LM845 Premium issue

[Zonk70]

Hi,
I have a problem with the lm-845 premium.. After 2 hours continous playing, the amp driftes in instabality, with light distortion, smearing mids and lose of three-dimensionality..

Any idea?

Bias is stable at 70 ma and the tubes have about 200 hours runnning time,
the amp plays at low volume always..

Best regards
André

 

[Thermionic emission]

Hi,
I have a problem with the lm-845 premium.. After 2 hours continous playing, the amp driftes in instabality, with light distortion, smearing mids and lose of three-dimensionality..

Any idea?

Bias is stable at 70 ma and the tubes have about 200 hours runnning time,
the amp plays at low volume always..

Best regards
André

Hi André,
May i ask how long you have had the premium?

 

[Wrm57]

Hi Andre,

Have you gotten anywhere with your amp issue? I've been thinking about buying the LM-845 Premium myself and I'm curious how you're faring with it.

Bill

 

[Thermionic emission]

Hi Andre,

Have you gotten anywhere with your amp issue? I've been thinking about buying the LM-845 Premium myself and I'm curious how you're faring with it.

Bill

Hi Bill,
i was hoping that Andre would have answered my reply above. I was trying to establish if there were problems associated with the recent production units of the lm 845 premium. I purchased mine last October 2020, but have now traded it back in to the dealer. I was getting excessive gain problems with the amp, on integrated and power amp modes. I think that part of the problem was my dac output was too hot, due to the valves. However i would always sit in trepidation waiting to see how the lm would respond during a listening session. this was an intermittent problem, and basically what would happen is this. After a certain time maybe hours or days, you would get “explosions” coming out of your speakers. This was quite frightening. You would immediately have to get up and power it off. On restart. You would have to re-bias either the 300b’s or the 845’s, or both get them back onto the centre mark as shown by the indicator. They were well outside of the arc, shown by the 3 points on the indicator. This would happen with the stock supplied valves, or any combination of my own purchased valves, including 4 different pairs of 300B’s. Another problem I encountered was drifting bias. This was a constant pain as if it drifted out of the ‘arc’, i was half expecting the “explosions” to reoccur. So i was constantly watching the bias settings, instead of enjoying the music. As I mentioned earlier, do not consider using this amp with the supplied 12ax7’s. There is far too much gain in this system. Replace these with 5751’s. However if you intend to use as a power amp, these are not in circuit, and can be removed. I believe the input sensitivity is 250mv. Beware if you feed it from a higher output level like 2v rms. I did purchase inline attenuators, and also changed the output valves in my dac, but i was never confident that the amp would not return to being a “Frankensteins Monster”. The 845’s are run with 1250v on the Anode/plate, so quite concerning. The European distributor was quite condescending, as they considered that all my issues were caused by me, and that their unit could not possibly be faulty. I came to the conclusion that the warranty was not worth the paper it was written on. Please ensure that you get a long home trial period before you purchase, to ascertain if you have any issues. It takes at least 200 hours before you can hear it at its best.
Thermionic Emission.

 

[Wrm57]

Hi Bill,
i was hoping that Andre would have answered my reply above. I was trying to establish if there were problems associated with the recent production units of the lm 845 premium. I purchased mine last October 2020, but have now traded it back in to the dealer. I was getting excessive gain problems with the amp, on integrated and power amp modes. I think that part of the problem was my dac output was too hot, due to the valves. However i would always sit in trepidation waiting to see how the lm would respond during a listening session. this was an intermittent problem, and basically what would happen is this. After a certain time maybe hours or days, you would get “explosions” coming out of your speakers. This was quite frightening. You would immediately have to get up and power it off. On restart. You would have to re-bias either the 300b’s or the 845’s, or both get them back onto the centre mark as shown by the indicator. They were well outside of the arc, shown by the 3 points on the indicator. This would happen with the stock supplied valves, or any combination of my own purchased valves, including 4 different pairs of 300B’s. Another problem I encountered was drifting bias. This was a constant pain as if it drifted out of the ‘arc’, i was half expecting the “explosions” to reoccur. So i was constantly watching the bias settings, instead of enjoying the music. As I mentioned earlier, do not consider using this amp with the supplied 12ax7’s. There is far too much gain in this system. Replace these with 5751’s. However if you intend to use as a power amp, these are not in circuit, and can be removed. I believe the input sensitivity is 250mv. Beware if you feed it from a higher output level like 2v rms. I did purchase inline attenuators, and also changed the output valves in my dac, but i was never confident that the amp would not return to being a “Frankensteins Monster”. The 845’s are run with 1250v on the Anode/plate, so quite concerning. The European distributor was quite condescending, as they considered that all my issues were caused by me, and that their unit could not possibly be faulty. I came to the conclusion that the warranty was not worth the paper it was written on. Please ensure that you get a long home trial period before you purchase, to ascertain if you have any issues. It takes at least 200 hours before you can hear it at its best.
Thermionic Emission.

Hi Thermionic,

Thank you very much for the detailed information. This is exactly the kind of user feedback I was hoping to get before I make my decision. Problems like this too often go unreported on the web. Reviewers don't like to publish bad reviews; forums posters are frequently more inclined to talk about component successes than failures. It's human nature, I guess. I must say, your experience gives me pause. What did you end up with instead, if I may ask?

Bill

 

[Thermionic emission]

Hi Thermionic,

Thank you very much for the detailed information. This is exactly the kind of user feedback I was hoping to get before I make my decision. Problems like this too often go unreported on the web. Reviewers don't like to publish bad reviews; forums posters are frequently more inclined to talk about component successes than failures. It's human nature, I guess. I must say, your experience gives me pause. What did you end up with instead, if I may ask?

Bill

Hi Bill,
Thank you for your reply. When these problems started to happen, I couldn’t find any information elsewhere to see if other owners were having issues as well. I really wanted the premium to be my “end game“amplifier. Such a shame, as prior to the trade in back to the dealer, it was really sounding superb. I haven’t as yet decided on another amplifier at the moment. I have a Mastersound 845 compact on loan at the moment. I will also be trying out a “curved ball” in the AGD Audions. As always, the choice will be what sounds best in my system. Maybe i was just unlucky with my unit, however the response from LM was not something that i expected.
Thermionic Emission.

 

[Wrm57]

Hi Bill,
Thank you for your reply. When these problems started to happen, I couldn’t find any information elsewhere to see if other owners were having issues as well. I really wanted the premium to be my “end game“amplifier. Such a shame, as prior to the trade in back to the dealer, it was really sounding superb. I haven’t as yet decided on another amplifier at the moment. I have a Mastersound 845 compact on loan at the moment. I will also be trying out a “curved ball” in the AGD Audions. As always, the choice will be what sounds best in my system. Maybe i was just unlucky with my unit, however the response from LM was not something that i expected.
Thermionic Emission.

Thermionic,

Did I read correctly that the input sensitivity of the amp section through the pre-amp input is 250mV? That is extremely sensitive. I have a Class A solid state amp that was designed to be used with a passive pre-amp; its input sensitivity is 470mV. I'm not sure many active pre-amps could be used with the LM-845 Prem amp section, given that sensitivity. And if it reacts poorly to high gain inputs, as yours apparently did, that would seem a bad recipe. But perhaps I'm missing something.

I just looked up the AGD Audions. What a wild amp! More power than I need but very cool looking.

Bill

 

[Thermionic emission]

Thermionic,

Did I read correctly that the input sensitivity of the amp section through the pre-amp input is 250mV? That is extremely sensitive. I have a Class A solid state amp that was designed to be used with a passive pre-amp; its input sensitivity is 470mV. I'm not sure many active pre-amps could be used with the LM-845 Prem amp section, given that sensitivity. And if it reacts poorly to high gain inputs, as yours apparently did, that would seem a bad recipe. But perhaps I'm missing something.

I just looked up the AGD Audions. What a wild amp! More power than I need but very cool looking.

Bill

Hi Bill,
Apologies for the confusion. The preamp input sensitivity is 1v when used as a power amp, and 250mv when used an an integrated amplifier. Excessive gain is a problem, when you have reasonably efficient speakers. Mine are Tannoy Kensington’s at 93db. The stock 12ax7’s were far to much and I couldn’t understand why lm chose them. However you can replace them with 5751’s. I’m sure that with a re design, lm could have used a 12au7 instead. There is no user switch on the back of the unit to change input level gain. This is another point to consider.
I am interested to hear the Audions, and will keep an open mind and not write them off as they are “Class D” without giving them a chance. Top quality 845’s & 300b’s are not cheap consumables. Tech should / does get better over time. My Tannoys don’t need the power either.
Thermionic Emission.

 

[Wrm57]

Ah, that makes more sense. Thanks for the clarification. I would be using as a power amp almost exclusively, so it is good to know.

 

[Saleh84]

Hi,
Have had my LM845 premium for a year now.
My dac is rockna wavedream signature. It has it own volume control. At 0db, max volume, the SE output is 3.6 vrms.
I have never had any issues with the LM845. Its strange but could be a defect with your unit. Volume pot position would be between 8 o'clock and even 11 o'clock (on very low level recordings). My speakers are cube audio nenuphars, 91db efficient.
I also tried dac direct driving LM as power amp, on the dac i would be at -25 db to -15 db. No issues at all. Tried with stock tubes, with upgraded ones, zero issues.
I just think you probably had a unit with issues. This amp is a reliable beast.
I even have some videos up on YouTube if you wish to check them,

Saleh

 

[Thermionic emission]

Hi,
Have had my LM845 premium for a year now.
My dac is rockna wavedream signature. It has it own volume control. At 0db, max volume, the SE output is 3.6 vrms.
I have never had any issues with the LM845. Its strange but could be a defect with your unit. Volume pot position would be between 8 o'clock and even 11 o'clock (on very low level recordings). My speakers are cube audio nenuphars, 91db efficient.
I also tried dac direct driving LM as power amp, on the dac i would be at -25 db to -15 db. No issues at all. Tried with stock tubes, with upgraded ones, zero issues.
I just think you probably had a unit with issues. This amp is a reliable beast.
I even have some videos up on YouTube if you wish to check them,

Saleh

Hi Saleh,
thank you for your post. You could be correct. I sold it back to the dealer, and traded for another type of amp. I cannot say if it was sold on or sent back to line magnetic.
Thermionic.

 

[Zonk70]

Sorry, I haven't been here for a while..
I sent my 845 premium to a service check at the european distributor..
They say there is no issue and everything workes perfect.. Dont know, if this is the right adress for a highend amp check?!
But thats the way LM handles the guarantee requests...
I find out, that this amp is very very sensetive to power stability and cables..
My issues remain most of the time, but i can't exclude, that is due to the power stability here.. In the night or at weekends it sometimes sounds wounderful for hours and hours..
But mostly there is a overall distortion after 2-3 hours playtime..
André

 

[Saleh84]

From what you are describing, it could be just faulty tubes. I have been there when tubes behave strangely after being on for a couple of hours, it doesn't show immediately as soon as you switch on the amp.
If there was something wrong with the amp itself, you won't be able to run it normally for two or three hours.
I also doubt its your electricity. The main suspect is tubes. possibly only a pair out of the four pairs the amp utilises, you can tell only by swapping a pair in a session and wait for that phenomenon to happen again.

 

[Kingrex]

The plant would have found a bad tube.


Could be arching somewhere in the house, or a bad ground. I rarely find the issue to be the utility. But I see bad power ruin playback. Bad power is most always poor electrical infastructure. And I'm not talking about the dedicated circuit you brought to your rack. It's somewhere else. Audio will amplify any noise on your electrical grid. It could also be the LM is not grounded and the DAC is. So now the LM is grounded and it does not want to be.

Heat can cause intermittent shorts or open faults in gear. But the plant should have seen that.

 

[Zonk70]

From what you are describing, it could be just faulty tubes. I have been there when tubes behave strangely after being on for a couple of hours, it doesn't show immediately as soon as you switch on the amp.
If there was something wrong with the amp itself, you won't be able to run it normally for two or three hours.
I also doubt its your electricity. The main suspect is tubes. possibly only a pair out of the four pairs the amp utilises, you can tell only by swapping a pair in a session and wait for that phenomenon to happen again.

That was my first thought too : the tubes! I changed them all.. Except of the 310A.. thats the last pair remaining unchanged. I will change them also, then we will see..

 

[Zonk70]

T

The plant would have found a bad tube.


Could be arching somewhere in the house, or a bad ground. I rarely find the issue to be the utility. But I see bad power ruin playback. Bad power is most always poor electrical infastructure. And I'm not talking about the dedicated circuit you brought to your rack. It's somewhere else. Audio will amplify any noise on your electrical grid. It could also be the LM is not grounded and the DAC is. So now the LM is grounded and it does not want to be.

Heat can cause intermittent shorts or open faults in gear. But the plant should have seen that.

This is my fear and you could be right.. This makes the search even more complicated..

 

[Saleh84]

That was my first thought too : the tubes! I changed them all.. Except of the 310A.. thats the last pair remaining unchanged. I will change them also, then we will see..

My friend had an LM219ia, same tube complement like the premium. He ran into issues with the 310a, got them replaced and he was golden after.
It might not be the same for you, but try that out if possible.

 

[Zonk70]

My friend had an LM219ia, same tube complement like the premium. He ran into issues with the 310a, got them replaced and he was golden after.
It might not be the same for you, but try that out if possible.

YES.. I did that yesterday.. And exactly.. It was the 310A tubes! That was an expensive try and error situation.. I changed them all, except of the 310a.. now i have stability over hours of continous listenig!

 

[Saleh84]

Guys, I would be selling my LM tube amp soon as I need the cash to fund another audio project, I have plenty for tubes with very few hours on them including psvane ACME 845 & 300b, elrog 300b, a pair of vintage RCA black 845s. which i want to sell for an attractive price. Also available some other tubes that works with LM845 premium like psvane WE 310a. Please PM me if of interest will share more details. I'm based in Dubai, but I can ship anywhere.