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The Kuartlotron - keantoken's simple error-correction superbuffer
The Kuartlotron - keantoken's simple error-correction superbuffer
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Old 7th March 2021, 12:02 PM   #991
Zoran is online now Zoran  Serbia
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Ahaa.
I see now. I will try. Thanks.
.
In case of increasing PD voltages, should I also increase values of R6, R3 and R4 from 1K to a bit higher say 1.2K-1.5K? Proportionaly to voltage increase. Seems somehow logical if the currents ramain the same or not significantlu increased?
.
What is some max input signal before clipping? With +-10V supply?
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Old 8th March 2021, 09:50 AM   #992
Zoran is online now Zoran  Serbia
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Hi
I done some measurements last evening.
I measured the circuit just like it was in the schematic.
.
BUT i switched output transistors with say 10mV offset. Kean was right
Also I spot (and measure) that in the input branch was about 0.38mA not 4mA cca.
About 4mA was total from +V with 1K-Rtrim-1K to -V
With 56ohm R at emitters.
So in the initial original values of the buffer, with Ge devices AC188/AC187 currents are
0.37mA input, 4mA shunt, 8.4mA output.
.
With batteries of +- 8.35V cca
- The buffer holds input signal of 3.3V P-P cca. without clipping. I didnt have more output on the computer...
- Distortion is below sensitivity of the measurement equipment and didnt show almost any increase of distortion WITH Ge Buffer.
- Transfer is the same as without Buffer.
- But sound is much better WITH the Gee Buffer.
(Some moderate measurements indicate that Distortion at HF region are smaller with buffer with a same transfer and phase shift.)
- Distortion with Ge buffer is a bit smaller against the JFET classic buffer (with same battery supply)
.
[For measurements I use old MBP17 in. Soft for distortion measurements REW, for transfer FuzzMeasurePro, other AcousticToolBox...
MBP17in have 27.3K of input R measured as the Load. Impulse is negative because I dint use compensation. It is tha same with and withput buffer, so buffer does NOT invert phase...]
.
Attached Images
File Type: png MBP17.png (108.3 KB, 260 views)
File Type: png output Ge Buffer.png (113.2 KB, 259 views)
File Type: png JFET buffer.png (107.4 KB, 255 views)
File Type: png response.png (184.6 KB, 255 views)
File Type: png HF dist.png (209.6 KB, 255 views)
File Type: jpg IMG_4994.JPG (303.4 KB, 75 views)
File Type: jpg IMG_4998.JPG (281.1 KB, 81 views)
File Type: jpg IMG_4999.JPG (303.6 KB, 70 views)
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Last edited by Zoran; 8th March 2021 at 09:55 AM.
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Old 8th March 2021, 10:10 AM   #993
keantoken is offline keantoken  United States
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Very cool, so the Kuartlotron has pretty low THD even with Ge transistors. The difference is 0.0002%, and it's actually lower with the buffer. Can't really say whether that is due to unloading the source or some beneficial harmonic cancellation.
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Old 8th March 2021, 01:45 PM   #994
Zoran is online now Zoran  Serbia
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Yes. It is lower with buffer in critical domain for Digital sources... But something that it could not be seen from the measurements - the sound is really strong, with natural echoes coming from low end. NOT from HF end as usual. And without making a focus and emphesizing "end" of musical "event", but start of the event. All instruments and Voices. (Interestingly guitars are neutral...). For my ears, removing crispy ends, and sharp edges with opening space among events. It is not like good tube design does, Ge-s are somehow different? BUT i think that will be good with tube followed?
.
I didnt stand and made other tests:
- moved input branch Ge-s from 0.37ma to about 0.7mA adding parallel to 56ohm 100ohm resistors. (And adjust 1/2+Vb, and offsets)
-with 22ohms parallel to 56ohms 2xR cirrent was 1.04mA.
Everythig else could be adjusted with minimum offset arround 10mV or smaller.
.
I even short-cut resitors and it was without 56ohm resitors about 1.4mA in input branch.
.
So I stay with 1mA with input and measure the device - pretty much the same results. But again I dont know what happening below, and with generating signal with proper analog genarator, maybe some square signals... I will borrow from a friend and make tests later.
.
I didnt spot any change about changing values of "upper" R (56ohms), so I measure and set the same currents to the input transistors. Maybe not the same because of leackege curents from output bases which are higher than the Si BJTs?
.
Anyway somehow the circuit always showed pretty much the same behaviour and sound.
.
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Last edited by Zoran; 8th March 2021 at 02:11 PM.
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Old 8th March 2021, 01:59 PM   #995
Zoran is online now Zoran  Serbia
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I forgot to say all this i prepared without thermal coupling of pairs. Without coupling, device slowly coming to the point values. I think that with thermal coupling things will be better in that way?
I had some holders, but as ysusal, they was bigger diameter and for other type of Ge devices
.
I will try with thick copper?
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Old 9th March 2021, 08:25 AM   #996
keantoken is offline keantoken  United States
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In my experience it is not likely to make much of a difference as long a TP is set correctly.
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Old 13th March 2021, 06:58 PM   #997
Zoran is online now Zoran  Serbia
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I spot the same with Ge-s too...
.
I tried yesterday AD161 in the "output". (for now also without thermal coupling.) And it wotking good too.
Also find some mistake and correct it. C in the collector of input transistor is opposite polarity. At this point voltage is negative and about slight more from 1/2 -Vb.
.
After that I add 470uF value of capacitors and also in the power rails. Put the buffer from batteries to +-12V power supply. Every TP was adusted. Absolutly any hum, hiss or anything comimg from the speaker...
And sound was even better. Better body and low mids with these bigger Cs...
.
Tried 32K input resistor (10K+22K series) and offset was adustable to zero. output segment from AD161 vintage Siemens parts, consumed 12mA. (I just need higher input value because of the fiter before buffer, Has to be higher termination impedance to avoid peaks at the cut off F...)
At he input of the buffer I put 4x1uF C.
.
With this bigger value of 4 x C (470uF) I didnt have any clicks or anything with power ON/OFF. So the Ge version coud be used without relay at the output.
.
I will post the measured values of the components and bias points.
All distortion remain the same like it was from the beguining. Nothinf is changed.
.
I didnt solder RC input (270ohm-15pF), beacuse I have already lowpass filter at tinput. Also I prepare but didnt solder 2.2uH FB because I think that Ge-s are much lower Fcutoff than Si-s is it OK?
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Last edited by Zoran; 13th March 2021 at 07:11 PM.
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Old 13th March 2021, 07:05 PM   #998
Zoran is online now Zoran  Serbia
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I tried but I could not attach a picture?
it is not big Mb, maybe later... sorry
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Old 14th March 2021, 07:12 AM   #999
Zoran is online now Zoran  Serbia
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pic

C2 should be in opposite polarity, because at the collector we have something about 1/2 -Vb... First I didnt spot this and solder in wrong way, later in proper way connected somehow offset was easy to adjust and it was more stabile? With additionof 470uF to 10uF everything was better.

Conclusion is:

-This buffer can work with AC188 inoput pair
-and AC187 output couple, as with AD161 output. Probably with other Germanium devices but not tested
-Tested with +-9V and +-12V power supply.
-Tested with input signal of 3.4V P-P. probably can accept more p-p...
-No hum or his, no on/off clicks and pops.
-Ditortion is wery low with Ge-s, and lower than source with HF region. Wich is from crucial for digital sources...
-Sound is - just BIG and natural
.
Attached Images
File Type: jpg AD161 output Buffer.jpg (152.2 KB, 57 views)
File Type: jpg 4 copy.jpg (279.0 KB, 98 views)
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Last edited by Zoran; 14th March 2021 at 07:31 AM.
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Old 14th March 2021, 07:37 AM   #1000
Zoran is online now Zoran  Serbia
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Oliver Barney have had simillar aproach in his amplifier.

Germanium investigations
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