As Mr. MR told in his video, this in is a "weird" amp intended for fullranges, as it was born for a Fostex-like speaker in a bass reflex tower that sounded great with a 300B SET amp and a bit of 2nd harmonic.
Indeed strange Amp
if I understand correctly the tube is a buffer and the mosfet gives voltage gain?
if I understand correctly the tube is a buffer and the mosfet gives voltage gain?
As Nelson Said & Hes correct I "break into a sweat when confronted with the three legged critters"
Ok I couldn’t wait….hooked up to 94db garage BIC speakers with iPhone. It’s sounds very good. Quiet no hum/hiss. More to follow
OK. This was a learning curve for me. Let me first thank Mr. Rothacher for his patience/support in helping me to understand the basics of how an AMP works.
From fabrication to the simple circuit, it is a fun AMP to build. In the attached schematic I have included some of the parts originations and voltages.
I built my own power supply (PS) & was quite surprised to find the simple CRC B+ puts that resistor (10ohm, 50W) into "heat heaven". Used Pete Millett filament boards (www.pmillett.com/dc_filament_supp). I used Antek AS-0509, and AS-3450 transformers.
After adding heatsinks (www.heatsinkonline.com) to the PS, I played for 5 hours. I hooked up a pair of JBL JRX115 (98db) using my iPhone 6 through a topping DAC, streaming Tidal. After adjusting for 1.6a bias & 6.3 heaters I plugged in the speakers. It was/is dead quiet. No buzz, no hiss, no hum.
I used a pair of NOS Baldwin 6SN7GTB's. Those did require R2 to be changed from 1K to 500 ohm's.
Creating my own PCB was a journey but it made things much easier to assemble. I used KiCad & would offer the Gerbers for free. JLCPCB did the fab.
The sound is very smooth. Tight bass. Not fatiguing. Surprised at the power they displayed. Will have to wait to hook--up to main system while I play with different drivers in my test lab (AKA garage). With the giant (500W) bulb these are impressive in the dark. I did double the size of the heatsink (not necessary) which kinda acts as a mirror & matches that big bulb.
All told this is a great AMP to build since it offers so many assembly options & provides a great learning experience with so few parts. Is it powerful? No. Is the sound surprisingly good? YES!
Thanks to BAF2021 and a great design from Mr. Rothacher.
From fabrication to the simple circuit, it is a fun AMP to build. In the attached schematic I have included some of the parts originations and voltages.
I built my own power supply (PS) & was quite surprised to find the simple CRC B+ puts that resistor (10ohm, 50W) into "heat heaven". Used Pete Millett filament boards (www.pmillett.com/dc_filament_supp). I used Antek AS-0509, and AS-3450 transformers.
After adding heatsinks (www.heatsinkonline.com) to the PS, I played for 5 hours. I hooked up a pair of JBL JRX115 (98db) using my iPhone 6 through a topping DAC, streaming Tidal. After adjusting for 1.6a bias & 6.3 heaters I plugged in the speakers. It was/is dead quiet. No buzz, no hiss, no hum.
I used a pair of NOS Baldwin 6SN7GTB's. Those did require R2 to be changed from 1K to 500 ohm's.
Creating my own PCB was a journey but it made things much easier to assemble. I used KiCad & would offer the Gerbers for free. JLCPCB did the fab.
The sound is very smooth. Tight bass. Not fatiguing. Surprised at the power they displayed. Will have to wait to hook--up to main system while I play with different drivers in my test lab (AKA garage). With the giant (500W) bulb these are impressive in the dark. I did double the size of the heatsink (not necessary) which kinda acts as a mirror & matches that big bulb.
All told this is a great AMP to build since it offers so many assembly options & provides a great learning experience with so few parts. Is it powerful? No. Is the sound surprisingly good? YES!
Thanks to BAF2021 and a great design from Mr. Rothacher.
Attachments
