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February 24, 2020, 09:14:41 AM

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1
The Newcomer's Forum / Re: JLH 1969
« Last post by phatt on Today at 07:22:34 AM »
Hi Loudthudsy,
                     I tried to search for that MC12DAR circuit but got nothing meaningful.
I'm interested to try it out as long as it does not need unobtainium reverse wound diodes. :lmao:
I think my problem with trying to get SS PwrAmps to respond like a Valve PwrStage is that
Even if one can reproduce a tuby SS Pwr Stage one is still stuck with the same limitation as A valve pwr stage. That being, they only sound good when they are cranked up. I noticed this with some of the Peavy gear.
So having built quite a few amps now both valve and SS I just use pedals for all the dirt tricks and the amp is a clean simple SS PwrAmp.
I also have built a few ReAmp systems for myself and a couple of local players with quite stunning results.
A small 10w pp Valve amp driving a resistive load and line out to a clean all SS second amp.
This removes the limitation of having to play loud to get the magic OD of Valve pwramp.
So from bedroom to gig SPL's the sound/tone/dynamics are much the same.
BTW my resistive load is NOT the common 8 Ohm load on 8 Ohm tap which as you may already know kills the magic.
Thanks for posting the plots, very helpful.
Phil.
2
No worries Lex, Happy to help. :tu:
Yes mate That is the program I use.
How fast you learn to use it depends on how much you already understand about electronic circuits.
But as I mentioned what's to loose because you can't blow anything up and you can't kill yourself by touching high voltage or burn your fingers on a hot soldering irons.  :lmao:
You will still need to read up on some of the basics of audio circuits, a lot can be found on the dub,dub,dub and help is also here of course. 8|

The program comes with a whole library of circuits for you to learn from, some of which will be useless for Audio but no matter just start using it and don't expect to understand it all in a few weeks. It took me 6 months to fully grasp what the hell I was doing and it does send you loco at times.  :loco
Be warned it's a highly addictive hobby, And I'm just so grateful for the friend who introduced me to simulations years back. Even though i already had a fairly good grasp of how amps worked, sims just saved me years of building land fill.
As they say "a picture is worth a 1,000 words"
check your pm's, Phil.
3
Guitar News / I love battery amps: Blackstar releases new Fly 3 Acoustic Mini-Amp
« Last post by joecool85 on February 23, 2020, 04:27:34 PM »
For under $100 USD (exact price not released), you can get 55 hours of play time on this flat response acoustic amp.  Perfect for vocals, acoustic guitar, or (my thoughts), electric guitar with a pedal board!

https://www.guitarplayer.com/frets/blackstar-debuts-new-fly-3-acoustic-mini-amplifier
4
Amplifier Discussion / Re: Marshall MG 50DFX transformer
« Last post by Jazz P Bass on February 23, 2020, 02:57:16 PM »
Who have you 'tried'?

I would suggest Part Is Parts. 1-800-590-0014 USA/Canada
1-802-365-7257 International

And/ or Full Compass. 800 356 5844

They will do there best to get the part from Marshall.
5
Amplifier Discussion / Re: Marshall MG 50DFX transformer
« Last post by ccork on February 23, 2020, 12:36:42 PM »
Having a problem finding a part #: TRANSUD0012 POWER TRANSFORMER  for MG50.  Anyone have the specs so I can try to find one or know of a substitute transformer?
6
The Newcomer's Forum / Re: Introduction, a question and a hope for some insight / help
« Last post by Lex on February 23, 2020, 05:12:45 AM »
Ok Phil thanx,

still looking for the time to get into it.

Tell me please, that piece of the software is 'Circuit Maker 2000' ?

Could you share with me the 'project' file so I could import after the installation and test / learn / play .. ?

Im still not so familiar with the signs so it will take me weeks figure out

Greetings all and have a good Sunday

7
The Newcomer's Forum / Re: Some wisdom regarding speakers
« Last post by Lex on February 23, 2020, 05:07:40 AM »
Thanx all for your reply,

it's obvious .. buy them all, try them all .. and probably keep them all !!!

Cheers

I like the way you think lol.   :tu:

yeah .. have the same with the cars, bikes, ski's .. and probably other stuff

still much cheaper than keeping a women around

8
The Newcomer's Forum / Re: Some wisdom regarding speakers
« Last post by joecool85 on February 22, 2020, 07:52:42 PM »
Thanx all for your reply,

it's obvious .. buy them all, try them all .. and probably keep them all !!!

Cheers

I like the way you think lol.   :tu:
9
The Newcomer's Forum / Re: JLH 1969
« Last post by Loudthud on February 22, 2020, 10:46:04 AM »
For comparison below is a THD plot of a TDA2030 chip amp and the MC12DAR that I linked above.

Note the Chipamp has low THD for much of the graph, then rises steeply at the right where clipping starts to occur.

The MC12DAR has no global AC feedback to it's THD is higher but it has a lot more gain. The THD rises gently and reaches several percent before clipping occurs.
10
The Newcomer's Forum / Re: JLH 1969
« Last post by Loudthud on February 22, 2020, 09:29:06 AM »
I built a JLH last week and here's a THD graph I plotted. The power supply is only about 30V so power is about 10W at 8 Ohm. Notice how THD rises slowly and then takes a turn about 10W at .5% THD. This is where hard clipping starts to occur. The heatsink is 1 degree per Watt runs 55 degrees C. Too hot to keep your hand on.

Contrast the above to the Nelson Pass design called the ACA. This is a little amp that does about 10W at 4 Ohms. Two channels are bridged to give about 20W at 8 Ohms. Notice how THD is rising slowly but doesn't take the turn until you get near 20W at 5% THD. Much more tube like. The ACA kits you can find at diyAudio run on a 24V switching supply so you don't have to mess with mains wiring.
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