QRV07 & QRV08 build costs

[nightanole]

I was looking for a smt headphone amp to build and found these 2 guys.  However there is no BOM or anything, only the board cost.  I was wondering how much it would cost to populate a qrv08 or qrv08 board.  I know case, volume control, and connectors are left up to me.

[peranders]

QRV07: 2 opamps, TPA6120 regulators and transformers, those are the parts that cost, < 500 SEK

QRV08, lot's of expensive parts, 1000-2000 SEK.

[nightanole]

What are the dimensions of the qrv07 board, and the height of the tallest component?  This will give me a clue to see if i can fit it.

[peranders]

The dimensions can be found under technical data, see upper right corner at the web page.
The maximum height is 30-35 mm.

[peranders]

Elfa and Farnell have most of the parts and the rest you can get from me.

[wasp]

I've spent around 240 USD for my QRV-08. Most of them was ordered from Mouser, rest at ELFA.

[qusp]

Hi there guys and (gals)?? I am putting together my BOM for several builds from here including several regs, some rectifiers and 2 x QRV08 for a balanced build as standalone headamp/pre or perhaps as output stage for a high end sabre dac, my question is related to mainly the QRV08 and some JSR01, the BOM for the QRV08 is not as extensive or specific as the other excellent BOMs I have used from here before and yet it is the most sizeable by a long way; it was a bit painful going through such a long list and counting out the numbers or each part, search in excel to try to streamline this process did not help and loading the BOM into the digikey BOM tool just produced a heap of errors)

anyway thats not the issue, that was a good character building exercise  :mrgreen:

for the resistors, the only thing specified is 0805 size and 1%, can I use thick film here or is thin film needed? not only are thick film much easier to find in all values and with a better choice, but they are of course considerably cheaper as there are so many, especially since I am ordering for 2. I was thinking it might be possible to use thick film (vishay or yageo) for the majority and thin film for some more critical positions, does this sound viable? if so what are the areas of interest that really should be thin? thick or thin all are still 1% or less and 100ppm or less

same question regarding the caps, can I use X7R for most and NPO for critical areas? also NPO in 0805 are not easy to find at digikey in these values and elfa shipping cost is through the roof to australia, I have put together an order from digikey that will supply all parts for a couple of dacs (different dac for my studio), an ASRC board, some AA NIMH cells, 5 x JSR01 and most of 2 x QRV08 and i'm at about the same cost as just the parts for 2 x QRV08 from elfa, though they have pretty much everything in the right size and type, I assume the BOM was made with elfa in mind and with local shipping

so considering this is a balanced build, can I get away with slightly lower quality parts for some areas because of the added noise rejection of the common mode? or will I just end up spending more money on stuffing 2 boards and get only a tiny bit more (if any) performance compared to using highest quality parts for a single board? the transformers i'm using are custom wound and fully encapsulated with core band and it is matching with a VERY high quality DAC, so I would like to keep performance high, but I would like to save some money if I can, as my wallet has been rendered into a sorry state from my audio addiction over the last few months in particular. as it is I dont know if thin film are even recommended as they are mot specified.

thanks for any help

[peranders]

X7R is fine for decoupling. NP0 is better where the audio signal is involved.

Any resistor type is the "minimum" so go ahead using more advanced types.

[qusp]

ok excellent, looks like I need to examine the BOM and layout more closely then, so I can separate which can be X7R or NPO.

can I use Nichicon FW SMD or panasonic FK in place of the 100uf elna? again I cant get these at digikey in SMD or at farnell. I like the silmic II so I believe the elnas will produce great sound, but I just cant buy them anywhere that doesnt charge through the roof for shipping. I wish someone would be a middle man ;) hint hint ;)

also are there any other suggestions for the onboard XFMR's? is the pinout fairly universal?? just wondering if I have to give sumR any special instructions?

any good suggestions for a balanced pot for use with 2 x QRV08? would be good if it is supplied in kit form for a stepped attenuator, as I will probably leave quite a bit unpopulated and use very high quality ZFoils for key positions once I find my way with this amp. I was even thinking of going as bare as using a 4p4t or similar rotary switch with only zfoils. any suggestions for suitable pots? any limits on the value, I suppose I should try to keep it to 10K for higher performance correct? even thinking of a relay based volume control

[peranders]

The Elna cap I have chosen is a general purpose type and this is also the minimum but still will establish ultra high end sound quality. Feel free to test other types.

The transformer is pretty standard over here at least.

The last question may someone else answer because I have not clue there. 10 kohms as pot value is a good choice here

[renlute]

For the QRV07 parts I've spent $127.43 from Digikey and Newark in the USA, including shipping.

It's taken an awful lot of time to find everything, trying to match parts with specs. I hope there's been no mistake in part selection. If I did this again I would order everything possible from Elfa, despite paying more for shipping and maybe customs duty, since most of the part numbers are already on the BOM.

There's one last little part I can't find that no distributor in the US has in stock (and some want to sell me over 1000 pieces to back-order it). It's the two Kemet/Evox Rifa foil capacitors (Elfa part 65-557-59) for C1 and C8.  Would anybody have a couple of these lying around? I can pay via Paypal or wire transfer in EUR, or US$$.

Alternatively, how closely do the specs have to match that particular capacitor? Newark has a similar one in stock, Kemet part #LDEEC3100KA5N00, but it's rated at higher voltage and tolerance: 0.1 microfarad, 100V, +/-10%, 2220, polyethylene naphthalate. Another is rated 1.0uF, 10%, 50V. Would those ruin the QRV07 board or its performance? Mouser has a closer one in stock in a smaller size -- 0.1uF, 10%, 50V, 0.8 DF, but size 1210 (3225 metric), only half as big. Mouser has another at 0.1uF, 10%, 63V. 0.8DF, size 1812 (4532 metric).

I'm no electronics expert at all so all this is confusing.
Doug

[peranders]

Noone wants me to pay me for making kits and I think you could guess why.

I may a couple of those caps at home. I can check this next weekend.

Basic spec for this cap is:
> 100 nF
> 50 V
Plastic dielectricum
Not too big
Using holemounted is OK to use.

[renlute]

It would be great if you had a couple extra of those caps you could sell me. 

If none are available, which of the following would be the most appropriate and would not compromise the amp's output specs? Or will specs suffer if not exactly as originally designed? (All below are Kemet polyurethane film SMDs.)

Mouser:
0.1uF, 10% tolerance, 63V, 1812/4532 size, 0.8DF

Newark:
0.47uF, 10%, 50V, 2220
1.0uF, 10%, 50V, 2220
0.1uF, 10%, 100V, 2220

[peranders]

I have spare PPS caps. How many do you want?

[renlute]

SUPER! Thanks for checking.

The BOM calls for two. I just sent you an email.