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October 20, 2021, 07:28:50 PM

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1
Amplifier Discussion / Remote channel/FX switch
« Last post by ampetrosillo on Today at 10:51:02 AM »
I'd like to implement a clean/dirty channel switch for my design, and also a vibrato/reverb on-off switch. I'm using DG419 parts (nice and reliable, clean if a bit fast, etc.) for switching, although I could use simple relays as well (but the cost and complexity is basically the same, with the added bonus that the DG part is solid state, therefore potentially more reliable) and I'd like to be able to both operate the switch from the panel and via a footswitch. Are there any schematics you could point me to? Secondly, I'd actually like to have a remote reverb mixer (as well as the panel-mounted one), this screams VCA of course, but what would you suggest?
2
The Newcomer's Forum / Re: Busking Amp for Bass & Vocals
« Last post by joecool85 on October 19, 2021, 12:01:23 PM »
I just looked at the TDA2003 spec sheet, it looks like you would get 4 watts at 12 volts, not enough for bass in my opinion, but I am not an expert.
If you have the kit, build it and run your send/line out/ to effects output of your amp into it, and run the output to a separate cab and see what it sounds like.
Or get the signal from your stereo/phone/MP3 player and try it, see how loud the music sounds.
If its not enough the just get another amp module, like I mentioned before, the TPA3116D2 has 15 watts at 12v on the spec sheet at 4 ohm speaker.
You will not us a lot of extra power with a TPA3116D2 if you keep the volume down.
Class D power amps are very efficient and only use a bit more then what you use, if you use a 100w class D amp and only turn it up to 10Watt you will only use about 12-13 watts of power, at least that's my understanding.
Check the spec sheets of the power amp you are thinking off using and find the power rating for the voltage you intend to use, that's what I would do.
Class D amps don't need big heatsinks as well which saves money and weight.

This is correct.  One thing to note though is the TPA3116D2 is an SMD component and difficult to solder.  TPA3122D2N is a through-hole component and much easier to work with.  There are several kits available with this chip, or you could do something on your own.
3
Amplifier Discussion / Re: Sunn SL260 Help Needed With Pot Orientation
« Last post by Tassieviking on October 15, 2021, 06:16:01 AM »
Thanks for all that info Phatt.
I definitely live in Tassie, where the Devils roam free. ( I have had them under the bedroom, makes you jump when they scream at night. )
I was born in Sweden but moved to Australia when I was 12, I still remember climbing on Viking rune-stones as a kid, they were all around the area where I lived.
I went back to Sweden in 1976 when I was 16 for a holiday, but it was still too bloody cold, stayed down under since then.

I am interested in solid state guitar amps off all kinds, I am going to order PCB's for Marshall Mosfet 3310 and Sunn Beta very soon and I just wanted another type of preamp for the order.
I order my PCB's from JLCPCB and find it better if I have a lot of different boards in one order, postage is the killer, but does not increase too much for more boards.

I like to stick circuits into KiCad and making circuit boards up for myself, I find it relaxing, I will have to learn the simulation bit soon in KiCad or some other software.
I don't have much experience in audio circuits, but been a sparky since 1980, mainly industrial maintenance repairing DC and AC drives and any other electronic boards that needed it to keep machinery running. My only tube experience was with high voltage spark testers checking insulation in cable manufacturing.

I have never seen a Sunn SL160 or SL260 in my life, but I might just have the preamp made by Xmas. (Just for fun)
I do love Rod's circuits and have looked at nearly all of them, I have read up on the reverb circuits on his page, but I will stick to what was original on the Sunn SL260 circuit.

Again, thank you for your help, I' gonna start reading up on what you mentioned now.
Michael
4
Amplifier Discussion / Re: Sunn SL260 Help Needed With Pot Orientation
« Last post by phatt 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?
5
The Newcomer's Forum / Re: Busking Amp for Bass & Vocals
« Last post by Tassieviking on October 12, 2021, 12:39:11 PM »
I just looked at the TDA2003 spec sheet, it looks like you would get 4 watts at 12 volts, not enough for bass in my opinion, but I am not an expert.
If you have the kit, build it and run your send/line out/ to effects output of your amp into it, and run the output to a separate cab and see what it sounds like.
Or get the signal from your stereo/phone/MP3 player and try it, see how loud the music sounds.
If its not enough the just get another amp module, like I mentioned before, the TPA3116D2 has 15 watts at 12v on the spec sheet at 4 ohm speaker.
You will not us a lot of extra power with a TPA3116D2 if you keep the volume down.
Class D power amps are very efficient and only use a bit more then what you use, if you use a 100w class D amp and only turn it up to 10Watt you will only use about 12-13 watts of power, at least that's my understanding.
Check the spec sheets of the power amp you are thinking off using and find the power rating for the voltage you intend to use, that's what I would do.
Class D amps don't need big heatsinks as well which saves money and weight.
6
The Newcomer's Forum / Re: Busking Amp for Bass & Vocals
« Last post by Tassieviking on October 12, 2021, 11:47:20 AM »
If you are busking I imagine you might be doing it mainly during the day, have you considered a small solar cell ?
You can get a 20 watt panel that would be smaller then the top of a small amp with a 10" speaker in it.
The solar panel would continuously top up the battery as you are using it, you might possibly be able to use a smaller battery.
The solar panel does not need to supply enough power for continuous use, just enough to prolong the use, ie. using 2 amps playing and putting 1 amp back in at the same time. And the solar panel keeps working while you have a break.
Just a crazy thought that popped into my mind.
7
The Newcomer's Forum / Re: Busking Amp for Bass & Vocals
« Last post by Tassieviking on October 12, 2021, 09:28:00 AM »
Another small amp module I think might be good is the TPA3116D2, very cheap on Ebay ($8 up).
In stereo at 12 volts it can go up to 15 watts per channel into 4 ohm speakers.
If you needed more power you could use 2 x 12 volts batteries for 24 volts, then you can get 60 watts per channel into 4 ohm speakers
If you do go with a stereo amp module you could run one channel Bass amp and one for voice / guitar, 2 different speakers.
The TPA3116 can run on 4.5 volts to 26 volts.
I have 2 100 watt mono  modules I bought ages ago, they are small enough to fit into a 1590B stomp box, I was thinking of using one with a laptop power supply for a small pedal amp.
I think that would go nicely with the Sunn Beta preamp pedal I made.
8
Amplifier Discussion / Re: Sunn SL260 Help Needed With Pot Orientation
« Last post by Tassieviking on October 12, 2021, 08:52:51 AM »
Thank you LoudThud for that information.
I don't suppose you would know the Dual Pot orientation in the variable frequency circuit for the Mid control, If I can't find out I could just leave the viper (leg2) disconnected, and then short it to the correct leg after i build it. The viper (leg2) has to be shorted to leg 1 or 3 of the pot.
Even better if someone could identify what kind of circuit it is so I can do some research on it, it has to be some kind of active notch filter I presume.
Again, thanks LoudThud for your help.
Michael
9
Amplifier Discussion / Re: Sunn SL260 Help Needed With Pot Orientation
« Last post by Loudthud on October 10, 2021, 04:08:27 PM »
Pin 3 of your pot symbol appears to be the clockwise terminal, therefore, the Mid, Treble and Bass controls are backwards.
10
Amplifier Discussion / Re: First attempt to do upgrade
« Last post by Jazz P Bass on October 10, 2021, 12:21:05 PM »
From the Web: "Made in the sixties for film editing, this little squawk box amp is all kinds of fuzzy fun. You can play straight into the amp through its rattly tiny speaker, or use the headphone jack to run it into another amp …"
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