What is the maximum peak voltage that can appear on the speaker terminal?
Let's assume Vsupply is 25Vdc.
Let's assume voltage drop through the cables and devices from PSU to speaker terminal is 2V.
That leaves 23Vpk at the output.
You have 50r (100r//100r) + 10r determining the peak current through the feedback circuit.
Maximum current is Vpk/Rtotal = 23/60 = 383mA.
Power dissipated in the three resistors is
for 10r
10 * 0.383^2 = 1.47Wpk.
for 100r
100 * (0.383/2)^2 = 3.67Wpk.
These are instantaneous worst case dissipations for a +-25Vdc supply.
The continuous dissipation for all the feedback resistors will be less than a quarter of the peak figure. Each feedback reaches peak current when the other is at near zero current.
These figures are for flat out on a sinewave test signal that just reaches output clipping.
On real very loud music the peak figures will be similar, the continuous dissipations will be much lower.
Let's assume Vsupply is 25Vdc.
Let's assume voltage drop through the cables and devices from PSU to speaker terminal is 2V.
That leaves 23Vpk at the output.
You have 50r (100r//100r) + 10r determining the peak current through the feedback circuit.
Maximum current is Vpk/Rtotal = 23/60 = 383mA.
Power dissipated in the three resistors is
for 10r
10 * 0.383^2 = 1.47Wpk.
for 100r
100 * (0.383/2)^2 = 3.67Wpk.
These are instantaneous worst case dissipations for a +-25Vdc supply.
The continuous dissipation for all the feedback resistors will be less than a quarter of the peak figure. Each feedback reaches peak current when the other is at near zero current.
These figures are for flat out on a sinewave test signal that just reaches output clipping.
On real very loud music the peak figures will be similar, the continuous dissipations will be much lower.
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Jack, what's up with your site? went to look for F-5 components, nothing shows?
Russellc
Jack, what's up with your site? went to look for F-5 components, nothing shows?
Russellc
We had floods here last month and I had let some stuff get wet -- so I've been repairing equipment, plus it just takes a lot of time to assemble the kits and get them out so I am taking a breather for a while. I still have plenty of JFETs but IRF MOSFETs (thanks Vishay) are on 32 week backorder.
While you are quick to call me out as being wrong I simply went by the BOM's found in this and other F5 threads by PD and went by what I observed as the CMF50 resistors as posted by PD himslef HERE
And HERE
The only mention of larger 3W resistors I saw when collecting parts were R5-R8 and R11 and R12.
Those specs sounds perfect for the project.
And yes, I still have boards available. If you have more questions about my boards, please ask them in this thread:
http://www.diyaudio.com/forums/group-buys/134554-gb-f5-pcb-new-post.html
or on my blog (see my signature).
Those specs sounds perfect for the project.
Yep, the long finning makes the difference, and probably the best you can get
I was so enthusiastic I bought 1 full meter ..... dammed expencive, and not too clever ..... I can barely lift it
but base is 100% smooth, top quality hum in one F5 channel
My diy f5 has (recently and instantaneously as far as I can tell) developed a strong low hum in one channel. The other channel plays music fine. It occurs as soon as the amp is powered up, with or without rca's hooked up. I've checked the binding posts and rca inputs and I don't see anything touching the case where it shouldn't. Ideas for what else to check?
Thanks!
My diy f5 has (recently and instantaneously as far as I can tell) developed a strong low hum in one channel. The other channel plays music fine. It occurs as soon as the amp is powered up, with or without rca's hooked up. I've checked the binding posts and rca inputs and I don't see anything touching the case where it shouldn't. Ideas for what else to check?
Thanks!
F5 + jfetboz =
WOW...just fired up my JFETBOZ hooked up to the F5 and I think this setup will stay for a while.
The JFETBOZ is running off a Dell laptop supply that runs about 19.5V. The PSU is a modified example of the BOZ. After the zeners and IRF610 I am running exacly 14V.
Dale CMF resistors
Dale 3W power resistors
Nichicon UKW and UPW electrolytics
Matched Toshiba 2SK170
ERSE audio coupling caps
Alps dual pot RK27
Thank you Nelson Pass and DIYAudio!
WOW...just fired up my JFETBOZ hooked up to the F5 and I think this setup will stay for a while.
The JFETBOZ is running off a Dell laptop supply that runs about 19.5V. The PSU is a modified example of the BOZ. After the zeners and IRF610 I am running exacly 14V.
Dale CMF resistors
Dale 3W power resistors
Nichicon UKW and UPW electrolytics
Matched Toshiba 2SK170
ERSE audio coupling caps
Alps dual pot RK27
Thank you Nelson Pass and DIYAudio!
Vantec Stealth fans are all I use. Quieter than a lot, dual ball bearings (as opposed to sleeve "bearings") and lifetime warranty. Never had one fail, and some of them have years of service. Currently I run them on 10.5V though, so slightly slower than rated. Also, the larger the fan, the quieter it is at the same airflow.
I still wouldn't use a fan in any amp I make, as my listening area is extremely quiet.
I still wouldn't use a fan in any amp I make, as my listening area is extremely quiet.
Yep, Vantec Stealth are great fans.
120mm fans slowed down are my favorites, lots of air pushed softly
Agreed, I too prefer heatsinks to fans in amps. Quiet is quiet.
Ron
Hi all, i have a few questions, there is low humming noise from my speaker when i put my ears next to the speaker drivers in the range of ~5cm, the story goes like this:
1. My F5 is running naked, there is no earth wire from my wall plug.
2. The humming noise only occur when i connecting a potential-meter across the signal to work as volume control.
3. I tried 100k and the humming noise is loud, and 10k (ALPS RK27) will reduce the noise dramatically but still exist between when my ears near to the speaker around 5cm.
4. I believe it's not a ground loop problem, because when i shorten the in and out leads at the potential-meter, the noise gone totally.
5. The problem Don't occur when i connect the naked F5 to a preamp without any potential-meter between the signal to preamp.
6. The potential-meter washer was tightly grounded to the signal's ground.
7. I tried to connecting different star-ground in many ways to avoid possible ground loop but it don't cure.
[-]
Thanks
CHONG
1. My F5 is running naked, there is no earth wire from my wall plug.
2. The humming noise only occur when i connecting a potential-meter across the signal to work as volume control.
3. I tried 100k and the humming noise is loud, and 10k (ALPS RK27) will reduce the noise dramatically but still exist between when my ears near to the speaker around 5cm.
4. I believe it's not a ground loop problem, because when i shorten the in and out leads at the potential-meter, the noise gone totally.
5. The problem Don't occur when i connect the naked F5 to a preamp without any potential-meter between the signal to preamp.
6. The potential-meter washer was tightly grounded to the signal's ground.
7. I tried to connecting different star-ground in many ways to avoid possible ground loop but it don't cure.
[-]
Thanks
CHONG
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Th F5 input impedance is 100k .
Using a 10k pot. reduces the hum but also the available signal.
The fact you have no hum without a pot. says the hum is either induced ino the pot by the transformer. (are they close together?)
...or you introduce a ground loop with your pot. wiring.
Could you show us your pot. wiring/laying out?
Using a 10k pot. reduces the hum but also the available signal.
The fact you have no hum without a pot. says the hum is either induced ino the pot by the transformer. (are they close together?)
...or you introduce a ground loop with your pot. wiring.
Could you show us your pot. wiring/laying out?
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