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Old 24th March 2013, 07:04 AM   #191
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Concerning power supply rejection issue I recommend:

1. to twist psu and loudspeaker conductors to make them less inductive
2. to cross input, psu and loudspeaker conductors only if necessary and at 90 degrees
3. to distance input, psu and loudspeaker conductors as much as possible
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Old 24th March 2013, 07:48 AM   #192
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@PMI

My dear cold friend
you are in the beginning of a long journey to details ...Hifi and far more hi end is about detail
Miller caps cannot be ceramics but most of all you should be able ( or trained ) to spot the difference In some ppls case the beginning is to be able to measure the difference...

So yes the 2 v output will be very able to drive the P3A point is that using a pot in the input will kill the dynamics in low listening level which actually is the sweet spot of listening on the P3A

though listening to mid and high levels you will not be able to tell the difference ...

something with a little gain is needed

Other details like construction , power supply , matched parts will also increase sound quality amplifiers is all about precision and symmetry ....It will play any way circuits like that are very forgiving but the point is to get the max out of it

Kind regards
Sakis
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Old 24th March 2013, 02:05 PM   #193
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Temperatures are supposed to break 32F (that's 0 degrees C, to everyone else), so my brain may thaw out enough to get something done today.

@ivanlukic: I am still considering this my prototype, so I am sure that the wiring is not ideal, but signal wire (shielded) and speaker wires are the same for bench supply or the rectified/filtered AC supply, and separate. Listening power level is low, no great demand placed on either supply Difference is small, but noticable in a quiet room with rested ears (morning).

I plan to make the changes recommended by Sakis, and then try this again. Never called myself an audio expert or audiophile, but I do have a general understanding of analog circuit design and linear supplies. There may be some other simple wiring or grounding issue here, I am sure I will figure it out. Main reason why I commented on power supply, I was surprised that the bench supply (with current limit engaged and variable output set lower than my intended 36 V rail voltage, and a few loose leads), sounded even OK, let alone better.

The other way is from wall outlet to Variac (7.5KVA), to transformer, to rectifier/filter, and separate pwr/gnd to amplifier boards.

@sakis: Advice noted, ceramics gone, terminated, with prejudice (and clippers)...

I must say it sounded fine with them in place, too. Wait... was I supposed to replace them with something...?

Ok, jokes aside, I now have a handful both silver mica and some nice Wima film caps in hot pink. No more ceramic Miller caps. Main reason I used those is because they were listed as the default choice in Rod's parts list.
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Old 24th March 2013, 02:23 PM   #194
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The reason why I commented on the P12... since this is a thread about making comparisons, it seemed like a good opportunity to compare the two designs, made by the same person (Rod), with similar drivers and output stages.

Most comparisons are nowhere near being useful to the average person (like me), because they are always an apples-oranges comparison. Completely different designs from power supply to output stage, so any difference between current and voltage fb is lost in the mix.

Along the same lines of thinking, the attraction to me of using a single, passive, point volume control (i.e. pot or attenuator), is obvious. Right now, I have to turn the signal down quite a bit at the source, just to listen to the amp. If I use a conventional preamp, it will be hard to know what I am listening to, the preamp, or the P3A circuit...
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Old 11th May 2013, 08:39 PM   #195
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Quote:
Originally Posted by tinitus View Post
I guess that answers it .... maximum reliabity sounds good for my bass guitar... and intended for dummies, spot on too

I expect to hardwire on proto board

regarding the Darlingtons
with their high current gain, I suppose they are easy to drive, and might have been chosen for that reason ?

http://www.onsemi.com/pub_link/Collateral/TIP140-D.PDF
tinitus. Check out www.mcmelectronics.com . Find part #28-12890. It is a kit for an amp which has a schematic like that of AB100 ; but with a lower output power.
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Old 11th May 2013, 08:47 PM   #196
tinitus is offline tinitus  Europe
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wow....25USD for a kit
I really dont need more amps at all ....but thanks anyway

but would be fun to own the only existing Pass bass guitar amp
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Old 12th May 2013, 05:14 AM   #197
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Quote:
Originally Posted by Antoinel View Post
tinitus. Check out www.mcmelectronics.com . Find part #28-12890. It is a kit for an amp which has a schematic like that of AB100 ; but with a lower output power.


That kit is a velleman thing eventhough it doesn't sell much cause is pretty expensive and outdated for this range of product and its actually a similar product to this Hi-Fi Amplifier 100W MetaTitle which exist in the market for more than 25 years .

even though it is constructed with heavier limiter = ( input filtering, miller caps+additional miller caps ,and full I limiter ) has a history of fail world wide

Obviously except the history of fail there is a history of not possibility to repair cause NB that get the kit blow it and go to the shop asking for one BDV 166 and one BDV 67 usually gets one BDV 66 from Philips and one BDV 67 from ST cause this was available at the shop at the time ,And that one on its own was a very good reason for a big kabooom and magic blue smoke !!!

most of them gave up

for the record and history :
The kit shown in the picture was made in Greece ( still is ) and is as said more than 25 years in the market . The 100 W title is pretty catchy like the most hated amplifier with the catchy title ""Cheap 150W amplifier "" the John Fisher amplifier .

Thousands of modules sold in Greece, thousands in USSR, and world wide but also the real Market was UK where some company was reselling Smart kit with some other name . ( poor Brits they got thousands of defective modules !!! )

From the first board and for more than 15 years there was a PCB error where part of the bias was tied in the output and probably output signal was modulating bias with unknown or catastrophic results PCB error together with a new pcb was fixed i think 7-10 years ago

Kind regards
Sakis
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Last edited by east electronics; 12th May 2013 at 05:22 AM.
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Old 12th May 2013, 09:51 AM   #198
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Thanks sakis for the incredible history of this 'velleman/MetaTitle"amp.
Best regards.
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Old 12th May 2013, 10:27 AM   #199
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Quote:
Originally Posted by Antoinel View Post
Thanks sakis for the incredible history of this 'velleman/MetaTitle"amp.
Best regards.

privilege of the age ....Monday i am 47 and i am in the market since i was 13...Many many years of audio pleasure wouldn't change this job for anything in the world ...

PS
At the age of 16 my mastoras ( master probably = the old highly experienced fellow ) said to me you are good ...learn television and you will make money ...

Said to him NO!!!! sound is what i like to do ...money came later while i never made a fortune at least i wake up every morning with a big smile going to work . ( probably because my brain was processing some amplifier through the night rather than processing my wife )

Happy regards
Sakis
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Old 13th July 2013, 12:32 PM   #200
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Through the economical crises .... been way too busy as usual but favorite projects will always consume some space in my mind ...

Box , case, chassis, looking good easy to produce but most of all in a reasonable cost was always the question in diy

Huge mistake everybody does including me is to design circuit and pcb and then look for the enclosure ...

Best way and more cost effective is to choose an enclosure and then built the pcb around it

With these in mind i made a new lay out ( i think now i should be in version 125 or so) that features all of the above described goodies plus a couple new mostly in the power supply + some degeneration and its made to fit in a simple 2U chassis with drills onatop for ventilation and a simple but thick U shaped aluminum for heat sink ( given that bias will stay in a low to reasonable level )

Notice that transistors are mounted onatop but backwards so heat sink is directly screwed on them, the all board is to be secured on the chassis bottom ...

Will produce this pcb also , put it to work and evaluate the couple of new goodies and always post my findings here

Kind regards
Sakis
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