great photo! missing the f5t in the middle on a nice furniture
good and best luck to you !
The F5T are 'hiding' behind the TV. I don't like looking at equipment in my home. Maybe that's why I like the look of the ML speakers.
Anyway, enough of chat and on with the build. Hum, maybe that's why it's taken 5 years to get to here....
to shteve #6280
Hello Shteve,
I am using my F5-T-Monoblocks with ESLs Audiostatic ES-300R).
O.K., those are not Martin Logans but in a way similar.
I use an active crossover at 80Hz for the ESLs. They don't like to play loud at those low frequencies. The foil would have to move to far (danger of contact to the stators).
I use a JBL-Subwoofer (15-inch/38cm) below 80Hz (driven by the BA-3 amp).
It sounds absolutely awsome! The ESLs are fast and extremely detailed.
The F-5Ts do not too much in the upper frequency range with these ESLs (as reported from some members who are using horn-speakers).
I also listened to many Martin Logans. They have the same good qualities
as most ESLs (fast, coherence,....)
But I know that the Martin Logans expect an stable amp. Should be no problem with an F-5T.
You will have fun!!!!
Greets
Dirk
Hello Shteve,
I am using my F5-T-Monoblocks with ESLs Audiostatic ES-300R).
O.K., those are not Martin Logans but in a way similar.
I use an active crossover at 80Hz for the ESLs. They don't like to play loud at those low frequencies. The foil would have to move to far (danger of contact to the stators).
I use a JBL-Subwoofer (15-inch/38cm) below 80Hz (driven by the BA-3 amp).
It sounds absolutely awsome! The ESLs are fast and extremely detailed.
The F-5Ts do not too much in the upper frequency range with these ESLs (as reported from some members who are using horn-speakers).
I also listened to many Martin Logans. They have the same good qualities
as most ESLs (fast, coherence,....)
But I know that the Martin Logans expect an stable amp. Should be no problem with an F-5T.
You will have fun!!!!
Greets
Dirk
Attachments
Lovely build Gem.. seriously... art there my friend.
JT
thank you very much for the kind words thompsontechks. I really appreciate your words. Be well my friend.
I'm currently off-load testing the power supply on the first of my monoblock F5T v2. Since I already had a pair of 2x30V 625VA transformers and I didn't want the extra expense of buying two lower voltage transformers, in they went.
Each rail is CCRCC, 26mF - 26mF - 0.067R - 26mF - 26mF. The off-load voltage is 41.5V.
My plan is to use the cascoding that Nelson described in the v3 circuit to protect the jfets from running too far outside their nominal operating range, but to keep the v2 output stages. Am I able to use the cascoding as shown on the v3 schematic or will I have to change some of the component values?
I would be very grateful for any advice please.
Each rail is CCRCC, 26mF - 26mF - 0.067R - 26mF - 26mF. The off-load voltage is 41.5V.
My plan is to use the cascoding that Nelson described in the v3 circuit to protect the jfets from running too far outside their nominal operating range, but to keep the v2 output stages. Am I able to use the cascoding as shown on the v3 schematic or will I have to change some of the component values?
I would be very grateful for any advice please.
If you leave the 10k and 4.75 k resistors in place you should have somewhere around 12v on the drains of the Jfets. If you replace the 10ks with 8.2k resistors you should be in the 14v range. I believe anything between 11 and 16 is supposed to be the ideal range. Some people experiment with the voltage. I never did. I left the stock resistors in place on my V3 monoblocks. I have 46-47v PS rails. I think I ended up around 14-15volts on the Jfets.
May I ask for some hints to cross-check my F5T:
It started absolutely nicely. The amp strated, very quietly from the transforer, only slight buzz, and quiet on the audio channels from the beginning on.
Once I made the mistake, that I stwitched it on with open inputs...loud buzzing...
I than connected it back and since that eventI have some issues:
- When the amp is cold, it buzzes very loud from the PSU for like 20 minutes and when it warms up, the PSU buzz reduces quiet a bit but not as quiet as before.
- Same with audio from the speakers: loud buzzing inthe beginning, later nearly quiet.
What would be your procedure to find this mistake ? I am afraid that I damage some silicon in the input...
It started absolutely nicely. The amp strated, very quietly from the transforer, only slight buzz, and quiet on the audio channels from the beginning on.
Once I made the mistake, that I stwitched it on with open inputs...loud buzzing...
I than connected it back and since that eventI have some issues:
- When the amp is cold, it buzzes very loud from the PSU for like 20 minutes and when it warms up, the PSU buzz reduces quiet a bit but not as quiet as before.
- Same with audio from the speakers: loud buzzing inthe beginning, later nearly quiet.
What would be your procedure to find this mistake ? I am afraid that I damage some silicon in the input...
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Do you still get us distorted audio from both channels even with the buzzing? If you do then you have not blown the. Front end transistors.
If you have a DVM, I would disconnect the speakers to prevent any damage while troubleshooting.
The first thing I would try is to short the inputs and see if the buzzing from the speakers, or the hum voltage at the outputs when using a DVM to troubleshoot, goes away. If it does not stop you need to check your power supply to see if all is well there. Also check the dc offset at the output and the bias levels.
Toroid transformers will hum/buzz more as the load increases, or if you have a DC offset, even a small offset, on your AC power input. You could also have a bad connection somewhere causing a grounding issue, but the fact that you have both buzzing in the transformer and at the outputs points to a load related problem on the power supply side.
So check the power supply DC output and AC ripple levels for both + and- sides and compare them to each other and what you had before. Check your connections, solder joints etc. The most common failure in a DIY project is a bad connection. As far as failed parts goes, the rectifiers and filter capacitors are the most likely suspects in the power supply.
You should also check for abnormal “something is too hot or burning” smells and check that the heatsink temperature is not abnorally high. After the amp has been running for a while, shut it down, allow time for the ps to discharge and then feel around for any components that are running abnormally hot.
See if these tests yield any results. Good luck!!
If you have a DVM, I would disconnect the speakers to prevent any damage while troubleshooting.
The first thing I would try is to short the inputs and see if the buzzing from the speakers, or the hum voltage at the outputs when using a DVM to troubleshoot, goes away. If it does not stop you need to check your power supply to see if all is well there. Also check the dc offset at the output and the bias levels.
Toroid transformers will hum/buzz more as the load increases, or if you have a DC offset, even a small offset, on your AC power input. You could also have a bad connection somewhere causing a grounding issue, but the fact that you have both buzzing in the transformer and at the outputs points to a load related problem on the power supply side.
So check the power supply DC output and AC ripple levels for both + and- sides and compare them to each other and what you had before. Check your connections, solder joints etc. The most common failure in a DIY project is a bad connection. As far as failed parts goes, the rectifiers and filter capacitors are the most likely suspects in the power supply.
You should also check for abnormal “something is too hot or burning” smells and check that the heatsink temperature is not abnorally high. After the amp has been running for a while, shut it down, allow time for the ps to discharge and then feel around for any components that are running abnormally hot.
See if these tests yield any results. Good luck!!
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In general -yes, however I didn't do it, but I'm sure there are others that did.
Guidelines of balanced operation is described http://www.firstwatt.com/pdf/art_f5_turbo.pdf (page 14-15)
You need 2 sets of boards per channel of course.
Quick question about cascading for higher voltage rails. I know that R25 / R26 are adjusted to achieve a cascade voltage under 20V; are any differences caused by varying it under this value (i.e. effects of running it at 19.9V, 15V, 10v, etc.)? Running 58V rails and will probably use R25/R26 = 12.5kohm for ~16V cascode voltage. Thanks for any input, slowly building my knowledge.
Ya, it's a problem, you have traces that are lifted, and I bet there are other problems on the board. Even if there is continuity, anything with issues like that is/are untenable.
Epoxy Glued the lose tracks. the amp Work no problem. Used to big/stiff wire...
I have one of very similar size A soft start is inplace for the transformer, and a big thermistor gets switched out after 1 min.... a 4 amp fuse would *sometimes* blow at switchout time -- the current draw would spike near 15 amps,even at that late time.
I had to use a 5 amp slo blow.