Completed FirstWatt F6 amp build

atharva

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For some time I'd wanted to try a low powered SS amp with my Maargas instead of the Lyrita 2A3. A little over a year ago I found a used Valvet E2 and it sounded very good. That gave me some confidence and I always had a FirstWatt at the back of my mind given the fan following. I thought to try a FirstWatt SIT3 but they sold out and my only option was to get an F8. The SIT were special but I wasn't sure about the F8. I had considered the DIY route but most of the designs the Toshiba JFETs (or the Semisouth In the J2) which are no longer available. I was very lucky to find someone who had all the parts for an F6 and decided to bite. The F6 is rated 25W into 8 Ohm and 50W into 4 Ohm. That was much more than I needed but I had no choice. Figured if I liked the amp that much I could use it with lower sensitivity speakers as well.

Here is the final build of the amp. It's just been a few hours so still breaking in but it is super silent and sounds wonderful. The enclosure is also DIY - sketched it in CAD and got it laser cut on 3mm Aluminium and then anodised. I'm currently playing the amp with my DIY Open Baffles and will try it with the Maargas as well. It gets very hot though especially with the ambient temp around 42C. Plan to try PC cooling fan inside the chassis. Sharing a few pics.

Thanks for reading!

1651676238514.jpeg 1651676257650.jpeg

1651676283127.jpeg 1651676307294.jpeg
 

Kannan

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Awesome build. Neat and perfect. You should have gone with deeper fins on the heatsink.
It is a wonderful sounding amp and a keeper for sure.
 

Subbu68

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Nice build.

That was in my radar or F5 but getting a proper chassis is a pain for me in UAE.

Where did you source the chassis?

BTW on a ACA build right now. To work as Mono blocks.
 

atharva

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Thanks! Had to DIY the chassis. I'm not sure what duties+taxes you have to pay but if not as high as for us (42%) you can explore option to import
1. Modushop in Italy https://modushop.biz/site/ . They are the ones that make the diyaudiostore chassis'. If you get the UMS heatsinks they are predrilled to accomodate different PCBs making it easy to try out different amps.
2. Try AliExpress. They have good choice. But may require you to drill and thread some holes. Not very difficult.

I saw your ACA build. Looks nice!
 

kaushik

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for people looking for chessis
i suggest
1.get heatsinks
2.front and bottom 3mm alumium via amazon
3.top make with 10mm acrylic .
for Airvent keep 2 openings
u can fit honeycomb net
or you can fit Airvents cut fromold pc case

once you fit withallen screws it looks nice
4.for all these take help of garage
backplate can be fR4 boards drilled as per a drillplan made in some 3d software
 

csd508868306kant

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for people looking for chessis
i suggest
1.get heatsinks
2.front and bottom 3mm alumium via amazon
3.top make with 10mm acrylic .
for Airvent keep 2 openings
u can fit honeycomb net
or you can fit Airvents cut fromold pc case

once you fit withallen screws it looks nice
4.for all these take help of garage
backplate can be fR4 boards drilled as per a drillplan made in some 3d software
If you have any link handy ,please share it
 

kaushik

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If you have any link handy ,please share it
for heatsinks i dont have but audiomakers in group will get u or many Ampmakers of kerala side can supply.Refer youtube or search in facebook groups.
amazon india has AL plates and acrylic
scrap pcCPU COVERS you can pic for vent holes .

if you need honeycomb net i have a few
(hope this helps)
 

Subbu68

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Thanks! Had to DIY the chassis. I'm not sure what duties+taxes you have to pay but if not as high as for us (42%) you can explore option to import
1. Modushop in Italy https://modushop.biz/site/ . They are the ones that make the diyaudiostore chassis'. If you get the UMS heatsinks they are predrilled to accomodate different PCBs making it easy to try out different amps.
2. Try AliExpress. They have good choice. But may require you to drill and thread some holes. Not very difficult.

I saw your ACA build. Looks nice!
Hi

Thanks for the comment on my ACA build.

I was placing order on diyaudiostore for F5 with chassis. They do not ship outside US for VAT reasons and directed me to Modushop. Oh my!! the shipping was about 114 Euros. We have to pay 5% import duty for above $275 and VAT 5% for all imports at the landed cost - Cost + shipping + insurance. So the total for me is around 438 Euros for a 280 Euro chassis!! Their shipping is killing.

I did not find the quality of ACA chassis that super. Assembly is a pain due to the design they have. The screws are not so smooth.

For that Japanese trounce Italians. I have done Elekit TU-8200 amp and TU-8500 preamp. Superb design and is butter smooth to assemble. Covers and screws fit perfect.
 

saikatbiswas82

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For some time I'd wanted to try a low powered SS amp with my Maargas instead of the Lyrita 2A3. A little over a year ago I found a used Valvet E2 and it sounded very good. That gave me some confidence and I always had a FirstWatt at the back of my mind given the fan following. I thought to try a FirstWatt SIT3 but they sold out and my only option was to get an F8. The SIT were special but I wasn't sure about the F8. I had considered the DIY route but most of the designs the Toshiba JFETs (or the Semisouth In the J2) which are no longer available. I was very lucky to find someone who had all the parts for an F6 and decided to bite. The F6 is rated 25W into 8 Ohm and 50W into 4 Ohm. That was much more than I needed but I had no choice. Figured if I liked the amp that much I could use it with lower sensitivity speakers as well.

Here is the final build of the amp. It's just been a few hours so still breaking in but it is super silent and sounds wonderful. The enclosure is also DIY - sketched it in CAD and got it laser cut on 3mm Aluminium and then anodised. I'm currently playing the amp with my DIY Open Baffles and will try it with the Maargas as well. It gets very hot though especially with the ambient temp around 42C. Plan to try PC cooling fan inside the chassis. Sharing a few pics.

Thanks for reading!

View attachment 69131 View attachment 69132

View attachment 69133 View attachment 69134
Nice build and congratulations!
 

Hari Iyer

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Hi

Thanks for the comment on my ACA build.

I was placing order on diyaudiostore for F5 with chassis. They do not ship outside US for VAT reasons and directed me to Modushop. Oh my!! the shipping was about 114 Euros. We have to pay 5% import duty for above $275 and VAT 5% for all imports at the landed cost - Cost + shipping + insurance. So the total for me is around 438 Euros for a 280 Euro chassis!! Their shipping is killing.

I did not find the quality of ACA chassis that super. Assembly is a pain due to the design they have. The screws are not so smooth.

For that Japanese trounce Italians. I have done Elekit TU-8200 amp and TU-8500 preamp. Superb design and is butter smooth to assemble. Covers and screws fit perfect.
Theaudiocrafts.com supply chassis as per your design. You will need to speak with them. Rest of the pcb and components can be separately sourced.
 

rajan-

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Feb 26, 2014
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Hi

Thanks for the comment on my ACA build.

I was placing order on diyaudiostore for F5 with chassis. They do not ship outside US for VAT reasons and directed me to Modushop. Oh my!! the shipping was about 114 Euros. We have to pay 5% import duty for above $275 and VAT 5% for all imports at the landed cost - Cost + shipping + insurance. So the total for me is around 438 Euros for a 280 Euro chassis!! Their shipping is killing.

I did not find the quality of ACA chassis that super. Assembly is a pain due to the design they have. The screws are not so smooth.

For that Japanese trounce Italians. I have done Elekit TU-8200 amp and TU-8500 preamp. Superb design and is butter smooth to assemble. Covers and screws fit perfect.
not surprising.

Italians (..ahem... ) like to be persuaded, passionate and loves long conversations :)

also gives you the satisfaction that YOU made it work. so get into it with all that passion.

very clever design principles. lol

Bellissimo.
 

atharva

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Location
Pune
Thanks @saikatbiswas82. A big thanks to all those who've liked it as well.

@Subbu68
Don't know about the ACA but the chassis from Modushop at least for FirstWatt clones is very popular on diyaudio.com. Practically a standard. Surprised that the quality is poor.

@Hari Iyer, I had contacted Amarinder but he told me that the price of Aluminium (and most metals) has gone up significantly since the Ukraine crisis and so the cost would be prohibitive and he couldn't build one.

The chassis actually wasn't too hard to do. Just that it was my first time and doing the CAD design, finding the vendors and getting a single piece done was time consuming. Also, my OCD was to do it in Aluminium instead of MS, I wanted that base plate so no mounting screws are visible in the bottom plate and I wanted all the holes precision drilled and tapped to avoid home drilling. All that added to the efforts. The vendors are (naturally) not too keen for small quantities and then making them deliver good quality was the biggest challenge.
 

sbg

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..... the price of Aluminium (and most metals) has gone up significantly since the Ukraine crisis and so the cost......
I was still under the impression that India was one of the major country exporting Aluminium ! strange Economics and its Dynamics!
 

VSTEREO

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It is true that Aluminium prices has gone up. Recently, I bought 3mm aluminium sheets from Gandhi market,chennai and prices are gone up almost 30%.
 

Subbu68

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I was still under the impression that India was one of the major country exporting Aluminium ! strange Economics and its Dynamics!
It is a chain. Energy prices go up, transportation and production cots go up, metals go up and sadly life goes downhill.
 

rikhav

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It is true that Aluminium prices has gone up. Recently, I bought 3mm aluminium sheets from Gandhi market,chennai and prices are gone up almost 30%.
Each and every commodity prices have increased massively.
Before the war they were holding on but not falling. Then after war again massive increment every few days
 
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