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Aleph (Single Ended) + Larvadin (no Memory Distortion) = Ultimate Aleph?
Aleph (Single Ended) + Larvadin (no Memory Distortion) = Ultimate Aleph?
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Old 30th July 2009, 06:39 PM   #11
tiefbassuebertr is offline tiefbassuebertr  Germany
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Quote:
Originally posted by Nelson Pass


This would be true if the tube amplifiers were operated that way, but
when you look at real power amplifier circuits, this causes such
inefficiency that power stages must be operated to the extremes
of voltage and current. They do not have the luxury of staying in
a small space on the load-line range.

this is particularly pronounced in all OTL tube amps - the Graaf GM-20 is such a device, that I know from a friend of me - go to
http://www.diyaudio.com/forums/showt...hreadid=142528
for the schematic, that I have created, and some comments.
In the original condition the quiescent current is 300mA through each triode 6C33C (150VDC from anode to cathode), i.e 4x45W idle dissipation and only 2x 10 to max 15 watts undistorted output power at 8 ohms.

However, by normal hifi sonic volume a normal Class AB transistor amplifier (even Mark Levinson or Bryston) sounds by high frequencies like scratch mashine resp. circular saw in action by AB comparison. Only solid state power amplifiers with "Single Ended" output stage sounds like a GM20. Class AB are ideal for the lower frequencies below arround 400-500 Hz.
Cause the bad realibility I cannot recommend to buy the GM20 (despite the very good sound quality), because it is nessecary to redesign the complete circuit to enhance the realibility (e. g. only max. 90 VDC instead 150VDC and so on)

Concerning the efficiency is the very heavy weight model TVA1 (TVA-1) from the old company "Michaelson and Austin" (later "Papworth") exactly the contrary from Graaf GM20 - i. e. high power output (approximately 2x100W / 8 ohms, and comparatively low idle power (4x12,5 W, 4x25mA). It also sounds better than all Class AB transistor amplifier, that I know, especially by upper frequency range, but not quite as pure and clean as transistor power amplifiers with "single-ended"output stages. This tube power amplifier outperform clearly the No 23.5 (both amps I have for service at the same time - some years ago.
Schematic of me - made a few years ago - is here as a PDF
Attached Files
File Type: pdf c ...-tube tva-1.ckt.pdf (40.3 KB, 338 views)
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Old 30th July 2009, 07:05 PM   #12
Nelson Pass is offline Nelson Pass  United States
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Aleph (Single Ended) + Larvadin (no Memory Distortion) = Ultimate Aleph?
Mmmmmm

Well, it's easy enough to alleviate memory distortion with proper
design and money, both of which are routinely lacking.

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Old 12th January 2011, 07:31 PM   #13
tiefbassuebertr is offline tiefbassuebertr  Germany
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Quote:
Originally Posted by Nelson Pass View Post
Mmmmmm
Well, it's easy enough to alleviate memory distortion with proper
design and money, both of which are routinely lacking.
I now doubt also the existence of memory distortion. But nevertheless the Lavardin model "IS Reference" is one of the best sounded amp with used low idle current through the output (i. e. Class AB with 30mA quiescent current).
This I have experienced while a sound check after replace the main caps.
What about the circuit topology by VAS in fig. 8-2 about
Memory Distortion Philosophies - Part 8 : More tests
Perhaps the fusion of that topology with that one from Aleph isn't the badest idea - especially in cases, where an extremly sweet sounded amplifier for high frequency and high efficiency horns is wanted.
Attached Images
File Type: jpg lavardin_is_reference_galeria1.jpg (320.3 KB, 907 views)

Last edited by tiefbassuebertr; 12th January 2011 at 07:39 PM.
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Old 13th January 2011, 12:25 AM   #14
eyoung is offline eyoung  United States
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just a note... there was a discussion in the Hafler DH200(long thread) about memory distortion (Fab, I think) with some details about implimentation on a DIY level...

Regards All, Elwood
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Old 13th January 2011, 11:37 AM   #15
tiefbassuebertr is offline tiefbassuebertr  Germany
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Quote:
Originally Posted by eyoung View Post
just a note... there was a discussion in the Hafler DH200(long thread) about memory distortion (Fab, I think) with some details about implimentation on a DIY level...
Regards All, Elwood
I think, you mean post #22 about
Hafler DH-200/220 Mods
There this phenomenon was descriptive only regarded to the differential amplifier at the input and not regarded the VAS.
If the open loop gain factor is high, then the voltage swing at the input stage is very low and thus the advantage of this modification rather of academic interest and less for audible sonic quality enhancing.

Last edited by tiefbassuebertr; 13th January 2011 at 11:43 AM.
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Old 9th January 2012, 01:18 PM   #16
tiefbassuebertr is offline tiefbassuebertr  Germany
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in this case this thread is of interest, because the approach there goes in the direction to my consideration:
http://www.diyaudio.com/forums/solid...fet-class.html
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Old 9th January 2012, 01:36 PM   #17
kenpeter is offline kenpeter  United States
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The really absurd part is when Lavardin bases a hypothesis upon
his 300B having no memory. Are we forgetting Iron? Hysteresis?

Last edited by kenpeter; 9th January 2012 at 01:51 PM.
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Old 9th January 2012, 02:10 PM   #18
kenpeter is offline kenpeter  United States
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You want to defeat thermal memory in semiconductors? Then use
a quadrature feedback from constant temperature current sensors
to control and shape bias in real time. Actively shape for whatever
class you desire, and thermal memory ceases to be a problem.

Constant temp current sensors need then be compared to constant
temp references. Here too, it often goes wrong...

Its class AB circuits that abuse hot variable output stage emitters
across a fixed or slow tracking voltage reference as the only form
of quadrature (common mode current) feedback that suffer worst.
Stop trusting variable temperature devices to shape crossings!

The emitter drop in Aleph is local example how to do this right.
The MOSFET doing all the hot work is not in control. The BJT at
constant current and voltage is making those critical decisions.
No thermal memory here, problem solved...

Last edited by kenpeter; 9th January 2012 at 02:30 PM.
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Old 24th January 2014, 11:51 AM   #19
padamiecki is offline padamiecki  Poland
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Default maybe this will work?

Quote:
Originally Posted by tiefbassuebertr View Post
...
What about the circuit topology by VAS in fig. 8-2 about
Memory Distortion Philosophies - Part 8 : More tests...
Hi
let me rewarm the discussion about memdist.
Please look at attached simulations, I think this idea is worth building (K170s should be used instead of BF245B):

Harmonic Frequency Fourier Normalized Phase Normalized
Number [Hz] Component Component [degree] Phase [deg]
1 1.000e+03 2.099e+01 1.000e+00 179.92 0.00
2 2.000e+03 7.876e-05 3.752e-06 121.23 -58.70
3 3.000e+03 6.382e-06 3.040e-07 -139.59 -319.52
4 4.000e+03 1.457e-06 6.941e-08 -0.77 -180.69
5 5.000e+03 2.902e-07 1.382e-08 62.42 -117.50
6 6.000e+03 1.213e-07 5.780e-09 95.36 -84.56
7 7.000e+03 8.862e-07 4.221e-08 -66.55 -246.47
8 8.000e+03 2.464e-07 1.174e-08 29.63 -150.29
9 9.000e+03 1.022e-06 4.868e-08 -54.24 -234.16
Total Harmonic Distortion: 0.000377%
Attached Images
File Type: png sch.png (21.2 KB, 450 views)
File Type: png sine.png (14.2 KB, 440 views)
File Type: png ac small.png (9.5 KB, 430 views)
File Type: png fft.png (13.5 KB, 430 views)
Attached Files
File Type: asc memdist fet sf inp.asc (12.0 KB, 26 views)
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Old 25th January 2014, 02:15 AM   #20
Nelson Pass is offline Nelson Pass  United States
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Aleph (Single Ended) + Larvadin (no Memory Distortion) = Ultimate Aleph?
Quote:
Originally Posted by kenpeter View Post
You want to defeat thermal memory in semiconductors?
You could use semiconductors with low or zero temp coefficient. A number of
Lateral Mosfets and (for example) Sony Vfets fit this description easily at
reasonable current values.

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