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Old 20th September 2012, 07:19 PM   #2561
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Quote:
Originally Posted by mikelm View Post
Thx Nico,

The Guy who developed this amp is called Tim Andrews ....

I thought some people ( like nelson pass ) like the sound of 3rd HD

cheers

mike
Hi Mike,

I did not mean to say that Tim amp was worse or better that JLH but it is a different design in my opinion.

I built a JLH only late last year purely to experience the charismatic sound that many enthusiasts claimed, but I did not become a converted. It does sound very nice but not for too long. (In my opinion) Most likely it does not partners well with my very inefficient speakers.

Have a look at the harmonic distribution that Tim creates with his design. Certainly how he perceives is tonally more accurate and many may prefer his design over that of JLH.
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Last edited by Nico Ras; 20th September 2012 at 07:28 PM.
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Old 20th September 2012, 07:21 PM   #2562
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maybe we ask:
are you towing a caravan, or transporting a blonde?
Would a blonde know the difference? Maybe the blonde and caravan is a better combination.
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Old 20th September 2012, 08:37 PM   #2563
ferret is offline ferret  South Africa
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Default Bedini amp and psu circuit

Here they are gents. Very roughly drawn on paper; I don't have software to do this neatly unfortunately. Notice the lack of regulation in the psu - very basic. When I rebuild the Bedini will add in regulator module to see (hear) the difference. This is going to take some time to get to but hopefully not more than a year. BTW I've had this amp for more than 25 years and only switched it off when we moved (3 times) and when minor repairs had to be done - replaced reservoir caps and feed-forward caps (47uF went soft to 25uF and gain climbed considerably in that channel; did both channels). The rebuild is going to be done into a new chassis (bigger) with separate transformer per channel and better heatsinking.

Regards,

Kevin
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Old 21st September 2012, 04:51 AM   #2564
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Here they are gents. Very roughly drawn on paper;
Kevin
Thank you Kevin, nice job. When you visit we can talk about how to rebuild your amp.
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Old 21st September 2012, 08:55 PM   #2565
mikelm is offline mikelm  England
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Quote:
Originally Posted by Nico Ras View Post
I built a JLH only late last year purely to experience the charismatic sound that many enthusiasts claimed, but I did not become a converted. It does sound very nice but not for too long. (In my opinion) Most likely it does not partners well with my very inefficient speakers.
I learn't my electronics by pouring over this cct for a long time and eventually I think I got the hang of what was going on

I also was not overly impressed with the sound and some of the mods I subsequently did that I thought improved things I think are regarded as a heresy by some true believers - I guess we are not all looking for the same things from our audio systems - and I think it would have to be quite a large implementation to deal well with inefficient speaker.
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Old 21st September 2012, 11:44 PM   #2566
Bigun is offline Bigun  Canada
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Originally Posted by mindutis View Post
I am building one again The chassis i am making weights 15Kg already without anything inside of it I expect total weight of about 25Kg. Found a very nice 2SC2922 output transistors. It needs about 10pcs to match them for a stereo amplifier. Not that many at all. The expected Power dissipation should be around 130W per chassis.

Just have no idea how much capacitance ill be needing with 30V power supply voltage. So far I ordered 90.000uF total. But i think it will be too little.
wow, that's what I call an amplifier !

I'd try the caps you've ordered. If it's not enough, maybe a choke could be helpful.
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Old 22nd September 2012, 06:28 AM   #2567
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Default choking up

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Originally Posted by Bigun View Post
it's not enough, maybe a choke could be helpful.
+1 But finding (vs ordering custom) iron can be hard. I've had some success with misusing the secondary of EI power transformers.

To date I've been too lazy to rewind anything but that should also be a possibility
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Old 22nd September 2012, 06:49 AM   #2568
mikelm is offline mikelm  England
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I routinely "misuse" the secondaries of EI transformers as chokes - some purist don't seem to like the idea because of the partial loss of inductance caused by core saturation but allowances can be made for that and what that leaves is a quick & easy, fairly cheap supply of chokes with different R / L combinations readily available ( for now ).
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Old 22nd September 2012, 07:22 AM   #2569
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Hmm, interesting idea with the secondary as a choke. Have never tried that. What is the worst case scenario doing that? I kinda think its cheapier to buy achooke instead of using a normal transformer.

PS
Cant find any suitable choke on the internet (only for tube amps). Has anyone a link maybe?
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Old 22nd September 2012, 07:58 AM   #2570
mikelm is offline mikelm  England
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I only use these for low Voltage / high current solid state class A type amps.

These only need very small choke values for extremely effective filtration ( 1 - 5mH ) so it is really easy to use any kind of a winding found in commercial EI trannies.

Valve amp designs need much bigger inductor values because of the high voltage / low current environment and this makes the design of the choke much more of a specialist "black art" kind of a thing, necessary to tailor the frequency & quality of resonance.

In the much smaller choke values that solid state amps need these problems don't really arise.

I suspect for valve amps you will need to buy purpose built chokes - sorry about that but laws of nature are not optional
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