My K10A build

MJL21193 · 2nd January 2009, 01:38 AM

The K10A is a 10 watt class A with a tube input stage. Original thread here.
I started this months ago, but put it on hold to work on some other projects. It is my way - a strong start where I do most of the work toward completion but then I stall, fearing the project will not work or I get distracted with other things. I do eventually finish everything I start (talk to my x wives

).

Glen designed the amp and provided the boards. This takes most of the "what if" factor away. I did get one channel up and running a couple months ago as mentioned in the K10A thread. It works very well.

The boards with the outputs and drivers mounted on my home made heatsinks:

The raw material for the rest of the chassis:

And the progress I had made initially. The chassis was mostly finished.

I have now committed myself to finishing this amp. In order to persuade myself to spend time in my home office doing business related work (I hate doing

) I have decided that this will be the destination for this amp playing on a new pair of bookshelf speakers (next project).

MJL21193 · 2nd January 2009, 01:57 AM

Up to a few days ago it sat idle, taking up space on a part of my bench.
I needed to finish the power supply. Now, as if it wasn't bad enough that each amp needs two transformers, I went the extra distance to put all of this in it's own enclosure. I thought it would be nice if the amp had an open skeletal look about it. More artsy. Heck the transparent amp will produce that transparent sound

So, I made a sheet metal can to house the power supplies. Two 24 volt, 60VA plus on dual 30 volt 8VA (or so). Bridge rectifiers and to add to the artistic presentation - the smoothing caps peeled and mounted on top:

In this pic, the can is empty. I had the 24 V transformers, but I needed to order the dual from Digikey to get one small enough to fit.
Also seen is one board populated.

Here's how that PS enclosure looks now, earlier today I finished packing the parts in. Making good use of cut up Christmas cards as insulation

MJL21193 · 2nd January 2009, 02:20 AM

I elected to go with just a straight grounded cord instead of the IEC connector. This was mostly to save space and it cleans up the appearance a bit.
The all important chassis ground connection:

Power supplies tested and closed up, ready for action.
Binding posts and RCA's installed:

Still lots of work to do. I finished stuffing the other amp board but haven't tested it yet.

MJL21193 · 2nd January 2009, 05:04 AM

That's all for today. I have both channels working and tested.

I took the liberty of adding some terminal blocks to the open areas of the boards to allow easier disconnecting for trouble shooting and fixes. I still need to run the input wires from the RCAs to the input terminal blocks and connect the front panel switch but overall, a neat wiring job.

sakis · 2nd January 2009, 10:54 AM

very nice work i think .... but also glens pcb is also joy !!!!!

hopefully when ever glen have the time he will also send me a couple of pcb .........

i ve been making like a gozilion amps ...this one is the first that will include a tube .....lets see

GK · 2nd January 2009, 02:23 PM

Well it certainly looks flash. Have you let is sit for a while to see how hot the heatsinks get?

Cheers,
Glen

GK · 2nd January 2009, 03:26 PM

Sakis, I replied to your email, but it bounced:

----- The following addresses had permanent fatal errors -----
<XXXXXXXXX>
(reason: 550 relaying denied for <XXXXXXXXXXXXX>)

----- Transcript of session follows -----
... while talking to mx1.mail.eu.yahoo.com.:
>>> DATA
<<< 550 relaying denied for <XXXXXXXXXXXXXXXX>
550 5.1.1 <XXXXXXXXXXXXX>... User unknown
<<< 504 At least one RCPT command is required

sakis · 2nd January 2009, 03:48 PM

Quote:

Originally posted by G.Kleinschmidt
Sakis, I replied to your email, but it bounced:

----- The following addresses had permanent fatal errors -----
<XXXXXXXXX>
(reason: 550 relaying denied for <XXXXXXXXXXXXX>)

----- Transcript of session follows -----
... while talking to mx1.mail.eu.yahoo.com.:
>>> DATA
<<< 550 relaying denied for <XXXXXXXXXXXXXXXX>
550 5.1.1 <XXXXXXXXXXXXX>... User unknown
<<< 504 At least one RCPT command is required

this has nothing to do with me ....i receive e mails normally but in case you need to get in touch with me you have also
east_electronics@yahoo.gr
service@eastelectronics.gr
info@eastelectronics.gr
devicemanager@eastelectronics.gr
www.eastelectronics.gr

thanks i was actually waiting for the boards or banking information days now

MJL21193 · 2nd January 2009, 10:10 PM

Quote:

Originally posted by sakis
very nice work i think ....

Hi sakis,
Thanks, I think...

Glen's board is a beaut, for sure. A few less jumpers would have been nice and a place to put a relay to keep the speaker from getting nailed with that brief jolt of 30VDC.

Actually, the relay would need to switch from a dummy load to the speaker load to avoid the 14+ VDC developing in the output cap. I will put a manual switch on the speaker itself to do the same thing.

Quote:

Originally posted by G.Kleinschmidt
Well it certainly looks flash. Have you let is sit for a while to see how hot the heatsinks get?

Thanks Glen,
The whole enclosure is the heatsink. I have screwed on the lid and turned it on:

With each output running at 800mA (200mV across the .25 emitter resistor) for nearly an hour I have 48*C at the top of each output, 46*C at back of the upright part of the mounting angle, 40*C at the outside thickest part of the heatsink and the lid is nicely warmed up to 35*C.
I think this will be fine.

I need to build the front panel power switch and put some feet on it. It has 4 - 5 watt resistors under it now (not in the pics) to allow air circulation underneath.
I'm seeing about 8.5 watts (into 8 ohms) before clipping with my power supply. Clipping starts on the bottom first and looks clean. With the 8 ohm dummy load, I have <5mV offset with the input open.
Looking forward to office work soon!

MJL21193 · 4th January 2009, 02:18 PM

I tested the newer amp with a speaker and the turn on thump is nearly non-existent. I don't know why this would be, maybe a difference in tubes? When I tried the first board 2 months ago I used an old and maybe worn out Hitachi Hitray tube that I'd found. I have replaced that with a new Electro Harmonix and the thump on that channel is less pronounced.

I have finished the power switch:

It is the third such switch I have built (the first went on my sub amp and the second on my computer case) and it gets a bit easier with practice. Basically a push button on/off mains rated switch with a box built around it containing 2 LEDs. In this case, high intensity red LEDs. The clear plastic ring illuminates. The switch has a new "button" that fits snuggly inside the ring and is glued to the switch button.
Needless to say, this takes a considerable amount of time but it is exactly what I want.

2nd January 2009, 01:38 AM	#1
MJL21193 Account disabled at member's request Join Date: Mar 2007	My K10A build The K10A is a 10 watt class A with a tube input stage. Original thread here. I started this months ago, but put it on hold to work on some other projects. It is my way - a strong start where I do most of the work toward completion but then I stall, fearing the project will not work or I get distracted with other things. I do eventually finish everything I start (talk to my x wives ). Glen designed the amp and provided the boards. This takes most of the "what if" factor away. I did get one channel up and running a couple months ago as mentioned in the K10A thread. It works very well. The boards with the outputs and drivers mounted on my home made heatsinks: The raw material for the rest of the chassis: And the progress I had made initially. The chassis was mostly finished. I have now committed myself to finishing this amp. In order to persuade myself to spend time in my home office doing business related work (I hate doing ) I have decided that this will be the destination for this amp playing on a new pair of bookshelf speakers (next project).

2nd January 2009, 10:54 AM	#5
sakis diyAudio Member Join Date: Jan 2006 Location: nea makri athens greece	very nice work very nice work i think .... but also glens pcb is also joy !!!!! hopefully when ever glen have the time he will also send me a couple of pcb ......... i ve been making like a gozilion amps ...this one is the first that will include a tube .....lets see __________________ SERVICE ΙΑΠΩΝΙΚΩΝ ΜΗΧΑΝΗΜΑΤΩΝ ΗΧΟΥ www.eastelectronics.gr

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2nd January 2009, 01:57 AM	#2
MJL21193 Account disabled at member's request Join Date: Mar 2007	Up to a few days ago it sat idle, taking up space on a part of my bench. I needed to finish the power supply. Now, as if it wasn't bad enough that each amp needs two transformers, I went the extra distance to put all of this in it's own enclosure. I thought it would be nice if the amp had an open skeletal look about it. More artsy. Heck the transparent amp will produce that transparent sound So, I made a sheet metal can to house the power supplies. Two 24 volt, 60VA plus on dual 30 volt 8VA (or so). Bridge rectifiers and to add to the artistic presentation - the smoothing caps peeled and mounted on top: In this pic, the can is empty. I had the 24 V transformers, but I needed to order the dual from Digikey to get one small enough to fit. Also seen is one board populated. Here's how that PS enclosure looks now, earlier today I finished packing the parts in. Making good use of cut up Christmas cards as insulation

2nd January 2009, 02:20 AM	#3
MJL21193 Account disabled at member's request Join Date: Mar 2007	I elected to go with just a straight grounded cord instead of the IEC connector. This was mostly to save space and it cleans up the appearance a bit. The all important chassis ground connection: Power supplies tested and closed up, ready for action. Binding posts and RCA's installed: Still lots of work to do. I finished stuffing the other amp board but haven't tested it yet.

2nd January 2009, 05:04 AM	#4
MJL21193 Account disabled at member's request Join Date: Mar 2007	That's all for today. I have both channels working and tested. I took the liberty of adding some terminal blocks to the open areas of the boards to allow easier disconnecting for trouble shooting and fixes. I still need to run the input wires from the RCAs to the input terminal blocks and connect the front panel switch but overall, a neat wiring job.

2nd January 2009, 02:23 PM	#6
GK Account disabled at member's request Join Date: Jan 2006	Well it certainly looks flash. Have you let is sit for a while to see how hot the heatsinks get? Cheers, Glen

2nd January 2009, 03:26 PM	#7
GK Account disabled at member's request Join Date: Jan 2006	Sakis, I replied to your email, but it bounced: ----- The following addresses had permanent fatal errors ----- <XXXXXXXXX> (reason: 550 relaying denied for <XXXXXXXXXXXXX>) ----- Transcript of session follows ----- ... while talking to mx1.mail.eu.yahoo.com.: >>> DATA <<< 550 relaying denied for <XXXXXXXXXXXXXXXX> 550 5.1.1 <XXXXXXXXXXXXX>... User unknown <<< 504 At least one RCPT command is required

4th January 2009, 02:18 PM	#10
MJL21193 Account disabled at member's request Join Date: Mar 2007	I tested the newer amp with a speaker and the turn on thump is nearly non-existent. I don't know why this would be, maybe a difference in tubes? When I tried the first board 2 months ago I used an old and maybe worn out Hitachi Hitray tube that I'd found. I have replaced that with a new Electro Harmonix and the thump on that channel is less pronounced. I have finished the power switch: It is the third such switch I have built (the first went on my sub amp and the second on my computer case) and it gets a bit easier with practice. Basically a push button on/off mains rated switch with a box built around it containing 2 LEDs. In this case, high intensity red LEDs. The clear plastic ring illuminates. The switch has a new "button" that fits snuggly inside the ring and is glued to the switch button. Needless to say, this takes a considerable amount of time but it is exactly what I want.

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