In Reply to: RE: hum is a non-issue. posted by Ralph on July 24, 2012 at 13:47:28:
IMHO it takes more effort (i.e. money) to make the OTL hum as low as in best conventional PP designs.
Several DIY people have privately written to me that they have not succeeded in making their DIY OTL as quiet as they wanted it to be, mainly because they had not planned in advance to build a quiet enough (i.e. more expensive) power supply.
When delivering several amperes of instantaneous current into the speaker load, the HV power supply of OTL amps is much more stressed than in conventional transformer coupled PP.
Hence you have to conservatively dimension the PS transformers in the 'above 500 VA' range even though the average audio power is only a few watts.
If I wanted to use my own OTL (non circlotron design) with very sensitive horns, I know that I would have to either modify the power supply or to reduce the sensitivity by increasing GFB above 8-10 dB.
We all know that you succeeded in making ultra quiet commercial OTL amps, but it is very very hard for me to say that they are affordable either.
DIY is by its very nature an affordable method to get the tube (and OTL) advantages.
I think that it would not be wise to say that OTL hum can be as low as in best conventional designs without adding that, in order to get that result, a more expensive power supply is necessary!
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Follow Ups
- RE: hum is a non-issue. - 6AS7_6SN7 02:26:19 07/25/12 (9)
- You don't need expensive power supplies - Ralph 08:17:25 07/25/12 (7)
- RE: You don't need expensive power supplies - 6AS7_6SN7 09:35:57 07/25/12 (6)
- Yes, I can see that in a totem pole, - Ralph 10:59:23 07/25/12 (5)
- RE: Yes, I can see that in a totem pole, - 6AS7_6SN7 23:41:55 07/25/12 (4)
- Did you forget about the EL509/PL509? - Ralph 09:58:04 07/26/12 (3)
- "Futterman legacy"? - Lew 10:42:26 07/27/12 (2)
- RE: "Futterman legacy"? - Ralph 14:33:07 07/27/12 (1)
- RE: "Futterman legacy"? - Lew 16:38:19 07/27/12 (0)
- RE: hum is a non-issue. - Lew 08:13:53 07/25/12 (0)