Slight humm from my new F-5
Greetings, I have just finished building my F-5. The Build Guide from 6L6 was very helpful. I have it biased correctly and it sounds very nice.
I have a couple questions. I am getting a slight hum even with the volume all the way down or with the preamp disconnected. I tried to follow best practices for internal wiring: cross psu wires and input/output at 90 degrees; keep input and output wires separated, etc. I think I followed the revised grounding scheme from the thread. But obviously I've missed something. It would be great to have a couple suggestions of what to look for.
Also I wondered if there are any particular guidelines for a preamp? I am building a B1 but in the interim I am using a McIntosh C36. I wonder if this is contributing to the problem?
Attached are a couple photos. I appreciate any assistance you can provide.
Greetings, I have just finished building my F-5. The Build Guide from 6L6 was very helpful. I have it biased correctly and it sounds very nice.
I have a couple questions. I am getting a slight hum even with the volume all the way down or with the preamp disconnected. I tried to follow best practices for internal wiring: cross psu wires and input/output at 90 degrees; keep input and output wires separated, etc. I think I followed the revised grounding scheme from the thread. But obviously I've missed something. It would be great to have a couple suggestions of what to look for.
Also I wondered if there are any particular guidelines for a preamp? I am building a B1 but in the interim I am using a McIntosh C36. I wonder if this is contributing to the problem?
Attached are a couple photos. I appreciate any assistance you can provide.
Attachments
Availability of LSJ74/LSK170 JFETs
Have been thinking about building an F5 for about a year, but have held off due to the lack of availability of matched LSJ74/LSK170 JFETs. Any possibility of these coming back to the diyAudio Store? Any reputable alternate suppliers?
Thanks in advance for any assistance.
Have been thinking about building an F5 for about a year, but have held off due to the lack of availability of matched LSJ74/LSK170 JFETs. Any possibility of these coming back to the diyAudio Store? Any reputable alternate suppliers?
Thanks in advance for any assistance.
V5T v2 or v3
Hello,
So if I understand this, the F5T boards using two outputs per rail, these can be mounted on one heat sink side, two channels per chassis. The v3 four outputs can't have two channels in one chassis (I was going to lower the bias a lot 😱), because it uses four output boards per channel, is this correct? The big diodes are mounted to heat sink? What idss is used on the j-fets?
Thanks,
Mad
Hello,
So if I understand this, the F5T boards using two outputs per rail, these can be mounted on one heat sink side, two channels per chassis. The v3 four outputs can't have two channels in one chassis (I was going to lower the bias a lot 😱), because it uses four output boards per channel, is this correct? The big diodes are mounted to heat sink? What idss is used on the j-fets?
Thanks,
Mad
I just fell off the wagon and ordered the boards, parts kit and JFETs for the F5.
I was going to wait for the new SIT amp but then realized I would much more likely go "why didn't I get those JFET pairs while they were available?" rather than "why do I have so many amps to choose from?".
Plus I have nephews that are done with college and it may be time to get one or both of them into audio with a nice gift.
I was going to wait for the new SIT amp but then realized I would much more likely go "why didn't I get those JFET pairs while they were available?" rather than "why do I have so many amps to choose from?".
Plus I have nephews that are done with college and it may be time to get one or both of them into audio with a nice gift.
Hello hirscwi,
Just finished my F5 and experience a minor hum on the speakers when listening closely.
I guess it’s power supply ripple residue on the outputs. My power supply looks pretty identical to yours. 400VA transformer, CRC with 4 times 15000uF and 0.47R per rail.
Anyone else have this?
Just finished my F5 and experience a minor hum on the speakers when listening closely.
I guess it’s power supply ripple residue on the outputs. My power supply looks pretty identical to yours. 400VA transformer, CRC with 4 times 15000uF and 0.47R per rail.
Anyone else have this?
I would also like to know if the matched JFETs will ever be available. Are the remainder of the kit parts that are available without these matched pieces or is there an alternative?
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Found them. Now all I would need is the PS PCBs to be available unless you have another source for those.
PSU boards should be back in stock in around 2 weeks or so. Following up now with our supplier.
Awesome. Thanks. Since I'm very new at this level of DIY I think I'll tackle the PS build first and be sure I can figure that out before I move forward to building the F5 it will be included in.
So in the build guide you talk about adding an LED and R35 that isn't included in the F5 component kit. I see the board has those positions on it, but I see neither in the schematic. Am I looking at the correct Schematic?
So neither R35 or the LED are required for the build? Again, I'm very new at this and getting in pretty deep pretty quickly. Trying my best to dot I's and cross T's as best I can to prevent problems. I really appreciate your help 6L6!!!!!!!
Yeah, it’s just a light. Shouldn’t affect the sound or function. You can leave it and r35 off if you want. What value is R35?
In the build guide 6L6 used a 15k. But not specified in the BOM or in the schematic. I assume you choose the LED brightness with the value.
Darn, had both the ACA and F-5 threads open at the same time and thought this was the ACA. Sorry, I’ll delete my post to avoid confusion. Still the info about the 20k resistor is useful to know for the ACA!
FYI Just got a heads-up from Jason that the Universal PS boards are in stock. I ordered two since I have a feeling the F5 isn't likely to be my last requirement for them. 😎