Happy New Year!
I have been enjoying the music for nearly a month now.
I have added 1K to the 2K@ and biasing is much easier now.
With 0.1 to 0.5mV offset after warming up, i have 0.6V on channel one but 0.7V on the channel two. It works alright.
The only issue i have now is a little humming on channel one. I found a cold solder and the input cable too close to the thermistors but still there is a faint hum. Channel two was dead quiet. Should I use some specific cables on the input to kill the hum?
I have been enjoying the music for nearly a month now.
I have added 1K to the 2K@ and biasing is much easier now.
With 0.1 to 0.5mV offset after warming up, i have 0.6V on channel one but 0.7V on the channel two. It works alright.
The only issue i have now is a little humming on channel one. I found a cold solder and the input cable too close to the thermistors but still there is a faint hum. Channel two was dead quiet. Should I use some specific cables on the input to kill the hum?
I burnt my FETS
Gents ,
I bought the kits from ebay paid 49 USD. Assembled all and try to bias with original values. Of U burnt both FETs on one side. Second on was working but couldnt get .59V on R11 and 12. but work checked the off set 400mv try to bias. Ops burnt that 2 FETs too.
oh How unlucky probably this kit came with cheap FETS. I order 2 sets from element 14 /farnell.
Ah my rail voltage is 26.2V is it too much?
Can u pls give more precautions and advice .
Many thanks
Charly
Gents ,
I bought the kits from ebay paid 49 USD. Assembled all and try to bias with original values. Of U burnt both FETs on one side. Second on was working but couldnt get .59V on R11 and 12. but work checked the off set 400mv try to bias. Ops burnt that 2 FETs too.
oh How unlucky probably this kit came with cheap FETS. I order 2 sets from element 14 /farnell.
Ah my rail voltage is 26.2V is it too much?
Can u pls give more precautions and advice .
Many thanks
Charly
Hi Gents after succesfully complete the first F5 I would like to share bit of my experience. First dont but tubeshunters crap kit. 2 as per the information from one member use 3.3K resistors than 2.2K. Good point use 2 multimeters one to check the voltage across 0.47Ohms other one Dc offset at output. so its easy to bias the amplifier buy keep monitoring the voltage across 0.47. Other wise chance to burn the FETs. I used fair child. now all good.
Yes I tried it and got .600 and .614 to get 0 offset with 23.8V rails.
thanks for pointing that out.
Tried a listen on one channel (only one is completed) but I must admit that there was a distinct lack of gain. Hooked to the dcb1 and volume was set to max. Read that this is a distinct property of the F5. I'll try to read up on getting more gain (ie: loudness)
thanks again.
thanks for pointing that out.
Tried a listen on one channel (only one is completed) but I must admit that there was a distinct lack of gain. Hooked to the dcb1 and volume was set to max. Read that this is a distinct property of the F5. I'll try to read up on getting more gain (ie: loudness)
thanks again.
Great to hear that it biases correctly!
Let it get nice and hot and check the bias again. (This is a normal procedure. Thermal stability when it's hot is important in this design. Make sure you have the chassis lid on when it 'cooks')
The F5 requires an input signal of about 4v to get max output. If you are using a CD, DVD, iPod for your source you will only have 2v maximum at the input and in turn only be using about 10W of your amp.
For some people this isn't a problem, usually because they have speakers with decent efficiency, or don't listen particularly loud, have a small room, etc... Or they have a preamp with gain.
If you are stuck with no good preamp options, (and/or don't want to build something new) you can always change the value of the feedback resistors (R5, R6, R7, R8) -- these are the group of four 100ohm 3watt resistors in the center of the amp pcb. Replace them with 220ohm 3watt resistors and your input sensitivity will go up, giving you more output with the 2v sources that you have.
Oh, one last thing... Pictures please!!
Let it get nice and hot and check the bias again. (This is a normal procedure. Thermal stability when it's hot is important in this design. Make sure you have the chassis lid on when it 'cooks')
The F5 requires an input signal of about 4v to get max output. If you are using a CD, DVD, iPod for your source you will only have 2v maximum at the input and in turn only be using about 10W of your amp.
For some people this isn't a problem, usually because they have speakers with decent efficiency, or don't listen particularly loud, have a small room, etc... Or they have a preamp with gain.
If you are stuck with no good preamp options, (and/or don't want to build something new) you can always change the value of the feedback resistors (R5, R6, R7, R8) -- these are the group of four 100ohm 3watt resistors in the center of the amp pcb. Replace them with 220ohm 3watt resistors and your input sensitivity will go up, giving you more output with the 2v sources that you have.
Oh, one last thing... Pictures please!!
Last edited:
That's correct, I'm driving the F5 through a DCB1 from a tda1545a dac. Ultimately will be sourced from a TP B3. My understanding is that these dacs output 2V.
I will consider the mod but for now, the amp is making my speakers sound very detailed. much more than the GC although the GC sounds pretty good too. The Bass is much more precise with the F5.
Pictures will come but for now, the amp is on my work bench. Lots of pictures already out there that looks like my setup. Will be working on the case next.
thanks again for your help
I will consider the mod but for now, the amp is making my speakers sound very detailed. much more than the GC although the GC sounds pretty good too. The Bass is much more precise with the F5.
Pictures will come but for now, the amp is on my work bench. Lots of pictures already out there that looks like my setup. Will be working on the case next.
thanks again for your help
- Status
- This old topic is closed. If you want to reopen this topic, contact a moderator using the "Report Post" button.