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Hello from justinis
http://dcaudiodiy.com/phpBB3/viewtopic.php?f=6&t=663		 Page 1 of 2
Author:  justinis [ July 15th, 2016, 10:11 am ]
Post subject:  Hello from justinis
Hello, all! My name is Justin and I am an electrical engineer living in DC, working in Arlington. I love vintage and modern audio and visited the Capitol Audiofest 3 out of the last 4 years. This year I visited the DCAudioDIY room for the first time and found out about this forum. I'm so excited it exists and can't wait to jump in!

Past projects:
Restored Akai AP-207, Pioneer SA-6500, Marantz 1060, New Large Advent loudspeakers

Current project:
Building a 50W stereo power amp using a driver board for a Dynaco ST-70, tubes and transformers from a Heathkit AA-100

Future projects:
Marantz 2226B restoration

Current system:
Pioneer SA-6500, New Large Advent loudspeakers, Technics SL-QD33
Author:  FerdinandII [ July 15th, 2016, 10:47 am ]
Post subject:  Re: Hello from justinis
Welcome Justinis,

Those OPT transformers from the Heathkit AA-100 are excellent.
Which driver board are you using?
Author:  justinis [ July 15th, 2016, 11:16 am ]
Post subject:  Re: Hello from justinis
Thanks! The DIYtube one by Shannon Parks.
Author:  FerdinandII [ July 15th, 2016, 11:53 am ]
Post subject:  B+ Voltage too high
From another thread that disappeared......


++++++++++++++++++++++++++++++++++++++
Are you measuring the voltage with a load on the power supply? With no load, the voltage will rise quite a bit. Try a 10k power resistor, or something in that range, so that you are pulling 50mA or so from the PSU. You'll need a big one.... See if the voltage drops down to the specified 445-450 VDC.

Easy fixes are:

Drop a 5R4 rectifier in there.
or
Change it from capacitor-input to choke input.

Have you tried Duncan's PSU simulator? It's great for modeling the impact of component changes.
Author:  justinis [ July 15th, 2016, 1:33 pm ]
Post subject:  Re: Hello from justinis
Sorry, I deleted the thread cause I found an error in my calculations. Just put it back with new values: http://dcaudiodiy.com/phpBB3/viewtopic.php?f=4&t=665

Thanks for the tip! I do indeed have the powers supply loaded; the entire amp is built at this point.

The 5R4 is a good suggestion, thanks. I was trying to avoid it cause I thought the zeners would be cheaper/easier, but now that it's screwing up my neg supply that's probably not true anymore.

Don't understand the capacitor/choke vs choke input. Can you explain?

Thanks!
Author:  FerdinandII [ July 15th, 2016, 4:27 pm ]
Post subject:  Re: Hello from justinis
justinis wrote:
Sorry, I deleted the thread cause I found an error in my calculations. Just put it back with new values: http://dcaudiodiy.com/phpBB3/viewtopic.php?f=4&t=665

Don't understand the capacitor/choke vs choke input. Can you explain?
Thanks!


You put the choke first, directly downstream of the rectifier, then the filter caps.
It can be Just an "L-C" filter network, or "L-C-L", or "L-C-L-C" (big C at the end).

Image

N.B. For low-level amplifier circuits, the choke input minimizes any high frequency artifacts generated by the rectifier. This is critical for any PSU that uses solid state rectifiers.
Author:  brombo [ July 15th, 2016, 4:42 pm ]
Post subject:  Re: Hello from justinis
If you are running linux (probably for windows also) there are free circuit analysis (simulation) tools available. Tubes can be modeled as linear (small signal transconductance model) or non-linear (non-linear voltage controlled current sources). There are also digital design and simulation tools and pcb design tools available.
Author:  brombo [ July 15th, 2016, 4:45 pm ]
Post subject:  Re: Hello from justinis
Here is link to tube models in SPICE circuit simulation code -

http://www.normankoren.com/Audio/Tubemo ... ticle.html
Author:  FerdinandII [ July 15th, 2016, 4:51 pm ]
Post subject:  Re: Hello from justinis
Duncan's PSU Designer is the best, IMHO.....

http://www.duncanamps.com/psud2/download.html
Author:  brombo [ July 15th, 2016, 5:21 pm ]
Post subject:  Re: Hello from justinis
I was thinking more of simulating the entire amplifier.
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