(AK) classA HA/Preamplifier.

[XTRProf]

Feb 19, 2011 0:00:25 GMT @sandyk said:

Feb 18, 2011 22:30:15 GMT leo said:

Come on, lets see some pics

Hi Leo
When installed, mine will not look a great deal different to at present, because they will simply be replacing the existing modified SC PCBs.
Also, although Jeff C and myself each have a couple of tested PCBs, we are waiting on replacement 2 pin terminal blocks from the U.K. as all the locally available blocks have pins of only 3 or 3.5mm length. This means that connections using the existing are not reliable, as the twisting action of screwing and unscrewing cables can fracture the soldered joint due to the pins not protruding through the 3mm thick PCBs.The ones that I have ordered from Farnell (Element 14) are black,have 4.5mm long pins, and should look even nicer with those beautiful black PCBs.
BTW, when using OPA134 for the Offset corrector I.C. and a 3K resistor terminating the input, DC Out has been measured as 0mV
on Jeff's and my own PCBs.
Alex


Uploaded with ImageShack.us

Good work there, Alex! Btw, how hot is hot for the heatsinks? For egg frying, warm our hands up comfortably during winter or insignificantly of no practical concern?

[Will]

Nice and tidy, Alex, very nice.

You could consider these heatsinks au.element14.com/fischer-elektronik/sk-129-25-4-sts/heat-sink-extruded-pcb-mounting/dp/1319810 as they are the ones that match the footprint on the pcb, allowing for more heat dissipation. Just a thought.


Chong,

If Alex's heatsinks are anything like mine (they look the same as my current build) then they will be verging on stingy hot, but you can hold on to them for as long as you wish. This is at 20C ambient, mind you.

[Deleted]

Feb 19, 2011 16:14:54 GMT Will said:

Nice and tidy, Alex, very nice.

You could consider these heatsinks au.element14.com/fischer-elektronik/sk-129-25-4-sts/heat-sink-extruded-pcb-mounting/dp/1319810 as they are the ones that match the footprint on the pcb, allowing for more heat dissipation. Just a thought.


Chong,

If Alex's heatsinks are anything like mine (they look the same as my current build) then they will be verging on stingy hot, but you can hold on to them for as long as you wish. This is at 20C ambient, mind you.

Hi Will
Those are twice as efficient as mine, but more than 4 x the price for each, and unfortunately would need to come from the U.K. as nil stock locally.
Alex

[leo]

Looks real nice Alex, starting to get itchy fingers
Anybody know the supply current for each amp module rail?

[Deleted]

Feb 20, 2011 1:42:02 GMT leo said:

Looks real nice Alex, starting to get itchy fingers
Anybody know the supply current for each amp module rail?

Hi Leo
It should look even better after those black terminal blocks arrive.
The bias is set at 100mA per rail, so the overall current shouldn't be á great deal more than that per module. 120mA per rail should cover it ?
Alex

[XTRProf]

Feb 19, 2011 16:14:54 GMT Will said:

If Alex's heatsinks are anything like mine (they look the same as my current build) then they will be verging on stingy hot, but you can hold on to them for as long as you wish. This is at 20C ambient, mind you.

Oh, then that will be quite similarly hot as the MF X-Dac V3 3 Vregs after dropping voltage from about 17VDC to 5 and 3.3VDC. Then the box must be well ventilated.

[Deleted]

Attached are the specs for the heatsinks that Will mentioned in his post.They have a thermal resistance of 7.8C /W compared with 17C/W of the more usual type of the same height.This means that on a hot day in some parts of the world (say 40C) that they will be around 56C compared with the other type of around 74C. In places like the U.K. they are unlikely to even exceed 40C !


Manufacturer: FISCHER ELEKTRONIK
Order Code: 1319810
Manufacturer Part No: SK 129 25,4 STS RoHS : Yes

Description HEAT SINK, EXTRUDED, PCB MOUNTING
Packages Cooled:TO-220 / SOT-32 / TO-3P
Thermal Resistance:7.8°C/W
External Width:42mm
Height:25mm
Heat Sink Material:Aluminium
External Depth:25.4mm
External Length / Height:25mm
Material:Aluminium
Surface Finish:Black Anodized
External Height:25.4mm
Fixing Style:Screw
Length:25mm
Mounting Type:Screw Mount
Package / Case:TO-220, SOT-32, TO-3P
Weight:0.025kg

[Will]

Typing SK129 in to the Farnell/Element14 search will bring up the 4 heatsinks in this family, starting at 1" tall, through to 2.5" tall. I've four of the 1.5" ready for plonking into my PCB.

[Deleted]

I was just about to order my vol pot when I thought of another question I should of asked before.

For this particular project, is a log or linear pot of preference, and why?

I've four of the 1.5" ready for plonking into my PCB.

Without checking the box, which is somewhere in a stack of more boxes, I think that's the size I ordered too.

Edit= just had a check, mine are 2"(1319813), should be enough overkill then!

[Deleted]

I was just about to order my vol pot when I thought of another question I should of asked before.For this particular project, is a log or linear pot of preference, and why?

Hi Chris
Virtually all volume controls/attenuators are "Audio taper" or Logarithmic.A Logarithmic taper matches the human ear's response,
so it gives a smoother control of the volume .
Alex

[Deleted]

Alex,

That's what I had understood from previous discussions, thanks.

I asked mainly after the posts on changing the pot in the Neco amplifiers, with those involved seeming to prefer the linear version.

Chris

[jonclancy]

Feb 20, 2011 22:21:26 GMT @cjarchez said:

Edit= just had a check, mine are 2"(1319813), should be enough overkill then!

Same here - I don't think we'll have a problem with getting rid of the heat, Chris!!

[FritzS]

Feb 16, 2011 6:27:41 GMT @sandyk said:

2 pin terminal blocks.
Please ,make sure that the terminal blocks you use have pins longer than 3.5mm.
Both Jeff C and myself have 2 working PCBs, but we had to use the locally available blocks with 3mm or 3.5mm long pins.
These blocks will almost certainly cause trouble after the terminals have been tightened and untightened a couple of times, and may even fall out if turned upside down.
Mine is now awaiting some TERMINALBLOCK, PCB, 2WAY, 5MM CTB1202/2 CAMDEN from Farnell (Element 14) in the U.K. as locally there are no stocks.These blocks have 4.5mm long pins and will protude through the bottom for a proper soldered joint.
Alex

I got have some from Weidmueller, they have only 3.5mm long pins.
1791610000 PM 5.00/02/90 3.5SN OR BX
catalog.weidmueller.com/procat/Product.jsp;jsessionid=6EB3932904DF25AFC999AA61A31CC691?productId=(%5b1791610000%5d)&page=Product

1791620000 PM 5.00/03/90 3.5SN OR BX
catalog.weidmueller.com/procat/Product.jsp;jsessionid=6EB3932904DF25AFC999AA61A31CC691?productId=(%5b1791620000%5d)&page=Product

9500410000 PCF 5.00/02/180 3.5SN OR BX
catalog.weidmueller.com/procat/Product.jsp;jsessionid=6EB3932904DF25AFC999AA61A31CC691?productId=(%5b9500410000%5d)&page=Product

9500420000 PCF 5.00/03/180 3.5SN OR BX
catalog.weidmueller.com/procat/Product.jsp;jsessionid=6EB3932904DF25AFC999AA61A31CC691?productId=(%5b9500420000%5d)&page=Product

But I can use them for the other PCP's.

Another thing - AFAIK all this terminal blocks use steel in pins and other parts - is using copper in the signal path a better way?

[Deleted]

Feb 24, 2011 11:35:58 GMT FritzS said:

Feb 16, 2011 6:27:41 GMT @sandyk said:

2 pin terminal blocks.
Please ,make sure that the terminal blocks you use have pins longer than 3.5mm.
Both Jeff C and myself have 2 working PCBs, but we had to use the locally available blocks with 3mm or 3.5mm long pins.
These blocks will almost certainly cause trouble after the terminals have been tightened and untightened a couple of times, and may even fall out if turned upside down.
Mine is now awaiting some TERMINALBLOCK, PCB, 2WAY, 5MM CTB1202/2 CAMDEN from Farnell (Element 14) in the U.K. as locally there are no stocks.These blocks have 4.5mm long pins and will protude through the bottom for a proper soldered joint.
Alex

I got found some from Weidmueller, they have only 3.5mm long pins.
1791610000 PM 5.00/02/90 3.5SN OR BX (VPE500Stk)
catalog.weidmueller.com/procat/Product.jsp;jsessionid=6EB3932904DF25AFC999AA61A31CC691?productId=(%5b1791610000%5d)&page=Product
1791620000 PM 5.00/03/90 3.5SN OR BX (VPE500Stk)
catalog.weidmueller.com/procat/Product.jsp;jsessionid=6EB3932904DF25AFC999AA61A31CC691?productId=(%5b1791620000%5d)&page=Product
und
9500410000 PCF 5.00/02/180 3.5SN OR BX (VPE 100Stk)
catalog.weidmueller.com/procat/Product.jsp;jsessionid=6EB3932904DF25AFC999AA61A31CC691?productId=(%5b9500410000%5d)&page=Product
9500420000 PCF 5.00/03/180 3.5SN OR BX (VPE 100Stk)
catalog.weidmueller.com/procat/Product.jsp;jsessionid=6EB3932904DF25AFC999AA61A31CC691?productId=(%5b9500420000%5d)&page=Product

Friedrich
Due to the thickness of the PCB (3mm) you may get into all sorts of trouble unless you use terminal blocks with 4.5mm pins as mentioned in a recent post by Will. You are then likely to have lots of fun and games if you try to replace the ones with shorter pins !
Take my advice and do it right the first time, using the terminal blocks that Will provided a link to.
Alex

P.S.
After sorting out a few problems due to the terminal blocks, I now have a fully functional HA with performance perhaps slightly better than my original HA using the same schematic.The supplied LS313 appear to have much better than average HFE, which undoubtedly helps.
Hopefully, a photo tomorrow.
Alex

[Deleted]

Another thing - AFAIK all this terminal blocks use steel in pins and other parts - is using copper in the signal path a better way?

It may make a very small difference in a PCB where the manufacturer has fitted numerous steel links.
If you believe it will make a difference, then it will undoubtedly make a difference !

[FritzS]

Another thing - AFAIK all this terminal blocks use steel in pins and other parts - is using copper in the signal path a better way?

What did you think about steel wire in the signal path - on other way OFC and silver is using - here ist a little peace of steel?

[Deleted]

Feb 24, 2011 12:17:04 GMT FritzS said:

Another thing - AFAIK all this terminal blocks use steel in pins and other parts - is using copper in the signal path a better way?

What did you think about steel wire in the signal path - on other way OFC and silver is using - here ist a little peace of steel?

Friedrich
I am highly sceptical of this, as the more commonly available MF 1% resistors have copper clad steel leads.
Only recently did Jaycar start supplying MF resistors with the much softer copper leads.And that would have only been because they bought out Soanar that supplied the packaged MFs with copper leads.
Alex

[jonclancy]

Hi Guys,

While I am waiting for Farnell to deliver more bits for this project...

AD744 or OPA134?

Cheers

Jon

BTW, I missed the comment Will made about mounting the 10R a few mm above the board. How hot do these get, please?

[Deleted]

Hi All

I've had the DACT in for about 5 days so i thought it might be time to give a little feedback on how it compares to the Vlab.

i don't do reviews but here are a few thoughts

My ears My system

i think that the first thing that struck me when swapping to the DACT was how smooth and detailed the top end had become. the Vlab sounded a tough Grey and sibilant by comparison but i would emphasize that it's not a huge margin. the DACT had a far more Technicolor presentation and just seemed to let more of the music through.

so no huge differences but noticeable all the same.

as for construction no contest.

the Elma switch used in the DACT is even smoother than i remembered and is just plain lovely to use. i did read somewhere that the spring tension had been altered by DACT , maybe thats what I've noticed.

the Vlab is still a very good stepper for the money and I'd happily use one again (outstanding for the money) but quality really shows with the DACT and I'm pretty happy with it.

I've silver wired the inputs with 0.5mm solid for the inputs and 1mm solid on the outs. i think that the extra smoothness of the DACT makes this combination work well in my setup.

so I'll post some pictures if my precision metal work (when the wife gives me the camera back).

the Class A really is superb and I'm still really loving it.

a reference piece of kit IMHO

take care

[Will]

Feb 24, 2011 15:11:18 GMT jonclancy said:

Hi Guys,

While I am waiting for Farnell to deliver more bits for this project...

AD744 or OPA134?

Cheers

Jon

BTW, I missed the comment Will made about mounting the 10R a few mm above the board. How hot do these get, please?

For the ad744/opa134 question, I'd say whatever you can find cheapest, really. If you can buy enough, you can then swap the op-amps until you get two with the best performance (lowest offset). Frans made an interesting post earlier in the thread about sticking a pot across the offset pins, and dialling in for 0mV offset, which might be worth a look. I use ad744 in my current original build. I think that Chong has some metal can versions of these, because he is Chong

I've pulled all my kit out of storage, where it's been for the last month or so, and had a look at the group of 10R resistors. None of those are raised from the PCB, and there is no sign of scorched pcb at all (thats after a years worth of use) The mention of raising those resistors off the PCB is a 'best practise' observation. If you have soldered them close, it's not really a big problem, or at least not worth mentioning to the house insurance company

[Will]

Shaun,

Nice write up and observations

Apart from the obvious high quality in the switch (which as you say, this amp deserves), do you reckon it's the quality of the resistors that DACT use that are giving an improved top end?

And yes, photos would be lovely!

[Deleted]

Feb 24, 2011 17:35:40 GMT Will said:

Shaun,

Nice write up and observations

Apart from the obvious high quality in the switch (which as you say, this amp deserves), do you reckon it's the quality of the resistors that DACT use that are giving an improved top end?

And yes, photos would be lovely!

Hi Will

I think it's a bit of both that's contributing to the over all sound. I'm in the resistors make a difference sound wise camp and IMHO they do.

the DACT definitely sounds clearer and more focused which is good. i have been pretty impressed with the VLAB but it is not in the same league as the DACT.at that price difference who would expect it to be?

i think that those Dale/Vishay steppers have the same switch as the Vlab but the D/V I've used always suffered with bounce (pop pop POP pop pop kind of thing). not the Vlab it's pretty well behaved but not one for the wire swappers I'm afraid it's just not well constructed enough for that constant action.

which is best VFM?

well thats tough.

i think that they both offer true VFM at their price points. do i regret the £91 for the DACT well NO WAY I'm really appreciating the extra depth and clarity to much to send it back.

I'll post some pictures but I've had a touch of ''stage fright'' which for which I'm taking a good rioja reserve 1999 for which has helped.

i must say I'm feeling pretty lucky to have the Class A after doing so little to own it. Alex and your good self have done such a good job on making it possible .

without making too much of it

the Class A and K701 is by far the most musically complete sound I've ever had the pleasure of hearing. just wonderful.

I'd closed my ears and mind to solid state and built tube amps because thats what i knew. but the SCHA and Class A have really made me think again. both outstanding both worth owning.

yes i still use both

Thanks

take care

[Deleted]

Class A HA with Will's PCBs.



P.S.
Ian (Rabbit)
You would love the bottom end with your 701s.
It goes Loooow !
Alex

[Deleted]

Feb 24, 2011 22:55:08 GMT @sandyk said:

Class A HA with Will's PCBs.



P.S.
Ian (Rabbit)
You would love the bottom end with your 701s.
It goes Loooow !
Alex

Hi Alex

nice build

makes mine look pretty shabby by comparison.

yes the thing i really like about the Class A's bass through the K701 is that it manages the trick of going low without sacrificing speed and tunefulness. It just sounds so effortless.

a rare beast indeed.

as an aside

with the Class A i get no listener fatigue even after hours of listening.

some HA I've listened to leave me with that knot in the middle of my head feeling (if you know what i mean) that's just uncomfortable and tiring.

take care

[mrarroyo]

Feb 24, 2011 22:55:08 GMT @sandyk said:

Class A HA with Will's PCBs.



P.S.
Ian (Rabbit)
You would love the bottom end with your 701s.
It goes Loooow !
Alex

Alex, is the transformer in a separate box?

Is any one here willing to build one for a third party?