25W Single Ended Hammond 193V Choke Loaded 2SK180 L'Amp

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Joined 2005
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Hi Ben. Really interesting project, I have most bits to get started, just wondering about the chokes, I understand you have suggested two, would 195T5 be suitable? It seems to be in between at 100MH, 0.64 Ohm and 5A it's much smaller than the T10. Digi-Key has some good prices too.
Best wishes.
 
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Joined 2012
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Thanks everyone for your great comments.

jotom750, The choke that I recommend is the Hammond 193V. That is because that is the one that I used and tested with. The other chokes may also work but the results will probably be a bit different because of the lower inductance. I checked the Digikey United Kingdom website and the 193V has a lower price than the 195T5.
 
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Fantastic looking amps Ben! Most definitely gets a fugly! :cheers:

I just received 4pcs of 2SK180 today and I have to say that it's due to you inspiring me to get them. You are absolutely right about all the moaning about not being able to find Sony vfets but it seems like people only want them when they can no longer get them.

There is no shortage of different amps being built with the Tokin parts. Thanks for sharing your listening experiences as well!

:cheers:
 
The mono blocks are finished. Biasing is done. It takes over two hours for the temperature and bias to reach a maximum. There is quite a bit of heat sinking and chassis mass to heat. The final bias varies a bit depending on the time of day, as the wall VAC varies.

The sound is typical of my SIT amps - it is excellent. I am very happy with the results. From memory, I don't believe the sound is much different from my BAF2015 THF-51S mono blocks. If I were to listen to them separately I don't think I would be able to identify which amps were playing.

I am glad I built these amps. For those of you that are bemoaning the lack of Sony VFETs, there are still many Tokins available for purchase. They may not be as cheap as they used to be, but at least they are still available. There are various amps that can be built with them, and they will sound just as good or even better than Sony VFET amps. Another plus for the Tokins is that you can build higher power amps than with Sony VFETs.

This amp is like a solid state version of a single ended 211 amp. I used to be a big fan of tubes, although I never ventured into 211/845 land. However, solid state doesn't have the problem of tube aging and tube noise, and the dangers and cost of extremely high voltage power supplies. Also the very low parts count of this amp is great - simple to build and simple to trouble shoot. It is so simple that if you double and triple check and test at various stages of the build, trouble shooting is probably not necessary. My build was trouble free.

Happily listening to music, enjoying my new amps.
:):sing::note::sax::eguitar::Piano:


Very nice, i have built the same tokin amp but stereo amp. I love the sound, my amp is heavy though, I need to make them mono blocks. I have Nelson’s diy push pull Sony Vfet amp too and the tokin amp has more power and play louder. The Sony has a little more detail, the tokin seem to have better bass but, could be because of more power. I like them better than my Sony ta-4560 Vfet amp. I will sell my Sony because it does not get much use anymore since I have the other two Vfet amp.

Tony
 
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Joined 2012
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Thanks for the latest comments. :)

I am really happy with this amp and I am grooving to the music right now as I write this. I think it's because I and my system love the single ended SIT sound.

A diyAudio member PMed me asking asking about the the Vgs of suitable 2SK180. I am answering here on the forum so that the answer is available to everyone who may have the same question.

The bias voltage is supplied by the bias supply which covers a wide range, from approximately -12.5V to -2.0V. Also note that the operating point is Vds=35V and Iq=2.5A. However, the bias supply should be able to work with most if not all 2SK180. If the Vgs needs to be lower than -2.0V, it is just a matter of changing one resistor in the bias supply.
 
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The Sound of Silence

The amps have running for a while now and I'm very happy with their sound.

Lately the temperature has dropped because of an Arctic front blowing in, and the AC voltage out of the wall have been fluctuating from about 115VAC to 119VAC. I've been monitoring Iq and have noticed maybe 200 to 300mA differences due to the VAC variations. So I have set Iq to about 2.6A at 119VAC.

Now my speakers are 20 year old Avantgarde Unos and their sensitivity is about 103dB. Because of such high sensitivity I have been forced to learn how to build quiet amps (and preamp too). It has taken me a while, searching the internet for information, and then trial and error, since not all information on the internet is correct.

There is a lot of information out there but the most useful and user friendly information that I found is this by diyAudio member Bonsai:

Ground Loops

http://hifisonix.com/wordpress/wp-content/uploads/2019/02/Ground-Loops.pdf

I have now built one preamp and five amplifiers (one shared bipolar supply, one single transformer with dual secondaries and dual unipolar supplies, one dual mono single chassis, and two pairs of monoblocks) and they are all quiet when powering my speakers. It took me a while to figure out what worked for me.

Things that I do to minimize system noise are as follows:

1. Plug everything into one wall AC outlet.

2. Keep all powered components close together and bundle all AC power cords together and much as possible.

3. Use some sort of ground lift device, whether rectifier bridge or thermistor, to connect audio ground to chassis safety ground.

4. Keep AC wires and power tranformers as far away as possible from audio circuitry and wires. For stereo chassis, AC wires are routed down the centreline of the chassis, and power transformer located at the front of the chassis, so transform EMI is located as far as possible from audio signals, especially low level input signals.

5. Rotate tranformers to find orientation of lowest noise.

6. Minimize loop areas of electrical circuits. For outside of the chassis, points 1 and 2 above are done with that in mind. Within the amplifier chassis, twisting all wires that form loops are done.

7. Monoblocks and dual monos are easier to make quiet because cross channel ground loops are not an issue. But as I have mentioned, I have built one amplifier with a shared power supply and with a bit of work I managed to make it quiet powering my speakers too. I followed the hifisonix recommendations.

I was unfamiliar with loop areas when I first started out hum busting. Basically electrical circuits are closed cicuits where electrons flow in continuous loops. An amplifier can have multiple loops, and each loop has electrons flowing continuously within that loop. For instance, one loop is the AC power loop. Within the chassis, this loop starts at the IEC jack, continues through the tranformer primaries, and back to the IEC connector. Within this loop would be the fuse, on-off switch, and soft start thermistors or soft start circuitry. Another loop would be the DC power loop, starting at the transformer secondary to the bridge rectifiers, CRC or CLC filters, to amplifier circuit and then returning to the CRC or CLC filters, bridge rectifiers, and transformer secondaries. Yet other loops would be signal input jack to amplifier circuit and back to input jack, and speaker positive connector to audio circuit and back to speaker negative connector.

For each of these loops the aim is the make the loop area physically as small as possible. If wires in a loop are physically separated and components in the loop are physically separated, the wires and components that form the loop create a large loop area. If wires and their returns are twisted together and components within the loop are located as close as possible to each other, then their loop area is minimized. See example below.

So in each monoblock there were four loops in the audio circuit, in addition to the AC power loops from IEC jack to transformer primaries. Wires in each loop were twisted together. So if you look at the picture of the amplifier internals, all wires are twisted except for the transformer shield wire to chassis ground, power supply ground in series with thermistor to chassis ground, and ground from the IEC jack to chassis ground.

In the speaker loop, I purposely took the speaker negative from the audio circuit board to minimize the loop area. I know that some builders take the speaker negative from the power supply board negative. However that makes the speaker-out loop area large, which is not what I want.

So this is what I do to make my amplifiers as quiet as possible. The sound of silence. Then the sound of music. Peace and quiet when the song ends, and no annoying hum during quiet passages.

In the 60s when I was a kid, I saw "The Sound of Music" at the theatre. The sound track was possibly played on tube amplified Voice of the Theatres. It's my favorite musical. R.I.P. Christopher Plummer.
 

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The amps have running for a while now and I'm very happy with their sound.

Lately the temperature has dropped because of an Arctic front blowing in, and the AC voltage out of the wall have been fluctuating from about 115VAC to 119VAC. I've been monitoring Iq and have noticed maybe 200 to 300mA differences due to the VAC variations. So I have set Iq to about 2.6A at 119VAC.

Now my speakers are 20 year old Avantgarde Unos and their sensitivity is about 103dB. Because of such high sensitivity I have been forced to learn how to build quiet amps (and preamp too). It has taken me a while, searching the internet for information, and then trial and error, since not all information on the internet is correct.

There is a lot of information out there but the most useful and user friendly information that I found is this by diyAudio member Bonsai:

Ground Loops

http://hifisonix.com/wordpress/wp-content/uploads/2019/02/Ground-Loops.pdf

I have now built one preamp and five amplifiers (one shared bipolar supply, one single transformer with dual secondaries and dual unipolar supplies, one dual mono single chassis, and two pairs of monoblocks) and they are all quiet when powering my speakers. It took me a while to figure out what worked for me.

Things that I do to minimize system noise are as follows:

1. Plug everything into one wall AC outlet.

2. Keep all powered components close together and bundle all AC power cords together and much as possible.

3. Use some sort of ground lift device, whether rectifier bridge or thermistor, to connect audio ground to chassis safety ground.

4. Keep AC wires and power tranformers as far away as possible from audio circuitry and wires. For stereo chassis, AC wires are routed down the centreline of the chassis, and power transformer located at the front of the chassis, so transform EMI is located as far as possible from audio signals, especially low level input signals.

5. Rotate tranformers to find orientation of lowest noise.

6. Minimize loop areas of electrical circuits. For outside of the chassis, points 1 and 2 above are done with that in mind. Within the amplifier chassis, twisting all wires that form loops are done.

7. Monoblocks and dual monos are easier to make quiet because cross channel ground loops are not an issue. But as I have mentioned, I have built one amplifier with a shared power supply and with a bit of work I managed to make it quiet powering my speakers too. I followed the hifisonix recommendations.

I was unfamiliar with loop areas when I first started out hum busting. Basically electrical circuits are closed cicuits where electrons flow in continuous loops. An amplifier can have multiple loops, and each loop has electrons flowing continuously within that loop. For instance, one loop is the AC power loop. Within the chassis, this loop starts at the IEC jack, continues through the tranformer primaries, and back to the IEC connector. Within this loop would be the fuse, on-off switch, and soft start thermistors or soft start circuitry. Another loop would be the DC power loop, starting at the transformer secondary to the bridge rectifiers, CRC or CLC filters, to amplifier circuit and then returning to the CRC or CLC filters, bridge rectifiers, and transformer secondaries. Yet other loops would be signal input jack to amplifier circuit and back to input jack, and speaker positive connector to audio circuit and back to speaker negative connector.

For each of these loops the aim is the make the loop area physically as small as possible. If wires in a loop are physically separated and components in the loop are physically separated, the wires and components that form the loop create a large loop area. If wires and their returns are twisted together and components within the loop are located as close as possible to each other, then their loop area is minimized. See example below.

So in each monoblock there were four loops in the audio circuit, in addition to the AC power loops from IEC jack to transformer primaries. Wires in each loop were twisted together. So if you look at the picture of the amplifier internals, all wires are twisted except for the transformer shield wire to chassis ground, power supply ground in series with thermistor to chassis ground, and ground from the IEC jack to chassis ground.

In the speaker loop, I purposely took the speaker negative from the audio circuit board to minimize the loop area. I know that some builders take the speaker negative from the power supply board negative. However that makes the speaker-out loop area large, which is not what I want.

So this is what I do to make my amplifiers as quiet as possible. The sound of silence. Then the sound of music. Peace and quiet when the song ends, and no annoying hum during quiet passages.

In the 60s when I was a kid, I saw "The Sound of Music" at the theatre. The sound track was possibly played on tube amplified Voice of the Theatres. It's my favorite musical. R.I.P. Christopher Plummer.


Great tips! I have a little hum but it’s not bad, you have to be within a couple feet before I can start to hear it. I will be going they my amp again with your tips, thanks

Tony