I took a break after getting one channel running. Sounds very good on the Radio Shack Minimus 7 shop speaker, which is a speaker I have listened to for 35+ years. If it sounds good on that speaker it’ll sound great in the main rig.
I’ve got Iq at ~1.5A and with the 3U is all the idle current I want. I will run squares and distortion measurements at some point…..
I’ve got Iq at ~1.5A and with the 3U is all the idle current I want. I will run squares and distortion measurements at some point…..
PC817C question, does the dot on the case correspond to the dot (just above the "1" of "OK1" on board?) looking at post 599 I do believe I can make it out?
Thanks,
Russellc
Thanks,
Russellc
Boards assembled with exception of GBR. Going to re read the posts concerning that, and how several members
dealt with it's value, and resulting hum, or no hum...then drill and tap heats sinks.
Russellc
dealt with it's value, and resulting hum, or no hum...then drill and tap heats sinks.
Russellc
I will have to see if I have 10R in resistor bag. I will start with zero and go from there.
Russellc
Russellc
and stay with 0R
10 or 15R there is more as possible remedy if you have hum problems, but position of that resistor is less than optimal
though, there is no possibility to arrange its position in circuit properly, due to construction of feedback net
The BFF8 has really impressed me Choky. I don’t know if the BC556 in the Fe and the high capacitance of the 150 is doing it but this is more my style of HF performance. This simple two stage design has huge soundstage layering and the way notes slowly collapse is epic. This is a really mature sounding design. Massive enjoyment. Great work.
Babelfish F8 isn't that much different to Papa's original F8, entire FE is practically one 2SJ74BL, while BC556 is nothing more (nor less) than cascode for 2SJ, bringing its pentodish transfer function even more pentodish, yadayada
anyhow, what you hear is sum of all details, major one being feedback arrangement - low impedance network tightly controlling JFet's source
and, HF performance better than expected, taking in account that I opted for IRFP150 (plenty of capacitance)
what I did differently (vs. Pa's) is not much - dual rails and fully DC coupled, JFet drain loading ensuring use of broad range of JFet Idss without change of OLG, Iq setting from just warm to hot (by personal preference)
That’s exactly what I’m hearing, more pentode-like than I’ve ever heard from Toshiba fe and IR FETs. I’m very used to the sound of both jfet and BJT in the fe but never together, however little it may be contributing, the BjT cascoded device MIGHT be doing great things here. it’s a very, very good fe and the HF performance is stunning: there’s depth to this performance that is just remarkable. We aren’t getting single notes but harmonics that decay on either side of the fundamental. I’ve personally never heard this from JFETs, whether SE or P-P, but they are in general lower noise than BJTs.
It’s a brilliant design, whatever is happening. Definitely pentode-ish.
and, now, Babelfish F8b and Babelfish F8m are singing practically the same
go figure
all pentodish parts, ending with THD Sprectra of regular SET amp
there are so many myths and legends in this area of fun, it demands years just to shed them all, ending with clean awareness that informed choice is one ring to rule them all
go figure
all pentodish parts, ending with THD Sprectra of regular SET amp
there are so many myths and legends in this area of fun, it demands years just to shed them all, ending with clean awareness that informed choice is one ring to rule them all
ZM's Babelfish F8 with Semisouth is my fave amp so far from all my builds - it is effortless and amazing.
Bridge rectifiers arrived yesterday, wire from Apex jr in mail box tonight when I got home.
Getting ready to be a F8 building weekend!
Russellc
Getting ready to be a F8 building weekend!
Russellc