Hi All
I noticed this article and were intrigued by it. As a matter of fact, the suggested design seems quite workable. Has anybody used this design (somewhere between a McIntosh and a UL Hafler design)?
See here http://oestex.com/tubes/ulo.html
I quote:
RECOMMENDED CONFIGURATION
For those who wish to build the ultimate in OPTIMISED ULTRA-LINEAR ? I would recommend the following configuration:
OUTPUT TRANSFORMER - High Fidelity
Primary winding for plates - 100% plate to plate load impedance and comprising FOUR separate sections each having equal turns. Connect two windings in series for each half.
Tertiary winding for screens - 50% of Plate to Plate Primary winding TURNS and comprising TWO separate sections each having equal turns.
The primary and tertiary sections are therefore of equal turns.
Secondary winding - 5 separate sections or 7 separate sections having equal turns and interleaved with the primary and tertiary windings. Connect in SERIES to make up full loudspeaker matching impedance.
Why 50% ratio??
Because it makes transformer design and manufacture simple (easier to count the same number of turns for each winding during manufacture), provides more flexible connection options, increases the level of AC signal feedback to the Screen-grids (increasing the damping factor), reduces the output impedance very slightly and provides better tone (than 43% turns tap).
A slight loss of power may be measured compared to the 43% configuration but with four pairs of tubes as recommended that should not be a problem.
OUTPUT TUBES - FOUR pairs of tubes in parallel-push-pull
This has the effect of reducing the output impedance to one quarter of that for one pair of tubes.
This has the effect of reducing the transformer turns ratio to one sixteenth of that for one pair of tubes.
AC signal drive voltage is the same as for one pair of tubes enabling cathode-follower drivers to be utilised (recommended also) - see GEC 400W amplifier circuit for a typical configuration.
A proportionately larger final filter cap is recommended to provide the extra current needed to handle transient signals - eg 500 uF.
Preferred output power tube type - BEAM POWER TETRODE TUBE with aligned grids
My picks for best results are:
2E26
6146, 6146A,
6146W, 6146WA, 7212
6146B/8298A
6159, 6159A, 6159B (26.5V)
6293 (check ratings)
6883A/8032 (12.6V)
6883B/ 8032A/ 8552 (12.6V)
807
813 (10V filament)
All have a top anode cap.
All are of broadcast/military quality and offer extra features (such as ruggedised construction and reliability) compared to domestic/receiving quality tubes.
I noticed this article and were intrigued by it. As a matter of fact, the suggested design seems quite workable. Has anybody used this design (somewhere between a McIntosh and a UL Hafler design)?
See here http://oestex.com/tubes/ulo.html
I quote:
RECOMMENDED CONFIGURATION
For those who wish to build the ultimate in OPTIMISED ULTRA-LINEAR ? I would recommend the following configuration:
OUTPUT TRANSFORMER - High Fidelity
Primary winding for plates - 100% plate to plate load impedance and comprising FOUR separate sections each having equal turns. Connect two windings in series for each half.
Tertiary winding for screens - 50% of Plate to Plate Primary winding TURNS and comprising TWO separate sections each having equal turns.
The primary and tertiary sections are therefore of equal turns.
Secondary winding - 5 separate sections or 7 separate sections having equal turns and interleaved with the primary and tertiary windings. Connect in SERIES to make up full loudspeaker matching impedance.
Why 50% ratio??
Because it makes transformer design and manufacture simple (easier to count the same number of turns for each winding during manufacture), provides more flexible connection options, increases the level of AC signal feedback to the Screen-grids (increasing the damping factor), reduces the output impedance very slightly and provides better tone (than 43% turns tap).
A slight loss of power may be measured compared to the 43% configuration but with four pairs of tubes as recommended that should not be a problem.
OUTPUT TUBES - FOUR pairs of tubes in parallel-push-pull
This has the effect of reducing the output impedance to one quarter of that for one pair of tubes.
This has the effect of reducing the transformer turns ratio to one sixteenth of that for one pair of tubes.
AC signal drive voltage is the same as for one pair of tubes enabling cathode-follower drivers to be utilised (recommended also) - see GEC 400W amplifier circuit for a typical configuration.
A proportionately larger final filter cap is recommended to provide the extra current needed to handle transient signals - eg 500 uF.
Preferred output power tube type - BEAM POWER TETRODE TUBE with aligned grids
My picks for best results are:
2E26
6146, 6146A,
6146W, 6146WA, 7212
6146B/8298A
6159, 6159A, 6159B (26.5V)
6293 (check ratings)
6883A/8032 (12.6V)
6883B/ 8032A/ 8552 (12.6V)
807
813 (10V filament)
All have a top anode cap.
All are of broadcast/military quality and offer extra features (such as ruggedised construction and reliability) compared to domestic/receiving quality tubes.
