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Messages - phatt

Pages: [1] 2 3 ... 144
1
Honey Amp / Re: Power supply suggestions
« on: July 19, 2021, 07:15:50 AM »
As you have built pedals then most pedal schematics show how to wire up the external supply.
They normally use a switching socket so that when you insert an external supply it switches off the battery.
many stomp box forums have close up pics of the actual switch wiring.
Phil.

2
Amplifier Discussion / Re: Rickenbacker TR50 4 x 10" speaker buzz
« on: June 29, 2021, 07:20:44 AM »
That Video shows an extreme example but it only takes the slightest dis-lodgement of voice coil to make it buzz.
you may not be able to hear it until there is signal.

Also don't forget the speaker braid wires at the back,, although it's more often a failing VC the braids take a lot of vibration. They tend to fail right at the solder points.
Gently wiggle them while the speaker is passing a signal and see if you can get a clean signal if you do you just found the failed braid solder joint.
Phil.

3
Amplifier Discussion / Re: Pedal Hiss?
« on: June 25, 2021, 02:13:41 AM »
If the Hiss is only present when using the converter then logic tells you there is a very good chance it IS the converter.

Be aware, If it's a Switchmode type DC/DC converter then it's a fair bet that is the source of the noise. In which case it's highly likely the converter is introducing hash as Smode setups are notorious for bleeding HiFeq crap into Audio gear.

If so you may be better off building a simple Analog regulator, i.e. using an LM7809 reg chip.

Also please consider that the explanations you give make sense to you because it's in front of you,,, we are not there so it's often hard to make out what exactly you mean.

Phil.

4
Amplifier Discussion / Re: Safety Tips
« on: May 23, 2021, 10:41:42 PM »
Seems like there's already commercialized version of "lightbulb limiter" with built-in multi-parameter (voltage, current, power, cos-φ, energy consumption and mains frequency) electrical meter and a GFCI-protected outlet...
Kinda fun to see a lightbulb socket on this factory-made version haha. I anticipated that it'd use a power resistor instead, but...lol

A power resistor won't work as a current limiter. 8|
R is fixed while a light bulb resistance is temperature sensitive.

Low resistance when cold and high resistance when hot.
i.e. a bulb that measures 10R cold will be 100R when hot.  (they do vary but x10 is somewhere in the ball park for most)

 The resistance change is fast enough for most analog guitar amp circuits it's all that is needed to establish a fault.
Way cheaper than a Variac. :tu:

As the current rises the bulb resistance increases and the brightness of the lamp gives a real time indication of how much current is flowing.  It's basic but good enough to save blowing parts.

Phil.

5
Amplifier Discussion / Re: 200 watt amplifier board.
« on: May 21, 2021, 11:54:31 PM »
You get what you pay for
I assume at that price you have to purchase all the parts?
I'd want verification that all the parts are available.
For me there are too many unknowns. xP

I'd be looking at something like this which is well researched.
Rod sells PCB's and you have a schematic as well as a full explanation of the circuit.
If you buy his kit you also have backup if needed.
Phil.

https://sound-au.com/project101.htm

main index here; https://sound-au.com/projects-0.htm#pwr

6
Amplifier Discussion / Re: Vox Pathfinder 10 as a modding platform
« on: May 11, 2021, 06:12:22 PM »
The Difference between the 2 chips is not worth the effort.
Your ears would hardly be able to notice the Difference between 10 Watts and 15 Watts.
Those chips will now likely be hard to find anyway so *Just buy a bigger amp*.
Re the headphone out. Well it's exactly what it says,,
for driving headphones,,, different Z and Voltage.
If you plug in a speaker you won't hear much. :-[
Phil.

7
Amplifier Discussion / Re: Vox Pathfinder 10 as a modding platform
« on: May 10, 2021, 07:18:18 AM »
If you can find space on the panel you can always replace R7 with a pot and re-solder the Leds.
That will give you much more control on how hard the leds (Or diodes if you prefer) activate.
I've never had this amp so just a thought.
Cheers, Phil.

8
Amplifier Discussion / Re: Power amp transistor choices??
« on: May 09, 2021, 09:42:22 AM »
Look for something with a bigger Safe Operating Area (SOA).

I agree. :tu: The power devices in my last amp build were way over speced on current and voltage.
Phil.

9
Amplifier Discussion / Re: Power amp transistor choices??
« on: May 09, 2021, 09:28:35 AM »

An old saying from an old bugga who has been around and seen/read enough to know this simple rule in regard to Guitar amplification;
"If you want to build a great guitar amp sound (Especially Overdriven) then build a really crappy amp"

If you do some simple maths you will realise that 90% percent of every fundamental freq /note you can play on a guitar is UNDER 1kHz.  add the essential harmonics and you are still well under 5kHz.
Basic rule of thumb, Anything past ~4kHz will just mess up the magic.

If all you ever do is strum a few chords with a clean signal then wide bandwidth won't matter much BUT the moment you introduce distortion and crank it up that excess bandwidth will just sound crap.
Wide bandwidth clutters the spectrum with way too much hash and you actually loose note definition

I know the average Joe will assume MORE is always better but wide bandwidth will just frustrate you and you will spend a fortune adding mare and more gizmos and never get anywhere close to the classic sound of years past.
Go listen to Carlos Santana's guitar sound,, You are hearing a very narrow and limited bandwidth.
If you took Carlos's guitar and plugged it into the latest over hyped fancy Amp sold these days (often with 20/20 bandwidth digi crap added) it would sound crap.
                          ***It's what you DO Not Hear that makes the magic *** 8|
Rant over and hope it helps. ;)
Phil.

10
My money is on a blown chip.
Phil

11
Preamps and Effects / Re: pre-amp suggestions
« on: April 27, 2021, 02:00:16 AM »
Ta mate ,,Yep I found some of your circuits on MEF and when time permits,,, one day :(
I notice your circuit also uses a CD4069UB which I can find locally but I'm a little lost as to how the pins are all wired up. ???
Anyway no hurry as my Bread board is full up with another project at the mo and once I've resolved a couple of small issues on that circuit I'll try it out. :tu:
I'm not looking for the metal Shred grind ,,more like a sweet smooth OD if that is possible.

My experience is limited but I do recall using a small Laney HC15R (I think) which has something similar to get the OD effect. It sounded ok but like a lot of Amps as well as a lot of those all in one pedal boards there is just way too much bandwidth giving that brittle edge which is just horrible. (to my ears at least).
I'm really happy with what I've designed and achieved over many years and it does a darn fine job,, but always interested in other ideas.
Phil.

12
If you have Hum,,,Measure the DC voltage at the speaker output and post your findings.
It Should be VERY close to Zero Volts if not then remove the speaker connection or you could burn out the Voice Coil in the speaker.
Phil.

13
Preamps and Effects / Re: pre-amp suggestions
« on: April 24, 2021, 04:14:47 AM »
Thanks , interesting. Q Will a 4007UBE work in this application?
Phil.

14
Schematics and Layouts / LM386 H/phone amp options
« on: April 18, 2021, 09:55:38 AM »
The recent Honey amp got me searching my backups and I found The Nobels Mycro Amp circuit.
I don't know if this is of any use but this is a Headphone circuit using the LM386 chip.
Gives clues as to how to implement a preamp with clean OD and Dist.
Of course it does require more parts than the honey amp but the second stage has filtering which may help with small speakers. :-\
Phil.

15
Sorry but you are doing it the hard way.  xP
It's a common mistake to assume that the ACTIVE components make or break the mojo.
OK you had a win by replacing some opamps but mainly that improved noise issues.
But note;
wide bandwidth requires hi spec chips OK fine BUT if the bandwidth is limited then by design you remove most of the hizz fizz and buzz which means that lower spec chips work just fine. (That's a general comment and not always so but still worth noting)

Tone is all about the circuit design and that comes from the passives, not the quality of the passives but the Values of those define the final result.
Sure speakers and power stage can have effect on this as well as PU's in the guitar but a whole world of tone mojo comes from knowing how to tweak the circuit and most of that is PASSIVES. in guitar circuits it's often just understanding some R/C maths

Doing this by willynilly swapping out parts and hope for the best can end up destroying the PCB tracks so I'd suggest learning how to use simulations and a Bread board and recreate some of the Showman preamp to test out the many options before you open up the lid on the amp.

I would recreate the 2 preamps on a testboard then link into the power amp of the Showman to hear how tweaks alter the sonic result.
No need to do all the switching as that has little to do with tone shape.

The Dirt circuit is a little tricky but still doable.
It has the CD4007 which I'm assuming is just a bunch of mosfets setup to create a lot of Dirt but as there is little tone shaping after it then likely a lot of fizzle and hash is the result.

Note that a lot of amps are built to what the market wants and many amps are built to create a whole lot of hashy distortion which the kids with tin ears seem to like,, so if you want sweet OD then it's unlikely to work well for a sweet OD tone without a lot of tweaking.

You can always Bboard some cab sim circuits and temporally insert them in the FX loop or Preout /PwrAmp input to wipe of the excess bandwidth. That would be less work than testing out the whole preamp section.
I'd guess that the preamps will still be an issue.

If I had a clear schematic to work from I could simulate some of the preamp sections to get some idea where the tone is going wrong,, no chance as that Schematic is unclear.
Phil.

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