DIY Audio Projects Forum
http://diyaudioprojects.com/Forum/

300B SET Design Project
http://diyaudioprojects.com/Forum/viewtopic.php?f=9&t=2699
Page 51 of 53

Author:  Woodo [ 24 Jul 2019, 04:43 ]
Post subject:  Re: 300B SET Design Project

not sure if the issue is temperature related? In the heater circuit after the bridge rectifier, i would have expected more than 6.1v rectified ac ie 6v * root 2 less voltage drop but that’s all I could muster. Hammond did suggest going to a 7v or even 8v transformer, but the 6.3v @2.5 amp has worked out ok i think and that is what the thermal design (heatsinks) is based on. I think I will go for that unless there are any reservations I should consider.

Author:  ILoveHiFi [ 24 Jul 2019, 21:35 ]
Post subject:  Re: 300B SET Design Project

7-8v Is deffintaley what you want, you need extra voltage head room so it can regulate properly
But of course comes at the expensive of increaced heat in the regulator

Author:  ILoveHiFi [ 24 Jul 2019, 22:27 ]
Post subject:  Re: 300B SET Design Project

Temeprature only reduces the output voltage at regulator input.
As long as you have enough voltage then is not a concern

Author:  Woodo [ 31 Jul 2019, 20:22 ]
Post subject:  Re: 300B SET Design Project

Thought I would post the circuit as currently stands for my build of this great sounding amp and prepare to move on to next project albeit slowly which I hope will be simpler and cheaper on vacuum tubes at least. Some differences to the circuit on page 33 are noted in the schematic. Have to order a new filament transformer that will reach 5v quietly. May try going back to the capacitors in the original circuit after the transformer arrives and put into the box . Thanks for all the input everyone. :up: If mistakes are spotted, happy to receive input.

Author:  ILoveHiFi [ 31 Jul 2019, 22:16 ]
Post subject:  Re: 300B SET Design Project

For the powersuplly, add a 0.1uF in parallel with the caps in all the filtered rails.
This will provide a low impedance path for HF and improve the sound quality
large caps have high inductance, dosen't work at HF

Author:  Woodo [ 01 Aug 2019, 04:02 ]
Post subject:  Re: 300B SET Design Project

Thanks mate. Will go to see my friendly Jaycar shop again. The staff will probably suggest I make a list, the number of times I have been in there lately.

Author:  ILoveHiFi [ 02 Aug 2019, 04:56 ]
Post subject:  Re: 300B SET Design Project

If you look at rs components you can get metalised polypropene hv caps for cheap.
Its unlikley jcar will have the voltage ratings your currently at I think

RS components does free shipping even if your buying $1 of components.

Author:  Woodo [ 08 Aug 2019, 01:49 ]
Post subject:  Re: 300B SET Design Project

Would there be any issues using the following filament transformer to supply the 5v regs?
https://au.rs-online.com/mobile/p/toroi ... s/6718937/
The price is good compared to the hammond 266L12 at about $55aud. No deliver charge either for the Rs components. Comments welcome. Thanks.

Author:  Chris65 [ 11 Aug 2019, 19:31 ]
Post subject:  Re: 300B SET Design Project

I've used Triad Magnetics transformers in similar applications, much cheaper than the equivalent Hammonds.
Mouser has F-344X 12.6V@2A A$22 and F-326X 12.6V@2.5A A$28.

Author:  Woodo [ 12 Aug 2019, 01:36 ]
Post subject:  Re: 300B SET Design Project

Chris65 wrote:
I've used Triad Magnetics transformers in similar applications, much cheaper than the equivalent Hammonds.
Mouser has F-344X 12.6V@2A A$22 and F-326X 12.6V@2.5A A$28.


Thanks for info Chris. Will check it out.

Page 51 of 53 All times are UTC - 6 hours [ DST ]
Powered by phpBB® Forum Software © phpBB Group
http://www.phpbb.com/