[CopperFox]

Hello and my apologies for inactivity here, most of my free time has gone to following the unexpected major war in Europe. Fairly historic things going on.

Haven't done any work on the amp in the meanwhile but will do something soon. The DMM has been less useful than expected so far - tried to find out if the diodes are blown but the manual is vague on how it's done and every instruction I found online differs significantly from the others. I'll probably just replace the transistors and diodes as that appears less complicated and cheaper than another DMM.

As for the reason why the amp stopped working, I've deduced that in addition to changing the vu meter, it also coincided with some wiring changes. The pure silver wires that I had had in the amp were proving troublesome in that they were solid silver compound, so they would break off if bent and twisted long enough, and to stop having to replace those I decided to try 2.5 mm thick copper wires for even lower resistance and that is also the point where the problems started. Maybe there is something about those wires that was incompatible with the rest of the amp. Don't know what exactly. I've read that thick wires may have problematic capacitance. And also that having a resistance too low can have similar function as a short circuit.

 

[CopperFox]

Haha, I didn't expect this.

First the Wimas with Shuguang power tubes:

Hey @CopperFox I've got most of my dynamics back! Over 200 hours burn in and with the Shuguangs in, it was worth sticking with it. As you said the sound has become clearer and opened up a lot, treble is nice and bass weight good and soundstage very good. Everything is there, I would say it's a tad warm and mellow and only the sharp edges are missing but if it's mellow you want this is it. I don't really see the sub bass tightening up that much though which is the reason for trying the Wimas.

Hey happy that the burn-in worked and you like them! Thinking back about my burn-in process for them it came back to me that there was a point in it too when the bass dynamics returned. But the treble took longer still.

The reason why the burn-in takes such a long time with the DCL Wimas is likely to do with the 6SL7 tubes having very, very low current output at only ~2 mA. The electrolytic caps are rated for 1000-2000 mA, while these DCL Wimas are rated for 20-30 A and are certified for use in electric vehicle power trains.

Even for the coupling caps, I noticed the Duelund 0,56uf caps would burn in a lot faster in the WCF position (30 to 70 mA current?) than as coupling caps after the 6SL7s.

(So one way to speed up the burn-in of the DCL Wimas could be to first run then in some other position with higher current, which for this capacitance could be the PSU output cap position.)

The bass deficit in mid to subbass with a soft sound the lower you go down has all but gone, with the bass now it is like there is a whole new dimension to music which I really like. I listened to an album that had bass which was very difficult to hear at all originally and it sounds really excellent now, punchy, powerful, but not overly so, and good definition.

This set up is staying for me! The uprated WCF caps give excellent weight to the sound, similar to uprated coupling caps so if it's bass you want you could do either with probably the same results. The Wima's are a must in the cathode bypass position now, they allow the music to flow.

These are exactly how I would describe them too - a lot more clarity and detail in the low bass without lacking punch. Also, that "they allow the music to flow" is exactly what I thought to myself about them but didn't post it here as it is something that's kind of hard to elaborate on.


Something else that I found to not be a good change/addition was replacing the PSU electrolytics. I put four 2200uf TKD caps there with the best published specs but the difference that they made was mainly a recess in the treble. So I will put the original caps back there. Interestingly, for the majority of applicable caps for that position on Mouser and Digikey, the specifications of most of their relevant electrical properties are not published, including the stock caps of the MKVI+.

 

[baronbeehive]

Hello and my apologies for inactivity here, most of my free time has gone to following the unexpected major war in Europe. Fairly historic things going on.

Haven't done any work on the amp in the meanwhile but will do something soon. The DMM has been less useful than expected so far - tried to find out if the diodes are blown but the manual is vague on how it's done and every instruction I found online differs significantly from the others. I'll probably just replace the transistors and diodes as that appears less complicated and cheaper than another DMM.

As for the reason why the amp stopped working, I've deduced that in addition to changing the vu meter, it also coincided with some wiring changes. The pure silver wires that I had had in the amp were proving troublesome in that they were solid silver compound, so they would break off if bent and twisted long enough, and to stop having to replace those I decided to try 2.5 mm thick copper wires for even lower resistance and that is also the point where the problems started. Maybe there is something about those wires that was incompatible with the rest of the amp. Don't know what exactly. I've read that thick wires may have problematic capacitance. And also that having a resistance too low can have similar function as a short circuit.

Hey... good to hear from you, I thought maybe you had managed to electrocute yourself with your new DIMM lol.

You must be concerned about the political situation, I see that Finland is looking to join NATO, the sooner the better IMO with a big bully on your border.

I would still recommend you try first to use your DIMM to test for continuity which is easy to do and will show up any problems with connections, especially with the changes you have made to your circuit. If all is good there you can go on to test other things such as loose, broken or touching wires, resistances and such like. I have had problems with my amp at least 3 times where the amp wasn't functioning and managed to restore it eventually, we've all had similar experiences, par for the course! I haven't heard that about resistance in wires and short circuiting. I have used some thick solid copper wires in places such as the PSU caps without issue.

 

[baronbeehive]

Hey happy that the burn-in worked and you like them! Thinking back about my burn-in process for them it came back to me that there was a point in it too when the bass dynamics returned. But the treble took longer still.

The reason why the burn-in takes such a long time with the DCL Wimas is likely to do with the 6SL7 tubes having very, very low current output at only ~2 mA. The electrolytic caps are rated for 1000-2000 mA, while these DCL Wimas are rated for 20-30 A and are certified for use in electric vehicle power trains.

Even for the coupling caps, I noticed the Duelund 0,56uf caps would burn in a lot faster in the WCF position (30 to 70 mA current?) than as coupling caps after the 6SL7s.

(So one way to speed up the burn-in of the DCL Wimas could be to first run then in some other position with higher current, which for this capacitance could be the PSU output cap position.)



These are exactly how I would describe them too - a lot more clarity and detail in the low bass without lacking punch. Also, that "they allow the music to flow" is exactly what I thought to myself about them but didn't post it here as it is something that's kind of hard to elaborate on.


Something else that I found to not be a good change/addition was replacing the PSU electrolytics. I put four 2200uf TKD caps there with the best published specs but the difference that they made was mainly a recess in the treble. So I will put the original caps back there. Interestingly, for the majority of applicable caps for that position on Mouser and Digikey, the specifications of most of their relevant electrical properties are not published, including the stock caps of the MKVI+.

Yes several of us here have been a tad sceptical about the use of WIMA's in positions other than PSU. BUT... you are right the changes in the sound after a very long burn in are amazing frankly. Difficult to pinpoint as you say how the sound has changed but it hits you straight away. The bass, in particular hit me with a much better definition which is something I didn't expect that just changing the cathode bypasses would be able to achieve so I am pleased that I stuck with it re: those WIMA's. I definately would recommend them if you want the best sound possible.

Let us know how you get on with any problems with the amp .

 

[chezzer]

Hi all, I wonder if anyone can help me, my ld mk8 has developed a rather odd problem, with one set of headphones plugged into either the single balanced output I get no sound apart from if I turn the amp off and turn back on while the music is playing I have audio for a few seconds before it disappears again. However if I plug two sets of headphone into both the balanced and single outputs I have audio through both headphones, unplug one from either output and it disappears again, I've not changed or messed with a thing and all worked perfectly yesterday, I've tried swapping all tubes but still the same problem, any help is greatly appreciated

 

[baronbeehive]

Hi all, I wonder if anyone can help me, my ld mk8 has developed a rather odd problem, with one set of headphones plugged into either the single balanced output I get no sound apart from if I turn the amp off and turn back on while the music is playing I have audio for a few seconds before it disappears again. However if I plug two sets of headphone into both the balanced and single outputs I have audio through both headphones, unplug one from either output and it disappears again, I've not changed or messed with a thing and all worked perfectly yesterday, I've tried swapping all tubes but still the same problem, any help is greatly appreciated

Hi there, I'm having difficulty understanding that. Because you are getting sound it seems like nothing wrong basically except that somehow the circuitry only works when both headphone outputs are in use implying that the circuit is somehow broken when only one is used. The only thing I can suggest is to look at the output wiring to the SE out and the balanced out, circled in red to see if there are any loose connections. Be careful touching the insides, make sure if you do touch anything to give half an hour after use to let the capacitors fully discharge.

Sorry I can't be more help but if this doesn't work you could try PM'ing Maxx 134, he has a better knowledge of the circuitry, or failing that take the amp to an electronics technician such as a TV repair man to test the circuit to find any broken connections.

Good luck!

 

[chezzer]

Hi there, I'm having difficulty understanding that. Because you are getting sound it seems like nothing wrong basically except that somehow the circuitry only works when both headphone outputs are in use implying that the circuit is somehow broken when only one is used. The only thing I can suggest is to look at the output wiring to the SE out and the balanced out, circled in red to see if there are any loose connections. Be careful touching the insides, make sure if you do touch anything to give half an hour after use to let the capacitors fully discharge.

Sorry I can't be more help but if this doesn't work you could try PM'ing Maxx 134, he has a better knowledge of the circuitry, or failing that take the amp to an electronics technician such as a TV repair man to test the circuit to find any broken connections.

Good luck!

Thank you very much, in fact that is exactly what I did, I contacted @Maxx134 and he was incredibly helpful and this is was the outcome.
Thanks again @Maxx13.
Hello my friend I haven't checked into that thread so it is good you PMed me or I wouldn't know.
ok so from what I am hearing is that there is sound initially while the unit warms up until it clicks on. this is normalnto hear the sound that is from the driver stage pushing to the relays, before it kicks the signals to the rear tubes...

The issue then is that it shuts the output off. this is a protection relay. it means you blew up the output stage. most probably due to driving it with low impedance headphones. I never use the small singal ended outputs, because it only uses half the tubes circuit and stress the system.
also , if you treated it very well and not abuse it. this issue will still happen due to three issues. ..

1-The power resistors burn up over time.
2- The weak wire to the PSU transistors simply burned open
3-The PSU burn due to swapping power tubes alot.

So the bottom line is that you will need to open and both visually inspect (easy) and also check the PSU section after the caps because once the PSU goes you will see burn resistors or burn near the brittle fat wiring of the power transistors.
They will usually die so expect to replace them if your not getting the correct voltages to the tubes. in order to test that you need a fully competent person that will not shock himself with the high voltage there to the tubes. (about 200) I forget the details because when covid first came I had high fever for while week and I can tell my memory has never been the same.
I didn't know nothing how to save myself with ivermectin.
they say the only way to rejuvenate my brain is to fast for a few days I forget how long maybe a week and that's not easy as you need to be prepared.

anyways sorry for your loss but it can be repaired not hard and also do not ever put two headphones in at same time unless you want to blow it up again ! that's my dry humor but seriously it can be fixed go get a starving student in college electronics to do the job. do not waste money on some old timer tube gear repair place as they will rob you.
good luck!!

 

[baronbeehive]

There you are then!

Do what he says!!

The reason I was puzzling over it was because with the 2 headphones in you said it worked so that's what made me rule out the protection relay but that could be what's happening. These things are always tricky to diagnose.

 

[chezzer]

There you are then!

Do what he says!!

The reason I was puzzling over it was because with the 2 headphones in you said it worked so that's what made me rule out the protection relay but that could be what's happening. These things are always tricky to diagnose.

I could always send it your way if you're in the market for a repair/ upgrade job

 

[baronbeehive]

I could always send it your way if you're in the market for a repair/ upgrade job

Yeah, I don't want to get involved in that really, it can be time consuming, sorry. However I don't really think it would be a problem for an electronics engineer. I would suggest try around and mention it is an audio amp, the fact that it is tube amp shouldn't phase them, they only have to look at the circuit and deduce what is what from what you have said.

I used a TV repair man and an audio specialist who built his own guitar amps when I was starting out and he was able to do a lot of repairs when I messed up!! There are quite a few such people around if you google it in your area.

 

[chezzer]

Yeah, I don't want to get involved in that really, it can be time consuming, sorry. However I don't really think it would be a problem for an electronics engineer. I would suggest try around and mention it is an audio amp, the fact that it is tube amp shouldn't phase them, they only have to look at the circuit and deduce what is what from what you have said.

I used a TV repair man and an audio specialist who built his own guitar amps when I was starting out and he was able to do a lot of repairs when I messed up!! There are quite a few such people around if you google it in your area.

Thanks for the reply, it's fine, I know a guy in N London, I was due to see him tomorrow but he cancelled until next week, I've a cayin tube amp on the way but would like the little dot fixed and upgraded regardless, thanks for the help.

 

[MuhVNYP]

THAT person should have just made his own journey, rather than derailing shts on threads that is built in specific ways n goals in mind. Just bcs its the same product, doesnt mean its related if its not made with the same goals. Its not so hard to make another thread. Jeez.

 

[chezzer]

THAT person should have just made his own journey, rather than derailing shts on threads that is built in specific ways n goals in mind. Just bcs its the same product, doesnt mean its related if its not made with the same goals. Its not so hard to make another thread. Jeez.

What, you mean exactly like what you have just done, please tell us how your amazing post is related and why you didn't start your own thread to moan about other posters

 

[chezzer]

Another thing, at least my posts are coherent and not babbling bull