I am gathering the parts to build a pair of monoblock f5 amps. I have 2 chassis on the way and also 2 sets of f5turbo boards from the store. One issue with the F5tv3 is that I was looking to have balanced inputs on these amps. So the alternatives are to build a balanced F5(H or X ?) or get Jensen input transformers so I can use balanced inputs on a F5TV3 or to just use SE inputs.
I am leaning towards the simplicity of the V3 and the well documented path to getting good results. With the X the path forward is less defined and after reading the EUVL threads I wonder if all the extra work and dealing with offset and other issues is worth the effort.
So I am looking for some perspective from anyone who has built and or listened to both versions or used an input transformer such as Jensen or Lundahl etc. Is the X version worth it?
I am looking to get 80-100w at 8 ohms and don't need all of that to be class A. I'm thinking F5V3 with 42volt supplies and .5a bias/fet for 2 amps total bias, about 21w dissipation/fet and about 60w classA/ch.
When you go X those supply and bias numbers change but I would be aiming for similar output. Since it's time to order power transformers, I need to commit one way or the other soon.
I am leaning towards the simplicity of the V3 and the well documented path to getting good results. With the X the path forward is less defined and after reading the EUVL threads I wonder if all the extra work and dealing with offset and other issues is worth the effort.
So I am looking for some perspective from anyone who has built and or listened to both versions or used an input transformer such as Jensen or Lundahl etc. Is the X version worth it?
I am looking to get 80-100w at 8 ohms and don't need all of that to be class A. I'm thinking F5V3 with 42volt supplies and .5a bias/fet for 2 amps total bias, about 21w dissipation/fet and about 60w classA/ch.
When you go X those supply and bias numbers change but I would be aiming for similar output. Since it's time to order power transformers, I need to commit one way or the other soon.
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I don't have any of F5 nor F5x.
However I definitely would like to build in the distant future an EUVL kind of F5x.
You know me, I'm in a constant searching for trouble.
However I definitely would like to build in the distant future an EUVL kind of F5x.
You know me, I'm in a constant searching for trouble.
Thank You for the suggestion. I looked at F4 but having no voltage gain doesn't really fit with my needs. I have settled on F5T or F5X.
I'm using balanced F4 driven by balanced BA3 front end with satisfaction.
Especially because of generated heat, because cold outside! 🙂
Did you think about Aleph-JX?
Especially because of generated heat, because cold outside! 🙂
Did you think about Aleph-JX?
I just finished an Aleph J recently. I want to try Push Pull class A to get more power while keeping the heat generated somewhat reasonable. I did look at Aleph X but it gets pretty big and hot when trying to get 100w output.
I've never had the opportunity to see let alone hear an F5X 🙁
However I did build an F5TV3 with jensen balancing transformers for balanced inputs.
I can say that it sounds great, compared to some big commercial amps.
Don't know if that is what you want to hear though, as I have no experience with an F5X.
However I did build an F5TV3 with jensen balancing transformers for balanced inputs.
I can say that it sounds great, compared to some big commercial amps.
Don't know if that is what you want to hear though, as I have no experience with an F5X.
Thank you for your input. The Jensen have a good reputation and aren't too expensive. Was that your 4 box monoblock V3 build that was documented on Canuckaudiomart?
Verrry Nice!! I am seriously considering putting the PSs in their own boxes and making them part of stands for the monoblocks. I am not going for as much class A power as you designed for but getting the transformer rectifier and chokes (I'm going CLC filtering) and their heat out of the main box seems like a good idea to me.
Just wondering if you had any grounding related hum issues due to having monoblocks. Do you run everything on the same circuit?
Just wondering if you had any grounding related hum issues due to having monoblocks. Do you run everything on the same circuit?
Since you are shooting for 80 - 100 wpc you can get away with a single case per channel or even two channels in 1 case. (albiet a big heavy case) There have been quite a few people here that are able to get away with doing that and not have too much issue with heat.
If you want to go higher than 100wpc ie 130 and above, monoblocks or even 4 separate boxes is recommended. The PSU portion of such an amp takes up a lot of space, and the heat dissipation at idle with this kind of power on tap is enormous. This is of course based on regular convection cooling. You can of course go forced air or even water cooling and that can compact your size.
As far as hum, I don't get any. Its all about how you design your star ground circuit. When building multiple cases and off board power supplies, you need to plan how you ground everything as well as how power common is routed back to earth.
The other important part of designing higher power amps, is how much capacitance and how big your trafo is going to be. There will be a point where a simple soft start circuit will NOT be enough turn on your amp. 🙂
If you want to go higher than 100wpc ie 130 and above, monoblocks or even 4 separate boxes is recommended. The PSU portion of such an amp takes up a lot of space, and the heat dissipation at idle with this kind of power on tap is enormous. This is of course based on regular convection cooling. You can of course go forced air or even water cooling and that can compact your size.
As far as hum, I don't get any. Its all about how you design your star ground circuit. When building multiple cases and off board power supplies, you need to plan how you ground everything as well as how power common is routed back to earth.
The other important part of designing higher power amps, is how much capacitance and how big your trafo is going to be. There will be a point where a simple soft start circuit will NOT be enough turn on your amp. 🙂
I am going monoblocks for sure. If I go clc supply I will pretty much have to go with power supply boxes. I have some large ei chokes that are .12ohms and rated at 12.5 amps. The ac ripple on the DCsupply after a clc with these chokes is only a couple of mv. My Aleph J is dead quiet. The power supply is in one side of a large enclosure built by welding 2 narrow enclosures together. The amp circuitry is in the other side with fan cooled heat sinks. It's big and heavy though. Having 4 boxes will make each one easier to move. It will also keep the power Supply generated heat out of the amplifier box, making the heatsinks job easier. You can see some pics of this setup here.
http://www.diyaudio.com/forums/pass-labs/299178-another-aleph-j-fan-cooled-lc-filtered-supply.html
http://www.diyaudio.com/forums/pass-labs/299178-another-aleph-j-fan-cooled-lc-filtered-supply.html
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