SemiSouth power Jfets .......... FW J2

[Zen Mod]

ne

[generg]

Hi dear Zen Mod,I try to use the Borbely super buffer with Babelfish J2. And in the description is mentioned the possibility to get 0db or 6db amplification.But the pdf has a formatting problem there are ? in a black field. He writes "?Cinp is left open" what could he mean?I add both the text and the circuit, thanks for help.......

[generg]

and the original text

[Impuls]

if you want use this circuit like a buffer, then -inp must left open. In that case output signal is without reducing level returned to the - inp. If you want use this circuit with 6db gain you must connect - inp to the signal ground. In that case R8 and R7 reducing level for desired gain

[generg]

Thanks Impuls for solving the riddle for me .... I was irritated by the C in the word "?CInput"

[generg]

Nevertheless in the second moment I am irritated, I cannot use this circuit as a balanced input with unbalanced out? And when I use the input balanced I have o db ?

[Sipi]

... I cannot use this circuit as a balanced input with unbalanced out?

Yes you can.

And when I use the input balanced I have o db ?

Only if R7=R8. Ratio of those two resistor defines the gain. Gain (when using inverting input) equals R8/R7For overall symmetry make R2=R7 (to define same Zin on both inputs)

[Zen Mod]

Generg - that's too much complicated for my likingat least too much complicated in wrong ways

[Tea-Bag]

Finally got this boxed and starting to listen to it.Bias is .9v each side. One channel offset floats between .20mv and .70mv. The other is still near 0. Still need to play with it.There is a little 'buzz' you can hear up to 2feet away in both channels when the inputs are not shorted. Thinking I need to use some shielded wiring on input, but for now, just listening.You guys are more than welcome to comment on my primitive construction skills with aluminum sheets. :sarcastic_hand:The initial sound seems to have a mild velvet softness with no loss of detail, and control and quantity of the low end that I was not expecting.Gate resistors are 47RTomorrow I plan on letting it run all day, and turning off load stuff around the house for some serious listening.

[Zen Mod]

:Viannen_loungelizard:congrats !regarding buzzzzzzzzzz - that's something I didn't had , even in my most ikebana style first prototypemaybe is something in wiring or gnd layoutin any case - I'm glad that you are hearing good things .....

[sp300b]

Congratulation :sporty095_2:I'm surprised.It shoudn't work so nice with RED LED's (Green are the better ones)

[Tea-Bag]

The LED's are supposed to be 1.9v 20ma red one's. I believe I measured as such too. It does Vref a little low, around 10.5-11v.Latter I will add LED in to adjust to spec, change the gate resistors possibly.It's certainly reminiscent of the J2 at BAF09, and unlike the F2 and other SemiSouth contraptions with Aleph current source. Those devices have more upper mid - high clarity to it. More time will tell.

[sp300b]

The LED's are supposed to be 1.9v 20ma red one's. I believe I measured as such too. It does Vref a little low, around 10.5-11v.Latter I will add LED in to adjust to spec, change the gate resistors possibly.It's certainly reminiscent of the J2 at BAF09, and unlike the F2 and other SemiSouth contraptions with Aleph current source. Those devices have more upper mid - high clarity to it. More time will tell.

Very Good !I was joking about the Led color. I've measured (-12,5V) at the top of the Led array - LED green used. Anyhow, You are free to try with one more red led. Also, about gate resistors, I've put 100 Ohms and 100Khz square looks like square at the output on my scope . Was too lazy to try 47 Ohms...If You will try, please put here some thoughts about the change/notice you'll heard. Regards, sp300b

[generg]

Yippeeh, tea-bag you did it! Happy to hear all worked finally. what did you mean by the second part of this sentence I did not quite understand it "t's certainly reminiscent of the J2 at BAF09, and unlike the F2 and other SemiSouth contraptions with Aleph current source. Those devices have more upper mid - high clarity to it. More time will tell. "I know you have many experience with many many amplifiers, so I want to understand what you said....I am a little bit slow at the moment I will try to double the output devices and choose a higher current I´ll report end of the week

[Tea-Bag]

Generg,

The BJ-2 sounds a lot like I remember the FW J2 sounding like at Burning Amp 2009. AR2 might be able to comment here.

It appeared to have a little bit darker overtone than say my mini-A with R100 or the F2J, which to me sound a touch less dark and more of that clean upper mids and treble sound.

Of course, I did not have much time to compare, it could be some component break-in that needs to go on. From the gate, it's a different sounding amp using SemiSouth's.

Most of my future comparison will be from recent memory of tweaked out F5 clone, and then I can bring, Mini-AJ online to compare later.

[sp300b]

Looking forward for new information:bravo:

[Zen Mod]

another day ..... another amp

[sp300b]

I am a little bit slow at the moment I will try to double the output devices and choose a higher current I´ll report end of the week

Trust him, he knows what he's doing (

)

[AR2]

Generg,

The BJ-2 sounds a lot like I remember the FW J2 sounding like at Burning Amp 2009. AR2 might be able to comment here.

It appeared to have a little bit darker overtone than say my mini-A with R100 or the F2J, which to me sound a touch less dark and more of that clean upper mids and treble sound.

Of course, I did not have much time to compare, it could be some component break-in that needs to go on. From the gate, it's a different sounding amp using SemiSouth's.

Most of my future comparison will be from recent memory of tweaked out F5 clone, and then I can bring, Mini-AJ online to compare later.

It is very hard to translate the hearing experience to words, but regardless, I think you nailed it very well. It certainly is different than anything we dealt so far with MOSFETS. I think the most impressive part is bass. If this amp has more juice it would be the bass reference amp. When I say more juice, I am thinking in the range of 300 - 600 W, so that it could be used for anything and any purpose in oppose to existing 28W. The bass is sick. If the output works for your system - combination of speakers and room size, than you are happy camper right there. On the top I completely agree with your description that upper mids and highs are clean but a tad darker. Certainly much darker than F5, that has a clinical precision. In that department it is the closest I ever heard to the SE triode. Where it differentiate from it, and as far as I could tell since I do not consider having it long enough, is in the lower mids. I do not know what to say, but I think it slightly missing body in that department, but that is ever slightly, tiny bitty. I mean I am right now going into the painful details and that is really not right since I didn't even move it to my main listening room to give you the full answer. One thing is certain, every recording sounds different what is about normal and right. The good recordings are exactly that and the shity ones come just like that. No lies there, what tells you that amp does what it suppose to do. Overall it is very magical and powerful at the same time, and after switching to some other amp produces a burning desire to switch back to it.

[sp300b]

It is very hard to translate the hearing experience to words, but regardless, I think you nailed it very well. It certainly is different than anything we dealt so far with MOSFETS. I think the most impressive part is bass. If this amp has more juice it would be the bass reference amp. When I say more juice, I am thinking in the range of 300 - 600 W, so that it could be used for anything and any purpose in oppose to existing 28W. The bass is sick. If the output works for your system - combination of speakers and room size, than you are happy camper right there. On the top I completely agree with your description that upper mids and highs are clean but a tad darker. Certainly much darker than F5, that has a clinical precision. In that department it is the closest I ever heard to the SE triode. Where it differentiate from it, and as far as I could tell since I do not consider having it long enough, is in the lower mids. I do not know what to say, but I think it slightly missing body in that department, but that is ever slightly, tiny bitty. I mean I am right now going into the painful details and that is really not right since I didn't even move it to my main listening room to give you the full answer. One thing is certain, every recording sounds different what is about normal and right. The good recordings are exactly that and the shity ones come just like that. No lies there, what tells you that amp does what it suppose to do. Overall it is very magical and powerful at the same time, and after switching to some other amp produces a burning desire to switch back to it.

Thanks AR2.Comparing to FJ2, in my opinion, sorry to say, but BJ2 should be technically better (better CCS, LTP cascoded ! with LED Vref). Obvious difference is only in output stage where Pass is using 1,4A and Big resistors of 0,47Ohm (two in parallel). Maybe this makes a difference. I will test BJ2 with lower bias and lower output resistors, for sure, soon...

[Tea-Bag]

Listening to the BJ2......Also some 24/96/192k stuff.No vinyl today.

[sp300b]

:Viannen_loungelizard:Me too