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 Post subject: ZCA problem
PostPosted: 06 Oct 2020, 22:58 
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Joined: 03 Oct 2020, 14:20
Posts: 3
Hi
I’m trying to build the zca project and I have assembled one channel of the amplifier and I’m having problems getting any output. Instead of getting the 2sk1058 for the MOSFET, I got a pair of 2sk2221 because they were cheaper and easier to get a hold of. I saw at the bottom of the project page that there was another person that had used this MOSFET with success and figured it would be a safe option.

When connecting the 2sk2221 to my circuit using the pin out listed on a data sheet I found online, (GSD) the load resistor and the transistor would not even get warm and the voltage across the source and drain was around 24.5v (roughly the input voltage). When plugging in an audio source and a speaker the music came through very faintly.

I checked over the circuit multiple times and verified that everything is connected according to the schematics. I was looking at other form posts to try and resolve the issue and I came across one claiming some transistors had the source and drain pins switched with the pin out being GDS so I tried switching those pins in my circuit with no real success. The load resistor did get warm and the voltage across the drain and source dropped to around 13v but I didn’t get any sound out of my speaker.

Does anyone have any suggestions cause I’m out of any ideas.

Thanks


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 Post subject: Re: ZCA problem
PostPosted: 14 Oct 2020, 21:37 
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Joined: 03 Oct 2020, 14:20
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I decided to order a 2sk1058 and now the amp works. Either I got some bad 2sk2221s or they just don’t work in the circuit


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 Post subject: Re: ZCA problem
PostPosted: 22 Oct 2020, 14:39 
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Joined: 28 May 2008, 21:53
Posts: 4591
Location: Winnipeg, CANADA
hi Alex, welcome to the forum and thanks for your notes. It's too bad about the 2SK2221. As you noted, we had a report from the Netherlands that worked. Unfortunately I no longer trust the authenticity of transistors unless I am getting them from a reputable source.

Cheers

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[ DIY Mains AC Power Cable Cord ] - [ Gobo LM1875 Amp Kit ] - [ Tang Band D4-1 Horn Speaker Kit ] - [ Monoblock Push-Pull KT88 Tube Amp Kit ]


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 Post subject: Re: ZCA problem
PostPosted: 23 Oct 2020, 18:31 
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Joined: 06 Jun 2008, 18:23
Posts: 5301
Location: Australia
Gio wrote:
hi Alex, welcome to the forum and thanks for your notes. It's too bad about the 2SK2221. As you noted, we had a report from the Netherlands that worked. Unfortunately I no longer trust the authenticity of transistors unless I am getting them from a reputable source.

Cheers

Gio, this particularly true for OPA2134s. You must get them from a reliable source. You may pay more but you know they are genuine. I have come up with three points with this chip which can identify the real from fake. I’m guessing the same issue happened here.

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Projects: "Carbon” - MM phono preamp | 180W RAW Class D amp | "Illusion" - 6SN7 SRPP preamp in a plastic jiffy box | “Salt Cellar” - Mono 807 triode integrated amp |


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 Post subject: Re: ZCA problem
PostPosted: 23 Oct 2020, 18:36 
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Joined: 06 Jun 2008, 18:23
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Location: Australia
alexbc2999 wrote:
I decided to order a 2sk1058 and now the amp works. Either I got some bad 2sk2221s or they just don’t work in the circuit


This is an amp I designed many years back. It’s simple and those who have built them love them. The 2SK1058 power FET is the way to go for best results. One builder got more wattage by using a different voltage. You should find the thread and have a read.

Also if you like the ZCA the MCA will really impress you. I think a better sound. This time 2N3055 based. Chase up the thread. Also with either the input cap should be 0.1uf not what was on the original schematic.

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Projects: "Carbon” - MM phono preamp | 180W RAW Class D amp | "Illusion" - 6SN7 SRPP preamp in a plastic jiffy box | “Salt Cellar” - Mono 807 triode integrated amp |


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 Post subject: Re: ZCA problem
PostPosted: 26 Nov 2020, 22:12 
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Joined: 03 Oct 2020, 14:20
Posts: 3
I took a look at the MCA thread and it looks like a good project to try. I already have a few spare lsk170's laying around (luckily I know they're genuine) so I ordered the remaining parts (I also ordered a couple extra 0.1 uf caps for the ZCA as suggested) and designed a board that I'll etch for it. I'm gonna give it a try with the power supply I made for the ZCA.

I'm really enjoying the sound I'm getting from the ZCA but in my opinion I feel like it has some trouble with brass, especially higher pitched trumpets, but it could just be my ears/speakers. Hopefully I'll notice an audible difference between the two amps once I get the MCA built up as I don't have the best speakers (specifically Technics sb-x10)

Thanks for the suggestions with possible fake transistors, I'm going to take extra precautions to make sure I order from reliable sources


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