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Old 21st November 2013, 11:41 AM   #121
CFT is offline CFT  United States
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Could you please describe the difference in terms of sonic perception between this amp and the VFET PP?
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Old 21st November 2013, 11:20 PM   #122
juma is offline juma  Serbia
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Skorpio,
the circuit from post #66 had to be severely redesigned to make it work with +/-12V. R4, R5 should be replaced with CCSs and R7, R11 should be 6k8. Usable output swing will be much lower (up to 5V_peak max) and the original idea compromised. I wouldn't do it, although it can be made to work. Try it - you might like it...

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MASantos,
I would use the amp in post #118 with preamp giving 20V_peak output swing and Laterals working at +/-24V with 1.2A bias which will produce about 25W_avg at 8 Ohms load. We may push it to 30V_peak swing and use two pairs of Laterals (supplying them with +/-35V, 0.8A bias per pair) for total of about 55W at 8 Ohms. For lower impedance load we would go lower with voltage and raise the current. Of course, something like F4 or some other power follower is a viable option, it's only that I prefer Laterals in Source Follower arrangement.
Anyway, when you know what you need/want, the most appropriate solution will present itself.

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CFT,
I listened both amps on all of my speakers (Canton CT-1000, Rogers LS3/5a, Epos M5, Cabasse MiniDoris, Dynaudio DIY 3-way sealed+variovent) and the only things I could differentiate out of realm of very subtle nuances is a tiny bit of added gentleness in presentation of female voices on LS3/5a with amp from post #118 of this thread, as well as a tad of more resolute dynamics presented in complex orchestral passages with VFET_PP amp on Canton CT-1000. Otherwise, both amps present the same naturalness, transparency, tonal and spatial balance.
I'm sure that someone else might have a different impressions - I give you mine...
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Old 22nd November 2013, 08:02 AM   #123
CFT is offline CFT  United States
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Quote:
Otherwise, both amps present the same naturalness, transparency, tonal and spatial balance.
I'm sure that someone else might have a different impressions - I give you mine...
Thanks. Interesting to know their similarities despite using different types of output devices and having feedback vs none....
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Old 22nd November 2013, 08:42 AM   #124
juma is offline juma  Serbia
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Yes. I can only confirm what Mr. Pass and others already said - the feedback loop is just a tool, like a fork. You can use it to eat easier or you can stab your self in the eye with it...
When you have a nice, linear circuit, the feedback loop is welcome to define/limit the gain, bandwidth and lower the Zout a bit. Using it to correct the obvious errors made in previous process won't bring much happiness.
The same goes for active devices of different types - using them in accordance with their properties and the with the well chosen aim in mind is what brings fine results. They don't have the 'sound' of their own - it's just the way people use them.

It's just my experience and few grains of knowledge collected during the years that tells me so...
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Old 22nd November 2013, 09:34 AM   #125
CeeVee is offline CeeVee  Portugal
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Quote:
Originally Posted by juma View Post
Yes. I can only confirm what Mr. Pass and others already said - the feedback loop is just a tool, like a fork. You can use it to eat easier or you can stab your self in the eye with it...
When you have a nice, linear circuit, the feedback loop is welcome to define/limit the gain, bandwidth and lower the Zout a bit. Using it to correct the obvious errors made in previous process won't bring much happiness.
The same goes for active devices of different types - using them in accordance with their properties and the with the well chosen aim in mind is what brings fine results. They don't have the 'sound' of their own - it's just the way people use them.

It's just my experience and few grains of knowledge collected during the years that tells me so...

Great insight...wise words.
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Old 22nd November 2013, 09:42 AM   #126
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I have played with a balanced LTP and balanced complimentary version of this circuit and really like what I have heard. I followed that trail after listening to the Salas RIAA that uses a folded cascode as the gain stage. Wonderful sound. I am trying to decide between the balance version and the balanced version of the BA3 FE. Both can sound very, very good.
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Old 22nd November 2013, 09:48 AM   #127
CFT is offline CFT  United States
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Great remarks!
I always use my eyes to do the hearing, or judging how amps sound fron the way they look @@"
But reality is often like... a box of chocolates.. haha.
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Old 22nd November 2013, 10:34 AM   #128
Skorpio is offline Skorpio  Denmark
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Originally Posted by juma View Post
Skorpio,
the circuit from post #66 had to be severely redesigned to make it work with +/-12V. R4, R5 should be replaced with CCSs and R7, R11 should be 6k8. Usable output swing will be much lower (up to 5V_peak max) and the original idea compromised. I wouldn't do it, although it can be made to work. Try it - you might like it...
Thank you for the answer

My need is a linestage with little gain, and the 12V supply was only to make it easyer (already have one).

But I will make a new with +30V to give the JFETs optimum performance....

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Old 22nd November 2013, 02:09 PM   #129
juma is offline juma  Serbia
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Originally Posted by Skorpio View Post
... My need is a linestage with little gain, and the 12V supply was only to make it easyer (already have one)....
It's not all about gain, but the available output voltage swing too - if you are OK with 5V, go for it (+/-12V PS voltage).
Adjust the circuit accordingly - reserve about 4V for CCS (meaning about 8V of Vds for JFETs), set the Id through JFETs to 80-90% of Idss and account for 8-10mA through BJTs and you'll have a winner.
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Old 23rd November 2013, 06:39 PM   #130
indra1 is online now indra1  Indonesia
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Hi Juma, I think polarity of C2 on post #118 should be reversed
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