It's worse than the photo shows. There are three separate PSs for the DAC: 5V, 8V & 12V. They are tucked under the ground plane board that is visible (barely) under the DAC. The board on top of the DAC is an I2S receiver board for the PS Audio I2S over HDMI protocol.
To answer your question, yes it is quiet. Choke input B+ and negative supplies, separate current source fed shunt reg. for the B+ and current source "tail" impedance on the LTP 6N30s help. Also, the DAC PSs only power on when the digital input is selected.
I put the DAC in the same chassis to save a gain stage in the analog chain. The DAC uses a PCM1794 balanced current output chip that is directly connected to two pairs of I/V conversion resistors on the input board. Relays then connect to the input resistors of shunt style attenuator. The LL1690 input transformers can also be seem on this board. Analog RCA inputs connect to the primaries, the balanced input connects to the secondaries (acts as a CT grid choke).
This line stage started life as a cover story in AudioXpress. Over the years I've modified it many times over. If you are interested it is chronicled here:
Tracy
To answer your question, yes it is quiet. Choke input B+ and negative supplies, separate current source fed shunt reg. for the B+ and current source "tail" impedance on the LTP 6N30s help. Also, the DAC PSs only power on when the digital input is selected.
I put the DAC in the same chassis to save a gain stage in the analog chain. The DAC uses a PCM1794 balanced current output chip that is directly connected to two pairs of I/V conversion resistors on the input board. Relays then connect to the input resistors of shunt style attenuator. The LL1690 input transformers can also be seem on this board. Analog RCA inputs connect to the primaries, the balanced input connects to the secondaries (acts as a CT grid choke).
This line stage started life as a cover story in AudioXpress. Over the years I've modified it many times over. If you are interested it is chronicled here:
Tracy
A jam-packed amp can be seen here. The best part of the chasis was that all the three sides (front, left, right) panels can be removed by unscrewing for easy repairs The front panel holds the active xover and preamp and comes out with the panel.
http://www.diyaudio.com/forums/solid-state/103152-tri-amp-completed.html
Gajanan Phadte
http://www.diyaudio.com/forums/solid-state/103152-tri-amp-completed.html
Gajanan Phadte
If you have the holes in the PCB as a guide, find out the ID of those holes (preferably by vernier caliper or more accurate methods) and use a transfer punch sized exactly. Then use a small countersinking bit, the type which are typically used as center drills, to start each hole. Finish each hole with the correctly-sized drill bit.
https://www.youtube.com/watch?v=Nyj0wgffcFI
Drill and tap guide, might be of interest.
Gajanan Phadte
Drill and tap guide, might be of interest.
Gajanan Phadte
good use of twisted pairs in what appears to be quite tightly packaged modules.
Yes, it takes time and guidance to get the combination of "speed and feed rate" just right.
Then one has to learn how to sharpen a drill so that it drills to size and not oversize.
Talking about size.
Is there a rule that determines how much the drill is "undersize" compared to it's marked diameter?
Then the next question becomes:
when a correctly undersized drill is used, does the resulting hole equal the marked diameter?
and
does the resulting hole diameter depend on the material being drilled? eg, copper, brass, softer grades of aluminium, harder grades of aluminium, mild steel, harder steels?
Can you tell that I am not a machinist?
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If you drill a 1/4" hole, you will not be able to put a 1/4" dowel pin in it without extra force! That is because a normally drilled hole is not round or exact dimension as you have noted.
If you are sharpening your own bits you should have a drill gauge. McMaster-Carr
This is used to make sure your tip is actually centered. When the tip is off center, no surprise you will get an off size hole.
Normal drilled hole tolerance is .005". However if you are doing thicker material the bit may bend a small amount during drilling and again yield an oversize hole. Now thick softer material will often have less of this effect.
Then there is the drill angle typically 118 degrees for drilling steel and considered multipurpose bits. The wrong angle and you will either grab too much material and bind or too little and possibly overheat. Of course there are lubricants to make drilling easier.
Now for a while you could bullet point bits for metal similar to the brad point bits used for wood or similar material. They make centering easier.
Now as to drilling speed, I use 60 surface feet per minute for high quality steel. With a lubricant you can do 250 SFM in aluminum. To calculate surface feet per minute all you need to know is the drills diameter (2 x pi x diameter, that is the surface!) and the drill motor RPM. A bit of arithmetic can be used, but most will just look it up on a chart.
Drill feed speed should be around .004" x drill diameter per revolution. This is a ballpark estimate only as materials differ greatly.
Machinist ?? Are you kidding 
?
This is DIY. 20$ Walmart black & decker drill , 7/64" dewalt bit +
a 3mm and 6-32 tap !
For amps/ preamps - PC motherboard standoffs are common fare.
For some reason they are commonly either 3mm or 6-32 thread. They all terminate 6-32 to chassis.
TO-264 / TO-3P / and MT-100 -200 are all 3.2 - 3.4mm (3mm screw)
Just 2 threads + one bit size (7/64 - 2.5mm) ,does them all.
TO-126 is also 3mm .
The only other hole sizes would be for the Toriod , main star ground , bridges.
4-5mm for ground / bridges .... Trafo could be anything ??
The only scenario that would get to the "machinist" level , is where the builder
would have to add his own ventilation , or thermally join heatsinking. Most
Chassis's are pre -punched (power amp) , some with power/input/output
holes. A builder that lacks a full shop would purchase an EBAY chassis
regardless.
OS
?This is DIY. 20$ Walmart black & decker drill , 7/64" dewalt bit +
a 3mm and 6-32 tap !
For amps/ preamps - PC motherboard standoffs are common fare.
For some reason they are commonly either 3mm or 6-32 thread. They all terminate 6-32 to chassis.
TO-264 / TO-3P / and MT-100 -200 are all 3.2 - 3.4mm (3mm screw)
Just 2 threads + one bit size (7/64 - 2.5mm) ,does them all.
TO-126 is also 3mm .
The only other hole sizes would be for the Toriod , main star ground , bridges.
4-5mm for ground / bridges .... Trafo could be anything ??
The only scenario that would get to the "machinist" level , is where the builder
would have to add his own ventilation , or thermally join heatsinking. Most
Chassis's are pre -punched (power amp) , some with power/input/output
holes. A builder that lacks a full shop would purchase an EBAY chassis
regardless.
OS
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Did you mis-read my question?Machinist ?? Are you kidding
The only scenario that would get to the "machinist" level ,............
I said NOT before machinist.
Around here you can get all the gauges and specialty stuff at garage sales. Add a small drill press for under $65 and you can do it all nicely, professionally and still keep all of your fingers intact!
The best part is when you go to sell the tools you will get at least what you paid for them.
I have a decent shop and quite simply, with few exceptions every good tool would sell used for more than I originally paid for it. The cheap fill in tools won't.
The best part is when you go to sell the tools you will get at least what you paid for them.
I have a decent shop and quite simply, with few exceptions every good tool would sell used for more than I originally paid for it. The cheap fill in tools won't.
It's kind of a blessing for serious hobbiests in North America that most machining is going offshore. There are lots of great deals to be had on machines if you have the space and the power to feed them. A few years ago I purchased 3 Bridgeport mills. A week later I sold 2 for more than I paid for the three.
If hole size is critical you drill undersize and ream to finish dimension. In most cases you actually want the hole quite oversize. A 1/4" bolt won't fit in a 1/4" hole. Usually pass holes are drilled 1/32" oversize.
But the thread was going in that "direction".
I was just looking at the typical DIYA project. You can
tell they are NOT using advanced milling equipment.
Most "rush" their projects , not even considering some
electrical - layout considerations.
Yes , Simon ... harbor freight has cheap 50$ chinese presses. But
90% of builds are done on kitchen table's , wives DO NOT like
milling equipment in their kitchens !
OS
OS
The threads of a 1/4" bolt will easily pass through an accurately drilled 1/4" hole.
Getting the shank of the bolt through should be a push fit, or slightly slacker.
What is critical ?
While accuracy is important for that final "finished look" , DIY will always
have a certain amount of "slop".
De-burring (or having a chamfered hole) is so very electrically important at
the output devices.
Most modern plastic packages DO have a plastic ring around the mounting
hole. If a burr was near the hole , it (might) be under the plastic.
TO-220's have no such "slop" factor , a burr here will short.
Be gentle with your extrusions , a slip of a centerpunch under the "body"
area of a TO-xxx device can perforate the mica/kapton insulator after
torquing the semi.
With a hand drill , there are some "tricks". You can "steer" your pilot hole
right at the surface by angling the drill . Don't do this at depth (SNAP !).
Once you are at a final diameter , a "steered hole" will still be perfect.
For a novice , just drill some holes in scrap material to know (by hand)
the limits of the bits / material.
After some time , you can "feel" the tool / material - and know when bad
things are about to happen. Tapping is the same , hand tapping might actually
require breaking one off to know how much it takes (when to "back off") to
never do it again.
This might be why many amp builds gravitate towards angle aluminum OP
mounting methods - "fear of the tap". BUT , tapped direct mounted
OP's are superior.
OS
While accuracy is important for that final "finished look" , DIY will always
have a certain amount of "slop".
De-burring (or having a chamfered hole) is so very electrically important at
the output devices.
Most modern plastic packages DO have a plastic ring around the mounting
hole. If a burr was near the hole , it (might) be under the plastic.
TO-220's have no such "slop" factor , a burr here will short.
Be gentle with your extrusions , a slip of a centerpunch under the "body"
area of a TO-xxx device can perforate the mica/kapton insulator after
torquing the semi.
With a hand drill , there are some "tricks". You can "steer" your pilot hole
right at the surface by angling the drill . Don't do this at depth (SNAP !).
Once you are at a final diameter , a "steered hole" will still be perfect.
For a novice , just drill some holes in scrap material to know (by hand)
the limits of the bits / material.
After some time , you can "feel" the tool / material - and know when bad
things are about to happen. Tapping is the same , hand tapping might actually
require breaking one off to know how much it takes (when to "back off") to
never do it again.
This might be why many amp builds gravitate towards angle aluminum OP
mounting methods - "fear of the tap". BUT , tapped direct mounted
OP's are superior.
OS
Not easily, but possibly. "Accurately drilled" is a misnomer anyway because twist drill bits do not make true negative cylinders in material. A hole that is cut by a twist drill bit will never be perfectly round, axially-aligned, to size, or even on position.
Given the tolerances of typical screws and bolts and drilled holes, it is considered terrible practice to size a hole ID the same as the nominal diameter of a cap screw or machine screw. Holes for clearance fits are oversized for a reason, and the only reason you want the same size (transitional or interference fit) is for locating purposes. For this, you would either use a locating pin, dowel pin, or shoulder screw.
Consider that a hole that must be dead-on, must first be drilled undersize by less than 0.2 mm (depending on the final ID), then bored to a few hundredths of a mm undersize, and then finally reamed to exact size. This ensures (almost) perfect cylindricity.
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