JoaMat

A very early layout attempt. Have to figure out how to spread the parts. Board size 2.65in x 0.87in.

Increasing trimmers resistance always increase corresponding side’s current and vice versa. If upper trimmer (ksa1156) increases corresponding side’s output voltage increases and the other decreases. If lower trimmer (ksc2752) increases corresponding side’s output voltage decreases and other side increases. So far I’ve preadjusted all eight trimmers to the same resistance. Resulting in roughly the same current of all for channels and in an output voltage of some positive volts - all good and not needing any further action. To me it has been a bit tricky to turn all trimmers to achieve better balance and offset than when the preadjusted.

OK, now I’ve reached further. Replaced all eight 2K resistors with 2K trimmers. Makes it easier to change the current. Set at 1.6K current start at 2.5 mA and climbs to 4.5 mA. IMO it’s still an interesting amplifier and I believe it’s possible to build an all SMD version.

Reduced the 2k resistors at base of input transistors by 100 ohms steps. 1.7k give approximately 7.5 mA and I have decided to keep it there until further…

Thanks folks. No matching. I use our kitchen table as workbench and to avoid some nasty conflicts with wife….

Nice! and thanks for files.

Modushop heat sink 300 mm X 80 mm and Modushop Galaxy Maggiorato front and back panels. I buy them as spare parts. Brackets and aluminium plates for top and bottom I get from a local shop. I've drilled and tapped M4 holes at both ends of heat sinks to fasten the panels. Below is a board attached to 200 mm X 80 mm heat sink - temperature stabilazed at about 50 degrees Celsius. With 300 mm heat sink temperature stabilized at 42 degees. Current stabilized at 20 mA with resistors as silk screen.

Amplifier built on Gary’s (congo5) boards. I really like this one . Cheap and easy to build - and it sounds really good.

More Sort Guld. A Søren built amplifier is easily recognized. Very nice!!

Nice work indeed. I like the two box approach. The transformers – are they DIY made?

Maybe one could change resistors on Alexey’s board to achieve -20 V.

Happy Thanksgiving!

What is the thing with relays between the amp boards? Indeed a nice and interesting build. Great work. ...I’ll go to Biltema tomorrow and check what acrylic they have.

I don't remember, but capacity is 3.3Ah when new. How much is the current of the mini?

Found this in closet. I guess it’s some kind of charger I built a couple of years ago. Six Mean Wells and charger regulators and each cell has his own charger. Red light will probably turn green when fully charged. I don't remember but I will see in a couple of hours.

I used the battery pack summer 2016. LiPo 6 cells, one pack each rail, give you some 22 volts reduced by the regulator. Those LiPo packs are used by RC people. I bought from hobbyking.com.

See below.

I’m sorry, but - I will not compare my, in kitchen made, amplifier with the famous DIY T2. One way to compare… well, build one – it’s fun. Schematic above.

Have been listen to the new amplifier with EML 20B v4 tubes for a couple of days. Since 20B pinout and heater voltage differs from EL34 I use adapters. Maybe it’s about time to make a board dedicated for the Emission Labs tubes. The tubes looks amazing and have printing on the glass. In this early stage layout the printing and the front of the tubes are facing the listener. I found the big tube 3D model (300b) at grabcad.com, done by Andrew Whitham, United Kingdom.

I am very satisfied with the outcome of this build. Some background. I wanted to build an amplifier based on the T2 but simpler. There isn’t anything I’ve invented. I just copied and pasted pieces and ideas from Kevin, Kerry, Birgir et al - without asking for permission. Draw up a schematic this morning of the amplifier in the same “fashion” as DIY T2 by Kevin Gilmore. The amplifier doesn’t have R66, which is suggested by Kevin. Be aware of errors since I did this in a rush. As about the sound. I AM VERY HAPPY with her. But that’s maybe like asking me how much I love my four grandchildren.

Now with top plate. Aerial view, the two holes in front of outer small tubes are for balance trimmers. Adjust balance after some time of warm up and then insert jumpers for the servos.

but, but, nothing in the tubes - must be vacuum tubes……….. Looks absolutely beautiful. Very interesting with the modules.