Valve DAC from Linear Audio volume 13

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nautibuoy

nautibuoy

Member
Joined 2010
I have a quote for the cost of my friend doing the smd soldering so we can proceed. I would like to get the PCB order submitted by the end of the month so I will leave the GB open until August 23rd and will need downpayments by August 30th. Clearly the cost to you will depend to some extent on the number of GB participants - I will pass on any reductions that accrue but you should also be prepared for the cost to increase a little if, for example, some subscribers pull out. Shipping costs will depend on where you are and what you take but I'll aim to give you a number for this before we get too far along. Does that all make sense and seem reasonable?

Here are the relevant 'working' costs that you will need to consider in order to make your GB choices:

  • PCB = £24 each (based on a GB of 20 PCBs, for a GB of 15 the cost will rise to £31 each)
  • SMD soldering = £45.50 per PCB
  • SMD parts = £51 (required if SMD soldering option taken, sourced from Digikey - Blocked - Depending on quantities, price breaks may reduce the cost)
  • Reconstruction Filter PCBs (pair) = £2 (This is the PCB I developed for the third order filter using Marcel's schematic)

Here are the options available;

  • Bare DAC PCBs
  • DAC PCBs with the smd parts soldered
  • Reconstruction filter PCBs

I need you to start making choices so can I ask you to start cutting and pasting the section below and entering your requirements as per the first line. I will put a spreadsheet together to start tracking these and calculating accurate costs so we can arrange payments.

diyAchim - 1 x PCB - ? x SMD Parts installed - ? x Filter PCB (pair) - Country = ?
Raj!1 - 1 PCB (UK)
dubulup - 2 PCB (USA)
ericoto -1 PCB
HenSch - 2 PCB (Germany)
mterbekke - 2 PCB (Netherlands, confirmed)
rfbrw - 1 PCB
Pistollero - 1 PCB (Portugal)
luchoh - 1 PCB (USA)
pgour - 1 PCB
agent.5 - 1 PCB (USA)
spm - 1 PCB (UK)
torb - 1 PCB (Finland)
thuanth43 - 1 PCB (Singapore)
 
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M

mterbekke

Member
Joined 2009
diyAchim - 1 x PCB - ? x SMD Parts installed - ? x Filter PCB (pair) - Country = ?
Raj!1 - 1 PCB (UK)
dubulup - 2 PCB (USA)
ericoto -1 PCB
HenSch - 2 PCB (Germany)
mterbekke - 2 times everything (2pcb+soldering+filter (Netherlands, confirmed)
rfbrw - 1 PCB
Pistollero - 1 PCB (Portugal)
luchoh - 1 PCB (USA)
pgour - 1 PCB
agent.5 - 1 PCB (USA)
spm - 1 PCB (UK)
torb - 1 PCB (Finland)
thuanth43 - 1 PCB (Singapore)
 
D

Dubulup

Member
Joined 2016
diyAchim - 1 x PCB - ? x SMD Parts installed - ? x Filter PCB (pair) - Country = ?
Raj!1 - 1 PCB (UK)
dubulup - 2 x PCB - 0 x SMD Parts installed - 2 x Filter PCB (pair) - Country = USA
ericoto -1 PCB
HenSch - 2 PCB (Germany)
mterbekke - 2 times everything (2pcb+soldering+filter (Netherlands, confirmed)
rfbrw - 1 PCB
Pistollero - 1 PCB (Portugal)
luchoh - 1 PCB (USA)
pgour - 1 PCB
agent.5 - 1 PCB (USA)
spm - 1 PCB (UK)
torb - 1 PCB (Finland)
thuanth43 - 1 PCB (Singapore)
 
R

Raj1

Member
Joined 2003
diyAchim - 1 x PCB - ? x SMD Parts installed - ? x Filter PCB (pair) - Country = ?
Raj!1 - 1 PCB - 1 x SMD parts installed - country = UK
dubulup - 2 x PCB - 0 x SMD Parts installed - 2 x Filter PCB (pair) - Country = USA
ericoto -1 PCB
HenSch - 2 PCB (Germany)
mterbekke - 2 times everything (2pcb+soldering+filter (Netherlands, confirmed)
rfbrw - 1 PCB
Pistollero - 1 PCB (Portugal)
luchoh - 1 PCB (USA)
pgour - 1 PCB
agent.5 - 1 PCB (USA)
spm - 1 PCB (UK)
torb - 1 PCB (Finland)
thuanth43 - 1 PCB (Singapore)
 
R

rfbrw

Member
Joined 2001
diyAchim - 1 x PCB - ? x SMD Parts installed - ? x Filter PCB (pair) - Country = ?
Raj!1 - 1 PCB - 1 x SMD parts installed - country = UK
dubulup - 2 x PCB - 0 x SMD Parts installed - 2 x Filter PCB (pair) - Country = USA
ericoto -1 PCB
HenSch - 2 PCB (Germany)
mterbekke - 2 times everything (2pcb+soldering+filter (Netherlands, confirmed)
rfbrw - 1 PCB Filter PCB 1 set.(UK)
Pistollero - 1 PCB (Portugal)
luchoh - 1 PCB (USA)
pgour - 1 PCB
agent.5 - 1 PCB (USA)
spm - 1 PCB (UK)
torb - 1 PCB (Finland)
thuanth43 - 1 PCB (Singapore)
 
A

agent.5

Member
Joined 2003
diyAchim - 1 x PCB - ? x SMD Parts installed - ? x Filter PCB (pair) - Country = ?
Raj!1 - 1 PCB - 1 x SMD parts installed - country = UK
dubulup - 2 x PCB - 0 x SMD Parts installed - 2 x Filter PCB (pair) - Country = USA
ericoto -1 PCB
HenSch - 2 PCB (Germany)
mterbekke - 2 times everything (2pcb+soldering+filter (Netherlands, confirmed)
rfbrw - 1 PCB Filter PCB 1 set.(UK)
Pistollero - 1 PCB (Portugal)
luchoh - 1 PCB (USA)
pgour - 1 PCB
agent.5 - 1 PCB + 1 SMD Parts installed + 2 Filter PCB -> USA
spm - 1 PCB (UK)
torb - 1 PCB (Finland)
thuanth43 - 1 PCB (Singapore)
 
HenSch

HenSch

Member
Joined 2016
diyAchim - 1 x PCB - ? x SMD Parts installed - ? x Filter PCB (pair) - Country = ?
Raj!1 - 1 PCB - 1 x SMD parts installed - country = UK
dubulup - 2 x PCB - 0 x SMD Parts installed - 2 x Filter PCB (pair) - Country = USA
ericoto -1 PCB
HenSch - 2x PCB, 2x Filter PCB (pair) country=Germany
mterbekke - 2 times everything (2pcb+soldering+filter (Netherlands, confirmed)
rfbrw - 1 PCB Filter PCB 1 set.(UK)
Pistollero - 1 PCB (Portugal)
luchoh - 1 PCB (USA)
pgour - 1 PCB
agent.5 - 1 PCB + 1 SMD Parts installed + 2 Filter PCB -> USA
spm - 1 PCB (UK)
torb - 1 PCB (Finland)
thuanth43 - 1 PCB (Singapore)
 
nautibuoy

nautibuoy

Member
Joined 2010
Thanks chaps.

Attached is a screengrab of the spreadsheet I've put together. I'll share it once I've checked my logic and worked out the best way to do so.

A couple of points in the interests of transparency;

  • The DAC PC cost is calculated based on the order qty required to address the GB divided by the number of subscriber requirements. (i.e. to deliver 17 PCBs will need me to order 20 so the unit cost is the cost of 20 PCBs divided by 17 (or whatever apply, the spreadsheet will automatically recalculate if the numbers go up (or down).
  • That potentially leaves spare PCBs and we'll need to think about what we do with them?
  • The DAC PC costs don't yet include the cost of shipping them from the fabricator to me - I'll update that later.
  • The same unit cost rational applies to the filter PCBs (but the cost of shipping them from the fabricator are included.
  • For those requiring SMD parts to be installed, once I know how many want this service I'll place a single Digikey order and then recalculate the unit costs to pass on the break point savings. The cost of the SMD installs will be less than is currently shown but I can't quantify by how much yet.

I still need to calculate onward shipping costs.
 

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nautibuoy

nautibuoy

Member
Joined 2010
Raj1 said:
No worries, least I can do given the help you’re providing us all. And no worries about testing the DAC. I’m sure it sounds great. I might reach out to Dave Slagle at some point also. Will see if he has some novel ideas about coupling the output stage.
Click to expand...

I was thinking some more about the CD-Enhancer output stage; My Lowther's take very little to drive them and I was thinking that with the 5844/6J6 version there would be sufficient gain to hook it up to a MoFo power buffer - that would be pretty minimalist.
 
M

MarcelvdG

Member
Joined 2003
thuanth43 said:
Now I have to think if it's possible for that tube regulator board to output -300v instead of +300v :-/
Click to expand...

If the whole secondary part from transformer to regulator output has no connection to ground anywhere, then its just a matter of grounding the positive output terminal and using the negative as the -300 V. Please keep in mind that what would normally be a ground plane is now a -300 V plane.

For the record, I have absolutely no hum issues with the original valve DAC, which uses a simple CRCRC filtered unregulated -300 V supply and AC for the heaters.
 
T

thuanth43

Member
Joined 2016
diyAchim - 1 x PCB - ? x SMD Parts installed - ? x Filter PCB (pair) - Country = ?
Raj!1 - 1 PCB - 1 x SMD parts installed - country = UK
dubulup - 2 x PCB - 0 x SMD Parts installed - 2 x Filter PCB (pair) - Country = USA
ericoto -1 PCB
HenSch - 2x PCB, 2x Filter PCB (pair) country=Germany
mterbekke - 2 times everything (2pcb+soldering+filter (Netherlands, confirmed)
rfbrw - 1 PCB Filter PCB 1 set.(UK)
Pistollero - 1 PCB (Portugal)
luchoh - 1 PCB (USA)
pgour - 1 PCB
agent.5 - 1 PCB + 1 SMD Parts installed + 2 Filter PCB -> USA
spm - 1 PCB (UK)
torb - 1 PCB (Finland)
thuanth43 - 1 PCB + 0 SMD parts installed (Singapore)
 
L

luchoh

Member
Joined 2006
luchoh.com
Paid Member
diyAchim - 1 x PCB - ? x SMD Parts installed - ? x Filter PCB (pair) - Country = ?
Raj!1 - 1 PCB - 1 x SMD parts installed - country = UK
dubulup - 2 x PCB - 0 x SMD Parts installed - 2 x Filter PCB (pair) - Country = USA
ericoto -1 PCB
HenSch - 2x PCB, 2x Filter PCB (pair) country=Germany
mterbekke - 2 times everything (2pcb+soldering+filter (Netherlands, confirmed)
rfbrw - 1 PCB Filter PCB 1 set.(UK)
Pistollero - 1 PCB (Portugal)
luchoh - 1 PCB + 1 SMD Parts installed + 2 Filter PCB (USA)
pgour - 1 PCB
agent.5 - 1 PCB + 1 SMD Parts installed + 2 Filter PCB -> USA
spm - 1 PCB (UK)
torb - 1 PCB (Finland)
thuanth43 - 1 PCB + 0 SMD parts installed (Singapore)

added SMD and filtering option for myself.
 
nautibuoy

nautibuoy

Member
Joined 2010
The Mofo has no voltage gain itself, just current gain, so Mr. Ohm tells me that to get 1W into my 15ohm Lowthers requires 3.88V input to the MoFo. The 3A5 version of the CD-Enhancer (14x gain) is designed to deliver around 2V output and the 5844 has double that gain, so around 4V.

My OTL amps deliver around 1-1.5W and that's plenty to play loud in my room.

The reason for using 15ohm drive units is because valves are less able to deliver current but with a MoFo power buffer type scenario using 8ohm drive units, 4V input would give you 2W. Hmm...
 
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