Ok Forgive me if it is a little simplistic but my electrical theory is pretty non existant 
I built the regular stereo F5 (with protection taken out) a year or so ago. Its biased a little higher, 0.75V for a bit more power.
The itch is now out for more power. After looking at the expense and massive weight it would be to build the Turbo version I'm concluding that building a second F5 may be a bit more cost effective.
Here is the idea.
Currently my pre-amp has balanced outputs. My thinking is that if I take my current stereo F5, and feed the +ve side of one balanced output channel to one channel and the -ve feed of that same balanced channel to the other channel I essentially would have a balanced mono F5. This should also mean that I would connect the one speaker to +ve and -ve side hot posts (red). This should also mean that it would essentially double the power of the F5 (25 -->50W) but will see the speaker at half the impedance.
Now all I have to do is build a second stereo F5 and I have two balanced monoblock F5's.
Does this make sense? Have I missed anything? Are there any downsides to this?
I built the regular stereo F5 (with protection taken out) a year or so ago. Its biased a little higher, 0.75V for a bit more power.
The itch is now out for more power. After looking at the expense and massive weight it would be to build the Turbo version I'm concluding that building a second F5 may be a bit more cost effective.
Here is the idea.
Currently my pre-amp has balanced outputs. My thinking is that if I take my current stereo F5, and feed the +ve side of one balanced output channel to one channel and the -ve feed of that same balanced channel to the other channel I essentially would have a balanced mono F5. This should also mean that I would connect the one speaker to +ve and -ve side hot posts (red). This should also mean that it would essentially double the power of the F5 (25 -->50W) but will see the speaker at half the impedance.
Now all I have to do is build a second stereo F5 and I have two balanced monoblock F5's.
Does this make sense? Have I missed anything? Are there any downsides to this?
You mean the 78 page thread? Yeah sort of... last year and then stopped....
But thats the thing I didn't want to start mucking around a built PCB and stacking components on top of each other and cascoding etc.
Thats why the "lazy approach" take something thats already built and the layout is tested and see if a simple wiring change will suffice.
and then stopped.... But thats the thing I didn't want to start mucking around a built PCB and stacking components on top of each other and cascoding etc.
Thats why the "lazy approach"
take something thats already built and the layout is tested and see if a simple wiring change will suffice.
Dazed2,
You may be able to modify your existing F5 to a F5 Turbo v1 without building another case...
From Article:
No need for cascoding or bridging. You will need to add extra mosfets and resistors attached to the output stage. Your just tapping off connections that are already in place.
You will need to include the thermistors, but not the limiter. A bigger transformer will be necessary, but if you build a new amp, you'll need a bigger transfo, if yuo don't have one on hand.
IMO, this is easier and faster than building a new case and all that goes with it.
Hope this helps,
Vince
You may be able to modify your existing F5 to a F5 Turbo v1 without building another case...
From Article:
No need for cascoding or bridging. You will need to add extra mosfets and resistors attached to the output stage. Your just tapping off connections that are already in place.
You will need to include the thermistors, but not the limiter. A bigger transformer will be necessary, but if you build a new amp, you'll need a bigger transfo, if yuo don't have one on hand.
IMO, this is easier and faster than building a new case and all that goes with it.
Hope this helps,
Vince
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Yes, bridged.
The problem with bridged is that you may run out of output device current, and the unit will move over to class AB... so again you may want to add (parallel) output devices.
increasing the B+ on the stock F5 was discussed extensively in the original thread, iirc. I think what was said is that increasing the B+ was problematic and maybe not a good idea because of reaching the voltage limit on the input Jfets (saturation) and also the current capability of the output devices vs. load impedance is reduced. (the max current remains the same, while the power requirement goes up as the voltage increases)
If the F5 bias is made higher, the output devices are more in class A, dissipating more current and therefore power. Lower bias means less into Class A, more into AB. So for a given load Z, the amp will leave class A and go to AB sooner... it's ok to do this, but it's no longer "pure class A" and technically there is a minor glitch at the point where it leaves Class A and goes into AB or more precisely Class B for a short period of time and then comes back to Class A (on each alternating polarity of a given cycle).
But bridging by using the balanced output of a preamp is perfectly ok, just keep in mind the issues. (if you had say a 16 ohm impedance speaker it is a non-issue).
_-_-bear
The problem with bridged is that you may run out of output device current, and the unit will move over to class AB... so again you may want to add (parallel) output devices.
increasing the B+ on the stock F5 was discussed extensively in the original thread, iirc. I think what was said is that increasing the B+ was problematic and maybe not a good idea because of reaching the voltage limit on the input Jfets (saturation) and also the current capability of the output devices vs. load impedance is reduced. (the max current remains the same, while the power requirement goes up as the voltage increases)
If the F5 bias is made higher, the output devices are more in class A, dissipating more current and therefore power. Lower bias means less into Class A, more into AB. So for a given load Z, the amp will leave class A and go to AB sooner... it's ok to do this, but it's no longer "pure class A" and technically there is a minor glitch at the point where it leaves Class A and goes into AB or more precisely Class B for a short period of time and then comes back to Class A (on each alternating polarity of a given cycle).
But bridging by using the balanced output of a preamp is perfectly ok, just keep in mind the issues. (if you had say a 16 ohm impedance speaker it is a non-issue).
_-_-bear
vdi - I thought about it but when I built the original F5 I bought two trafo's for the hell of it so I have one in use and the other one to use for another F5. going V1 turbo would mean getting more trafos.
bear - yes I read and re-read your meaning I think you are right.
Having said that, I went back to AndrewT's suggestion and looked up NYCone and JBL4435's balanced build and from my understanding I would have to lift R1 and R2 and cross them with the other board and I should be close....
I guess I may have to change R11 and R12 to 22R as well .
Since in my build I took out the protection circuit I think that would be it..?
Perhaps in this configuration it would be true balanced and it wouldn't see the speaker load as half impedance?
bear - yes I read and re-read your meaning I think you are right.
Having said that, I went back to AndrewT's suggestion and looked up NYCone and JBL4435's balanced build and from my understanding I would have to lift R1 and R2 and cross them with the other board and I should be close....
I guess I may have to change R11 and R12 to 22R as well .
Since in my build I took out the protection circuit I think that would be it..?
Perhaps in this configuration it would be true balanced and it wouldn't see the speaker load as half impedance?
bridged and balanced apply double the voltage to the speaker cf. a single version of the amplifier.
That doubled voltage necessarily requires a doubled current being fed to the speaker.
As far as the amplifier is concerned, it thinks and feels like each single half of the balanced/bridged amplifier is driving a load that is half the impedance of the actual load that is fitted between the outputs.
Each half of a balanced amplifier has to be designed to drive that half impedance load. Then one combines the two halves into an integrated pair of "balanced amplifiers". The balanced amplifier potentially offers much greater quality advantages over a pair of bridged amplifiers that started life as unbalanced.
If you don't believe this, then read the F5x more thoroughly. The supply voltage is substantially reduced. The bias current is substantially increased. These two changes were implemented specifically to allow the amplifier to drive the effectively halved load impedance.
The balanced version of the F5t achieves similar by increasing the output stage pairs cf. the original F5.
That doubled voltage necessarily requires a doubled current being fed to the speaker.
As far as the amplifier is concerned, it thinks and feels like each single half of the balanced/bridged amplifier is driving a load that is half the impedance of the actual load that is fitted between the outputs.
Each half of a balanced amplifier has to be designed to drive that half impedance load. Then one combines the two halves into an integrated pair of "balanced amplifiers". The balanced amplifier potentially offers much greater quality advantages over a pair of bridged amplifiers that started life as unbalanced.
If you don't believe this, then read the F5x more thoroughly. The supply voltage is substantially reduced. The bias current is substantially increased. These two changes were implemented specifically to allow the amplifier to drive the effectively halved load impedance.
The balanced version of the F5t achieves similar by increasing the output stage pairs cf. the original F5.
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the quality advantages may or may not translate into audible benefits, since the even order harmonics tend to cancel, and this is one of the "benefits" of the F5 (the even harmonics)...
I think this is one possibility...
Otoh, I always liked the early Jim Bongiorno SUMO amps, they were "bridged" amps internally. Maybe you could say balanced.
_-_-bear
I think this is one possibility...
Otoh, I always liked the early Jim Bongiorno SUMO amps, they were "bridged" amps internally. Maybe you could say balanced.
_-_-bear
Alright, so perhaps it is not as "simple" as I thought it may be.
Ok, so I tried the amp in its current form with a much higher sensitivity speaker (about 98db) and yes it is very good, and useable close to concert level volumes. I'm almost happy, if not for the fact that they cost about $7K to build
So having read NP's F5T write up, what would adding just the MUR3020W diode in parallel to the source resistor do in the regular F5? As long as I use anything other than the Toshiba MOSFET's (fairchilds, IRFP etc) this should allow peak currents to close to 20A. This should mean I would be better equipped to control big drivers?
This seems like a generally easy thing to do, in an existing setup.
Ok, so I tried the amp in its current form with a much higher sensitivity speaker (about 98db) and yes it is very good, and useable close to concert level volumes. I'm almost happy, if not for the fact that they cost about $7K to build
So having read NP's F5T write up, what would adding just the MUR3020W diode in parallel to the source resistor do in the regular F5? As long as I use anything other than the Toshiba MOSFET's (fairchilds, IRFP etc) this should allow peak currents to close to 20A. This should mean I would be better equipped to control big drivers?
This seems like a generally easy thing to do, in an existing setup.
Why not 6-7K?
Here is what they look like
http://www.diyaudio.com/forums/multi-way/80068-tad-th4001-clone-project-4.html
They were TAD clones
If someone can build and get the parts for less... I'm all ears!
PS I was wrong... I guess its about 95dB. But man did the combo sing!
Here is what they look like
http://www.diyaudio.com/forums/multi-way/80068-tad-th4001-clone-project-4.html
They were TAD clones
If someone can build and get the parts for less... I'm all ears!
PS I was wrong... I guess its about 95dB. But man did the combo sing!
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