Thorens TEM 3200 clone - diyAudio
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Old 23rd May 2012, 07:30 AM   #1
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Default Thorens TEM 3200 clone

After my good experience with the my Hybrid amplifiers:

Hybrid Amplifier by Andrea Ciuffoli

and the final

Amplifier End by Andrea Ciuffoli

I would like to try to develop a new dc coupled project following the Thorens TEM 3200 design.

I have tested yesterday the potential shifters created with a screen driven pentode and the results are good so I will continue in this direction.

Last edited by audiodesign; 23rd May 2012 at 07:49 AM.
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Old 23rd May 2012, 07:33 AM   #2
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Here the simulation result with LT Spice
Attached Images
File Type: gif Test2a.gif (54.5 KB, 1057 views)
Attached Files
File Type: asc Test2c.asc (5.2 KB, 32 views)
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Old 23rd May 2012, 07:39 AM   #3
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To support the simulation I have created one input circuit with 2 x D3a, one as input tube in triode connection and the other as screen driven pentode.

The output distortion is very low on both stages and the first D3a have no problem to drive the G2 (screen) of the second D3a.

Using my Clio system the frequency response is flat 0dB in the range 20-20KHz.

In the Simulation the result is 0dB in the range 0Hz-1MHz.
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Old 23rd May 2012, 07:46 AM   #4
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Now my problem is .......

if I apply the feedback this is not negative so it does not work


-----------

Some material about this design:

1) 6moons audio reviews: Thorens TEM 3200

2) 6moons audio reviews: Thorens TEP*3800

3) http://www.6moons.com/audioreviews/thorens/review.pdf
Attached Images
File Type: gif TEM3200.gif (18.3 KB, 1045 views)

Last edited by audiodesign; 23rd May 2012 at 07:52 AM.
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Old 23rd May 2012, 12:30 PM   #5
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some material about the circlotron/CSPP topology
SuSy Circlotron - jFET input Buffer + OPA1632 + 2SK135
CSPP/Cirlotron - Brand Names of Commercial Solid State Amplifiers
Biasing schemes for bipolar transistor circlotrons

more URLs:
Circlotron amp using N-channel mosfets
Best MOSFET for output stages
sumo amp schema here

Last edited by tiefbassuebertr; 23rd May 2012 at 12:36 PM.
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Old 23rd May 2012, 01:49 PM   #6
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The my design with a some more solid state devices have no problem with feedback because the pnp invert the phase.

I am searching someone to resolv the question of the TEM 3200 design ?
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File Type: gif D3a_hybrid_2013_by_Ciuffoly.gif (42.6 KB, 1009 views)
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Old 23rd May 2012, 02:26 PM   #7
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I am searching someone to resolv the question of the TEM 3200 design, about the possibility to add the feedback as original "schematic".
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Old 23rd May 2012, 04:08 PM   #8
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Quote:
Originally Posted by audiodesign View Post
Now my problem is .......
if I apply the feedback this is not negative so it does not work
I don't understand, what you want to reach.

By all kind of audio amplifiers there is only one kind of feedback possible:
the negative feedback (NFB), because by the use of a positive feedback your amp now operates as an oscillator.

You can choose in general a serial feedback (local feedback) and parallel feedback (both local feedback and global feedback).

What is your goal ?
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Old 23rd May 2012, 05:27 PM   #9
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I cannot apply the negative feedback because the second stage does not invert the phase.

The second stage is a potential shifters created with a screen driven pentode.

So probably Thorens use another configuration for this stage.
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Old 24th May 2012, 08:06 AM   #10
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Here some measurements of D3a in triode configuration and the first two stages with D3a screen driven
Attached Images
File Type: gif D3a_triode_300V_11K_100ohm_thd.gif (33.3 KB, 925 views)
File Type: gif D3a_triode_to_D3a_g2_driven_thd.gif (33.2 KB, 882 views)
File Type: gif D3a_triode_to_D3a_g2_driven_freq.gif (23.3 KB, 64 views)
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