education+diy

EDUCATIONAL AND DIY.
Click the pages you want :-
LAST update Nov 2011.

AUDIO IDEAS FOR THE HOME.
Listening pleasure, classA, log sawing, classB, class AB, solid state history,
measurements, enough is enough,
NFB, triodes and NFB,
NFB and sales, circuit development, in house transformers,
future amps, preamps, SS amps,
NFB, tubes not bad, bandwidth, parts quality, tube choice, capacitors,
NOS tubes, testing tubes, add ons, news groups.

VACUUM TUBE USE IN AUDIO AMPLIFIERS :-

TUBE OPERATION 1.
Basic tube operation, cathodes, anodes and grids, diodes, triodes and pentodes.
Parameters of Ra, µ and gm.
Fig1. Schematic for a basic triode amplifier based on 6SN7.
DC flow for quiescent conditions, dc equilibrium,
Mutual effect of anode voltage and grid voltage on Ia electron flow,
Effect of cathode bypassing biasing on Ra, and gain.
The tube modelled as a generator.
Fig 2. Schematic of basic 6SN7 generator model for illustrating ac operation
of a tube.
NFB in the triode, AC signal flow, Cathode capacitor bypass impedances,
tube gain formula, gain without capacitor bypassing.
Fig 3. Electrostatic effects in a 6SN7 triode.
NFB in the triode, how it reduces THD.
Fig 4. Electrostatic effects in the 6AU6 pentode,
pentode and beam tetrode operation, pentode Ra, µ and gm.
6AU6 triode connected and its amount of internal NFB.
NFB in 6SN7, and why ß = 1 / µ , with more NFB and gain equations.
The Miller effect.

TUBE OPERATION 2.
Fig 5. Graph of 6SN7 Ra curves with load lines for 47k and 32k.
How to find Ra for a given working point and plot loadlines in steps 1 to19.
Comment on THD and other topology outcomes.
Fig 6. Scanned Ra curves from Samuel Seely, 1958.
Explanations about the Ra curves. About gain with CCS load and µ.
6SN7 THD with CCS load calculations from data curves.

TUBE OPERATION 3.
How negative feedback works.
Fig 7. Schematic for Basic NFB around an amplifier.
Explanations and formula for NFB gain reductions and effects of NFB.
Fig 8. Schematic for Turner Audio 35 watt class AB triode amp using KT90.
General notes about this amp which has the same overall gain and NFB as the
basic example in Fig1.
Calculation methode for output resistance with NFB.
The Model of the tube gain stage as a voltage generator.
Fig 9. Schematic of a power tube gain stage modelled as a generator with
resistor to indicate Ra.
Explanations about the generator model.
Fig 10. Schematic of a tube gain stage using 6SN7.
Fig 11. Schematic of a tube amp drawn with each stage as a generator with
loads and positions of shunt C to analyse the HF response and graph all the
attenuation profiles.
A whole lot more about NFB, output resistance.
A simple formula for calculating output resistance of a real amp.
More on stability of amplifiers with NFB and the use of RC networks to
tailor open loop gain.
Fig 12. Graph of tube amp frequency response without global NFB and
with global NFB, with no attempts to tailor open loop gain or phase shift.
Fig 13. Graph of tube amp frequency response without and with NFB
but with RC gain and phase shift tailoring
networks in place.
More about stability and NFB.
Critical damping methods for tube amps with NFB.

TUBE OPERATION 4

About NFB within triodes,
Testing a 6550 to measure Ra, Gm and µ.
Fig 1. Schematic A and B for testing 6550.
Schematics A and B explained,
How to determine Beam Tetrode and Triode Ra,
µ, and Gm.
Simple method to find Beam Tetrode and Triode Ra,
µ, and Gm.
Equivalent Model, Beam Tetrode, UL, Triode, 6550
Fig 2. Equivalent Model for calculation gain of UL connected tubes.
Fig 3. Graph of Ra vs UL tap % for SE 6550.
SEUL 6550 and SEUL 6550 with CFB.
Fig 4. Schematics for SEUL and SEUL+CFB for 6550.
CFB with UL taps and wothout UL taps explained with maths.

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LOAD MATCHING 1. SE TRIODES.
Fig1. Anode resistance curves for GE6550A in triode from the 1950s.
Explanations of how the curves were obtained and what the curves mean.
Fig 2. Schematic for testing power triodes.
Triode voltage generator model is included in explanations.
Fig 3. GE6550 triode curves with 2.5k RL and tangent to calculate
Ra, µ and gm for any chosen working point.
Explanation of what load lines are.
How to plot LL graphically and read for gain, calculate power output, and 2H distortion.
Fig 4. Measured Po vs distortion for 3 load values used with EH6550 in triode.
Fig 5. Measured Po vs distortion for 3 load values used with GE6550A in triode.
Fig 6. Measured Po vs distortion for 3 load values used with KT88 JJ-Tesla in triode.
Fig 7. Measured Po vs distortion for 3 load values used with KT90EH in triode.
Fig 8. My corrected Ra curves for EH6550 in triode with 3 values of RL plotted.
Comments on loads recommended for EH6550 in triode.
Fig 9. My curves for EH6550 in triode without LL so you can download them for use.
Fig 10. Ra curves for 300B measured after 1990 with 4.5k loadline details.
Comparison of THD with beam tetrodes strapped as triodes.
Fig 11. Ra curves for trioded GE6550 measured after 1990 with 4.5k load line details.
List of conclusions about beam tetrodes used as SE triodes.
Fig 12. Intermodulation test rig schematic for measurement.
Fig 13. Measuring the intermodulation distortion using an oscilliscope wave form.
Comments about THD and IMD significance.

LOAD MATCHING 2. SE BEAM TETRODES and PENTODES.
This page has the following content :-
Operation of the beam tetrode with cut-away sketch by RCA.
Fig1. Graph of Ra curves for GE 6550A beam tetrode with screen supply = +350V.
Fig 2. Graph of Ra curves for GE 6550A beam tetrode with screen voltage = +350V
plus 3 load lines and calculated results for gain, power output and second harmonic
distortion.
Fig 3. Graph of Ra curves for GE6550A beam tetrode but with screen supply = +200V.
Fig 4. Graph of Ra curves for GE6550A with one load line for 3.5k and calculated
gain, power and 2H.
Explanation of the effects of NFB application for 6550 beam tetrodes.
Formulas for NFB and output resistance.
Fig 5. Graph for power output for single 6550 beam tetrode vs anode load value.
Choosing the OPT ratio.
Fig 6. Graph of 6550 Ra curves for 6550 in UL mode with 43% screen taps.
Calculated gain, power output and 2H for 4 different load values.
Data for Ra, µ and gm for UL and comment on the effects of NFB
and distortion outcomes.

LOAD MATCHING 3. PP TRIODES.
A very brief history of triode use. Class A Push Pull operation basics.
Fig 1. Schematic of basic PP triode output stage with current waveforms to explain
2H cancellations.
Comments on class AB1 amps, Williamson's amp, Class AB efficiency, preferences,
Class AB1 basics.
Fig 2. Graph of EH6550 triode curves with load lines for 5k a-a.
Minimum load for PP triode AB amps, Class AB1 operation explained.
How to plot a load line to give the outcome for class AB triodes,
Anode heat dissipation, Comment on B+ regulation, Biasing the class AB PP stage,
Distortion, Output resistance, Negative feedback.
Using a higher RL value.
Fig 3. Graph for PP 6550 triode class AB1 power output vs RL values.
Class AB power and portion of class A power listed for 8k : 6 ohms loading.
Fig 4. Schematic for 35 watt class AB1 PP triode amp with KT90.
Speaker SPLs with 25 watts. Output transformer ratios.
Comment on using KT90 or multiple tubes.

LOAD MATCHING 4. PP BEAM TETRODES.
Beam tetrode background,
Fig 1. Loadline graph for PP beam tetrode 6550 with 4k a-a load.
Plotting loadlines for PP tetrodes, 17 steps to find maximum class AB power,
class A power.
Heat dissipation considerations and measurement, 92 watt Class AB power
with Ea = 600V.
Biasing the output tubes, Distortion, Output resistance.
Using a higher RL such as 8ka-a,
Global NFB, its effect on output resistance, Calculation of amount of applied NFB
and the output resistance with applied NFB.
Fig 2. Graph of power out vs RL .
Loading the PP beam tetrode output stage, OPT ratios.
Ultralinear and other output tube configurations, Driver amplifier comments.
How to match loads to power tubes, load matching to 6550 & KT88
and to some other beam tetrodes, pentodes and triodes.
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OUTPUT TRANSFORMER THEORY .
Function of the output transformer, ( OPT ). How the OPT works.
Impedance and resistance transformation.
Fig1. Equivalant model of Ultralinear output stage tubes and OPT.
Functions in the model and prefered OPT chracteristics.
Test conditions for specifying OPT performance. Description of OPT No1,
wire and turns and insulation description.
Fig 2. Cross section of bobbin winding details.
Fig 3. Schematic of OPT No1 when used in UL with two impedance
matching settings shown.
Fig 4. Schematic of OPT No1 when used with 12.5% CFB windings
and with two impedance matching settings shown.
Notes re recommended amounts of CFB to be used. Impedance matching notes.
Table 1. Impedance matchings available with OPT No1.
Table 2. Recommended output tubes for OPT No1 with winding losses.
Comments about alternative tubes used with OPT No1.
Specification for OPT No1, notes re LF behaviour, power handling ability,
HF behaviour, HF resonances, and distortion. Description of PP OPT No2.
Description of SE OPT No3. Brief note about SE OPT No4.
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PUSH PULL OUTPUT TRANSFORMER CALCULATIONS.

There are now 5 pages covering this subject.

PP OPT Calc Page 1:-

This page is the first of 5 pages on PP OPTs.

Contents, this page 1 :-
Brief reference to Radiotron Designer's Handbook, 4th Ed, 1955.
Some general notes.

Design steps for 2 x 6550/KT88/KT90 tetrodes.

1. Define the aim of this design project.
           OPT-1A is for up to 75 Watts of audio power between 14Hz and
         65kHz using 2 x 6550, KT88, KT90, K120 beam tetrodes.
         Pda at idle should be 25Watts for each of these output tube types.

2. LOADLINE ANALYSIS for PP BEAM TETRODE (not including triode.)
      Fig 1. Ea vs Ia, Ra curves for 1 x 6550 beam tetrode.
        Fig 2. Loadlines for pure class A1, and minimum class B load.
2A. Plotting the Class A loadline, Fig 2.
        Fig 2. repeated.
        Fig 3. Ia waveform for one 6550 in pure class A.
        Fig 4. Class A and AB Ia waveforms in tube amplifier.
        Fig 5. Class AB Ia waveform in tube amplifier.
2B. Class AB1 loadlines.
          Plotting the minimum class AB1 RLa load.
        Fig 2. repeated.
3. Check the anode dissipation for sine wave operation.
        Formula for Pda for Class AB amp.
4. Calculate idling Ia bias current.
5. CALCULATIONS FOR PP BEAM TETRODES,
        without load line analysis :-
6. Calculate anode to anode load for maximum pure
        class A1 power.
7. Calculate maximum Class A1 power output.
8. Calculate minimum Class AB1 RLa-a load which will
        give maximum class AB1power.
        Fig 2. repeated.
        Fig 6. Ra curves for 6550 with 43% UL connection, and
        with loadlines for two minimum RLa values.
9. Calculate maximum AB1 power into minimum RLa-a.
        Two methods, 9A, 9B.
10. Calculate Middle RLa-a for intermediate power
        and for ideal Class AB1 for Hi-Fi use.
11. Calculate PO for middle RLa-a.
        PO max for middle RLa-a,
        class A1 PO for middle RLa-a.
12. CONCLUSIONS ABOUT LOAD CHOICE.
       Fig 7. Graph for PO Vs RLa-a for 6550 beam-tet, UL or CFB.
13. List the possible ranges of primary to secondary
          Load matches, list use possibilities.
          Table for wanted load match possibilities.
Some Notes about use of OPT-1A.
OPT Calculator Program?
About Metric Wire size table.
Fig 32. Blank Sheet 6550 tetrode, basic Ra curve for Eg1 = 0V.
Fig 33. Blank Sheet with All Ra curves for 6550 tetrode.
Fig 34. OPT No 1 Schematic from 2002.
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PP OPT Calc Page 2 :-

Design of OPT-1A continued....
14. Calculate minimum centre leg cross sectional area, Afe.
15. Calculate the core tongue dimension, T.
         Fig 8. Wasteless E&I lamination details.
         Fig 9. C-core details.
17. Confirm sizes for core.
18. Calculate the theoretical primary turns, thNp.
19. Calculate theoretical Primary wire dia, thPdia.
20. Find nearest suitable overall dia wire size from
         the wire size table.
         Table 1. Available Wire Sizes.
21. Caculate maximum safe working Idc.
22. Calculate the bobbin winding traverse width.
23. Calculate no of theoretical P turns per layer.
24. Calculate theoretical number of primary layers.
25. Calculate actual Np.
26. Calculate average turn length, TL.
27. Calculate primary winding resistance, Rwp.
28. Calculate pri winding loss % with minimum RLa-a,
29. Is the winding loss more than 3.0%?
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PP OPT Calc Page 3:-

Design of OPT-1A continued....
30. Choose the interleaving pattern.
         Fig 10. Cross section through a hypothetical transformer with
         concentric layered windings. Basics explained.
         Tables 2, 3, 4, 5, showing interleaving pattern possibilities
         for PP OPTs.
31. Choose insulation thicknesses.
         Table 6. Insulation Thickness Vs Voltage.
32. List layers of insulation which are to be used.
         Fig 11. OPT-1A bobbin winding diagram for CFB use.
33. Calculate height of Primary layers and all insulation.
34. Calculate the max theoretical oa dia of secondary wire.
35. Find nearest Sec oa dia wire size.
36. Calculate the theoretical Sec turns per layer.
         Table for ZR, TR, conclusions.
37. Choose Secondary sub-section pattern.
         Fig 12, Sec = 2L,
         Fig 13, Sec = 3L,
         Fig 14, Sec = 4L,
         Fig 15, Sec = 5L,
         Fig 16, Sec = 6L.
         Fig 17, Sec sub-section pattern 4A explained.
         Table for TR, ZR and loads. Conclusions.
   Fig 18, Sec sub-section pattern 4C explained.
         Table for TR, ZR and loads. Conclusions.
         Fig 19, Link pattern for 4C sub-sections.
         Fig 20, Link pattern for 4A sub-sections.
         Alternative Single Simple termination.
38. Calculate secondary winding loss %.
39. Calculate total winding losses.
40. Calculate total height of bobbin contents.
41. Draw sketches of bobbin details.
         Fig 21, OPT-1A, Ultralinear config.
         Fig 22, OPT-1A, CFB config.
         Fig 23, OPT-1A, Schematic of windings.
42. Calculate Fsat with Middle RLa-a.
43. Calculate minimum required Lp.
         Fig 24, E&I core Lp + µ vs Bac + Vac.
         Many notes and calcs.
44. Partial air gap for PP OPTs.
         Fig 25, Gapping effects.
45. Calculate leakage inductance.
         Is LL low enough? 2 methods.
46. Shunt capacitance of an OPT.
         12 Steps to determine C, many notes, calcs.
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PP OPT Calc Page 4 :-

TAPPED SECONDARY WINDINGS.

47. Nominate OPT Design name and its purpose. OPT-1ATS.
48. Nominate Wanted Load matches.
         Fig 26, Graph for PO Vs RL for 3 different Ns.
         Load matches available.
49. Calculate available height for layers of secondary.
50. Calculate the max theoretical oa dia of secondary wire.
       Determine no of layers per Sec section.
       Calculate winding heights in bobbin.
       Fig 27. Bobbin details for alternative OPT-1BTS.
       Conclusion, 4 options to optimise design are explored.
       Fig 28. OPT-1ATS bobbin details.
51. Calculate Total winding losses, Middle RLa-a.
52. Compare winding losses, Tapped and Wasteless Secs.
52. Compare LL, Tapped Secs to Wasteless Secs.
53. Shunt Capacitance with tapped Secondaries.
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PP OPT Calc Page 5 :-

FOR PP TRIODE CLASS
A1 AND AB1, OPT-2A

55. Understanding Ra curves for triodes.
Fig 29. Ra curves for 6550 and 300B.
56. Understanding Ra curves for triodes.
Fig 30. Ra curves for 6550 in triode.
57. Calculate the minimum PP Triode RLa-a for
maximum class AB1 power for OPT-2A.
Fig 31. Graph for Po vs RLa-a 6550 PP triodes.
58. Calculate maximum AB1 power for minimum RLa-a.
59. Calculate RLa-a for maximum pure class A1 power.
60. Calculate maximum class A1 PP triode power output.
61. Calculate the Middle RLa-a for triode PP operation.
62. Calculate PO for Middle RLa-a,
63. Conclusions about PP triode OPT design.
14T. Calculate minimum centre leg cross sectional area, Afe, triode PP amp.
15T. Calculate the core tongue dimension, T.
16T. Calculate theoretical Stack height.
17T. Confirm sizes for core.
18T. Calculate the theoretical primary turns, thNp.
19T. Calculate theoretical Primary wire dia, thPdia.
20T. Find nearest suitable overall dia wire size from wire tables.
21T. Calculate the bobbin winding traverse width.
22T. Calculate no of theoretical P turns per layer.
23T. Calculate theoretical number of primary layers.
24T. Calculate actual Np.
25T. Calculate average turn length, TL.
26T. Calculate primary winding resistance, Rwp.
27T. Calculate pri winding loss % with MIDDLE RLa-a.
28T. Is the winding loss more than 3.0%?
29T. Choose the interleaving pattern.
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End of list of contents for PP OPT calcs.
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SINGLE ENDED OUTPUT TRANSFORMER
CALCULATIONS.

There are now 3 pages for this subject.

SE OPT Calcs Page 1.

RDH4, SE amp history, trends and preferences.
     Table 1. SE Pentodes, Beam Tetrodes, CFB, UL,
   For operating conditions of common tubes.
   Table 2. SE Triodes.
     For operating conditions of common tubes.
     Interpreting Table 1 and Table 2.

SINGLE ENDED OPT4 DESIGN EXAMPLE.
1. DEFINE THE AIM OF THIS PROJECT.
     Fig 1. Graph for EL34 pentode PO vs RLa.
     HOW TO DRAW THE PO vs RLa GRAPH FOR ANY TUBE.
     Calculate Center Value RLa and PO for all RLa.
     A for pentodes and beam tetrodes only,
   B for triodes only.
2. LOADLINE ANALYSIS FOR ONE SE PENTODE.
     Fig 2. Graph Loadlines for EL34 pentode. How to draw loadlines,
     Steps A, B, C, D.
     LOADLINE ANALYSIS CONCLUSION.
3. Calculate Center Value RLa for OPT4, the design project, and confirm
     maximum PO and Va max.
4. Calculate theoretical core cross sectional area, Afe,
     for a nearly square core centre leg cross section.
5. Calculate the core tongue dimension, T.
6. Calculate theoretical stack height for chosen T
     from step 5.
7. Calculate usable Afe = chosen T x chosen S.
     Table of possible T and S for output powers.
8. Confirm L and H of the winding window.
9. Calculate theoretical primary winding turns, thNp.
10. Calculate theoretical Primary wire dia, thPdia.
11. Find nearest suitable theoretical oa wire size for Primary.
       Wire size table for Grade 2 winding wire, metric sizes.
12. Calculate the bobbin winding traverse width, Bww.
13. Calculate no of theoretical P turns per layer.
14. Calculate theoretical number of primary layers.
16. Calculate average turn length.
15. Calculate actual Np. Np = P layers x Ptpl, turns
17. Calculate Primary winding resistance.
18. Calculate primary winding loss %.
19. Is the primary winding close to 3.5%?
20. Is the Primary wire able to carry the
       intended Idc current?
21. Choose the winding interleaving pattern.
       Tables 2, 3, 4, 5, Pri and Sec interleaving patterns.
       Fig 3. Section view through sample wound bobbin.
       Fig 4. Bobbin winding detail for Fig 3 bobbin.
22. Calculate exact CFB winding percentage.
23. Choose insulation thickness used between primary
       layers with the same Vdc potential.
24. Choose insulation thickness used between Primary and
       Secondary layers, or between primary Anode layers
       and Cathode layers with full Vdc potential difference.
       Table 6. Insulation thickness Vs Voltage.
       Fig 5. OPT4 basic bobbin winding details.
25. Calculate height of Primary layers plus all insulation.
26. Calculate oa dia Secondary wire size.
27. Select select Secondary wire size from wire size table.
28. Calculate theoretical S turns per layer, thStpl.
29. Calculate load matches with Sec turns from Step 28.
       Table for turns, TR, ZR, Sec RL.
       Ask for 2 matches between 3 and 9 ohms.
30. Calculate Sec turns Ns for matches to 3, 6 and 12 ohms.

Notes about wire size table.
    Table for Metric Wire Sizes, Grade 2, magnetic winding wire.

Blank graph sheets :-
   Fig 25. Graph for Cu wire dia required for working idle DC current.
   Fig 26. Log scale F response sheet 15Hz to 25kHz.
   Fig 26. Log scale F response sheet 10Hz to 200kHz.
   Fig 27. Log scale F response sheet 4.7Hz to 320kHz.

SE OPT Calcs, Page 2.

31. Calculate sec winding losses for turns in Step 28,
       Calculate total P and S winding losses.
32. Choose Secondary Winding Sub Section pattern.
       Fig 6, 7, 8, 9, 10 Secondary sub-section patterns.
       Fig 11. Explanation for chosen 4A sub-section pattern.
33. Calculate Sec turns to suit a chosen sub-section pattern.
       Table for total turns vs configurations possible.
       Avoiding "illegal" configurations.
   Summary & Conclusions, 2 questions, A and B.

Re-calculate from step 24 to get better outcome :-

24A. Calculate insulations.
25A. Calculate height of Primary layers plus all insulation.
26A. Find nearest oa dia wire size from wire size tables.
27A. Calculate theoretical oa dia Secondary wire.
28A. Calculate Th sec oad Tpl.
29A. Calculate load matches with Sec turns from Step 28A.
         Tables of matches including legal and illegal configurations.
30A. Calculate Sec turns for matches to 3, 6 and 12 ohms.
31A. Calculate sec winding losses for turns in Step 28A,
         Calculate total P and S winding losses.
32A. Choose the same sub-section pattern as for Step 32.
         Fig 12. showing chosen 4A interleaving pattern.
         Table of resulting matches.
         Conclusion that design is OK.
33A. Check total height of all bobbin contents.

Proceed from Step 33....

34. Bobbin winding details.
       Fig 13. OPT4 bobbin winding details.

35. Tapped Secondary windings.
       Fig 14. OPT4TS bobbin winding details.
       Notes and conclusions.
36. Calculate leakage inductance.
37. Is the leakage inductance low enough?
38. Shunt capacitance and Primary Inductance of SE OPT.
       Fig 15. Test schematic for Csh and Lp.
       How to measure shunt capacitance and primary inductance, + notes.
   Fig 16. F response from test measurements.
   More notes.
   Table of Csh at points along primary winding.
39. Calculate wanted µe.
40. Calculate Lp.
41. Calculate XLp = RLa at F cut-off, Fco.
42. Calculate Fsat.
43. Calculate the air gap, Ag.
       Fig 17. Graph of Air gap sizes for µe Vs grade of iron.
44. Notes on testing OPT4.
   Fig 18. Photo of sample OPT and the home made pot.
   Notes about potting OPTs.

SE OPT Calcs, Page 3.

Practical Testing of 8 Watt SEUL OPT for 1 x EL34 for old AM radio.
       Fig 19. Schematic for rather good 8 Watt SE amp.
       Notes about schematic etc.
       Fig 20. Photo of old radio after restoration.
       Notes on testing amp and OPT.

Oscilloscope pictures of waveforms produced with 8 Watt SEUL OPT.
CRO 1. Healthy wave at clipping power at 1kHz.
CRO 2. Measuring Lp.
      How to adjust the air gap.
      Fig 21. Wasteless pattern lamination dimensions.
ALTERNATIVE METHOD to calculate max PO of any pentode
CRO 3, 4, 5, Waves during core saturation phenomena.
Fig 22. Graph of Air gap Vs Fsat and Lp.
CRO 6, 7, 8, Waves at -6dB level for 47Hz, 20Hz, 16Hz.
     Conclusions about SEUL for 1 x EL34,
     Notes and calculation checks for all.

SE OPT Easy Method for calculating any SE OPT.
For Basic Parameters only.
1E. Calculate RLa and PO.
2E. Calculate Afe.
3E. Calculate required Lp.
4E. Calculate Np.
5E. Calculate minimum primary wire size.
6E. Calculate miimum core window size L x H.
7E. Calculate Core T + S.
8E. Calculate µe.
9E. Check Lp, Fsat.
10E. Calculate Air gap.

High Voltage testing of transformers.
   Fig 23. Schematic for testing insulation of transformer.
   OPT3 bobbin details for 25W OPT from web pages created May 2006.

OPT3 from 2006.
   Fig 24. Details of OPT3.

END OF LIST OF CONTENTS FOR 3 PAGES ON SE OPTS.
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OUTPUT TRANSFORMERS FOR 1 x 13E1 OR PARALLEL OCTAL OUTPUT TUBES.
Design flow for a couple of 25W SE OPT to suit 1 x 13E1 or 3 or 4 KT88/6550/KT90/300B
or 4 x EL34, 5881, 6L6GC, 807.
Fig 1. OPT5 for SE 1.8k : 5 ohms with 44T x 50S core and details of bobbin layers,
insulation, wire etc.
Fig 2. OPT6 for SE 1.8k : 2.2, 3.5 6.2, 13.9 ohms with 51T x 51S core and details
of bobbin layers, insulation, wire etc.
Metric winding wire size chart for grade 2 polyester-imide wire.

WINDING OUTPUT TRANSFORMERS.
Practical winding methods and description.
What you need to consider if wanting to wind an OPT for yourself.
Image 1.    Bobbin winding details for OPT No1 mentioned in OPT transformer theory.
Image 2.   Four transformers on a work bench.
Image 3. Two 300w OPT on bench.
Image 4.   500w OPT on table.
Image 5.   Winding lathe with bobbin being wound.
Image 6.   Wound bobbin close up.
Image 7.    Close up of 300w OPT handmade bobbins on bench.
Winding procedure, varnishing, alternative to varnish is applying Estapol 7008.
Metric winding wire size chart for grade 2 polyester-imide wire.
_________________________________________________________________________

TUBE AMP POWER SUPPLIES.
Definition of linear power supplies.
Fig 1. Basic wave forms in rectifier circuits.
Single phase house wiring, ac waveform basics, filling the bath with water,
diode resistance, ripple voltagevs C vs Idc.
Cap ripple I and V ratings, ac to dc conversion ratios, doubler rectifiers.
Fig 2. Schematic of 8585 amp power supply used as example for PS calculations.
Minimum C value for resevoir C1 input cap, C reactance, Ripple voltage calcs,
peak charge currents, charge current limiting, CRC and CLC filters,
R and choke values, LC resonance, choke reactance, LC damping resistance,
CT cap values, need for chokes. DC heater supplies, B+ regulators.
CRCRC and CLCLC filters.
Fig 3. Schematic for solid state regulator for screen supplies in 300 watt amp.
Send me your SMPS schematics for B+ supplies.

POWER TRANSFORMERS AND CHOKES.

Due to huge demand for information about power transformer and choke design,
I have refurbished the 2006 page and created a sub page solely for chokes.
For choke info go to Choke Design for Audio Amplifiers.

This page concerns power transformer design only.
(1) Fig1 Tube amp PSU schematic for 5050 amplifier from 2006, and notes,
Fig2 480VA power supply schematic simplified for 2007 and
suitable for a range of amplifiers.
(2) Define the power requirements for the amplifier,
wanted secondary voltages and currents, and transformer VA rating.
(2a) AC Heater Supply.
(2b) B+ Anode Supply for range of class A and AB conditions.
(2c) Negative Bias Supply.
(2d) DC Heater Supply.
(2e) Summary of transformer secondary windings needed.
(2f) Primaries.

(3) Selecting the core type and size for the transformer.
(4) Calculating turns per volt, TPV.
(5) Check for iron heat losses in the core.
(6) Magnetizing current, iron µ check, measuring inductance and µ with a variac.

(7) Working out the winding layers and turns.
(7a) Mains Primaries, 480VA transformer.
(7b) AC heater windings.
(7c) HT for B+ anode supplies.
(7d) Negative Bias supply.
(7e) AC heater windings for DC heaters.
(8) Check that proposed windings will fit onto bobbin.
Fig3 480VA transformer bobbin winding details.

(9) Transformer Assembly, Varnishing, Potting.
______________________________________________________________________________
TURNER AM-FM TUNER.
A totally tubed radio tuner including tubed multiplex decoder.
Schematics, notes, and an image.
______________________________________________________________________________

MISCELLANEOUS SCHEMATICS 1.
1010w Integrated amp                              One channel shown with 2 x 6GW8, UL, classAB
Two triode phono stage NFB eq                1 x 12AX7, feedback RIAA eq
Three triode phono stage NFB eq              1 x 12AX7, feedback RIAA eq, buffer
Three triode phono stage Passive eq           1.5 x 12AX7, passive RIAA, buffer
Phono Amp PSU Schematic                      LowPower supply for 2 and 3 tube preamps
10 tube Preamp April 2000                        5 x twin triodes per channel
1 x j-fet 2SK369 simple pre-preamp           A test circuit showing THD for a single 2SK369 j-fet
Test filter, Reverse RIAA eq                      A simple test filter with discrete RC components

MISCELLANEOUS SCHEMATICS 2.
Basic Balanced Shunt FB                           2 x 6L6GC
Balanced Shunt FB 100W           4 x 6550 per channel
Automatic servo bias control                       1 x KT88 etc.
Error correction standard UL amp 2 x KT88 etc.
Error correction fully balanced    2 x KT88 etc.
Simple line preamps 1 and 2.                      2 triodes.
Simple line preamps 3, 4 and 5.        2 and 3 triodes.
Line preamp with switched gain and CCS    2 triodes.

Where appropriate I have included explanations.

Should you have any indispensible wisdom you'd like to have added then email me.

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