Emission Labs Tubes
(see notes below regarding rectifier usage)
20A / 20B $603
20A mesh $657
Output Tubes45 $590
45B - $634
PX4 Mesh - $938
300B Mesh - $938
520- V3 $1149
1605 - $1254
| Tube base glue for repairs
About filament quality
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Note 1) Good care should be taken when making the design of any DH rectifier. It must be prevented to have strong current peaks, through the first capacitor, because consequently this flows through the tube anode, and transformer windings as well. The transformer will produce mechanical hum by this, most specially if windings symmetry fails. Also the tube will suffer. For this reason, the first capacitor (C1) should never be larger than stated in the data sheet. The mechanical transformer hum, and also tube current peaks are greatly reduced by smaller capacitor values, and use higher choke values instead. Although higher capacitor values are at lower cost, using lower capacitors and higher chokes values instead, is always more satisfactory in the end. The result will be: Lower transformer hum, less electrical field radiation into the pre-amp, and more lifetime from the rectifier tube. This is why we recommend using largest chokes. From Lundahl, high value chokes are available at the same price as HiFi capacitors, like from a Mundorf or Black Gate. So we have to go back to the roots, and use high quality, large value chokes, like in the old days of radio design. For best ripple suppression, increase the choke to any value you need, or even use a C-L-C-L-C circuit, as also advised in the historical RCA data sheet.
Note 2) Higher capacitor values up to 20uF can be used, if you work at lower voltage and lower current than maximum. This will be the case for instance with smaller amplifiers, such as using the 45 tube.
Note 3) As a rule of thumb, high voltage power supplies are best built with large size chokes, especially at high output current, whereas low voltage power supplies can be built more easily with large capacitors.
Note 4) Winding symmetry is needed with HV transformers to prevent hum. A HV winding with center tap, requires FOUR separated HV windings inside the transformer, which are arranged for the end user as TWO windings which are in series. It is remarkable to see that this is widely unknown today by many transformer manufacturers. Also this is more expensive. So often, they build tube rectifier windings only from two internal windings, and not FOUR windings as needed for tube rectifiers. However we have a tube data sheet here, no transformer construction manual, so we can not explain this in more detail.