[oliverws]

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[oliverws]

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[oliverws]

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[FlukeII]

Quote:

But I really do not like when it becomes warm! I do not like when transistors are hot (over 60°C) and I do not care about commercial trick "it works best when it is warm". I am sure that class A amplifier can be cold and still operate in A class. Best amlifiers behave in that way, because designers are not trying to save money on the most important thing - cooling. But this minimalistic design just sucks. Small design involves high noise, too much heating and all components in it have shorter life.
 
I bought a few of these heatsinks: http://cgi.ebay.com/ws/eBayISAPI.dll?ViewItem&item=280498961521&ssPageName=STRK:MEWNX:IT I also bought a few heatsinks from local store that are higher than those supplied with LC. Because of mimimalistic design I will have to improvise (drill extra holes, etc)...
 
Output resistors (1W) become brown (I do not like that because they were white as new) and also know that good resistors do not change color, unless they are overloaded), so I concluded that 1W is not enough. Besides, I can not find who made them. Maybe some "Middle of nowhere" company from China? Mills is too big (5W). Riken, Shinkoh are to expensive (5-10 USD each) Vishay is sick (10-15 USD each), Takman (2 USD each) I like more in the signal circuit, Alan Bradley I have never tried... Kiwame 2W are the best choice...

What you're saying here sounds like something is wrong with the circuit - probably those fake components goofing things up - joke

 
What are the voltages across the 10E Emitter reistors in the output stage - from the designs we've played around with, it should be about 0.4V DC +/-0.05V DC; the range we measured across 6 amplifiers. The voltage will change when ac signal is fed into the input. These voltages were measured with the volume turned down to min and no input signal i.e. idle condition...
 
From a power / heat dissipation point of view the dissipation in those resistors is P=V^2/R or (0.4x0.4)/10 = 0.016W, If that resistor is getting warm, something is wrong - way wrong. You shouldn't be able to feel that heat in a reistor of that size (with your finger) until the heat dissipation gets around 0.25W - 0.3W - Some people are more sensitive - it just depends on how much skin is on your finger...

 

[FlukeII]

 
Quote:

Yesterday I ordered LME49720HA... I will try it in combination with 2N5087/5088 and matched MJE243/MJE253.
 
Hi FlukeII, what do you think about stock TO220 heatsinks (in LC)? I think that amplifier is too warm. I mean, I do not believe in sentence "it is A class so it has to be warm". Problem is there is not enough place for bigger heatsink...
 

 
How hot those transistors get depends on a few things, other than the DC operating point that they have been set to with the values of the resistors, namely the 1,5k resistors in the output stage.
 
Provided the Tjmax of the BD139/BD140s is not exceeded, you can run those transistors pretty hot to the touch - i.e. 50 deg C is not uncommon. (See the Datasheet for details of operating temp)
 
Personally I don't like 50degC as there is little margin if things go wrong or you stick the amplifier on a table in the Sun and the Sun cooks the enclosure and the BD139/BD140s get way hotter. When I've designed circuits with power transistors or just heat dissipating parts, I try to avoid getting the device hotter than 35degC under ambient temp conditions (e.g. 20degC Air Temp) - measured using a thermal imaging sensor.
 
Sometimes you just have to design it in to run hotter because of cost and / or design constraints, or use a fan: I don't like fans as they eventually break down and you have to put thermal protection circuits in to guard your circuit on the day the fan(s) fails else you might end up with a Fire in your box! Update: Actually fans are bad (IMO) generally, they're noisy, without filtering they will suck dirt and dust into your equipment, the new modern ones tend to create some electrical noise, especially conducted noise on the DC supply running the fan, Actually, on one design this was how we measured when the fan failed by sensing the ripple voltage noise created on the DC supply rail when the fan was running. Sometimes they are a necessary evil - you have no choice but to use one.
 
Remember the hotter you run those parts, the lower the MTBF: As a rule of thumb, for every 10 deg C hotter you run a device with a specific MTBF figure over the stated temp for that MTBF, you end up halving the MTBF figure. As an example, let's say a specific manufacturer quotes the MTBF for an OPAMP with 100,000 Hrs before failure at an operating temp of 25 deg C. If you now operate that OPAMP at 50 35 deg C, (correction) you can expect that OPAMP to fail after 50,000Hrs - whether it does actually fail or not depends on a lot other factors...
 
The Heatsinks in the original Lehmann I think were picked on a cost vs performance basis: As a manufacturer you try to avoid over-doing things, i.e. put more heatsinking in than you really need or can get away with; you're just wasting money and chewing into your profit margin if you do! (Don't forget Lehmann and any other manufacturer is in business to make money, the fact they do audio, is just the conduit they've decided to pursue to make money)
 
You can stand the transistors vertically on the board, as per the M-Stage, and use a heatsink that has a better dissipation capability e.g. One of the guys I know used this heatsink style vertically mounted on the board:

I don't have access to his gear to show you a photo, but the heatsinks stand vertically as per the M-Stage design, side by side, in the same position as the heatsinks that were lying flat on the board. He pulled out the pins and just used a PK Self-Tapping screw through the PCB to hold the heatsink down. He also earthed the heatsinks via the Self-Tapping screws to the ground plane.
 
Another guy wants to use a special heatsink similar to the following:
 

 
Again the transistors are mounted vertically, and the heatsink would be secured to the board via the holes in the PCB for the old heatsinks. I don't know where he's got with this - he was trying to find someone to mill the heatsink to fit the board last time we chatted about it. UPDATE: The reason for this is the design being used increased the current through the output transistors by replacing the 1,5k resistors with 1k Resistors ; I don't know if this works or not, we were talking about replacing the output devices with some SANKEN 2SC4883 and 2SA1859:
 
Personally, I used a slightly bigger version of the heatsinks used in Lehmann's original design, I bought them from RS Components: AAVID THERMALLOY TV4G:
 

 
 
 
I never actually thought about the heat dissipation being an issue with the Lehmann design: It's seems warm to the touch but, OK I guess. I focused my attention to the electrical performance and operation of the design more...

 
 
 

 

 

[BlaBlaBla]

FlukeII, you were right about resistors and voltage across them. Mine have also 0.45-0.5V. Even 0.5W will be enough. But resistors are not expensive. 2W or 1W it does not matter... Usually, people look at bigger resistors with greater respect.

 
 
Unfortunately TV4G will not fit in this small piece of sh--/box. Maybe, only in a place for regulator (LM) but not in a place for BD. When I see such a small space for heat sinks (in today's amplifiers and similar stuff), I become sick. But I found solution...
I buy the drugs. A lot of them. Word "optimization" makes me sick.
 
Recently, friend told me that adequate (working) temperature for regulators is 35-45°C. For output stage 40-50°C. That means 15-30°C above room temperature. This amp goes 30-45°C above. I always ask myself why all amplifier designers trying to spare money on few metal parts.  And I still can not find a good answer. Especially when "that something" comes from "not so cheap" and respectable company. Is the same situation in Burson HA160? I do not know. It seems that housing is the most expensive part of an amplifier.
 
On the other hand there are amplifiers that have excellent cooling. For example,Shiit Asgard (that has been my first choice, but then I decided to buy LC). In it transistors are connected directly to housing. But it is so hot that lots of users have found it good in a kitchen and have used it as a stove. (Maybe that is reason why Shiit Asgard is more prefered by women than men...) Unfortunately, I do not cook very often.

 

[FlukeII]

 
Quote:

FlukeII, you were right about resistors and voltage across them. Mine have also 0.45-0.5V. Even 0.5W will be enough. But resistors are not expensive. 2W or 1W it does not matter... Usually, people look at bigger resistors with greater respect.

 
Agree - Sometimes big  resistors look good, even a selling point may be! They tend to suffer from a slightly larger ESL than the smaller ones due to the physical dimensions of the resistor element. My friend using the VISHAY VSR Bulk Foil Resistors reckons his amp had a better slew-rate than mine - we haven't measured it, it just an opinion. (I'm talking about conventional spiral cut resistors such as the MBB 0207, SFR 25 or MRS 25. The thick film SMD resistors don't suffer this problem. In fact I was told once that the larger 1203 SMD resistors sound better than the smaller 0802 0805 or 0402 SMD Resistor devices by that guy in Texas I mentioned in a previous post)
(The MBB 0207 resistors use an advanced thin film technology  and offer a low TempCo: up to ±25/50 ppm/degK, they don't suffer from the same level of ESL as the MRS25's for example, they use a laser to achieve the target value by smoothly cutting a helical groove in the thick film element - they are not ESL free or as good as say an SMD 1203 resistor)
 
Unfortunately TV4G will not fit in this small piece of sh--/box. Maybe, only in a place for regulator (LM) but not in a place for BD. When I see such a small space for heat sinks (in today's amplifiers and similar stuff), I become sick. But I found solution...
I buy the drugs. A lot of them. Word "optimization" makes me sick.
 
Recently, friend told me that adequate (working) temperature for regulators is 35-45°C. For output stage 40-50°C. That means 15-30°C above room temperature. This amp goes 30-45°C above. I always ask myself why all amplifier designers trying to spare money on few metal parts.  And I still can not find a good answer. Especially when "that something" comes from "not so cheap" and respectable company. Is the same situation in Burson HA160? I do not know. It seems that housing is the most expensive part of an amplifier.
Engineering is as much an art as it is a science (you need both skills), different people have different philosophies - it's good as you can stand back and figure what works for you and what doesn't and then take the ideas from  a bunch of different designs and incorporate them into you own designs.
 
On the other hand there are amplifiers that have excellent cooling. For example,Shiit Asgard (that has been my first choice, but then I decided to buy LC). In it transistors are connected directly to housing. But it is so hot that lots of users have found it good in a kitchen and have used it as a stove. (Maybe that is reason why Shiit Asgard is more prefered by women than men...) Unfortunately, I do not cook very often.
 That's funny!

 

 

 

[BlaBlaBla]

Quote:

There is still very little impressions and comparisons being made regarding this amp, would be great if those of you who got it can send in some of your thoughts about the amp?

 
Hi, oliverws!

My subjective view... Compared to Matrix M Stage, Lovely Cube is less sterile and more involving. My Lovely Cube has 20% better sound stage (more wide and better positioning). Sound is more "into your face" than "laid back" as is in Matrix M Stage. DC offset is less (almost two times) and it is less warm. Matrix M Stage, compared to stock Matrix Mini I, compress sound stage. Lovely Cube represents stage as it is in Matrix Mini I amp.
 
Because sound stage, imaging and etc. depends on opamp, capacitors and everything in your circuit, and LC is tunable, you will not find exact comparation...
In my case there are ERO MKC and KP on input, KP is in opamp bypass, and stock Philips Tin Foil in a circuit connected with ground. Input caps are stock Nichicon Gold Tune 4700uF, output caps are Panasonic FM 470uF, regulator caps are stock ERO MKT (input and output) and tantalum 10uF on Vadj. Buffer transistors are BC109C and BC179C (CDIL and NXP), output transistors are stock BD139 and BD140. Others have something else.
 
If you want more data, you should ask FlukeII. Technically, he is more involved in LC project than others, and he has right equipment to measure it and take out a conclusion.
 
But the fact is that you should not take our measurements too serious because, as I said before, one component can change entire picture... My opinion is that LC is worth money, and sound wise, it will be better than Matrix M Stage. If you want try DIY, lovely Cube is "a must".
Here we have lots of advices. Sometimes fight is very close 

and that is because all people have different opinions. But after all, it is all about DIY.

 
Oliverws, do not bother with data. Just DIY!

 

[oliverws]

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[oliverws]

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[BlaBlaBla]

 
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And one more thing, about the things being said that it gets quite hot. It won't keep me from not having to place the musiland with rubber feet on top off the amp will it?

Lovely Cube goes hot but does not melt rubber...
 
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I listen to mainly Genesis and songs in general you'llwant to hear every nuance off every instrument. Will use it along side Musiland 02 US and a pair of AKG K701. Have had Audio-gd DAC19+C2 before but am now looking for something a little bit slimmer. And hoping im not downgrading myself too much with this purchase in comparison to the audio-gd setup.

 
Why you did not say earlier what headphones do you want to drive...
 
I will try to be as simple as possible. I think that AKG K701 are not good match for Matrix M Stage, Audio GD C2 or Lovely Cube. Those are cheap amplifiers. You should look above 1000 USD. WAY ABOVE.
 
People think that AKG K701 is best buy, and that they will have "ultimate sound" on every amplifier that has "enough power" to drive them. Well, that is not true. Because if you want to drive them properly, you will have to spend a lot on amplifier. A LOT. I had Matrix M Stage. A lot of people here were talking that "M Stage is match from heaven for AKG K701". Well it is my ass. It had power but for what? For moving drivers? I can do that with my finger... K701 sounded artificial, sterile and lifeless. But when my friend paired K701 with Leben, that was different world. Sound was warm, fast and full of life. There was SOMETHING.
 
If you want to try different amp and DIY, that is excellent. But do not expect wonders. No offense but you have not heard 30% of your K701 headphones (Like all others with cheap amplifiers (below 1500 USD) who believe in fairy tales written in well paid reviews) ... Lovely Cube will not help you in that. Asgard will not help you. Audio Gd will not help you. What will help you are VERY EXPENSIVE tube amps, because they will give K701 warmth and life. And they will use in a good way K701s ultimate precision, extra sound stage and flawless feeling for details.

 

[purrin]

^ You forgot to add that if you are going to get a very expensive tube amp (> $1,500 USD), you may as well throw the K701s in the trash and get something better. 

 But ya, I agree with you - the K701s need the right amp. Although it's possible that folks like the K701+LC combo for it's bass control and speed.
 
@oliverws: you may be going in the wrong direction moving from away from the AGD DAC19 + C2 to the Musiland + LC setup, at least for the K701s.

 

[taiyoyuden]

I thought this amp is supposed to be good with the k701. If it's not, at a reasonable price, what is?

 

[BlaBlaBla]

Quote:

I thought this amp is supposed to be good with the k701. If it's not, at a reasonable price, what is?

It is good, but not outstanding...
 

 

[purrin]

It's probably the cheapest amp I can think of that can power the K701 properly. K701 is a tough one to amp properly. It needs two things:
 

1. Enough power (which is hard but possible to find cheap, but LC fits the bill. Asgard, A-GD too for a bit more.)
2. The right kind of sound while not taking away the K701 strengths (which is not possible to find cheap.)

 
Personally, I wouldn't touch the K701 with the LC/M-Stage/LBCBCL. But the LC+K701 setup at ~$500? would be hard to beat if you are into that kind of sound (detailed, fast, and controlled.)