This has been covered under 'ground disconnect network', a search will help. Google has some info but the forum also has some good threads covering it, look for one started by AndrewT. You need a low-impedance path from signal ground to chassis ground (the thermistor basically does this, but it can also be done with a circuit using a bridge rectifier and a few passives for third-world cheapskates like me). The reason is that all exposed metal parts must be at chassis potential, and therefore the amplifier ground, which presents itself at the RCA inputs and binding posts, must be at earth potential.
As for grounding of the amplifier itself, the way I do it is have a star ground where all the signals return to, and then connect this to the input of the disconnect network. This ensures one-point ground. You can do without, but it tends to be noisier. In your case I would simply run a stiff wire from chassis to chassis. Disconnect network is not needed in the power supply unless your umbilical has any exposed metal parts (touchable by human) that are insulated from chassis.
As for grounding of the amplifier itself, the way I do it is have a star ground where all the signals return to, and then connect this to the input of the disconnect network. This ensures one-point ground. You can do without, but it tends to be noisier. In your case I would simply run a stiff wire from chassis to chassis. Disconnect network is not needed in the power supply unless your umbilical has any exposed metal parts (touchable by human) that are insulated from chassis.
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I checked and double checked all wiring. Everything is wired according to this build guide: http://www.diyaudio.com/media/build-guides/diyaudio-f5-build-guide.pdf
All voltages are OK. No DC at the speaker terminals. The transformer is humming very soft when both channels are connected. I tried switching off serveral devices that could possible couse DC over the mains power lines, but this had no effect. I've read that torroidal transformers protest quite loud when they are faced with DC on the line. For that reason I do also think that it has to do with the transformer itself, instead of DC on the line. Is there a way to measure DC on the line?
I've ordered a audio grade 400VA transformer from Torroidy and will replace the 300VA for the 400VA transformer. Hope this helps.
Note that I have not connected it to my pre-amp and speakers yet. I will try this soon.
All voltages are OK. No DC at the speaker terminals. The transformer is humming very soft when both channels are connected. I tried switching off serveral devices that could possible couse DC over the mains power lines, but this had no effect. I've read that torroidal transformers protest quite loud when they are faced with DC on the line. For that reason I do also think that it has to do with the transformer itself, instead of DC on the line. Is there a way to measure DC on the line?
I've ordered a audio grade 400VA transformer from Torroidy and will replace the 300VA for the 400VA transformer. Hope this helps.
Note that I have not connected it to my pre-amp and speakers yet. I will try this soon.
Another F5 has risen
And yet another F5 has risen.
A small summary of the components I used:
I used a hifi2000 4U chassis, like most others I quess...
All 3W resistors are Panasonic's metal film types.
All other resistors are Welwyn RC55 series precision resistors (0.1%) except for the one used for the LED's. These are Dale CMF's for the LED connected to the amp boards and Vishay MRS25 R's for the power supply LED's.
Oh and there are more, Dale CMF's 1W for R1 and R2.
The Caps are 15000uF from CDE, 381LX series, selected for high ripple current and long life.
2SK170's are all bought matched from Amut (Ebay), just like the IRFP9240 and IRFP240's.
BC560's where also matched, but by no other than me.
Transformer is produced by Amplimo, 300VA, 2x18V and likes to hum very softly. 🙁
As I mentioned the transformer will be replaced by a 400VA tranny from toroidy soon, but other than that it's playing fine. For now it's still connected to my test speaker to be sure to not ruin my good speakers. I'll hook it up to my good system tomorrow 🙂 Can't wait!
And yet another F5 has risen.
A small summary of the components I used:
I used a hifi2000 4U chassis, like most others I quess...
All 3W resistors are Panasonic's metal film types.
All other resistors are Welwyn RC55 series precision resistors (0.1%) except for the one used for the LED's. These are Dale CMF's for the LED connected to the amp boards and Vishay MRS25 R's for the power supply LED's.
Oh and there are more, Dale CMF's 1W for R1 and R2.
The Caps are 15000uF from CDE, 381LX series, selected for high ripple current and long life.
2SK170's are all bought matched from Amut (Ebay), just like the IRFP9240 and IRFP240's.
BC560's where also matched, but by no other than me.
Transformer is produced by Amplimo, 300VA, 2x18V and likes to hum very softly. 🙁
As I mentioned the transformer will be replaced by a 400VA tranny from toroidy soon, but other than that it's playing fine. For now it's still connected to my test speaker to be sure to not ruin my good speakers. I'll hook it up to my good system tomorrow 🙂 Can't wait!
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Corpius,
Nice neat build. Sometimes torroidal transformers hum. Bigger ones seem to hum more in my experience.
Evan
Nice neat build. Sometimes torroidal transformers hum. Bigger ones seem to hum more in my experience.
Evan
I have found the same, I have used a 400VA and a 600VA from the same manufacturer and the 600VA does hum more than the 400VA. I think you will have to make peace with it. I have also noted that the transformer hums more during certain times of the day. Maybe it has to do with load changes (demand) from the power grid.
Thanks for the complements. All credits belong to Nelson Pass, cviller, JojoD818 and all other who helped making it possible to build such beauties.
2SK170's are all bought matched from alweit (Ebay), just like the IRFP9240 and IRFP240's.
I need to correct this.
2SK170's are all bought matched from alweit (Ebay), just like the IRFP9240 and IRFP240's.
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is this hum with the same load? if so, give the manufacturer a call or mail.
a 600VA loaded with 500W will give you more hum then a 400VA loaded with 100W.
I can't say it is exactly the same load. The 600W was on a 25W JLH class A and the 400W is on a Nelson Pass F5 class A.
I recently built an F5, and the a cheap non-contact thermometer was invaluable in bringing up and monitoring the amp. I saw this ad today for the one I purchased two months ago. At US$16, with free shipping, a bargain. No sure if it is available outside the US.
Rakuten.com - Etekcity® ETC8380 Temperature Non-Contact Infrared Thermometer Gun w/ Laser Sight
Rakuten.com - Etekcity® ETC8380 Temperature Non-Contact Infrared Thermometer Gun w/ Laser Sight
I've wanted to get one of those for amps and other uses. Was looking at a Fluke I wondered how well the cheap ones perform. They're on ebay too.
I cannot vouch for the accuracy level, but it was fine for my build. I would measure the temperature of a black pad on the floor of my workshop (ambient temperature of the room), then measure the temperature of the black heatsink on the diy 4U Chassis. Monitored once each 10 minutes for an hour while adjusting bias. Goal was to keep the difference in ambient temperature below 25C. Leveled out at a difference of 23C with final bias adjustments. Perfect!
I have also done some measurement using an infrared thermometer. These are invaluable tools when it comes to monitoring the temperature of components and heatsinks. My heatsink temperature rises to 45C at 1.3A bias current. The room temperature is about 20C, so it's right on spec. The MOSFETS are measuring 62 to 65C. Not to hot imo.
I've been listening for two evenings in a row now to my newly build F5 (+CDPro + Rega DAC & Salas Hot Rod DCB1) and I must confess that it's a truly astonishing amplifier. The amount of control has blown me away. Especially in the low and mid regions. I also own a pair of Hypex Ncore amplifiers. These do also have lots of control, but the F5 simply has more. I tried to keep an open mind when I started listening, but I must confess that I had the feeling that it would not outperform the Ncore's, but it does. Not by much though.
The first two hours I was not convinced at all, but after it was playing for several hours it started to open up and really started showing what it's apparently capable of. I'm very pleased with it. The only downside is it's immense size imo, but I can live with that happily 🙂
The first two hours I was not convinced at all, but after it was playing for several hours it started to open up and really started showing what it's apparently capable of. I'm very pleased with it. The only downside is it's immense size imo, but I can live with that happily 🙂
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I have just a bit of listening time on my newly built F5. I agree, it sounds very good. I am limited by my speakers at this point, just an old pair of JBLs and a home-brew pair of Ariels. Hope to hook it up to a pair of Vandersteens 2Ci this weekend.
All and all, a great project. Invaluable help on these boards, and excellent products from diy store made it all possible.
All and all, a great project. Invaluable help on these boards, and excellent products from diy store made it all possible.
I have a pair of Focal 816W (special edition) speakers. I have these for several years now, but I'm still very pleased with them. They still keep amazing me on regular basis. I can recommend Focal speakers in general..., but that's just a matter of taste.
Nice build Corpius!
I hope you mean the 2SK170 and 2SJ74 are matched ? I hhought alweit didn't sell any J74's....
Walter
If the transformer 'humm' is a problem, it's a simple matter to make up a 'dc trap' and add it to the active line - Rod Elliot has a rather good description and explanation on how it works on his 'esp' website - couldn't be simpler!
I did mean the complementary pairs indeed. Alweit did sell these last August, but it seems like he's out of stock for now.