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Messages - phatt

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Amplifier Discussion / Re: Sunn SL260 Help Needed With Pot Orientation
« on: October 13, 2021, 04:06:48 AM »
Hi Michael,
for info on the Sweep mid section just search for Parametic circuits.
Yours is a mid sweep circuit with a set low Q.
(Q is the width of the boost or cut)
For Q control you need an extra pot.
It looks like it sweeps form ~200hZ up to about 1,200hZ.

Info here;

I just did a quick simulation of the tone section you posted and it's about a +/- 5~7db boost/cut at whatever freq is set.

Can I ask if you have used this Amp?
If not be aware there are a lot of pitfalls when one just goes straight into a build without at first Bread board testing to see if it actually does what it claims.

OK I'm no teck geek but I've spent 30 plus years building many amps/circuits and I can tell you the short cuts are the most painful learning curves. :'(

I bread board everything now which takes longer but you learn so much more and end up with a far better design. 8|

I have a bottom draw full of pcbs that seemed like a great idea at the time but ultimately ended up as land fill. but better to keep as spare parts. :tu:

If I find a circuit that looks promising then i break out the breadboard and test if it actually works ""Looong"" before I heat up the solder. ;)

Having just simmed the tone of the sun I'd be reluctant to go ahead as I question if it works as well as other circuits which may well prove far better. My best tone circuit design does a 30dB cut at 400hZ, while many parametric circuits can only achieve 15dB max.

Of course if this Sun circuit is *Exactly* what you want then disregard my ramblings. :dbtu:

Oh yeah I doubt the reverb is going to be stunning as it looks like the drive section will be too weak to give a strong reverb. I maybe wrong but I've built many reverb circuits and a lot of them are crap. :trouble :grr

If you want to get a better handle on Spring rev circuits it's hard to beat this page,
info here;
I use the Transformer circuit down the page,, I came up with this idea and Rod kindly perfected the Drive circuit.
Unlike a lot of rev circuits found on the net Rods basic Rev/mixer circuit worked as claimed.
hope it helps,, Phil.
ps judging by your handle I take you are in Tassie Au?

The Newcomer's Forum / Re: Danelectro Nifty Fifty distortion and hiss
« on: September 11, 2021, 09:22:06 AM »
One likely culprit is the TDA2030.
Check if the speaker output has any DC voltage on it, should read very close to zero DC at the speaker terminals. if way off then the power chip is likely blown.

Amplifier Discussion / Re: Roland JC120 - Split Line Out for Stereo?
« on: August 26, 2021, 07:12:50 AM »
I am simply going by Roland's recommended values.
Leaving out the ground resistor defeats the divider circuit.

Play with the values if you like.

Nice little cal page JazzP, thanks. :tu:

Amplifier Discussion / Re: Roland JC120 - Split Line Out for Stereo?
« on: August 26, 2021, 07:11:23 AM »
The speaker is 8-Ohm which is about 5,000 times lower than the 47k load of the line out.
So the current across the line out divider with no speaker connected is minuscule.

If your line out level is too low then just raise the value of R56.
My guess is some where around 1k~2k for R55 should improve things. :tu:

Schematics and Layouts / Re: Ibanez TSA30 Schematic and PCB Layout
« on: August 18, 2021, 12:06:38 AM »
To save a whole lot of guestamation :-\ just wire up a temporary 500k pot as variable resistor in place of R17. Tweak the pot till you find a happy medium then power off and measure the resistance of that pot and choose the closest fixed resistor for R17.

Another way, same thing but do it to R72.
Even do both of the above at once may reap subtle differences while tweaking the pots.
The outcome will only be correct when your ears are happy but my guess is these amps will always be a bit hissy so don't expect perfection.

I don't know the amp so inserting temporary parts might be tricky so you will have to make sure floating pots/wires don't short out.

I would change R4 and R5 at 100k First as that may tame it down enough and the above may not be needed.


Edit; I just realized that *Bajaman* resolved the hiss on previous page, a full explanation with pictures of the PCB mods.
I urge you to do that before you mod anything else. :tu:

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.

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.

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.


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,

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.


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.

main index here;

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. :-[

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.

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.

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. ;)

My money is on a blown chip.

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