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Messages - phatt

The Newcomer's Forum / Re: Carvin sx amp build
December 28, 2023, 07:09:46 AM
 I don't wish to dampen your enthusiasm but but you may eventually be defeated.
There is just so many nightmares waiting for you.

My advice would be to go buy a bread board and parts needed to run a 30 volt split rail supply and start experimenting.

You will spend many months getting the preamp to work.

Then you will have to learn how to use a cad program to make the preamp PCB, another few months will go by.
at that point your best bet is to purchase a poweramp kit.

Meantime you will then need to consider a case to mount it all.
Oh did I mention that layout of PCB can be a nightmare if you don't understand that sensitive sections will pick up hum from bad design as well you will need to learn how to NOT create ground loops a common issue when designing sensitive audio circuits.

AND heaps of other gotcha's that better minds on this forum will tell you about.

If it interests you,
My rig consists of a pedal board, most of which is my own designs and my main amp is nothing more than an old SS Keyboard amp.
I just posted an mp3 composition I wrote on here last week.
It will give you some idea of what can be achieved with average gear.;topicseen#new.
But keep in mind I've been doing this for over 30 years so I have learned a lot about how to get things to work together to get the Sound/Feel/dynamics to come together.

40 odd years back I was in your situation faced with a similar dilemma so I have a fairly good idea of what is ahead for you,,So I wish you luck.
Be aware DIY is rather addictive. ;)
The Newcomer's Forum / Re: Carvin sx amp build
December 27, 2023, 06:53:24 AM
Quote from: Tassieviking on December 09, 2023, 11:48:16 AMThe SX300 preamp on page 25 in the manual has a very similar input circuit as the SX50, the SX3000 uses 2N5457 fet's so I think we can say that Q21, Q22 are 2N5457 FET's

This might make a nice pedal from the overdrive channel, 2 FET's and 4 dual OP amps is all, 5 pots and 1 switch as well

That would be the best advice for something that would otherwise exceed the cost of trying to build a whole amp from scratch 8)  8)  8)
Quote from: Tassieviking on December 21, 2023, 10:29:13 AM
Quote from: phatt on December 20, 2023, 03:00:47 AMthe rest was me learning how NOT to waste time building land fill.
Have you figured out Phil ?
No more landfill ?
Please tell me the secret, I have been doing it since the mid 1970's and I am still working on landfill all the time. :)

Yep tiss easy to just dive in and build stuff but I think most of us fail to realise that it may have worked for the bloke on utube but we forget that while his guitar/amp setup might sound good,,, our setup will likely not reproduce the same results.
There are just way too many variables so you are just shooting arrows into the air and missing every time because you have no full knowledge of the target.

So I always BBoard test ideas first through as many amps & speakers as I have.(even head phones)
While it's all on the BB I also simulate it as well.
This is where you can clearly see just how each section is winning or loosing the magic.
You might find one section is hard clipping too early.
You can also tell where there is too much, to little bass or treble.
You then adjust the test circuit until you get a good balance.

If you put in the time for the R&D then you build far less land fill.

Same goes no matter if it's Pedals, SS Amps or Valve Amps.

I recently modded a small Mesa amp.
The balance between the 2 channels was unusable.
Again I could have wasted hours or dayze changing component values and guessing.
Just by using a simple sim of the preamp stages it only took 2 days to work out how to tweak the circuit to bring the 2 channels closer to a usable balance of drive and tone shaping.

I have built many circuits in my garage that I thought sounded great only to find that on stage they just turned in to crud. :'(

I think my brain has trained itself over the years to pick tone and harmonics.

A bit of trivia;
Some years back I was watching as SBS doco on the study of music where they had 20 or so Conservatorium students in a massive cathedral in Europe. (Names escape me)
The Cathedral housed one of the largest pipe organs on the planet. wow 8)
A blind test was setup for the students where they had to pick the REAL Organ from a Digital Organ which had been setup in the same cathedral.
The samples for the Digital organ were taken from that very same organ.

The same organist played the same piece on both the real and digital organs

Before the second piece had finished I picked the real one.
My Wife was struck by my ability,,, she asked how on earth could you tell?

I said that was easy to pick because the digital organ had far more bandwidth,, the real organ does not have all those hi freq artifacts.
(I may have had a slight advantage because I've heard a few big pipe organs in my youth)

This is why I keep trying to tell guitar players that they will never sound like the old amps because most gear now has way too much bandwidth.
Those old famous Valve amps had very limited bandwidth.
So modern gear including a lot of fancy pants Valve rigs suffer because of that very same issue.
hope it helps folks who are chasing the many secrets of amplification of musical gear.
Amplifier Discussion / Re: Demo Phatt Rig
December 26, 2023, 09:58:59 PM
Thanks, for the comments.
Yep I'll never be able to shred like the young ones do but I enjoy making music, writing new melodies and nice chord progressions.
Amplifier Discussion / Demo Phatt Rig
December 20, 2023, 11:34:35 PM
Just thought Some would like to hear what I've achieved over the last few years.
I wrote this little guitar composition for my wife who sadly passed away this year. She did get to hear it before she passed and she loved it.
   It's called Portable Healing by Phil J Abbott.
Backing is done with JJazzLab (sounds are using Virtual MIDI Synth)
My Guit/Pedals/Amp is miked into Presonus Audio Box into BandLab DAW.
All Efx are from my rig no added fancy plugin used.
The Guitar is my cheap Monterey strat copy with original cheap PU's.
Merry Christamus to ya all, Phil. 8) 
Hi Maddus,
Well be prepared to be disappointed if you think it will sound like a real Fender 5E3.

Some real world understanding is needed before you waste time and effort on ideas like this.

The reality is thus;
What is hardly ever mentioned by all these utube experts trying to sell a new pedal is that a lot of these over hyped pedals rely on the Valve amps they run through.

Rule of thumb for you, even a pedal with Valves will sound crappy through a lot of SS guitar amps.
While even a simple transistor pedal will likely sing when used in front of a well built Real Valve Amp.

WHY you ask?
You only need to send a good valve amp a bigger signal and the power section will gracefully OD/Distort. All that the pedal really does is make the signal a bigger which makes the valves drive harder. it's a magic combination that few seem to understand. the pedal can add a bit of dirt and tweak the tone but it's the Valve Amp that does the magic.

This does not happen with most SS circuits they just clip hard, part of the reason why Tranny Amps got a bad name.

If you want all SS then you have to do all the tricks in the preamp sections. So don't be surprised if the end result you build is a disappointment.

Tassieman has given some options for you and you can also download Teemu K's book on this site on this page and start learning;

I've been building gear for 30 + years and trust me it takes a lot of reading and testing to build a decent rig.

My best advice is to invest in a bread board and start building simple circuits and experiment.

I'm not a teck just a novice who refused to except the hype so I went out and spent the time learning to DIY.
in those years I have only has a handful of success circuits,, the rest was me learning how NOT to waste time building land fill.

While reading and breadboarding I used Cad Sim programs and that was a huge help for me to understand just where in these circuits the mojo is won and lost.
Hope it helps you out.  ;) Phil.
The Newcomer's Forum / Re: Carvin sx amp build
December 03, 2023, 05:31:48 PM
Can I suggest you mention the model and maybe a link to Schematic might help.
If you have the Amp open, take some gut shot pics of the internals would be helpful.
Phil. ;) 
Hi LB, and welcome,  8)
If the Channel led indicators are not working then the issue may well be in the switching circuit, (RL1 at top of drawing)
The relay contacts maybe faulty or power not going to B (the 1k5 1W resistor)..
 Should be over 50VDC at B. Then at the relay should be 12VDC controlled by the 12V Zener.
Oh and your sand box resistors are fine, that is just the filler crumbling nothing to worry about.
HTH, Phil.
I'm assuming you are using this for el guitar? If so then the lack of bottom end is likely due to the presence of the horns producing so much treble it drowns out the Bass.

If you are chasing the sweeter tones that good guitar rigs produce then the last thing you want is hi Freq horns.

Also if the amp has a Scorpion speaker they are already very bright when compared to other famous guitar speakers.

Should be easy enough to disconnect the horn and see if that sounds sweeter and improves the low end.
Yep this confused me years back, 2u2 would be 2.2uF

I did read somewhere that the point can be easy missed in drawings and after many photo copies and creases in the paper it may look like 22uF.
Same goes for R's 2k2 = 2.2k.
HTHelps, Phil.
I would consider Main Caps draining in a few seconds Normal.
Likely some will take longer.
Valve Amps, Yes they can hold a charge for much longer.

Regards the pots position,, maybe the pots have been changed in a repair job. Lin to Log swap will make that happen.
Is there any particular reason why you want to replace the Capacitors?
If the Amp works fine don't mess with it.
The Newcomer's Forum / Re: Newbie...Ampeg B15T
August 22, 2023, 08:38:06 PM
Ok easy stuff first,
I don't know the amp but from pictures the amp has 2 effects loops, one front the other on the back.
Just bridge them both with a couple of spare guitar cords.

If that fixes the issue then one of those FX loops has a failing contact switch.

FX loop failure is a VERY common issue as the sockets are often cheap crap.

If you want to save yourself a whole lot of work just get a couple of stumpy jumper leads and leave them plugged in.

If it's still not working then you look deeper.
HTH, Phil.
I think one needs to realise that the sound/tone/feel you hear are **Recordings** of a rig that has been tweaked in the studio.
There would have been a lot of post FX on the mix down. Modulations, Reverb reflections added to it.
Many people forget this fact and hence you can go in circles trying to replicate a sound/tone.
Trying to replicate a recording with any basic preamp is just not going to make the cut.

The raw sound of the Amp used may well sound very, shall I say Bland and somewhat lifeless.
Hi wim, first up, Does the Amp work as per normal?
For that era the Foot switch is likely a latching type.
Use what you have or use an open plug and bridge the terminals you will soon work out if it's latching or not.
I have no idea about the flying resistor, hard to tell what it's connected to??
As for the Caps padding, Yes often done when they run out of parts.
As I've never seen these amps, looks like it's a budget brand so could be factory layout.
(I've seen worse from Early Roland amps)

Re Speaker issue,, why not use the original spades?

80Watts clean from 130 Watt rig is par for most gear,, Sand or Glass