Quote:  

  Quote:   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...

Quote: 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...

And the different capacitors for the power supply stage; as well as alternatives to the United Chemicon LXZ 470uF 25V Electrolytic used to decouple the various stages in the amp...

Quote: There is more to come, I've just been busy with other things i.e. work.   Other things: User a Super Beta filter to fed the OpAmp OpAmp changes: I like the LME49720, but friends prefer the AD823, NE5532 even! Personally, I think the OPA2134P is a little dull sounding...

  Quote: Hi BlaBlaBla, Electrical Engineering is my livelihood and I learnt early on having good test instruments can save a lot of hassle and bother – they don’t have to be new, just good and reliable.   I guess if you want to make Electronics a long-term hobby, investment in a...

  Quote: Two extra clarifications to make here:   1. The total resistance of the resistors in each BD139 / BD140 Emitter Resistor should remain 10 Ohms: You can use 3x 30E in parallel, or even 10x 100E --> The total resistance is 10E   2. The Metex meters only measure Hfe (at a...

If you're interested, someone sent me this link on transistors matching:   http://www.musicfromouterspace.com/analogsynth/TRANSISTORMATCHER/TRANSISTORMATCHER.php   Happy experimenting...   If someone is looking for a book that ( I think) gives a good introduction to Electronics...

  Quote: I've found that 1W Resistors work OK in the output stage as the 10 Ohm Emitter Resistors, it's just they look kind of small on the board. Getting the ESL (Effective Series Resistance Inductance) down by putting smaller resistors in parallel I found helps to improve the slew...

  Quote: It our experiences, it's kind of like renovating a house - it's not complete until you've done everything. Yes you do get some gains replacing some parts, changing out the ELNA 4,700uF cap with a Low ESR type from VISHAY BC COMPONENTS - MAL205857472E3 - CAPACITOR, 4700UF, 40V...

I forgot to mention, the VISHAY Bulk Metal® Foil Technology Industrial Precision Resistors, VSR Series resistors are very expensive. $$$$   Personally I favour the VISAHY Vishay Beyschlag MBA 0207, Professional Leaded Resistors for all the positions in the circuit:     I used the...

Getting back to the main topic:   This is a schematic of one channel of the amp. Please note the component designators (R1, C2 etc) are wrong, but the values, 47E, 1,5K, BC550C I believe are correct.   The voltages are helpful if troubleshooting a faulty board or you want to get an idea...

  Quote: Ray, Ray, Ray,...   You're barking up the wrong tree...it occurred to me while I was in the Bathroom that your thinking the boards I bought were finished or fully populated. Sorry my mistake, again...   I interchangably use the term board to mean a PCB or PBA depending on...

  Quote: Let's square this up once for all - I haven't been completely honest here... I got the eBay Lovely Cube back in early 2010; It actually belonged to a friend who managed to blow it up and he asked me to fix it... Then when visiting Shanghai late last year I got to buy the...

hey rayshader     LOL...The clones of the Lehmann Black Cube Linear are widely available in China - Check out: Taobao's Auction site: For example: http://item.taobao.com/item.htm?id=170113383 for one....490 Yuan or USD$75 isn't bad for an amp in a box!!!   Sounds like you need...

Just to put things into perspective, when I was in Shanghai last year, I picked up 5 of the Lovely Cube clone PCBs at an Electronics Market that a work colleague took me too. They cost USD$5.00 each - USD$25.00 for the lot. I actually paid the guy in USD as I had ran out of Yuan!!   I think...

Incidentally, the orange axial capacitors used Vishay BCcomponents Polypropylene Film Foil Capacitors KP Axial Epoxy Lacquered Type:   22nF or 20nF, KP460 URdc = 63 V; URac = 40 V: Bypass the 470uF Electrolytics used around the OPAMP and also used to bypass the 1,5uF MKP EPCOS...

The 470uF 25V Electrolytic used to decouple the Diamond Output Buffer stages and the Op-Amp in the Lehmann Black Cube is a United Chemicon part, LXZ family.   This part seems to be LXZ25VB471M10X16LL, 10x16mm. The specs on this part are pretty good for a switchmode supply type application...

  Quote: Sorry I didn't get your line of reasoning, nor is this a place to get personal?   What we were trying to do was get as close to the real thing for as cheaply as possible...nothing more or less...we then thought we'd try some ideas; why not?   This isn't expertise...

It's good to have a go...it's only a $90.00 board compared to trying to mod a $800 genuine article. Someone asked me to MOD their Lehmann after they heard the moded Lovely Cube belonging to a mutual friend. I was seriously sweating when I was desoldering the parts on the board!! In NZ money...

  Quote: You need to be careful about the size of capacitance of the smoothing capacitor you use; this is complicated, as it depends on a number of factors as to whether or not you blow up or stress your rectifier diodes at switch-on, and / or burn out the series resistors inline with...

  Quote: Whoa! Sorry didn't mean to touch a raw nerve here...But, after a couple of friends re-worked their Lovely Cubes, one of them encouraged me to post this stuff up here.. After all we buy these Kits because they are a lot cheaper than the USD$800 for the real McCoy...but to get...

Does anyone own a BLOSSOM BLO-0299? What do you think of it?   The wood casing looks kind of cute, what about the sound?

  Quote: Hi Knusperfisch,   Fakes are important IMO: I once spent two weeks trying to figure out why a headphone amp that I was designing was unstable and then when I connected low impedance headphones (GRADO SR60s) would blow the output stage and then assert a DC offset on the...

  Quote: Hi BlaBlaBla,   Don't get too concerned about overloading the LM317T/LM337T regulators in the amp, provided they are heatsinked adequately, they will go into current limiting mode, on switch-on, (Iinrush to the caps will be limited to about 1,5A to 3,4A (depending on device...