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Old 14th November 2012, 12:53 PM   #1311
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Originally Posted by qusp View Post
no they arent ordered, I dont have >6K to put up for the GB, not a chance I would do it based on my previous experience with the number of people that normally back out when they find out the price even when theyve been warned, we arent talking normal signal level Zfoils here, they are considerably more expensive.

its all organized, but i'm sending out PM's tonight to make sure people are up for it. i'm just afraid that there is a large number of people that have put their name down just because they want good performance without having any idea what everything will cost.

this goes for the caps too, I can secure a better price for them than people will get through any retailer by putting them through as an OEM, but I dont know how many people have bothered to look at what they cost retail before putting their name down and will still balk at the price saying its too expensive even though its considerably lower than even the 20% sale discount price through PCX (who would probably not have enough of one value either). a lot of people pulling out would mean the price would have to be worked out and adjusted to fit the new number, I would have to say oh no sorry I dont want that many anymore and send out more messages again.

i'm also working out the details for the value, still only 2 people have said its OK for 4.7uf or not. I confirmed I only get the discounted price per value, so i'm trying to find a value that they have the full number ready for sale, to avoid the 5-6 week build time.

but i'm not getting a lot of help here guys as to what values people are OK with, its a bit chicken and egg.

in simple terms, no the GB's arent closed. but do realize that for 4 caps and 8 Zfoils is likely to cost $325-350 ballpark, i'm crunching the numbers in a moment so dont hold me to that.

i'm also trying to avoid sending out a message for caps and another one for resistors, same with chasing payments, I dont want to have to do everything 2 or 3 times, so i'll probably just send out the same message to everyone, just ignore the parts that dont apply to you.
I understand your hesitation completely. But to avoid that kind of situation, what kind of price are we talking about approximately? I've searched around for Z-foils, but I can only find low power stuff, at about $10-15 and Auricaps in the same range. I saw some 8W Zfoils in a Mouser pdf, but they were also around $10.

Regarding cap value, I'll be fine with 3.3 or 4.7uF. I'm planning to drive the Wire HP as well as the Wire power amp from the NTD1 and as far as I can tell, they both provide nice loads.
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Old 14th November 2012, 01:06 PM   #1312
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Originally Posted by Emphrygian View Post
I understand your hesitation completely. But to avoid that kind of situation, what kind of price are we talking about approximately? I've searched around for Z-foils, but I can only find low power stuff, at about $10-15 and Auricaps in the same range. I saw some 8W Zfoils in a Mouser pdf, but they were also around $10.

Regarding cap value, I'll be fine with 3.3 or 4.7uF. I'm planning to drive the Wire HP as well as the Wire power amp from the NTD1 and as far as I can tell, they both provide nice loads.
ermm I think you are mistaken on all counts. Auricaps are not even close to that same price range anywhere and if there was anywhere I think they would be very interested to know about it because they would be fakes, thats considerably less than their 1000 piece price for the 4.7uf. the 4.7uf are$38.91 for 4.7uf and 43.06 for the 6.8uf at partsconnection and you cannot get 8W Zfoils for $10 anywhere, thats less than even their SMD 1/10 W or the tx2575 are

i'll give details in PM, I cant post the cap pricing on the forum

edit, just remembered how low it is, actually the wire in stock form has pretty darn low input impedance of 600ohms. I plan to increase the resistors a bit at Owens advice and I may just end up going for the 10uf caps.

what are you using to drive your amps Owen, because 600ohms calls for a 135uf film cap...

the LPUHP are fine and the HP amp depends on your setup, but in stock form the big poweramp is a bit of a pita and I didnt even consider trying to deal with it with a film cap size.

this is why I asked if anyone needed the calculator, and kept harping on about people making sure they knew what they needed

Last edited by qusp; 14th November 2012 at 01:30 PM.
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Old 14th November 2012, 01:26 PM   #1313
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Originally Posted by qusp View Post
ermm I think you are mistaken on all counts. Auricaps are not even close to that same price range anywhere and if there was anywhere I think they would be very interested to know about it because they would be fakes, thats considerably less than their 1000 piece price for the 4.7uf. the 4.7uf are$38.91 for 4.7uf and 43.06 for the 6.8uf at partsconnection and you cannot get 8W Zfoils for $10 anywhere, thats less than even their SMD 1/10 W or the tx2575 are

i'll give details in PM, I cant post the cap pricing on the forum

actually not all counts, the wire will be fine unless you went a bit crazy with the pot, what pot are you using if any? if no pot, then what resistors are you using on the input?
Yes, I might well be mistaken on pricing, that's why I was asking. Regarding the Auricap, glancing through the list I found again, I saw that prices go up a a lot with value. That's what I get for trying to do this while at work

Still, the prices here seem pretty low, no?

I am not planning to use a pot, as I will control the volume in my (acko)DAC. Since my DAC isn't done yet (so many projects at the same time!), I at least plan to start out with the standard values (240R, right?).
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Old 14th November 2012, 01:32 PM   #1314
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Originally Posted by Emphrygian View Post
Regarding cap value, I'll be fine with 3.3 or 4.7uF. I'm planning to drive the Wire HP as well as the Wire power amp from the NTD1 and as far as I can tell, they both provide nice loads.
Be very careful with that! The SE-SE and BAL-SE versions come standard with 10k input impedance, but you can push that up as high as you like. The BAL-BAL has a much lower 1k input impedance, and 4.7uF would not be sufficient for that.

The Wire amp also has a rather low 1.2k input impedance if you configure it for balanced mode operation, which I'm assuming you would given it's being used with the NTD1.

If you did use the NTD1 with a 3.3uF cap and ran it directly to the BAL-BAL headphone amp, you'd get a -3dB point of 48Hz which I would consider unacceptable. You can either use a larger cap (closer to 22uF would give you an Fc of 7.5Hz) or you can replace the 4 1k resistors on the BAL-BAL with 10k resistors to get the input impedance up. The penalty for doing that will be slightly higher noise.

Cheers,
Owen
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Old 14th November 2012, 01:45 PM   #1315
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Thanks guys. I do feel bad that I haven't had the time to stay on top of all my projects lately

Anyway, I probably should have stated that the HP amp is the BAL-SE version. Even so, after crunching some numbers (how lazy of me to not do it before) I realize I probably need at least a 6.8uF cap for an Fc of 19.5 Hz. Unless I increase the input resistors in the power amp. So perhaps 10uF isn't such a bad idea if others are ok with that value.

Again, I'm sorry for not doing some (very simple, I might add) calculations before opening my mouth.
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Old 14th November 2012, 01:54 PM   #1316
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Originally Posted by Emphrygian View Post
Yes, I might well be mistaken on pricing, that's why I was asking. Regarding the Auricap, glancing through the list I found again, I saw that prices go up a a lot with value. That's what I get for trying to do this while at work

Still, the prices here seem pretty low, no?

I am not planning to use a pot, as I will control the volume in my (acko)DAC. Since my DAC isn't done yet (so many projects at the same time!), I at least plan to start out with the standard values (240R, right?).
they are OLD stock auricap, not the XO, auricap dont sell or make those anymore and I doubt very much theyve got stock anyway, certainly not enough for our order. doesnt look like theyve updated their website for ages, as an example, they still have Blackgate NX 47uf listed for sale, i'm going out on a limb to say they dont have those anymore, theyde be able to sell them for almost double that price now too.

i'm asking about the board mount Auricap in 10uf as well, as they are markedly cheaper, the only difference being they dont have OFHC leads, just nice copper leads
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Old 14th November 2012, 01:54 PM   #1317
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Just to clarify my stance on this a little further:

1) Using a lower value capacitor will cause a low frequency roll-off and phase shift with lower impedance inputs on the next stage. This is clearly measurable and would be clearly audible in double-blind test.

2) Using higher value resistors in the next stage to compensate for a low value capacitor in the NTD1 will increase the noise floor of the next stage. Again, this is easily measurable, and may be audible depending on how much higher it is. In the event that you're using IEM's on the output of the BAL-BAL with a sensitivity in the range of 120dB/1mW then you would definitely be able to hear the increased noise floor.

3) Using a good metallized PP cap like the one suggested in the schematic will not cause an LF rolloff, or increase noise, and will not result in a measurable difference from using a boutique film cap. I'll leave the question of audibility up to the end user, but I think it's pretty obvious where I stand on this.

The long and short of it is:

Feel free to use a boutique cap in this application, but please do not try and save money by using a smaller value, or I can promise you the end result will sound worse and cost more than just using what is in the BOM.


Cheers,
Owen

Last edited by opc; 14th November 2012 at 01:57 PM.
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Old 14th November 2012, 02:00 PM   #1318
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Originally Posted by opc View Post
Just to clarify my stance on this a little further:

1) Using a lower value capacitor will cause a low frequency roll-off and phase shift with lower impedance inputs on the next stage. This is clearly measurable and would be clearly audible in double-blind test.

2) Using higher value resistors in the next stage to compensate for a low value capacitor in the NTD1 will increase the noise floor of the next stage. Again, this is easily measurable, and may be audible depending on how much higher it is. If the event that you're using IEM's on the output of the BAL-BAL with a sensitivity in the range of 120dB/1mW then you would definitely be able to hear the increased noise floor.

3) Using a good metallized PP cap like the one suggested in the schematic will not cause an LF rolloff, or increase noise, and will not result in a measurable difference from using a boutique film cap. I'll leave the question of audibility up to the end user, but I think it's pretty obvious where I stand on this.

The long and short of it is:

Feel free to use a boutique cap in this application, but please do not try and save money by using a smaller value, or I can promise you the end result will sound worse and cost more than just using what is in the BOM.


Cheers,
Owen
we can cover the headphone amps pretty easily and it wont cost much more for the 10uf, ive asked about that too, but I cannot make even a proper inquiry if people dont do this basic level of thinking. it does require a larger than 4.7uf for the wire bal-bal, no problem to increase it, but if its not needed its not a value proposition, so I need feedback!!

but the BOM cap will not come anywhere near catering for 'the wire' poweramp 600ohms that Emphrygian was asking about, so you cant be using that either Owen
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Old 14th November 2012, 02:21 PM   #1319
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as a hint before I send the PM, I can get the 10uf in the new XO type for about the same price as the 4.7uf/200v in the link Emphrygian made above for the old version. cryptic enough for you? =) its a far cry from the PCX price, but of course its more than the BOM cap, but the BOM cap would be useless for the poweramp too.

of course we know or at least I know your view on caps opc, thats predictable, but its not a huge deal really at the discounted price, $50 increase in the total build for my peace of mind is pretty cheap.
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Old 14th November 2012, 03:21 PM   #1320
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as a hint before I send the PM, I can get the 10uf in the new XO type for about the same price as the 4.7uf/200v in the link Emphrygian made above for the old version. cryptic enough for you? =) its a far cry from the PCX price, but of course its more than the BOM cap, but the BOM cap would be useless for the poweramp too.

of course we know or at least I know your view on caps opc, thats predictable, but its not a huge deal really at the discounted price, $50 increase in the total build for my peace of mind is pretty cheap.
I'm certainly not against the use of fancy parts, and as you said, the price really isn't that bad all considered. Even the caps in the BOM are not exactly cheap. What I am against though is people making poor design decisions without really thinking anything through, and potentially spending more for a worse result. It's part of the reason I always caution people when they deviate from the BOM in any way... unless you know what you're doing, and pay close attention to all the details, then there's a good chance things can get worse.

As for the power amp, it's not quite as bad as you're thinking in terms of input impedance. The 600 ohms stated in the amp literature is a "differential" input impedance. It's the impedance across the + and - terminals of the amp. Another way to look at it would be the impedance from each input to GND which is 1.2k.

If you want to stick to the 600 ohm differential impedance, then you'd have to consider the two output caps in parallel and the output impedance of each leg of the NTD1 in parallel. In my mind it's easier to consider each leg of the differential pair separately and use the value as they are.

I have attached a simulation to show what I mean.

As you can see, with a 22uF cap on the output, you're down about 0.28dB at 20Hz and the -3dB point is roughly 7Hz. I consider this more than acceptable for use with loudspeakers (which suffer massive phase and rolloff issues at these frequencies) but I would probably hesitate to recommend that high of an Fc with headphones.

If you're a real stickler for perfectly flat LF response, then a 47uF output cap would be the better choice as it results in an Fc of closer to 2.5Hz and only 0.06dB roll-off at 20Hz.

I personally have been using The Wire power amp in balanced mode with the stock 22uF film caps, and I'm very happy with the result. I might consider a nicer pair of 47uF caps when I finally get around to putting it all in a proper case

Cheers,
Owen
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Last edited by opc; 14th November 2012 at 03:30 PM.
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