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Single-driver pentode test data

Last update: 8/10/03, added 6C45p-e and 6SN7 cascade for comparison

600彩好的i've been running a few tests on some reasonably high-gm pentodes, in pentode and triode mode.  these are tubes that you could use as a single-tube driver for an set, for example.

600彩好的i've pretty much gone through all the likely suspects from my tube boxes.   most of the tubes i had can all be obtained for under $10.00, some (like the 12hl7) for as little as $0.70!

600彩好的i've also tested a whole lot of tubes that were graciously loaned to me by others to test.  many thanks to don johnson, joezef tulinski and tom bavis in the us, grame smithson in new zealand, and nic wilshire in the uk.

600彩好的i tried to pick a reasonable operating point for the tests, based on the tube curves, and some trial and error.  no guarantees that these are the best op points for these tubes.  i also didn't play with screen voltage - i used either 75 or 150, depending on what i could get away with from a dissipation standpoint (normally, running close to the limits seems to work the best).  i also used a limited set of cathode bias resistors (26, 52, 100, 220, 330 ohms) and plate supply voltages (300 - 400 volts).

600彩好的note that the operating point may be limited by either of the plate or screen dissipation limits, or in come cases by maximum voltage ratings.  i may have pushed the limits a little in some cases.  hopefully this info will point you in a direction, and then you can go and make more detailed measurements and find the ideal operating point.

also, in general i only tested one tube.  there's a lot of tube-tube variation in high gm tubes, so keep in mind that you may see variations of 10-20% or even more.

i've now added some comparisons: the 6c45p-e, at a number of operating points, with resistor load and ccs.  it compares quite favorably with many of the pentodes.

i also tested a 6sn7 cascade driver, like the one used in the reichert 300b.  interesting comparison.  this is a well-regarded amplifier.

Definitions:

600彩好的gm is datasheet gm (transconductance) in ma/v

600彩好的pa(max) is maximum rated plate dissipation

600彩好的pg2(max) is max rated screen grid dissipation

b+ is supply voltage in volts

vp is plate voltage in volts

600彩好的vg2 is screen voltage in volts

rk is cathode resistor in ohms (unbypassed)

600彩好的ip is plate current in ma (this also includes the screen current in triode mode)

600彩好的pa is plate dissipation in watts

ig2 is screen current in ma

pg2 is screen dissipation in watts

rl is load resistance in ohms

5% thd vo is the output voltage in v rms at 5% thd

600彩好的10v thd is the thd at 10v rms out

600彩好的gain is... voltage gain!

 

600彩好的click on the tube type for a gif file of the fft spectrum at 10v rms out

Tube Gm Pa(max) Pg2(max) B+ Vp Vg2 Rk Ip Pa Ig2 Pg2 Rl 5% THD Vo 10V THD Gain
Triode mode, CCS load - note Ip is the CCS current and includes the sum of "real" plate current and screen current
12HG7 small RCA 32 10 1 400 175 Triode 50 35 5.1 6 1.05 CCS 121 0.04 43
12HG7 large RCA 32 10 1 400 227 Triode 50 35 6.6 6 1.36 CCS 103 0.11 50
12GN7/12HG7A GE 36 11.5 1.5 400 205 Triode 100 35 5.7 7 1.44 CCS 118 0.05 39
11HM7 GE 30 7 1 400 200 Triode 100 35 6.0 5 1.00 CCS 124 0.05 42
12HL7 RCA 21 10 1 400 149 Triode 100 35 4.2 7 1.04 CCS 88 0.08 29
6688 RCA 16.5 3 0.9 400 120 Triode 50 18 1.6 4.5 0.54 CCS 61 0.17 43
6197 RCA 11 7.5 2.5 400 219 Triode 150 35 6.2 6.5 1.42 CCS 121 0.12 24
6CL6 Sylvania 11 7.5 1.7 400 192 Triode 150 35 5.5 6.5 1.25 CCS 94 0.22 19
6EJ7/EF184 RCA (Amperex) 15 2.5 0.9 300 148 Triode 220 18 1.9 5.5 0.81 CCS 76 0.09 61
8077/7054 RCA 11.5 5 1 400 184 Triode 100 35 5.3 6 1.10 CCS 117 0.18 28
12BY7A/12BV7/12DQ7 GE 12 6.5 1.2 400 197 Triode 100 35 5.7 6 1.18 CCS 92 0.08 28
D3A (Telefunken) 35 4.2 1 400 167 Triode 52 26 3.2 6.7 1.12 CCS 94 0.04 70
CV4045 (RK) 13 12 2.5 400 147 Triode 52 50 6.6 5.3 0.78 CCS 55 0.07 27
SV83 (Svetlana) 15 12 1.5 400 175 Triode 220 50 7.5 7.4 1.30 CCS 86 0.13 23
6CW5/EL86 RCA 11 14 2.1 400 142 Triode 220 50 6.4 5 0.71 CCS ?? 0.49 7.4
6686/E81L Amperex 11 4.5 1.2 400 210 Triode 100 26 4.1 6.3 1.32 CCS 95 0.18 48
7788/E810F RCA (Amperex) 50 5 1 400 166 Triode 100 26 3.8 3.3 0.55 CCS 103 0.13 47
6JC6 Sylvania 15 2.5 0.6 400 170 Triode 100 18 2.3 4.3 0.73 CCS 85 0.15 60
PL802 40 6 2.5 400 207 Triode 52 35 6.1 5.6 1.16 CCS 119 0.05 69
6HF8 Amperex (pentode sect.) 12.5 5 1.1 400 170 Triode 150 26 3.4 5.9 1.00 CCS 91 0.21 22
6EB8 Sylvania (pentode sect.) 12.5 5 1.1 400 222 Triode 100 26 4.8 4.6 1.02 CCS 119 0.17 30
8608 Amperex 45 10 1.5 400 158 Triode 100 50 7.2 4.7 0.74 CCS 102 0.03 29
8233 GE (E55L) 45 10 1.5 400 162 Triode 100 50 7.3 4.9 0.79 CCS 97 0.08 28
6AG7 RCA 11 9 1.5 400 197 Triode 150 35 5.6 6.4 1.26 CCS 58 0.14 21
6EH5 Sylvania 14.6 5.5 2 400 187 Triode 330 35 5.5 5.6 1.05 CCS ?? 0.15 11
Tube Gm Pa(max) Pg2(max) B+ Vp Vg2 Rk Ip Pa Ig2 Pg2 Rl 5% THD Vo 10V THD Gain
Triode mode
12HG7 small RCA 32 10 1 400 207 Triode 52 40.8 8.4 7.5 1.55 4000 102 0.22 23
12HG7 large RCA 32 10 1 400 198 Triode 52 41.7 8.3 8.8 1.74 4000 84 0.17 24
12GN7/12HG7A GE 36 11.5 1.5 400 178 Triode 52 45.5 8.1 10 1.78 4000 78 0.32 22
11HM7 GE 30 7 1 400 183 Triode 52 46.3 8.5 8 1.46 4000 83 0.19 24
12HL7 RCA 21 10 1 400 104 Triode 52 30.0 3.1 7 0.73 8000 46 0.17 22
6688 RCA 16.5 3 0.9 300 128 Triode 52 17.5 2.2 4 0.51 8000 56 0.45 29
6197 RCA 11 7.5 2.5 400 288 Triode 100 8.0 2.3 6 1.73 8000 59 0.35 16
6CL6 Sylvania 11 7.5 1.7 400 136 Triode 100 27.0 3.7 6 0.82 8000 44 0.61 14
6EJ7/EF184 RCA (Amperex) 15 2.5 0.9 300 164 Triode 220 8.3 1.4 3 0.49 12000 81 0.33 24
8077/7054 RCA 11.5 5 1 400 155 Triode 100 25.6 4.0 5 0.78 8000 69 0.39 18
12BY7A/12BV7/12DQ7 GE 12 6.5 1.2 400 168 Triode 100 24.0 4.0 5 0.84 8000 62 0.25 17
D3A (Telefunken) 35 4.2 1 400 168 Triode 52 22.4 3.8 6.6 1.11 8000 84 0.16 42
CV4045 (RK) 13 12 2.5 400 196 Triode 52 44.4 8.7 6.6 1.29 4000 38 0.29 14
SV83 (Svetlana) 15 12 1.5 400 189 Triode 220 44.8 8.5 8 1.51 4000 71 0.32 13
6CW5/EL86 RCA 11 14 2.1 400 170 Triode 220 52.5 8.9 5 0.85 4000 ?? 0.74 5
6686/E81L Amperex 11 4.5 1.2 400 191 Triode 100 20.4 3.9 5.7 1.09 8000 69 0.19 20
7788/E810F RCA (Amperex) 50 5 1 400 165 Triode 100 26.0 4.3 3.4 0.56 8000 90 0.32 28
6JC6 Sylvania 15 2.5 0.6 400 147 Triode 100 13.1 1.9 3.8 0.56 15000 62 0.29 37
PL802 40 6 2.5 400 176 Triode 52 23.3 4.1 4.7 0.83 8000 85 0.26 41
6HF8 Amperex (pentode sect.) 12.5 5 1.1 400 166 Triode 220 23.5 3.9 5.8 0.96 8000 ?? 0.42 12
6EB8 Sylvania (pentode sect.) 12.5 5 1.1 400 214 Triode 220 19.8 4.2 3.5 0.75 8000 ?? 0.45 12
8608 Amperex 45 10 1.5 400 134 Triode 52 60.0 8.0 6.5 0.87 4000 69 0.04 19
8233 GE (E55L) 45 10 1.5 400 138 Triode 52 58.8 8.1 6.7 0.92 4000 58 0.1 19
6AG7 RCA 11 9 1.5 400 187 Triode 220 22.0 4.1 4.6 0.86 8000 ?? 0.35 11
6EH5 Sylvania 14.6 5.5 2 400 163 Triode 330 24.7 4.0 4.9 0.80 8000 ?? 0.32 7
Tube Gm Pa(max) Pg2(max) B+ Vp Vg2 Rk Ip Pa Ig2 Pg2 Rl 5% THD Vo 10V THD Gain
Pentode mode
12HG7 small RCA 32 10 1 400 275 150 50 31.3 8.6 4 0.60 4000 85 0.29 39
12HG7 large RCA 32 10 1 400 260 150 50 35.0 9.1 5 0.75 4000 93 0.13 37
12GN7/12HG7A GE 36 11.5 1.5 400 238 150 50 40.5 9.6 5 0.75 4000 104 0.08 40
11HM7 GE 30 7 1 400 245 150 50 38.8 9.5 5 0.75 4000 101 0.09 40
12HL7 RCA 21 10 1 400 207 75 50 24.1 5.0 4 0.30 8000 116 0.08 61
6688 RCA 16.5 3 0.9 300 130 150 50 21.3 2.8 5 0.75 8000 70 0.07 54
6197 RCA 11 7.5 2.5 400 288 150 100 14.0 4.0 5 0.75 8000 64 0.25 18
6CL6 Sylvania 11 7.5 1.7 400 166 150 100 29.3 4.9 7 1.05 8000 80 0.06 29
6EJ7/EF184 RCA (Amperex) 15 2.5 0.9 300 164 150 220 11.3 1.9 3 0.45 12000 58 0.34 27
8077/7054 RCA 11.5 5 1 400 180 150 100 27.5 5.0 5 0.75 8000 111 0.03 35
12BY7A/12BV7/12DQ7 GE 12 6.5 1.2 400 168 150 100 29.0 4.9 5 0.75 8000 109 0.23 32
D3A (Telefunken) 35 4.2 1 300 143 150 52 19.6 2.8 6 0.90 8000 78 0.15 69
CV4045 (RK) 13 12 2.5 400 253 150 52 36.8 9.3 3.8 0.57 4000 63 0.48 24
SV83 (Svetlana) 15 12 1.5 400 254 150 220 36.5 9.3 5.5 0.83 4000 89 0.42 24
6CW5/EL86 RCA 11 14 2.1 400 200 150 220 50.0 10.0 4.2 0.63 4000 ?? 0.14 9.2
6686/E81L Amperex 11 4.5 1.2 400 270 150 100 16.3 4.4 4.3 0.65 8000 78 0.44 33
7788/E810F RCA (Amperex) 50 5 1 400 206 150 100 24.3 5.0 3 0.45 8000 114 0.32 52
6JC6 Sylvania 15 2.5 0.6 350 156 150 100 12.9 2.0 3.8 0.57 15000 92 0.27 65
PL802 40 6 2.5 300 185 150 26 28.8 5.3 5.6 0.84 4000 82 0.11 61
6HF8 Amperex (pentode sect.) 12.5 5 1.1 400 170 150 100 28.8 4.9 7.1 1.07 8000 109 0.04 33
6EB8 Sylvania (pentode sect.) 12.5 5 1.1 400 200 150 100 25.0 5.0 4.2 0.63 8000 125 0.04 35
8608 Amperex 45 10 1.5 400 252 75 52 37.0 9.3 2.8 0.21 4000 95 0.23 46
8608 Amperex 45 10 1.5 400 235 150 100 41.3 9.7 2.7 0.41 4000 116 0.63 28
8233 GE (E55L) 45 10 1.5 400 252 75 52 37.0 9.3 2.8 0.21 4000 94 0.17 45
8233 GE (E55L) 45 10 1.5 400 238 150 100 40.5 9.6 4.1 0.62 4000 116 0.08 27
6AG7 RCA 11 9 1.5 400 221 150 150 22.4 4.9 4.4 0.66 8000 102 0.32 23
6EH5 Sylvania 14.6 5.5 2 400 194 75 100 25.8 5.0 4 0.30 8000 119 0.11 30

 

Tube Gm Pa(max) Pg2(max) B+ Vp Vg2 Rk Ip Pa Ig2 Pg2 Rl 5% THD Vo 10V THD Gain
Comparisons
6C45p-e 45 7.8 NA 400 166 NA 200 11.7 1.9 NA NA 20000 116 0.28 23
6C45p-e (cathode bypassed) 45 7.8 NA 400 166 NA 200 11.7 1.9 NA NA 20000 107 0.36 34
6C45p-e 45 7.8 NA 400 167 NA 100 23.3 3.9 NA NA 10000 113 0.26 25
6C45p-e (cathode bypassed) 45 7.8 NA 400 167 NA 100 23.3 3.9 NA NA 10000 109 0.39 35
6C45p-e 45 7.8 NA 400 200 NA 52 50.0 10.0 NA NA 4000 112 0.29 23
6C45p-e (cathode bypassed) 45 7.8 NA 400 200 NA 52 50.0 10.0 NA NA 4000 103 0.41 34
6C45p-e CCS 45 7.8 NA 400 194 NA 100 35.0 6.8 NA NA CCS 119 0.07 41
6C45p-e CCS 45 7.8 NA 400 156 NA 220 10.0 1.6 NA NA CCS 126 0.12 35
6C45p-e CCS 45 7.8 NA 400 194 NA 52 45.0 8.7 NA NA CCS 131 0.07 40
6SN7 cascade (Reichert) 400 70 1.6 110

 

600彩好的you can download the whole thing as a pdf file or excel spreadsheet below in the full pdf file below...

PDF file of results (LARGE 1.46M PDF file)

Excel spreadsheet of the data600彩好的 (892k .XLS file)

 

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