi Supply
Totally joking of course!!
But in seriousness, do they not make anything but 600V caps?
PS, I am following the thread because I still have a kit unassembled and may want just the components but haven't see that offered yet.
As far as different parts this is Dario and Tom's show. If they recommend a part and agree on it then thats the one I use. If they both recommend something different then I ask why and use my own discretion. Both have said that 1uf is more than enough and Tom is using .68uf. We are good with 1uf.
Troy. No kidding! What is the deal with only massive caps? I wish there were some 100V or 63V ones. These things are so big that I am sure they will not fit in a flat rate box with the rest of the stuff.
Uriah
Troy. No kidding! What is the deal with only massive caps? I wish there were some 100V or 63V ones. These things are so big that I am sure they will not fit in a flat rate box with the rest of the stuff.
Uriah
1uf is a good choice. If my amps lack anything, it is slam of the very lowest bass. I would gladly replace my 0.68 with 1uf or larger if they weren't so expensive (the Fostex caps that I'm using). I'm looking forward to trying the Obligatto's.
Last night I got an oppotunity to hear my amps playing through Eggleston Audra II speakers. I think these go for $18,000 the pair. They are awesome speakers, and the My Ref made them sound absolutely beautiful. I can only compare these to a very refined and powerful tube amp. The images were rock solid and completely three dimensional, with very pure and natural tonal characteristics. The hook-up was not optimal, as the owner typically runs his system balanced with multi-thousand dollar Siltech cables and power cord into an Aragon 8008BB amp. We had to use my little cheapo homemade IC's, and the power was supplied through a computer type power strip. As these amps are very sensitive to line supply and power cords, I have no doubt they could have sounded even better. As it was, they TOTALLY DESTROYED the Aragon in every respect except absolute bass slam. Not surprising, considering the reputation the Aragon has for Krell type bass. The My Ref bass was very well controlled and plenty deep; it just lacked that last bit of visceral impact. A larger input cap may have helped.
These amps are NOT for computer speakers! The Aragon owner is now considering a pair of My Ref's. I let him keep them overnight, and I'm going back there today to listen again.
Peace,
Tom E
Last night I got an oppotunity to hear my amps playing through Eggleston Audra II speakers. I think these go for $18,000 the pair. They are awesome speakers, and the My Ref made them sound absolutely beautiful. I can only compare these to a very refined and powerful tube amp. The images were rock solid and completely three dimensional, with very pure and natural tonal characteristics. The hook-up was not optimal, as the owner typically runs his system balanced with multi-thousand dollar Siltech cables and power cord into an Aragon 8008BB amp. We had to use my little cheapo homemade IC's, and the power was supplied through a computer type power strip. As these amps are very sensitive to line supply and power cords, I have no doubt they could have sounded even better. As it was, they TOTALLY DESTROYED the Aragon in every respect except absolute bass slam. Not surprising, considering the reputation the Aragon has for Krell type bass. The My Ref bass was very well controlled and plenty deep; it just lacked that last bit of visceral impact. A larger input cap may have helped.
These amps are NOT for computer speakers! The Aragon owner is now considering a pair of My Ref's. I let him keep them overnight, and I'm going back there today to listen again.
Peace,
Tom E
I've suggested Obligatos as the best price/performance ratio caps that let perceive the good that our mods give but my reccomended cap for this amp is the Mundorf MCAP Zn 1,2uF 250V.
Let me be absolutely clear: among the various caps I've tried Obbligatos and MCAP Zn are the only caps similar to DC coupling.
Both let pass through quite all details with MCAP Zn best for a perfectly transparent timbre, Obbligatos add a bit of very nice 'analog' colour.
Regarding bass slam I think you'll have a nice surprise from Silmics in C6/C11... in this regard Nichicons KZ are even better but overall I've preferred Silmics.
So we should try Silmic's in the power supply? I'm willing to give that a shot. They do have a nice bottom end. Do C6 and C11 affect the sound very much? I haven't tried anything there other than the Panny FM's. The price difference for Silmic's is not too much. Do they fit? Things get really tight on the board in that area.
Peace,
Tom E
Peace,
Tom E
if Parts ConneXion is part of the supplier equation somewhere, they DO have Nichicon KZ's at a VERY reasonable price, almost [if not] half of Silmic II's. I'm not too experienced at all to compere capacitors, but I DID stock up on a nice variety of KZ's on a very recent order with them, mainly due to Nichicon's data sheets continually pointing to KZ as their best for their purpose.
Parts Connexion is in Canada, though the web site prices are in U.S. doolars. As such, there may be a possibility of import duties, taxes and so forth on cross-border shipments from wherever into the U.S.
On the other hand, free trade is a weird thing in its applications.
While I'm in favor of exploring Obligatos, there are some very affordable Solen MKP's at Solen in Montreal at their on sale section. Older non-ROHS polyprops could be had for about $1 US in 1.5uf 250V and they have about 500 of them in stock. We could certainly make a good use out of an environmental passe item. Somebody has to properly utilize these potential toxins, perhaps we should. LOL.
Just something to be available as a possible alternative if costs were to be a strong factor.
Your excellent haggling with merchants does indeed make room for a nice option in this choice of capacitor, though...so, by all means go forth and haggle...
1.5uf 250V
1.8 uf 250V made in France.
That's one of the nice things I like about Solen in Montreal, their website shows the country of manufacture for each item...and the French girl who answers the phone has the loveliest voice...most pleasant to deal with.
Parts Connexion is in Canada, though the web site prices are in U.S. doolars. As such, there may be a possibility of import duties, taxes and so forth on cross-border shipments from wherever into the U.S.
On the other hand, free trade is a weird thing in its applications.
While I'm in favor of exploring Obligatos, there are some very affordable Solen MKP's at Solen in Montreal at their on sale section. Older non-ROHS polyprops could be had for about $1 US in 1.5uf 250V and they have about 500 of them in stock. We could certainly make a good use out of an environmental passe item. Somebody has to properly utilize these potential toxins, perhaps we should. LOL.
Just something to be available as a possible alternative if costs were to be a strong factor.
Your excellent haggling with merchants does indeed make room for a nice option in this choice of capacitor, though...so, by all means go forth and haggle...
1.5uf 250V
1.8 uf 250V made in France.
That's one of the nice things I like about Solen in Montreal, their website shows the country of manufacture for each item...and the French girl who answers the phone has the loveliest voice...most pleasant to deal with.
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