I am making 300B SE amp.
Chassis is 44cm x 36cm
Power transformer is EI 97mm , power is insufficient
Choke is UTC 8H 180mA
Output transformer is EI 86mm
I order the transformers from a forty years old store
I reserve three 9-pin tube sockets for one ECC88 and two E88C.
Currently user can choose ECC88 or E88C to drive 300B by solder.
ECC88's gain is not enough for 300B but there are many brands available so user can find your favorite tone.
I use a small choke (underneath chassis) to build luxury fixed bias voltage for 300B's as you can see in my drawn schematic.
Any comment or suggestion welcome.
Chassis is 44cm x 36cm
Power transformer is EI 97mm , power is insufficient
Choke is UTC 8H 180mA
Output transformer is EI 86mm
I order the transformers from a forty years old store
I reserve three 9-pin tube sockets for one ECC88 and two E88C.
Currently user can choose ECC88 or E88C to drive 300B by solder.
ECC88's gain is not enough for 300B but there are many brands available so user can find your favorite tone.
I use a small choke (underneath chassis) to build luxury fixed bias voltage for 300B's as you can see in my drawn schematic.
Any comment or suggestion welcome.
Attachments
I use two-stage ECC88 cathode follower to drive 300B, there are tons of gain ! More than I need.
Rolling ECC88 is a lot of fun, there are so many different ECC88/6DJ8 out there.
The 100 Ohm VR affects the tone of the amp quite a bit.
I bypass each arm of the VR with good quality resistors.
I use 5U4G rectifer, my B+ is only 310V, higher B+ yields too bright of a tone for my taste.
Rolling ECC88 is a lot of fun, there are so many different ECC88/6DJ8 out there.
The 100 Ohm VR affects the tone of the amp quite a bit.
I bypass each arm of the VR with good quality resistors.
I use 5U4G rectifer, my B+ is only 310V, higher B+ yields too bright of a tone for my taste.
5Z3 is old version of 5U4G.
I also consider C3M in the next amp so I like B+ around 400V.
I would like use E88C (not ECC88/E88CC) as an option because E88C's u=70 and Telefunken/Philips E88C is pretty cheap.
Regards.
a. CCS plate-load is beneficial, i.e. upgrade your 15K resistor to CCS !
b. ECC88 tends to oscillate, add grid-stopper and ferrite bead to alleviate the problem.
Good luck
I've done some experiments with e88cc e88c and ec 86 in the past. I had the best results with ec86 (Ra 27k, Rk 470 ohm Va 300v) and alternatively the e88cc as cascode. Although the e88c and ec86 look similar as to specs the ec86 sounded much better bigger soundstage and less shrill than the other tube.
As the ec86 (e86c) is not a particularly expensive tube either I would choose these as drivers and the two triodes of the e88cc as cathode followers.
As the ec86 (e86c) is not a particularly expensive tube either I would choose these as drivers and the two triodes of the e88cc as cathode followers.
EI-84 (and not EI-86) is a standard size !
What is the thickness of core lamination of the transformers ?
What is the resistance of the 350 Volt windings ?
What is the resistance of the choke ?
What is the anode current for the 300B tube ?
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I agree about the EC86. I have played with it as an input stage, and it was pretty linear, even at 120Vpp output swing:
I have a similar 2a3 SE amp and the tube I am using is the E180CC. I don't like the ECC88/6922 or 6N1P, but I do like the E180CC quite a lot. It's not what I am actually using - I use a 6SN7 input tube because I have a smallish room and listen at lower volumes. And also 6J5 types, some of which are really good. These give me just enough volume as a single stage. But for an amplifier that needs to be played louder I have yet to find a better sound than an E180CC. Try it - it's not expensive!
I have some EC86 and it's on my list to try. I hear a lot of good things about it.
I have some EC86 and it's on my list to try. I hear a lot of good things about it.
Thank you for your kindly information.
I am interested at E86C also.
Which brands of E86C/E88C do you have?
Regards.
I just opened the box with these tubes. The EC 88's are mainly Telefunken, Philips and Lorenz, the 86's Siemens, Tungsram, Philips and Pope (which is actually Philips according to the branded code near the under side of the tube). Then I have a number of PC 86\88's which are identical to the EC types except for the filament voltage which is 3.8 v.
350V-0 winding DCR is 85ohm
choke DCR is 100ohm
output transformer 5K primary winding DCR is 180ohm
300B anode current is around 60mA
Regards.