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Slewmaster - CFA vs. VFA "Rumble"
Slewmaster - CFA vs. VFA "Rumble"
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Old 10th January 2014, 07:17 AM   #101
ostripper is offline ostripper  United States
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Quote:
Originally Posted by ivanlukic View Post
Just use DIP footprint, not SMD. When everything is TH we don't need just one part to be of microscopic dimensions. I think LF411 is good for the job too.
TL071 .... $.62c

below is the damage ...
Same # of parts , did not need the IC Vcc diodes/e-caps ... just used .1u decoupling caps
at the IC Vcc-/+ - left the protection diodes at +/- IC input.
With a Jfet op-amp , 680k input resistor (real high-Z) ... smaller integrator
cap -2.2u.

Simulation is 20ppm 10hz - HF (much cleaner LF!)
No trimmers needed.
Improving the amplifier with current sources penalized me with "resistance"
to manually adjust offset. A resistive loaded Diamond would be easier to
adjust with a trimmer.

The NX (I was told) ... will start at 15mv and settle with time to 1-2mv.
This one will stay <1mv- regardless !!
PS - I don't wan't to make a "toy" for an amp - It should excel in every
aspect.
OS
Attached Images
File Type: jpg CFA-servo.jpg (315.4 KB, 1773 views)
File Type: jpg slewmasterCFA-schema.jpg (108.5 KB, 1648 views)
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Last edited by ostripper; 10th January 2014 at 07:26 AM.
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Old 10th January 2014, 11:23 AM   #102
ivanlukic is offline ivanlukic  Serbia
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My vote for (cheap) TL071. I completely agree with Doug Self that TL071 will serve the purpose of dc offset servo very good at very low price. And it is available anywhere.
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Old 10th January 2014, 12:04 PM   #103
Vostro is offline Vostro  South Africa
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Are R10/11 2W footprint

Regards
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Old 10th January 2014, 01:03 PM   #104
buzzforb is offline buzzforb  United States
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ostripper,
Why not combine CFA with Class A. I have anjoyed what I believe to be a quality CFA design in the TSSA v1.6 and it sounded wonderful. You could tell it was a high bandwidth design with wonderful clarity and pace. What it did not have was body and soul and from my limited experience, this tends to be a fault of AB designs.
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Old 10th January 2014, 01:16 PM   #105
ostripper is offline ostripper  United States
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I haven't labeled yet , but it's a goin' on (below 1/2).

Circled resistors can be 2/3/5 or 25- 50W !
... (to-220/5mm LS -below 3) ha !

Can a servo be "tricked" ?? Going from 0V, (no signal) to a 20-200hz full
power (120Vp-p) signal ... the first 2-3 waveforms are offset at .1-.2V.
After 4-5 cycles , all is well at the <1mV range again.

This "settling time" only happens at LF and with a large transient at LF. It is caused
by the charging of the integrator cap C3 at U1. Reducing this cap brings LF
rolloff up into the audio range.
2.2uf has rolloff of about 5 hz , 1hz is down 15db.

For this design , we are nearing the best quality to price ratio. DON'T
let a small IC scare you. As I have stated , the ne5532 servo in my
japanese unit has been "servo-ing" for 33 years.
OS
Attached Images
File Type: jpg nad-h-pcb.JPG (130.9 KB, 1585 views)
File Type: jpg slewmasterCFA-schema.jpg (110.4 KB, 1588 views)
File Type: jpg 35wR.jpg (3.9 KB, 1498 views)
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Old 10th January 2014, 01:23 PM   #106
ostripper is offline ostripper  United States
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Quote:
Originally Posted by buzzforb View Post
ostripper,
Why not combine CFA with Class A. I have anjoyed what I believe to be a quality CFA design in the TSSA v1.6 and it sounded wonderful. You could tell it was a high bandwidth design with wonderful clarity and pace. What it did not have was body and soul and from my limited experience, this tends to be a fault of AB designs.
Those AB stages were not this EF3 OPS. It is highly reviewed and
used by Marantz , harmon/Kardon and sansui.

Very warm and powerful BJT bass. Plus 30 year durabilty (I own 2).

OS
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Last edited by ostripper; 10th January 2014 at 01:39 PM.
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Old 10th January 2014, 04:05 PM   #107
MiiB is offline MiiB  Denmark
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Is tripper, please look at the front end I posted, there you see a less signal intrusive way of implementing a servo.
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Old 10th January 2014, 06:41 PM   #108
ostripper is offline ostripper  United States
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Quote:
Originally Posted by MiiB View Post
Is tripper, please look at the front end I posted, there you see a less signal intrusive way of implementing a servo.
I could not find it ... link please ??

OS
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Old 10th January 2014, 11:01 PM   #109
Bonsai is online now Bonsai  Europe
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OS, what's that resistor you are using?
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Old 11th January 2014, 12:27 AM   #110
ostripper is offline ostripper  United States
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Quote:
Originally Posted by Bonsai View Post
OS, what's that resistor you are using?
You mean the thick film 25 watter. Bob "turned me on" to these.
My 2 choices are :
http://www.ohmite.com/cat/res_tbh25.pdf

or .. for the poor (like me) ...

http://www.irctt.com/file.aspx?produ...type=datasheet

My pcb will take em' all ...

It's done ...

OS
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