Quote from: Tassieviking on May 06, 2025, 11:20:12 AMI would like to add that some heat transfer paste is conductive and will cause shorts if used with heatsinks and mica washers.
The conductive heat transfer paste is often used in computers for the main processor heatsink, it makes no difference in there since there are no electrical terminals close by.

Make sure you only get non conductive heatsink paste if you get some, a small tube of really good expensive paste will last forever and ever so don't get anything cheap and nasty.

I have Radio Shack branded thermal paste I've been using for almost two decades lol.  I don't need it often, but when I do it sure does come in handy.  Still in good condition too.  Cheap stuff "goes bad" and either gets dry or runny.

Quote from: J M Fahey on May 06, 2025, 05:53:44 PM   

If at all possible upload a copy, it may help others.

I've not bought anything from musicparts.com, but depending on their EULA you wouldn't want to do that.  While I do enjoy all the schematics, I want to try to make sure things posted here are legal.

Quote from: g1 on March 20, 2025, 10:30:21 AM

Quote from: saturated on March 19, 2025, 08:41:56 PMI got to thinking I guess these guys flash sixty times a second. 

The LED elements run on DC.  Under the plastic cover of the bulb is a circuit board with the electronics.

Early LED bulbs didn't do a very good job with this and still flickered.  But yeah, current ones run on regulated DC with decent filtering for no visible flicker.  That said, dimmable LEDs are PWM (pulse width modulated) and are technically flickering all the time, just at a frequency WAY too fast for us to notice (on the order of several thousand times per second).

Quote from: g1 on March 29, 2025, 11:39:23 AMYes that is it, touching 2 component leads with the same probe.
But also, the meter is reconfigured as a short when you are in the current (Amps or mA) ranges.  That is why we must 'break' the circuit and insert the meter in series to measure current.
If you do a current measurement, then forget and try to measure voltage with the meter still set for current, you are essentially putting a piece of wire across the points your 2 probes connect to.  Hopefully the meter fuse will save the piece of gear you are working on.

For complete clarity, the meter set in amp mode will actually not be a short, but a VERY low ohm reading, something on the order of 0.1 ohm if I recall.  So, effectively a short, but not quite.  The reason this matters is because the meter will measure the voltage across that resistor and calculate the amperage draw.

Marshall has announced new pedals that cover all the bases of Marshall sound: The 1959, DSL, JCM800, JCM900, and JVM.

Pricing in the US is $149 each.

If you're looking to get some Marshall sound, but don't want to move around a heavy 4x12 stack and tube head - this might be an option for you!

https://www.guitarworld.com/gear/guitar-pedals/marshall-amp-in-a-box-pedals-namm-2025

Welcome aboard!  Always glad to have engineers joining up!

Orange has released three "baby" amps: Dual Baby, Gain Baby, and Tour Baby as well as a 40w combo single channel amp, the O Tone 40.  While the Baby series are all variants of a 100w two channel head, the O Tone 40 is a single channel 1x12 combo.  All four of these offerings sound, quite frankly, incredible.

MSRP is 499 euro each for the Baby amps and 599 euru for the O Tone 40.

More info from Gear News: https://www.gearnews.com/orange-baby-amps-guitar/

I have decided to close the SSGuitar.com web store.  For those that did business with me - thank you!  I may do another Kickstarter project for SSGuitar, but running the store really isn't in the cards at this time.

Thanks again, and enjoy the site.

I am closing the SSGuitar store but have shared my project on OSHPark so folks can still purchase legit boards.  I do not get any kickback from this, you are only paying OSHPark for these boards - but these are exactly the same as the production boards I sold.

https://oshpark.com/shared_projects/DLReeaHK

Vintage has released the Retro 15 and 25 modeling amplifiers.  These amplifiers come with all your expected amp models on tap, as well as some basic effects and even a drum machine on the 25.

MSRP starts at $150 USD

https://www.guitarworld.com/gear/amps/vintage-retro-amp-modelers

Quote from: g1 on February 21, 2025, 02:41:58 PM

Quote from: J M Fahey on February 20, 2025, 05:42:01 PMThat´s why each of the channels is already BTL, you can´t undo that.

Now if you wire both BTL amps in parallel, you can get twice the current but peak voltage does not change.

I'm still wondering if Ch.1 and Ch.2 can be put together in regular bridged configuration, rather than the parallel PBTL.
If so, it would give full chip output into 8 ohms (rather than the 2 ohms of PBTL).
The reason I raise the question is that if it were possible, that may be what the Pandora is doing and how they get that high power figure into 8 ohms.  If so, I guess the amp would be marked 'minimum load 8 ohms'.  (edit:  minimum load 8 ohms confirmed here:  https://lichtlaermaudio.com/shop/pandora )

To my knowledge, you can't bridge the already bridged outputs.  This chip is designed to do mono as PBTL only and for sure can do 60w of output, just not at 8ohm but rather at 4ohm.

Quote from: J M Fahey on February 19, 2025, 03:42:40 PMIt will certainly change volume, but I guess variation will not be that big, probably a few dB.

For bedroom playing we need, say, something between 20dB and 30dB or so.

Tiny Terror offers a 7W-15W switch, Mesa Boogie a 60W-100W one (cutting 2 x 6L6 out), neither as effective as it seems.
One modern Mesa offers a 50W-5W-0.5W switch ... now THAT one is useful.

My K20-X mod brings it down to about 0.6w when switched, and honestly I probably should have brought it to about 0.25w to be ideal.  It does work well enough for me that I'm not going to change it though.

Quote from: vintagelove on February 16, 2025, 03:20:47 PM

Quote from: DavesNotHere on February 03, 2025, 01:49:34 PMHi, newcomer here. I've got a Fender Frontman that I'm upgrading. I replaced the reverb tank and am replacing a bad pot next. While looking up other mods, I saw that replacing the op amps is popular for upgrading the sound and reducing the noise floor, so I'm planning to do this using the NE5532 op amp. I'm pretty experienced with microelectronics, and have done a lot of wiring on guitars and other micro projects, but this is my first time working on an amp. I've seen the process for desoldering and replacing the stock op amps, it looks pretty straightforward, but I've also heard there can be problems with messing up the board, etc. I'm pretty confident in my skills but don't want to brick my amp. What tips or other advice do you have for me? Is this as straightforward as it looks, or should I just leave it alone?

thanks,
-Dave

Might I suggest rather than swapping opamps, you figure out sticking a "master volume" pot somewhere around u3b or u4a. I know at least one guy successfully put an fx loop right after u3b.

That little amp is ridiculously loud, and the reality is you're probably playing it at like 1, in a quiet environment, and the idle noise is bothersome in that setting.

You could easily knock off a few db with a master volume, that would lower the noise floor to where it's barely noticeable. It would still have plenty of power set like that, and if you wanted full power, just turn the master up all the way. In that kind of setting (jamming with others), the stock noise floor would be barely noticeable.

My 2 cents... Anyway... maybe someone can chime in with the best place to put it. Here's the schematic.

Alternatively you could place an attenuator at the speaker output.  I did this by way of a couple large resistors on my Dean Markley for the reasons you mentioned.  I was always running it at 1-2 on volume and there was still noise.  By attenuating the overall output it allowed me to increase the preamp volume and lower the noise floor.

I chose to do an attenuator even though it is less power efficient because of two reasons:
1. I rarely use this amp as I'm normally playing my Positive Grid Spark Mini
2. I was able to put in a switch with the attenuator so I can go from <1w to 20w at the flick of a switch and make a meaningful difference, all without modifying the circuit at all.  This was important to me because I've already played around with this a lot and didn't want to keep doing this haha.

TLDR: this amp is going to be outputting roughly 30w @ 8ohm and 15w @ 16ohm given a 24v PSU.  For reference, this is inline with the TPA3122D2N that I am working with as well.

Quote from: J M Fahey on February 18, 2025, 02:06:32 AMThose power specs are, should we say .... too optimistic?

I think someone misunderstood how PBTL works and/or didn't look at all the graphs.  This chip does 2x BTL outputs.  At 24v, 8ohm, it puts out a solid 33w per BTL output with 1% THD.  At 4ohm, it is 60w.  This chip does offer PBTL, but he graphs only show 2ohm and 3ohm.  At 2ohm you can do an impressive 120w.  This makes sense because each side of the chip would see 4ohms (making 60w), adding up to 120w.  PBTL allows you to run lower ohm loads and higher wattage.  But my understanding is that running PBTL with 8ohm would still only yield about 30w, not 60w.

Attached is the datasheet as well as a couple screenshots of data graphs.