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Messages - phatt

Pages: [1] 2 3 ... 145
1
Amplifier Discussion / Re: Hum increases with 3-prong cord
« on: December 06, 2021, 06:18:25 AM »
Seems strange it's happening to many Amps?
Some other possible things to check
1/
Check you have continuity from power cord Earth to the chassis.
(maybe get your electrician to check house Earth)
2/
Try other wall outlets

3/ Are you using the same guitar? & Is it single coil? (as they are prone to hum)

4/
If using the one guitar, have you checked it is all grounded correctly?

5/ Are you running the guitar through a pedal board setup then into amp?
If so plug direct to Amp,, if it removes hum then you may have psu issues in the pedal board supply.
(you can unknowingly create a ground loop with some pedal psu types)

Many guitar amps do tend to have some background hum and buzz as they are all unbalanced setups.
Phil.

2
Amplifier Discussion / Re: Peavey Bandit as speaker cab
« on: November 19, 2021, 01:13:33 AM »
Here is one way to do the connection.
A DPDT switch is likely the best way , just make sure it is a quality switch.
Phil.

3
Amplifier Discussion / Re: Peavey Bandit as speaker cab
« on: November 18, 2021, 07:39:30 AM »
Hi Enzo thanks for the input but my concern with that setup is when the external Amp plug is inserted into the socket in the bandit cab, the Hot tip of external Amp output will momentarily be in contact with the neg terminal of the bandit output (until it is fully inserted)
With both Amps powered off that would work but there is always the chance one forgets to turn off amps.
As you noted the speaker neg of the Peavey output is not at ground. :-\

If I get time tomorrow I'll try to pull the back off one of my Amps to show how my setup works.
I agree the idea of a hot tip floating around is not ideal.

I believe most bandits have the speaker wires hard wired and drop through the bottom of chassis which makes it harder to find a good safe work around.
My amp has a chassis mounted speaker socket which allows one to disconnect the cable from the amp therefore no floating plug.

The  speaker in my combo Amp is wired to one 6.5mm socket mounted on a short alloy angle. so I just remove the speaker cable from the internal Amp and then plug in the external amp with a longer speaker cable.
So it's darn near impossible for both Amp outputs to ever come in contact with each other.

A Double Pole switch would work but would have to be quality Break before Make.
The quality of some switches I've used is not great as I've had a couple fall apart inside.
Phil.

4
Amplifier Discussion / Re: Peavey Bandit as speaker cab
« on: November 17, 2021, 07:16:41 AM »
Just a word of warning,
When switching 2 Amp outputs to the same speaker there is always a risk of damage to one or both Amps if the 2 amplifier outputs ever join, even momentary. You would have to make sure the switch is a break before make design for that to work.

My option would be to cut the speaker wires in the Bandit and insert 6.5 sockets.
So the Bandit output goes to one socket while the Bandit speaker goes to the other socket.
Both sockets can be mounted on a bracket and screwed to the insidewall of Bandit Cab. Mark one socket as Bandit output and the other as speaker input.

Now make up a short speaker lead to join the sockets and jumper the sockets to use the Bandit's internal speaker,, then just remove the jumper and plug the other amp output into the speaker input of the bandit.
This way the 2 Amps can never accidentally come in contact with each other.
I've done this idea to a few rigs and works fine.
I'm sure others here my have other options
Phil.

5
Amplifier Discussion / Re: Remote channel/FX switch
« on: October 24, 2021, 12:17:25 AM »
Switching is simple, it was his desire to have a remote reverb level control that was a challenge.

Maybe I was not clear?
Surely it would be so much simpler to use a multi FX pedal board of which there are dozens to choose from, many now for sale cheap SecHand.
A lot of those FX units have a foot control which can be assigned to FX paremeters.
Simply assign Reverb depth to the pedal and you have real time hands free control over Reverb depth.

To my understanding that makes a lot more sense than reinventing the wheel again. :loco

One way means it's dedicated to one Amp Only, the other means it's totally independent of the amplifier which means if Amp fails you swap to another amp and still keep all the FX tricks you wish to use.
Either way you still end up with a pedal on the floor. ;)
Phil.

6
Amplifier Discussion / Re: Remote channel/FX switch
« on: October 22, 2021, 08:43:05 AM »
It  baffles me why people go chasing the most complex way around simple problems.
I'm old enough to remember all the old amps that came with 2 "Separate independent" channels. Often one Ch had Trem/Rev.
One only needs a 2 way splitter,, guitar in with 2 cables out to the 2 channels.
No convoluted switching systems needed. :-X
If you want much more than that it's likely far better to build a simple Amp setup and use use a pedal board for all the tricks. 8|
Just my 2 cents worth.
Phil.

7
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; http://www.geofex.com/article_folders/eqs/paramet.htm

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; https://sound-au.com/articles/reverb.htm
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?

8
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.
Phil.

9
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.
https://ohmslawcalculator.com/voltage-divider-calculator

Nice little cal page JazzP, thanks. :tu:

10
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:
Phil.

11
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.

Phil.

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:

12
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.

13
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.

14
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.

15
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.

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