I had an audible hum coming from a very nice looking toroidal transformer in a GT-102 from Akitika. Couple of interesting things you can try.
Plug it in somewhere else in your house. Hopefully something on a different breaker. Put a lamp in a different outlet in the house. Turn off breaker making sure amp goes off, and lamp is still ON = different breaker. As you’re troubleshooting a hum from amp only, you’ll only have to move the amp, not your whole setup.
Bring amp to neighbors house and plug in there. See if transformer hum changes. Try one more neighbor, just for giggles.
Dan at Akitika was terrific in helping troubleshoot and eventually solve my problem. He dealings and sells what he calls an”dc scraper kit,” $25.
Akitika Store
DC Scraper Kit for the GT-102 Nullifies the Effect of Asymmetric Power - YouTube
I did a bit of googling, and I can’t figure how to measure for “DC noise” on your AC wall plug
Plug it in somewhere else in your house. Hopefully something on a different breaker. Put a lamp in a different outlet in the house. Turn off breaker making sure amp goes off, and lamp is still ON = different breaker. As you’re troubleshooting a hum from amp only, you’ll only have to move the amp, not your whole setup.
Bring amp to neighbors house and plug in there. See if transformer hum changes. Try one more neighbor, just for giggles.
Dan at Akitika was terrific in helping troubleshoot and eventually solve my problem. He dealings and sells what he calls an”dc scraper kit,” $25.
Akitika Store
DC Scraper Kit for the GT-102 Nullifies the Effect of Asymmetric Power - YouTube
I did a bit of googling, and I can’t figure how to measure for “DC noise” on your AC wall plug
lazy, greedy boy question:
what rank do the K170/J74 need to be, in order to be usable for the F5?
what rank do the K170/J74 need to be, in order to be usable for the F5?
Hi,
I'm planning to build an F5 turbo v2 as a project to do with my kid before they leave the nest off to college. I have a background in software engineering, mechanical engineering, and a smattering of electrical engineering (I wrote code for FPGA design software and have done various home electronics projects with my kid). I'm not a complete electronics noob, but this will be the most complex project I've done to date.
I have been reading Nelson Pass's articles, reading through the schematics, reading through build guides, as well as skipping through this thread (it's a lot of posts!). While there is a wealth of information, I still have some questions.
I've started sourcing parts, but have questions about which specific toroidal transformer (or transformers) to get. From the NP F5 turbo article:
"A stereo F-5T v2 requires a bipolar power supply of (+/- 32V). This will require an 24V+24V (or 48V Center Tapped) transformer from 600-800VA, and PSU capacitance of 80,000uF per rail or more. "
I've seen suggestions to buy a transformer from AnTek, but I can't tell whether they are center tapped or not. Here's the one I am considering:AN-8448 - 800VA 48V Transformer - AnTek Products Corp
Thoughts?
I watched a very recent YouTube series ("Robert builds an F5 turbo v2") where he used two separate 400VA (I think) transformers and referred to the variant at F5 turbo v2.5. I am curious whether there is more information on this build.
Any guidance here would be appreciated 🙂
LP
I'm planning to build an F5 turbo v2 as a project to do with my kid before they leave the nest off to college. I have a background in software engineering, mechanical engineering, and a smattering of electrical engineering (I wrote code for FPGA design software and have done various home electronics projects with my kid). I'm not a complete electronics noob, but this will be the most complex project I've done to date.
I have been reading Nelson Pass's articles, reading through the schematics, reading through build guides, as well as skipping through this thread (it's a lot of posts!). While there is a wealth of information, I still have some questions.
I've started sourcing parts, but have questions about which specific toroidal transformer (or transformers) to get. From the NP F5 turbo article:
"A stereo F-5T v2 requires a bipolar power supply of (+/- 32V). This will require an 24V+24V (or 48V Center Tapped) transformer from 600-800VA, and PSU capacitance of 80,000uF per rail or more. "
I've seen suggestions to buy a transformer from AnTek, but I can't tell whether they are center tapped or not. Here's the one I am considering:AN-8448 - 800VA 48V Transformer - AnTek Products Corp
Thoughts?
I watched a very recent YouTube series ("Robert builds an F5 turbo v2") where he used two separate 400VA (I think) transformers and referred to the variant at F5 turbo v2.5. I am curious whether there is more information on this build.
Any guidance here would be appreciated 🙂
LP
The Antek8448 does have a center tap when you tie the “middle” leads together. There is a Pass article out there that talks about the power supply most of these amps require. They are all similar in that respect.
Im not familiar with the v2.5 build but what you are describing is dual mono. probably adds unnecessary complexity for a first build.
Thank you for the quick response!
Ah, that makes sense about the AN-8448 and the middle leads. And yes, I'll avoid dual mono and look more at the F5 and Aleph. We've done a fair number of PCB kits over the years for robotics and random home automation (my kid, now college age, is quite good at stuffing/soldering a board cleanly) and the F5 turbo looked doable but we can dial back. It appears the diyaudio psu kit, if overbuilt, can be used on the F5 or F5 turbo with a swap of the toroid assuming it's in a 5u case. So maybe start with an F5 and reuse the case and psu if we still want to do a F5 turbo later.
So, assuming an F5 build...
1. Using the diyaudio PSU, we can replace the rectifiers with these, correct? Vishay GBPC2501-E4/51 or a Rectron MP254
2. Antek doesn't seem to sell 36V 300VA or 400VA toroids - they have 35V and 38V. Is that a problem to be a tad over or under, or is there a preference?
Ah, that makes sense about the AN-8448 and the middle leads. And yes, I'll avoid dual mono and look more at the F5 and Aleph. We've done a fair number of PCB kits over the years for robotics and random home automation (my kid, now college age, is quite good at stuffing/soldering a board cleanly) and the F5 turbo looked doable but we can dial back. It appears the diyaudio psu kit, if overbuilt, can be used on the F5 or F5 turbo with a swap of the toroid assuming it's in a 5u case. So maybe start with an F5 and reuse the case and psu if we still want to do a F5 turbo later.
So, assuming an F5 build...
1. Using the diyaudio PSU, we can replace the rectifiers with these, correct? Vishay GBPC2501-E4/51 or a Rectron MP254
2. Antek doesn't seem to sell 36V 300VA or 400VA toroids - they have 35V and 38V. Is that a problem to be a tad over or under, or is there a preference?
Last edited:
1. Yes, these bridge rectifiers work very well.
2. Better to be slightly under than over unless you make provisions to handle higher voltages, such as higher rated capacitors, cascoding input JFETs, etc. 35V will work well if the F5 calls for 36V.
2. Better to be slightly under than over unless you make provisions to handle higher voltages, such as higher rated capacitors, cascoding input JFETs, etc. 35V will work well if the F5 calls for 36V.
Silentpanda,
The two transformers you linked to have voltages too high for an F5. You
might want to look at these instead:
AS-4218 - 400VA 18V Transformer - AnTek Products Corp
AS-4220 - 400VA 20V Transformer - AnTek Products Corp
The two transformers you linked to have voltages too high for an F5. You
might want to look at these instead:
AS-4218 - 400VA 18V Transformer - AnTek Products Corp
AS-4220 - 400VA 20V Transformer - AnTek Products Corp
^^ This. You need a 18V+18V or 20V+20V transformer for F5. 300VA is more than enough. Get the “AS-“ series as they are shielded.
Can i use CL50 thermistor instead of CL60 for ground loop isolation between the chassis and the circuit ground?
Sorry, after closer inspection i have two CL40. It this one ok too? Or i can put two in series?
Thank you in advance.
Thank you in advance.
Apparently my picture post has to be vetted before posting. Please feel free to ask for other images that might prove helpful.
Pretty sure not my issue but PS had 2 CL60s instead of a CL 30 for power lead and 60 for ground. I see TP 1 and 2 I know which pts control those points the other end of the test point is ground?
Hi,
Yes, that is a "hummer", I have several (8) of these in other constructions and they hum a lot - but mostly because they are extra sensitive to DC. Lately I have had so much DC on the net that even one standard bridge will not remove it all, and they hum again.
I had a small one in my CD' player where the problem was solved with softer damping, e.g. mechanical issue.
I have had less hummmmmm with Toroidy and Sedlbauer's "premium" series. - And even more with Talema 1Kva
Hope that helps