[sup27606]

Tried all the usual tests. Have communicated with Yuking, he believes that something has become displaced in the circuit due to shipping vibrations. He’s advised me to check for shorts to ground across the signal pathway (I don’t know how to do that, even need to learn how to use a multimeter). Is the “high resistance” and “bypass path” you mention something do to with wrong connections/shorting?
I’ve found that both sides of my amp have the exact same loud crackling problem, are the two sides completely discrete? Would that help isolate the problem to any particular area, or was I just unlucky that the same connection on both sides failed? Is a fault on one side of the amp able to cause the other side to exhibit the same problem?

First of all, I don't have too much experience in hands on electronics stuff, but you make a good point. If both sides show the same problem, then may be the issue arises in the signal path between the two volume pots and the headphone input jack, because before that, the two channels are supposed to be completely discrete. If you open up the chassis, I think the first thing to check is loose parts likes screws that are dislodged between two electrical contacts (or a contact and the chassis) and making a short or ground connection. Also, using a multimeter, check for continuity between different contacts that are not ground and the chassis. Again, focus on the front section near the volume pot first. I have never opened my amp, but there are circuit diagrams of LF339 available, if that helps.
Post #22
Post #1570

I think, you may get a lot of helpful tips by posting a question in the DIY forum: https://www.head-fi.org/forums/diy-do-it-yourself-discussions.6/

Bypass path could be created, if there is say a loose piece of solder lodged between the L/R terminals of the neutrik jack.
Also, if something came loose during shipping, it might be dislodged if you tap the top and sides of the amp (not too hard, and remove all tubes first), and the problem might be resolved. I am sure, they tested each amp before shipping, so hopefully this is just a small issue.

 

[tintinsnowydog]

First of all, I don't have too much experience in hands on electronics stuff, but you make a good point. If both sides show the same problem, then may be the issue arises in the signal path between the two volume pots and the headphone input jack, because before that, the two channels are supposed to be completely discrete. If you open up the chassis, I think the first thing to check is loose parts likes screws that are dislodged between two electrical contacts (or a contact and the chassis) and making a short or ground connection. Also, using a multimeter, check for continuity between different contacts that are not ground and the chassis. Again, focus on the front section near the volume pot first. I have never opened my amp, but there are circuit diagrams of LF339 available, if that helps.
Post #22
Post #1570

I think, you may get a lot of helpful tips by posting a question in the DIY forum: https://www.head-fi.org/forums/diy-do-it-yourself-discussions.6/

Bypass path could be created, if there is say a loose piece of solder lodged between the L/R terminals of the neutrik jack.
Also, if something came loose during shipping, it might be dislodged if you tap the top and sides of the amp (not too hard, and remove all tubes first), and the problem might be resolved. I am sure, they tested each amp before shipping, so hopefully this is just a small issue.

Firstly, thank you so much for the detailed reply. The thing that’s nagging me is that the issue seems so simple, everything else about the amp is perfect except for the final sound output and I can’t find the reason...

Thanks for link to the circuit layout, I have no clue how to read it but I will try to learn.

Might be a stupid question but what is the push button for on the headphone jack? Is there some special trick to using the jack? I really hope I haven’t been doing something wrong with it...

 

[sup27606]

Might be a stupid question but what is the push button for on the headphone jack? Is there some special trick to using the jack? I really hope I haven’t been doing something wrong with it...

You are most welcome. I wish I could help you more. I think you should take it up with Yuking and ask him to give you the steps needed to troubleshoot the problem. I once had some issues with a Burson opamp, and Burson really helped me to troubleshoot the issue over email.

The input jack is a combo jack that accepts both TRS (middle hole) and 3 pin XLR plugs (the three holes around it). The push button is for ejecting the XLR plug I think, although I have never used it. You can use a standard 1/4" plug the same way you would use in any other amp.

 

[tintinsnowydog]

Update on the situation, Yuking is sending me a video of how to run a thorough test of the amp tomorrow. Communication is not easy but he has been very direct and to the point. Hope I can fix the problem by the weekend

 

[tintinsnowydog]

Amp has been fixed! 2 points linking to the 6 cathode resistors (the same corresponding pair of points on both the left and right side, by coincidence) had become desoldered, presumably from shipping and rough handling. Took a few days due to it being the weekend and communication/timezones being a little difficult. I was lucky I could communicate with yuking in chinese. He was very helpful and answered all my questions in the process, and has additionally offered to teach me how to upgrade the components of the amp when I'm ready to.

I was happy that I didn't cave in and mail the amp back to yuking to fix, as I have learnt a lot about basic electronics and the amp's circuitry in particular on this journey, thanks to yuking's patient explanation. Anyone afraid of buying this amp because of fears of difficulty with warranty/repairs/contacting manufacturer should be reassured that yuking is 100% dedicated to fixing the problem and providing assistance. He clearly claimed full responsibility from the very start of our conversation for any potential faults in the amp, confirmed that every point in the circuitry was tested before being shipped, and immediately began explaining step by step how to test for and resolve the problem. Heck, he was in hospital in the daytime, and in the factory at night to take pictures and videos to explain the amp's internals to me. If anyone experiences any problems in the future with this amp, I can explain all the preliminary testing steps and necessary readings in English.

Now time to tube roll! This is my first tube amp, and I am in love with the sound from the very start. Everything sounds so warm and comforting. I have all the best tubes ready to roll; gec 6as7g, 5998, 7236, mullard&raytheon6080s, rca5693, tung sol mesh 6sj7gt, ef800s. Will add my own subjective impressions and pictures (those have been lacking in this thread lately) to this thread in the coming days

I will spend my time with the stock tubes first to have a reference point, and compare what they sound like in relation to my two other previous amps; a solid state (cavalli liquid carbon) and tube hybrid (massdrop cavalli tube hybrid).

 

[sup27606]

Thats great to hear. Yuking takes his customer service responsibilities seriously. No wonder he is in business for all these years. I would be interested to learn how to upgrade the amp as well, and it would work out economically to upgrade individual components over time to achieve SQ improvement.

You seem to have all the recommended tubes for this amp. After multiple testing, I have figured out the best tube combination for my Sennheiser 6XX and HD800. It would be a lot of fun tube rolling!

 

[Mizicke5273]

No, but the HE-500s are great with the 339. DT880 (600 ohm) were very good too. I would imagine exceptional synergy with the Beyers listed, but I have heard neither.

You might also consider LCD-2C, but I need more time with that pairing to be definitive.

So, how do the LCD-2C sound with the La Figaro? I'm thinking about picking up a pair to try. Anyone else with experience with the LCD-2C and the La Figaro that can add their thoughts? I have also started to consider the Aeon Flow Opens.

 

[djj65]

They sound amazing. I alternate between a Little Dot MKVI+ and the LF339, love them both with the LCD2C since they both have a lot of power to drive them. The LCD2C is my first Audeze headphone and I totally love them. I sold my HD800s. I also use the Focal Clears when I want a more aggressive sound, but find myself using the LCD2C about 80% of the time.

 

[tintinsnowydog]

Thats great to hear. Yuking takes his customer service responsibilities seriously. No wonder he is in business for all these years. I would be interested to learn how to upgrade the amp as well, and it would work out economically to upgrade individual components over time to achieve SQ improvement.

You seem to have all the recommended tubes for this amp. After multiple testing, I have figured out the best tube combination for my Sennheiser 6XX and HD800. It would be a lot of fun tube rolling!

The exact 2 headphones I will be using as well. Excited to compare our findings

So, how do the LCD-2C sound with the La Figaro? I'm thinking about picking up a pair to try. Anyone else with experience with the LCD-2C and the La Figaro that can add their thoughts? I have also started to consider the Aeon Flow Opens.

I’m planning on grabbing a pair of lcd2c to try out soon. Will post impressions of it when I do

 

[xmdkq]

Just repair it, and then guide you to transform 339, so that performance is improved step by step, business is not the purpose, hobby is the goal.

Not satisfactory, not my heart

 

[tintinsnowydog]

incoming tube porn, this thread needs more!!

Best my phone camera could do! Raytheon 6080WC (construction suggests relabelled bendix6080wb w/slotted graphite plates) + Tung Sol mesh plate 6SJ7GT

Impressions (own HD800 and HD650):

I'm a predominantly classical/acoustic music fan. Imaging, soundstage, and good musicality are more important to me than exact tone and bass slam. I am also immune to spicy treble, preferring the stock HD800 over modded. Having spent 5-6 hours with stock tubes, then switching over to the above combination, I must reiterate the advice of everyone else in the thread to immediately swap out the stock tubes. Stock tubes were quite microphonic, turning the volume pots was very scratchy, and above 1 o'clock the background noise was problematic. The tone was not spectacular and I wasn't particularly wowed by any tracks i played through (though the underlying tone of the amp was still very enjoyable)

Warm up is very funky with the raytheon. The glass seems to be very strong/stronger than other tubes, so the pinging and clicking noises during warmup are very frequent and loud as it expands. Dead silent after warmup of around 4-5 min with volume right up to 4:30 oclock, much higher than peak listening levels (12:30-1 oclock for quietest Bach solo pieces, around 11 oclock regularly)

This combination is superb, probably most jack of all trades combination so far. All sounds are very clean and well separated. Bass is just right with hd800, fast and accurate but with slightest hint of bloom and decay that translates to appropriate degree of warmth, . Mids liquid smooth; in fact, i would describe the whole range as quite smooth, just a hint of nice tube distortion. Treble is rolled off slightly, which isn't always a bad thing either (i still enjoy stock hd800, but the rolled treble makes big cymbal crashes in orchestral music, the only thing at high volumes that has me reaching for the volume knob, slightly more bearable). Violins lose energy in their final 1.5 octave; lots of large Mahler textures are less brilliant than they are on a solid state, and in particular the big sweeps in Gerswhin's American in Paris lose substantial energy on each peak. There is a decent solution; treble weakness is alleviated by swapping in rca 5693s, but the rest of the range loses warmth.

I would prefer HD800 and this combination with chamber music, cello/viola concertos, baroque/classical era, and acoustic that doesn't feature or emphasise too high frequencies. HD650 would work with anything and sound very intimate and accurate, and additionally male vocals would be very sweet.

Will be familiarising and testing TS7236+RCA5693 next.

 

[tintinsnowydog]

Is the first type of tube considered better than the second one in general? I have a few of the second type, but not impressed by them. Hence, I would like to know whether the first type (so called mesh one?) is generally better. Your inputs will be appreciated.

Also, is the red 5693 significantly better than the black 6SJ7?

in the process of testing through these 6sj7 variants right now. The mesh ones are ever so slightly better than the straight metal jacket across the board. Slightly more detail and accuracy. RCA 5693 is the brightest of the bunch, very analytical (which i enjoy very much). But these differences are miniscule compared to changing power tubes. I was satisfied by the sound of the smooth metal jacket tubes already, the others are just slight tweaks to sound sig. I'll update this if I find a power tube pairing that accentuates the differences between these signal tubes.

 

[Liu Junyuan]

So, how do the LCD-2C sound with the La Figaro? I'm thinking about picking up a pair to try. Anyone else with experience with the LCD-2C and the La Figaro that can add their thoughts? I have also started to consider the Aeon Flow Opens.

It's been too long since I tried the pairing. I will try this week or weekend and post back. The Autuer pairing is outstanding.

incoming tube porn, this thread needs more!!




Best my phone camera could do! Raytheon 6080WC (construction suggests relabelled bendix6080wb w/slotted graphite plates) + Tung Sol mesh plate 6SJ7GT

Impressions (own HD800 and HD650):

I'm a predominantly classical/acoustic music fan. Imaging, soundstage, and good musicality are more important to me than exact tone and bass slam. I am also immune to spicy treble, preferring the stock HD800 over modded. Having spent 5-6 hours with stock tubes, then switching over to the above combination, I must reiterate the advice of everyone else in the thread to immediately swap out the stock tubes. Stock tubes were quite microphonic, turning the volume pots was very scratchy, and above 1 o'clock the background noise was problematic. The tone was not spectacular and I wasn't particularly wowed by any tracks i played through (though the underlying tone of the amp was still very enjoyable)

Warm up is very funky with the raytheon. The glass seems to be very strong/stronger than other tubes, so the pinging and clicking noises during warmup are very frequent and loud as it expands. Dead silent after warmup of around 4-5 min with volume right up to 4:30 oclock, much higher than peak listening levels (12:30-1 oclock for quietest Bach solo pieces, around 11 oclock regularly)

This combination is superb, probably most jack of all trades combination so far. All sounds are very clean and well separated. Bass is just right with hd800, fast and accurate but with slightest hint of bloom and decay that translates to appropriate degree of warmth, . Mids liquid smooth; in fact, i would describe the whole range as quite smooth, just a hint of nice tube distortion. Treble is rolled off slightly, which isn't always a bad thing either (i still enjoy stock hd800, but the rolled treble makes big cymbal crashes in orchestral music, the only thing at high volumes that has me reaching for the volume knob, slightly more bearable). Violins lose energy in their final 1.5 octave; lots of large Mahler textures are less brilliant than they are on a solid state, and in particular the big sweeps in Gerswhin's American in Paris lose substantial energy on each peak. There is a decent solution; treble weakness is alleviated by swapping in rca 5693s, but the rest of the range loses warmth.

I would prefer HD800 and this combination with chamber music, cello/viola concertos, baroque/classical era, and acoustic that doesn't feature or emphasise too high frequencies. HD650 would work with anything and sound very intimate and accurate, and additionally male vocals would be very sweet.

Will be familiarising and testing TS7236+RCA5693 next.

Looks like you have a pair of the slotted Bendix. One of the supreme pairings I've heard from the 339 are pictured in your post.

 

[tintinsnowydog]

Yes, that pairing was really the warmest sound I've ever heard out of my HD800, even better with HD650.

My second GEC 6as7g finally arrived about 15 minutes ago! Going to try that out with some ef800s and see if that works out. Pictures tonight when it is dark In the meantime, here are some pics that yuking sent me, hope he doesn't mind the sneak peak into his workshop!

 

[MJS242]

Just a heads up, adapters are getting added to the website in the next day or two and you can order them there. It's easier for them vs me trying to coordinate. Price will be the same as previously mentioned, $50 per pair + $17 shipping.