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Messages - phatt

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1
Guitar News / Re: Coronavirus hitting the music industry
« on: March 19, 2020, 08:05:08 AM »
The Elephant in the room; :o
It took ~~ 40,000 Yrs to reach 200 Million people on this planet
At the time of Christ it's estimated that it was a shade under 200Million.
By the 1830's we cracked the 1 Billion mark.
Less that 200 Years later we have hit the 7.8 Billion.
Now if that does not tell you the real reason for the worlds problem I don't know what will. 8|
Unlike the FAKE hockey stick curve presented by Al Gore this one is REAL.
https://www.worldometers.info/world-population/
Scroll down a bit for the graph,, scary :'(

There are people that suggest that the human population on Earth be limited to 500 million. The first place I ran across this was here:
https://en.wikipedia.org/wiki/Georgia_Guidestones
It's interesting that they can't seem to be able to track down the people that paid to put these things up.

Thanks, Interesting find, I did not know about that one.
Maybe they wanted to stay anonymous as they would have been persecuted. 
Although a bit hard for us all to swallow it's a fair assessment as there is a limit to how many people the planet can sustain.
Phil.

2
Amplifier Discussion / Re: Adding spring reverb to a 6V6 guitar amp
« on: March 19, 2020, 07:50:27 AM »
Assuming you have this new rev circuit on a separate board.
Then my first thought is,,,Check you have a ground path back to the main amp circuit?
Phil.

3
Guitar News / Re: Coronavirus hitting the music industry
« on: March 14, 2020, 09:17:52 AM »
The Elephant in the room; :o
It took ~~ 40,000 Yrs to reach 200 Million people on this planet
At the time of Christ it's estimated that it was a shade under 200Million.
By the 1830's we cracked the 1 Billion mark.
Less that 200 Years later we have hit the 7.8 Billion.
Now if that does not tell you the real reason for the worlds problem I don't know what will. 8|
Unlike the FAKE hockey stick curve presented by Al Gore this one is REAL.
https://www.worldometers.info/world-population/
Scroll down a bit for the graph,, scary :'(

Anyone who is familiar with the world of Stock markets will likely know of the bell curve. It goes up and then crashes.
That graph shows it's about to fall over and crash. xP

I do realise that no Politician or world science geek is ever going to mention it in public but that is a reality that we as a species will ALL have to face in the not to distant future.

Regarding *Joecools* comments staying healthy;
Same problem as my fish aquariums when I was a kid,, once they breed and the tank gets over crowded then disease often takes over.
It's darn hard to stay healthy when the whole place is full of pollutants from being packed in a sardine tin while eating organically dead processed food. xP

We fall victim to bad health because we are feed crap food so hence our health in general is starting to fail us, especially in western countries.
If you buy packaged food from supermarkets then it's highly likely you are eating unhealthy highly processed crap foods.
Wheat was hybridized in the 40's and went world wide by the 70's. At that time the world was in famine and it solved a problem. That bloke got the nobel prize, but guess what?  We just kept breeding more people. Durh!!!
As the old saying goes you solve one problem only to find you just created a much bigger problem. opps!
Sadly modern hybrid wheat has a higher GI level than sugar. Sugar is 55 while white bread is in the~60's :o  **Ed opps,, Sugar is 59, Wheat is 69**
It's estimated that 1 in 4 people in the western world now have diabetes. (another Hockey stick curve)
Before sugar was refined and wheat was hybridized Diabetes was hardly ever noted. Now it's off the scale.
If you don't know, Hybrid wheat products of some kind are in nearly all processed foods, that's just about everything in packets, boxes or cans.
I have not used the bread or cereal isle for many years now and I'm in far better health than I have ever been.
Really good info is very very hard to find and you have to read a lot, Do your own research and stay away from doctors as they will make you sicker than you already are. 8|
I've had debilitating health issues since my teens and in the end I was forced to heal myself. It was a lot of work but I no longer live in fear of silly viruses.
Phil.

4
Without the output Tx cutting all the fizz I don't see any great advantage.
SS power amps are DC coupled and hence don't cut the fizz generated by over driven stages. :'(
The OTx is part of the magic of Valve amps,, most of the great Valve amps did not use hi spec OTx's and so they smooth out the hi freq crud.
Valve pwr stages also cut very low freq because of caps (AC coupled circuits) and maybe some miller effect.
Most SS pwr stages (Especially ones like you mentioned) are dead flat,,, So unless you have an intricate understanding of how to circumvent all that then my advice is leave the SS pwr stage stock and do all the fancy stuff in a well designed preamp.
Or just research some pedals there are plenty out there 8|
Phil.

5
Amplifier Discussion / Re: Peavey CS400
« on: March 10, 2020, 12:53:58 AM »
First check the DC Voltage at the speaker output?
If not very close to Zero then the circuit is faulty.
Yes could be HF problems.
If the amp is working (No DCV on output) then I'd replace the burnt components and see if they run hot. Better minds here will know more. :tu:
Phil

6
Tubes and Hybrids / Re: JTM60 Combo rectified diodes fried
« on: March 04, 2020, 06:34:13 AM »

Resistance across tip and sleeve with tubes in is 138k
I assume that is the resistance reading on the secondary of the output Tx?
Well if so then the output Tx is open,, sounds like a complete failure and taken out both tx's and power valves all at once. :'(
To the best of my understanding;
If the amp is trying to drive such a high output resistance (130k) then you may end up just repeating the same destruction. Never run a valve amplifier with a high or no load resistance you will blow it all (As above)
Pull the Valves and repeat the DC voltage testing, as you did before,, if they read ok then check the Output Tx.
Phil.

7
The Newcomer's Forum / Re: JLH 1969
« on: February 27, 2020, 10:33:16 PM »
@ Loudthud,
Oh thanks for that,, I just realised that I was not logged on so did not notice the schematic,, durh me. :duh
well as luck would have it i have a pair of TIP142/147 and a few 2N7000.
Not about to build, just wanted to Bboard the circuit and see how it performs.
I'm not expecting the same Grind I get from my little 10 watt valve amps but if it gives a nice little rattle I might pursue it further.
I agree, pwramps sound good when driven hard but then I'm back to the SPL issue, even a 10Watt amp is often too loud for home practice. :-\
I assume there is no short circuit protection and only about 20 watt output??
thanks for your help, Phil.

8
The Newcomer's Forum / Re: JLH 1969
« on: February 24, 2020, 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.

9
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.

10
Hi Lex it's ok ,, i've got time at the mo as I'm waiting for a bathroom reno to be finished so can't do much else cept wait. :'(

Although some parts might be in a slightly different position you will find it is electrically the same thing.

Pic2 just shows how the signal swing gets bigger and smaller as it passes through each section.
in this case the ,,gain 1 pot (R6) is set at 70% rotation, while gain pot 2 (R8) is set at 40% rotation.
The input voltage is 100mV and the output at U4 (Yellow trace) is still under 200mV so the preamp is basically clean until gain2 (R8) passes 60% rotation.
Which is why I'm fairly sure the preamp is working mostly clean so if you have distortion at low level then  I would look at the schematic of power amp and see that R18 which sets the gain around the powerchip is 130k and my guess is that resistor is way too large and hence the amp distorts long before the diodes conduct in the preamp. Normally R18 would be about 20k~ 50k max.
the other screen shot is the tone response curve at different points on the schematic which gives you a clue as to what frequencies are being amplified.
The tone controls are set with Bass Full up Mid full off and Treb Full up.
so the output at U4 (top of R17) is the purple trace of the frequency curve from the preamp. 
Phil.

11
The Newcomer's Forum / Re: JLH 1969
« on: February 22, 2020, 07:07:28 AM »

I Agree with *Loudthud* :tu:
I would simply add that the term Class A is kinda meaningless for Guitar amps,, Leave that silly stuff for the HiFi cork sniffers.
Most of all the greatest guitar sounds you have ever heard were played on mainly Class A/B amps,,, NOT Class A.

With SS Poweramps there is only a small benefit to be gained by trying to emulate Tubey sound. Yes there are tricks like current FB which help. Peavey uses the term TransTube,,,, But I must be the worlds worse Cork sniffer  :lmao: 
Cause I've never heard anything that even comes close to tube sound from the Peaveys I've played. xP
Transtube only seems to work at loud SPL but at lower levels it's snake oils to my ears.

The best you can do with a SS rig is trick up the preamps and just build a simple SS Poweramp.
Chip amps are dead easy to assemble and work very well,, especially if you are new to this amp building fun game.  Spend time reading up on the subject before you commit to building.

Plenty here to wet your appetite;
https://sound-au.com/projects-0.htm#pwr

Well written and with the novice in mind.
You can purchase pcbs from him with backup help if needed.

If this is your first build attempt then I'd go with Project 19, Single Chip 50W Power Amplifier.
It's for LM3876 or LM3886.

Tons of good info on this site.
Rod E has helped me with a few issues even though I have not purchased any projects. :tu:
Phil

12
Amplifier Discussion / Re: marshall 5212 channel bleed fix?
« on: February 19, 2020, 01:23:24 AM »
As to your suggestion; No because VR1 is Not A voltage divider (aka plian old volume control) it's a gain control for IC1b.

Rather than all the work why not just split the input into 2 separate input sockets, (if you have room on the panel).
now just use an A/B box to select channels. That will cancel bleed over.
But you would need to kill the switching setup

As for the imbalance of the 2 channels I doubt there is a simple solution.
Best I can think of is to lift the output of R10 (clean out) and mirror IC1a section and mix back into send out at output of R27. but again a lot of work,, which may or may not work.

You are correct in thinking these circuits like most amp circuits now are NOT 2 separate channels they are either channel switching or multi channel rigs and I'm yet to meet the owner of one of these multi channel rigs who is happy with all channels,, lol.
Most end up using one section (often the clean) and resort to pedals for all the other sounds. Also I've found single channel rigs are less likely to have problems, Or like the older rigs 2 separate channels with maybe common reverb. The amount of times I've had to trouble shoot circuits only to find the audio path actually works fine,,but it's all the crappy switching stuff that fails.
Phil.

13
I'm working on a new pedal for that.  It's called the Degrader.  :cheesy:

Good idea,,Keep us posted :tu:

If it helps I've built the cab sim from Marshall JTM 60 schematic, the one I used on the Quadraverb recording I mentioned.
I built a few of those for local muso's. good feedback from them.
I've also built one loosely based on the cab sim from an old Nobels SST1 preamp box.
(looks like a rockman belt pak gizmo)
That is the one built into my pedal board now.

If you want to experiment, I've found some of those old telephone 1/1 Line Isolation Tx's do roll of excess top end, small and only rated to about 3~4khZ.
Some work ok some not so well as they tend to roll off bass too much.
I figure if you found the right one it would work.
Phil.

14
Hey Joe,
I hazzard a guess that Digi models just have way too much bandwidth,, = Fizz at high gain.
Well that is what my ears tell me every time I have to repair one of those all in one COSM roland pedal gizmos. yuk
I have a crappy digiteck modeling pedal thing here that I got for nothing and it's the same issue.

Years back I went nuts trying to resolve the 20/20 bandwidth on an old Quadraverb. For their day they were top shelf gear.
while trying to record some guitar tracks with it I ended up just inserting a simple ANALOG Marshall cab sim between the quad and deck,,,, huge improvement.
From what I can gather not much has changed.
So as you can probably guess I'm not a fan of modeling setups.
A young lad asked me only last week why can't I get the sound of the great players from years ago?
Answer, TOO MUCH friggin bandwidth in modern amps and gear lad.  8|
Phil.

15
regards to sims,, FANTASTIC learning/ teaching tool for noobs like me who wish to understand what the hell goes on inside amplifiers. :dbtu: :dbtu: :dbtu:
And you can't  blow them up if wired wrong or burn yourself with hot irons  :lmao:
Your preamp circuit looks like this with Circuitmaker,, it's not top shelf sim but it's all you need to come to grips with basic amp circuits. (even does Valve circuits if you want)
Cheers Phil.

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