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August 19, 2022, 07:01:22 AM

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#1
Amplifier Discussion / Re: Reducing Power Output on M...
Last post by Dino Boreanaz - August 18, 2022, 09:55:49 PM
Great now I've got more work to do ... just when I thought I was done tinkering!  This actually seems like a fantastic option to make the taper more gradual at the low end.  I will have to try this and I'll reply with my results when I do.
#2
Amplifier Discussion / Re: Reducing Power Output on M...
Last post by Tassieviking - August 18, 2022, 07:52:36 PM
I can think of one more thing you can try, increase the taper of the pot.
place a resistor between pin 1 and pin 2 of the pot and the audio taper curve will increase.
The taper effect will be more pronounced at low volumes, you can buy audio pots with different taper curves, but the easiest way is just add the resistor.
You can read more here :http://www.geofex.com/article_folders/potsecrets/potscret.htm
It would give you even more control at low volumes.
#3
Amplifier Discussion / Re: Reducing Power Output on M...
Last post by Dino Boreanaz - August 18, 2022, 09:18:35 AM
Well it's been quite a while since I first posted this topic and I just wanted to provide an update for the sake of completeness.

I did try a few different values of audio taper pots to replace the stock linear pots and I found that they made the volume controls slightly less sensitive at the low end of their rotation as compared to the stock linear pots.  It was not as dramatic a change as I had hoped it would be, so I also tried using a reverse audio taper pot and this did not work well at all (being more sensitive at the low end of the rotation ... as it should).

Since the different values did not have any noticeable affect on the behaviour of the volume controls, I stuck with the stock value of 4.7k but used the audio taper pots in both the treble volume and bass volume controls.

I should also note that I am running this amp into a 16 ohm load rather than the rated 4 ohm load.  So, according to Marshall's senior service engineer, the amp should be putting out approximately 75 watts.  Even at this power level, I find that I have both volume controls set at (or slightly below) 1 out of 10 on the dial which still makes it quite sensitive to small changes.  But I have found a balance that I'm happy with and have no plans to make further changes at this point.  I will post a new topic if I change my mind and decide to start tweaking things again.

Thanks again to everyone who contributed their time, knowledge, and ideas.
#4
The Newcomer's Forum / Re: Busking Amp for Bass & Voc...
Last post by Puguglybonehead - August 10, 2022, 11:36:34 AM
At this point I'm switching to building something for guitar. (and maybe vocals) Going to put the TDA2003 board to good use, I hope.
#5
The Newcomer's Forum / Re: Busking Amp for Bass & Voc...
Last post by joecool85 - August 09, 2022, 09:08:10 PM
No buffer needed between the power amp and the preamp (Bluesbreaker).  That said, I've never used a BB as a preamp.  You won't know if you like it till you try it.  My guess, you won't have enough tonal control.  You like the sound of them which is great, but you don't send it into a flat eq'd amplifier - you send it to a guitar amp.  Even when you set a guitar amp eq to look flat, it has a large mid cut and sometimes other shaping.
#6
The Newcomer's Forum / Re: Busking Amp for Bass & Voc...
Last post by Puguglybonehead - August 09, 2022, 01:36:41 AM
Still haven't made progress with this project yet due to being sidetracked with other problems. I've decided that building a busking amp for just the guitar or maybe guitar and vocals would be a better approach for now.

I was considering using this Blues Breaker pedal kit as a guitar preamp. (I like the sound)

https://www.musikding.de/docs/musikding/breaker/breakerschalt.pdf

I already have a premade TDA2003 board around that I could use for a power amp.

https://www.jameco.com/z/VM114-Velleman-7W-Amplifier-Kit-Assembled_2151881.html

Or I could go with this TPA3122 kit to have a channel for guitar and a channel for a mic. 

https://www.parts-express.com/Sure-AA-AK32151-2x15W-Class-D-Stereo-Power-Amp-Kit-TPA3122-320-322

I was just wondering if I would need a buffer between the Blues Breaker and the power amp board?
#7
Amplifier Discussion / Re: 12w Marshall
Last post by joecool85 - August 08, 2022, 08:51:11 AM
Great work!  I split the topic though and made this it's own so it can be an easy resource for others later.
#8
Amplifier Discussion / Re: Re: Adafruit PAM8302 Ampli...
Last post by Jazz P Bass - July 30, 2022, 12:41:30 PM
Nice work!
#9
Schematics and Layouts / Re: Ibanez TSA30 Schematic and...
Last post by theaterguy - July 28, 2022, 03:49:53 PM
Hi all, I finally made myself open this thing and did those easy mods that everyone should do. Resistors R4 and R5 changed to 100K. Tames a lot off noise.
#10
Amplifier Discussion / Re: Fender 112 Deluxe Plus
Last post by FenderDeluxe112Plus - July 24, 2022, 10:09:07 AM
Thanks Phil,

This is the method I have been using so far, I thought there might be other ways to test in circuit.