[adeadcrab]

The old, old version had yellow resistors. The old version has black resistors (my version) . The new version has all of what yuking mentioned above.

What is the purpose of the green 10UF capacitor and CADDOCK power resistors?

 

[MJS242]

Here are the changes over time (from oldest-top to newest/current-bottom)

 

[Jacobal]

-

 

[sup27606]

Here are the changes over time (from oldest-top to newest/current-bottom)

Thanks for the very useful info. Mine is the middle version, sans the blue rectangles that Jacobal referred to.

Now, only if someone could sonically compare the different versions.

 

[adeadcrab]

Can anyone check their amps for hum? I noticed over the last few days that some tubes were making a hum in the left channel. A very faint hum that is noticeable when not playing music and unplugging headphones from the amp to actually notice it. But it's there. The right channel is silent, so I figured it might have been a quirk of the circuitry. But it's a dual mono setup, so there must be something going on in the left channel circuitry. What could it be? A bad resistor? Capacitor?

Some tubes are much more noticeable (6SJ7GT mesh) and some I thought were totally silent (5693 reds) but I just checked with the reds and they have this hum also.


edit: it's a 60hz hum, almost undetectable with 5693 reds unless the room is totally silent. 300 ohm HD650 produce this 'ground loop' hum, 600 ohm DT880 do not. Changing driver tube changes the volume of the hum, 5693 reds are the most silent, 6SJ7GT mesh can be quite noticeable

edit: hum remains with base plate off, and adds hissing on right channel. Does the amp really have zero noise floor? Do I just have a bad resistor somewhere?

 

[adeadcrab]

MJS242- The one I have seems to be the 2nd one but without the blue rectangle things. I’m confused. Maybe it’s a combination of the 1st and 2nd?

Mine is the same, black resistors and without the blue/green tuning capacitors

 

[xmdkq]

We can provide materials for everyone to discuss together. I don't use English for GOOgle translation.
Now only the overseas version is produced. The previous version is not produced. The next step is to improve the overseas version. The structure and performance will be further improved.

 

[wwmhf]

We can provide materials for everyone to discuss together. I don't use English for GOOgle translation.
Now only the overseas version is produced. The previous version is not produced. The next step is to improve the overseas version. The structure and performance will be further improved.

This is a good news to us

 

[wwmhf]

We can provide materials for everyone to discuss together. I don't use English for GOOgle translation.
Now only the overseas version is produced. The previous version is not produced. The next step is to improve the overseas version. The structure and performance will be further improved.

One suggestion I would like to make is the preamp output. I will definitely buy another 339 if the preamp out is added.

 

[Mizicke5273]

We can provide materials for everyone to discuss together. I don't use English for GOOgle translation.
Now only the overseas version is produced. The previous version is not produced. The next step is to improve the overseas version. The structure and performance will be further improved.

Will the performance increase be a minor or major increase?

 

[adeadcrab]

One suggestion I would like to make is the preamp output. I will definitely buy another 339 if the preamp out is added.

Would this work from the headphone output? https://www.storedj.com.au/hosa-trs-201-1-4-trs-to-dual-rca-insert-cable-1m

Will the performance increase be a minor or major increase?

I think a minor improvement, the amp is quite good as it is

We can provide materials for everyone to discuss together. I don't use English for GOOgle translation.
Now only the overseas version is produced. The previous version is not produced. The next step is to improve the overseas version. The structure and performance will be further improved.

Thank you.

 

[xmdkq]

Many domestic users are driving the power amplifier from the headphone jack output signal, which works well.
Note the size of the output level.

 

[wwmhf]

Many domestic users are driving the power amplifier from the headphone jack output signal, which works well.
Note the size of the output level.

Using the output from the headphone jack has some drawbacks. (1) the level might be too high as mentioned by your post (2) the inconvenience for switching between playing music by amplified speakers and playing music by the headphones. (3) ...

 

[adeadcrab]

Regarding my previous issue.. I've left the amp off, with power + rca unplugged, and just plugged this in to check if it may be ground loop hum related to another amp's issue.. and the noise is gone from the LF339

Perhaps leaving it unplugged for a week did something good to it.. or maybe I should've leave it on 24/7?

edit - no hum on Grados, I think a first for me..

 

[africanus]

Can someone provide a list of compatible tubes for the latest version (Massdrop's)? Yuking's website is down and it is a nightmare to find out which tubes are compatible with what version: the bright one (supossedly the latest and still in production) and the former warm one (now discontinued).

TIA