Bloody great amp! It's got a veryl powerful sound. Thanks again, it was certainly worth finishing.
Speakers are 4 ohm, so that monster amp is operating at about 20 Watts average/peak to 40 in the class A envelope.Which is enough considering they are 93 dB/1 watt, 1 meter efficient. Dub sounds incredible. Walls, doors and things not nailed down in the room are rattling with the bass. And that's in a basement with a poured concrete floor! It moves a LOT of air. Never could do that before....
P3 is untouched. May want a little less H2 at some point.
Do people try to balance the amount of H2 between channels? It seems sensible to make them sound the same..... And it can be done with the speakers attached.
Speakers are 4 ohm, so that monster amp is operating at about 20 Watts average/peak to 40 in the class A envelope.Which is enough considering they are 93 dB/1 watt, 1 meter efficient. Dub sounds incredible. Walls, doors and things not nailed down in the room are rattling with the bass. And that's in a basement with a poured concrete floor! It moves a LOT of air. Never could do that before....
P3 is untouched. May want a little less H2 at some point.
Do people try to balance the amount of H2 between channels? It seems sensible to make them sound the same..... And it can be done with the speakers attached.
Don’t leave your speakers attached when adjusting P3. When you adjust P3 it can disturb bias/offset, which then needs to be readjusted. So you do not want speakers connected when messing with P3. When testing an amplifier for whatever reason you should always have a dummy load attached, and never speakers.
If you want to experiment with H2 why not build one of Mr Pass’s clever H2 units that works with the input signal to allow you to hear what H2 sounds like in different levels and phases. That way there is no need to disturb your carefully built and adjusted F5 until you know for sure that it is something you want to have on a permanent basis. Besides, it’s another DIY project!!
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Ok, it's a little more involved than I had hoped. the H2 box won't lower the amount of H2 already there though.
I will wait another week or two and check if rebiasing is needed. Then, at that time, I might do the P3. But gently... I heard its another way I could blow this up if adjusting too far from center
After being on for 6 hours, the dc offsets with speakers and DAC attached was 5mV per channel. I''m very happy how this has turned out
I will wait another week or two and check if rebiasing is needed. Then, at that time, I might do the P3. But gently... I heard its another way I could blow this up if adjusting too far from center
After being on for 6 hours, the dc offsets with speakers and DAC attached was 5mV per channel. I''m very happy how this has turned out
OK. So no damage thus far.
I tried to attach the DCB1 to use another DAC. This DAC has 0.4mV DC on one of the outputs.
The amp starts in stages....
1) Delay 1 minute to let the thermistor cool, in the event of power cycling.
2) Start with thermistor to cap bank in place.
3) After 1 minute delay, bypass thermistor.
Everything was fine until step 3. The fuse blew.
I changed the fuse, put the benchmark DAC 1 back in place and started it,
Playing music once more.
I measured the output of the DCB1, it was 0.4 mV on one channel, 0 on the other. Even with 23 dB of gain on a 0.004 V input, thats only 0.056 V. That should not trigger speaker protection, much less blow a fuse.
dc offset is 2mv per channel with dac in place and volume down.
The DAC in question was being connected via store bought balanced to single ended cable. They been used many times before from crossover to amps. no problem
I tried to attach the DCB1 to use another DAC. This DAC has 0.4mV DC on one of the outputs.
The amp starts in stages....
1) Delay 1 minute to let the thermistor cool, in the event of power cycling.
2) Start with thermistor to cap bank in place.
3) After 1 minute delay, bypass thermistor.
Everything was fine until step 3. The fuse blew.
I changed the fuse, put the benchmark DAC 1 back in place and started it,
Playing music once more.
I measured the output of the DCB1, it was 0.4 mV on one channel, 0 on the other. Even with 23 dB of gain on a 0.004 V input, thats only 0.056 V. That should not trigger speaker protection, much less blow a fuse.
dc offset is 2mv per channel with dac in place and volume down.
The DAC in question was being connected via store bought balanced to single ended cable. They been used many times before from crossover to amps. no problem
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I'm going to hazard a guess that somethings up with the cheap RCA's in the box. I have some replacments that are much better isolated. Though these show fine on the ohmeter, it may be wrestling with locking rca jacks attached to them did something....I should swap them out to these better jacks. Never trust a jack with a shoulder washer that has a 1mm tall shoulder. The other jacks have threaded plastic to fit through the entire hole. MUCH better isolation.
Hello BigE,
I also had problems with RCA too close to the case. I tried shrink tube...
Centering the RCA carefully and so on.
The last few years I prefer NEUTRIK - RCAs. No problems, no loosening/spinning...
But there are also other good brands.
Greets
Dirk
I also had problems with RCA too close to the case. I tried shrink tube...
Centering the RCA carefully and so on.
The last few years I prefer NEUTRIK - RCAs. No problems, no loosening/spinning...
But there are also other good brands.
Greets
Dirk
Attachments
I've since hooked up the other dac via DCB1 and am listening to it... it is fine. I've switched back and forth from the Behringermods DEQ2496 ( latest AI/AO board update ) and Benchmark a few times, no problem. It's nice that the DCB1 can be powered up/down without powering off the F5T.
The only way that it could be an input issue that blows a fuse, is if the input was disconnected. But, if it were disconnected, an output device would blow before the fuse did -- is it guaranteed that an output would go first?
There is one other potential issue... the relays switching the thermistor out must be Make Before Break, to ensure that the outputs do not drain the capacitors before the load is added. If they do, the whole purpose of the slow start is defeated.
I cannot imagine buying the wrong relays and this is the first time I have ever seen this happen.
The only way that it could be an input issue that blows a fuse, is if the input was disconnected. But, if it were disconnected, an output device would blow before the fuse did -- is it guaranteed that an output would go first?
There is one other potential issue... the relays switching the thermistor out must be Make Before Break, to ensure that the outputs do not drain the capacitors before the load is added. If they do, the whole purpose of the slow start is defeated.
I cannot imagine buying the wrong relays and this is the first time I have ever seen this happen.
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Happy Memorial Day Weekend. I am trying to finish up my F5T v3 Monoblocks with XLR input. Is there a schematic or build guide for the monoblocks? I would like to double check my work and understand how to properly connect the XLR input to the circuit.
Thanks
Images of completed PCBs
Use "Open link in new tab" worked for me to open the images below:
Thanks
Images of completed PCBs
Use "Open link in new tab" worked for me to open the images below:
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An externally hosted image should be here but it was not working when we last tested it.
An externally hosted image should be here but it was not working when we last tested it.
An externally hosted image should be here but it was not working when we last tested it.
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I think there is a balanced thread with that info. I know that Nelson Pass’s article has a balanced schematic in it.
Yes, balanced. I realize now that I have to add another main board. After that, do I connect XLR Ground to ground of the two circuits? Then the XLR + to one "channel" and XLR - to the other "channel"?
Thanks, your observation got me to see the balanced vs. single ended differences.
Best,
If you want to go with balanced inputs you could also use input transformers. That way no extra circuitry is required. That is what I have done on my F5V3 monoblocks. Jensen is what I used.
Here is a link to the Jensen page. Line Input | Jensen Transformers
Transformers have their advantages and drawbacks. With these little input transformers they are easy to implement with excellent results. You can simply change the input resistor to 10k and that is it. On mine I got a great square wave response, Flat to 20khz,-3db at 80khz With a 2nd order roll off that acts as a RFI filter. You also break any ground loops you may have between other equipment and your power amps. This can be particularly troublesome with monoblocks.
This would be a lot less work than going with more circuit boards. I am not sure how you would configure an extra input board to allow balanced inputs. I did not consider it.
To wire the transformers to an XLR you do not need to connect the “ground,pin1” at all and can leave it floating. Just positive to pin 2 and negative to pin 3. You can wire an RCA to the transformer as well and use whichever input type you need but not both at the same time unless you add a switch. I have done this in my F5s with no issues. Transformers are very good balancing devices and will have higher CMMR than pretty much all simple active balanced stages.
The cost is about 70$ ea.
Jensen Transformer Part Number F5T
What is the part number of the Jensen Transformers that you used?
What is the part number of the Jensen Transformers that you used?
JT-11P-1 Was what I used
Here is a link back to where I built my F5’s
F5 Turbo Builders Thread
You can see that I mounted the transformers to small blocks of wood(cherry). A cup was drilled out with a Forstner bit and the TX fastened in with silicone. They come with tiny steel brackets for mounting, but I felt It seemed a bit flimsy for an amp that was otherwise very substantial.
Here is a link back to where I built my F5’s
F5 Turbo Builders Thread
You can see that I mounted the transformers to small blocks of wood(cherry). A cup was drilled out with a Forstner bit and the TX fastened in with silicone. They come with tiny steel brackets for mounting, but I felt It seemed a bit flimsy for an amp that was otherwise very substantial.
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They are not designed to handle DC. How much offset do you have? As a general rule, a source component should not output DC.
If you have no reason to go balanced and don’t have a ground loop problem there would be no need to use a transformer.I have a DIY dac that sounds better in balanced mode and a balanced preamp, so I wanted to try a balanced amplifier.
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