I just had a thought, I have a recollection of talk about running the amp without an FE board. Could I take the signal wires direct from the plugs into the VFET board? If the sound is still imbalanced it would narrow it down to the output stage, if not, then it's the FE.....I've just finished putting together my one of these with 2SJ18s in and I have an issue with a very quiet channel....
I've switched the output and input cables around, so it's definitely the left channel. I recleaned the boards incase a piece of flux was causing an issue, no obvious bad solder joints either. I disconnected and reconnected the wiring with no luck.
I don't suppose could help with any ideas on what to check next? It biased up fine and the other channel sounds great, no hum or hiss either, just very, very quiet.
I would say, it's my first amplifier build so there is a bit of potential for me doing something a little daft
Yes, you can connect the signal from your preamp directly to the output stage. Take the RCA positive directly to -I on the output stage board. Be sure that ground from the RCA also has a path to the output stage board. Depending on the voltage output of your preamp the volume may not be very loud, but if there is sound then the output stage is working.
High resolution pictures may also help in the diagnosis.
High resolution pictures may also help in the diagnosis.
Yes can avoid output, I have choke loaded too running. Transformer is an impedance converter just like the Mu-stage, but just not as good.
Thanks Ben, I just had a quick play with the wiring and it's definitely the output stage, it's dead silent without the FE behind it. I'll take a closer look at it and some photos tomorrow when I get have some time at home.
I'm not particularly experienced but the solder joints on the output stage look OK and the board clean. I used a diode tester and the diodes still show as diodes.
The output stage did measure fine on bias and the heatsink was warming up when testing. Is there anything obvious I might be missing in the photos? Is there a way to measure output at the speaker terminals / connections at the output stage to eliminate a bad connection there?
A dead VFET would be a worst case scenario but I do have a couple spare of a different rank...
The output stage did measure fine on bias and the heatsink was warming up when testing. Is there anything obvious I might be missing in the photos? Is there a way to measure output at the speaker terminals / connections at the output stage to eliminate a bad connection there?
A dead VFET would be a worst case scenario but I do have a couple spare of a different rank...
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If the bias measures fine (did you measure 20V at 2SJ18 source pin relative to ground?) and the heat sink warms, perhaps you have an input/speaker wiring error.
Please post pictures of the whole amplifier, showing all wiring.
Also carefully compare the good channel pcb to the bad channel pcb and check each resistor, capacitor, zener, etc to make sure that everything is identical. Especially check R10.
Also check all solder joints and redo any that may be suspect.
Please post pictures of the whole amplifier, showing all wiring.
Also carefully compare the good channel pcb to the bad channel pcb and check each resistor, capacitor, zener, etc to make sure that everything is identical. Especially check R10.
Also check all solder joints and redo any that may be suspect.
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A 'big' problem is the fact that some joints that are soldered from the bottom in fact have the trace on the top.
I remedy this: I presoldered the pins lightly before inserrting (flows easier) and twist the parts around a bit and add a little bit extra solder to pass through the small tunnel'
I used WBT-0820. It is the best. Simple.
I remedy this: I presoldered the pins lightly before inserrting (flows easier) and twist the parts around a bit and add a little bit extra solder to pass through the small tunnel'
I used WBT-0820. It is the best. Simple.
- Any 'modern' high temp solder is lead free but not care free. It requires special equipment and methods. Not for amateurs. Amateurs cannot let it flow. I lost a few years of work that way: solders were not through, brittle and incomplete. Connections broke down after some time.
Just before getting into details a bit, I measured the bias as ground vs the zener as per a build guide...
After much checking, I did have a signal wiring mix up, which when fixed means I DO get sound out the output stage when bypassing the FE but there must still be another issue. Both output stages are identical.
I've reflowed all solder joints on the output stage and FE and added a bit more solder - that could have been lead free originally by the way, I've been living out in Dubai recently and when I first got here I recollect soldering a board or two with lead free before I managed to find some leaded.
Still overall it's very quiet however, I'm leaning towards it having to be an issue with the FE now. I'll check components are identical on both sides next / switch the signal outputs from FE > output to different channels and see if that flips the quiet side.
I've attached some (bad) photos, to complicate things I'm using Missouri boards from the Ship of Theseus and that filter board as well. The wiring is slightly messier now I've taken it apart and put it together 5 times today
Thanks for all the help so far by the way guys!
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Finished the P channels and listening to in the test setup as yet to find a nice cabinet for this amp. This amp definitely needs a good amount of sinking as after an hour it was running hot in this 300/150mm sinks which I got over eBay with horizontal fins.
Absolutely no turn on/off thump using Mark's SMPS filter board and right now using the Scourge FE card.
Absolutely no turn on/off thump using Mark's SMPS filter board and right now using the Scourge FE card.
Got a quick question on the usage of the Tuba smps filter board. I see that it has 2 pins on the output side marked SPKR_01_02 from the relay and I could not find its usage from the posts or I am missing something. When I use these pins as output speaker binding posts ground and after the relay clicks I do not get any sound but when I connect the binding post ground directly from the amp ground I get the music fine but their is a good amount of thump when I switch off the amp. No thump sound while switching on the amp. Any guidance or the post which states the usage of these pins would be great.
Thanks
Thanks
Thanks, my only sort point is that the IEC socket hole need to be closed with 2-3mm aluminum plate and I want to mount the 2 pin molex socket on the plate rather than the current wires hanging outside. I got some SS plates from Amazon but I did not like those and also drilling holes was a pain. Any pointers for small 2"/2-3" aluminum plates?Congratulations! That's a very good looking build.
Thanks
I do not have the required tools to cut a long aluminum panel so looking at other options. Let me search over eBay or Ali
Thanks
A hand held router will mill 3mm alu sheet with ease, else a local engineering shop could cut it for a small price.
My (limited) understanding is that those connections are part of the “anti-thump” circuit. The positions you describe are used to ground the speaker output temporarily, not allowing the thump to reach your speakers. The speaker output wire should go to the speaker binding post, and to the position that you reference. The speaker ground wire just goes to the speaker binding post.
Not sure where you live, in my small US city, I can find both aluminum, and copper, stock. Mainly bars and sheets. Hardware stores, and Lowes/Home Depot. Both easily cut with a hacksaw, and drill with hand tools easily. A little black spay paint, and you are good to go.
Working steel without proper tools can be difficult, but possible with hacksaw, drill, dremel.