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Messages - edvard

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1
Schematics and Layouts / Re: Schematic sites for different brands of amps
« on: January 26, 2020, 07:52:34 PM »
I've seen this posted around the forum, but it should be here.

Schematics for Crate amplifiers (and others):
https://supportloudtech.netx.net/loud-public/#category/10641

Also, for those who have a schematic for the Sunn Beta Lead and disappointed that the power amp schematic is unreadable, the schematic for the Sunn "Alpha Series" mixers is the exact same thing.  Page 3 here:
https://support.fender.com/hc/en-us/article_attachments/115007761663/Alpha_Series.pdf
can drop in to page 1 here:
https://support.fender.com/hc/en-us/article_attachments/115007663026/Beta_Lead.PDF


2
Schematics and Layouts / Re: guitar amp diagram revision help
« on: January 26, 2020, 07:04:37 PM »
...
TDA2050 is marked as obsolete anywhere I've looked.  You could probably source one on eBay though.  That said, LM1875 is a great chip and I think it is a direct replacement pinout wise (you'd want to double check).
...

Beware TDA2050s from anybody but reputable parts sellers.  Some folks may have made a "reserve buy" when they were going out of production and are selling NOS, but NEW production is all counterfeit.
Obligatory JohnAudioTech video: "Counterfeit vs Authentic TDA2050 audio amplifier IC test"
https://www.youtube.com/watch?v=R2J5xrSiNrI

Looking at the datasheets, I can confirm the LM1875 is a pin-for-pin match with very similar performance.

3
Amplifier Discussion / Re: Info on Sunn Stinger 100 amp
« on: November 06, 2019, 01:07:29 AM »
I found out that the Fender Stage Lead II amp(Japan) and the Sunn Stinger 100(Taiwan) are the same amp..guess Fender just Re-Branded the same amp for Sunn & Fender during that time frame. I could not find any reviews on the Sunn Stinger 100 Amp, but I did find reviews on the Fender Stage Lead II, which are all positive. I guess that Sunn at that time did not have a very big fan base.
 
Thanks to everyone for all the info..good food for thought. Respects. PoorOtis.

There's some information here:
https://www.stratopastor.org.uk/strato/amps/twoseriessolidstatefenders/twoseriessolidstatefenders.html

He says email him for the Japan schematic.

EL34world has a Stage Lead II schematic, no idea if it's the "Japan" schematic or not:
https://el34world.com/charts/Schematics/files/Fender/Fender_stage_lead_ii.PDF

4
Amplifier Discussion / Re: Info on Sunn Stinger 100 amp
« on: November 06, 2019, 12:54:58 AM »
hey teemuk can you throw me a schematic for the sunn stinger 60, I am working on a stinger 20, sound the the preamp is of the same design.

There's a .gif file of the Stinger 60 Rev. B here (3rd post down):
https://forum.sunnstillshines.online/index.php?topic=7082.msg34495#msg34495

You are correct.  According to the User Manual (https://support.fender.com/hc/en-us/articles/115002388866-SUNN-Guitar-and-Bass-Amplifier-Owner-s-Manuals), the Stinger 20 and 60 were the same amp with different power sections.  I think even the power sections could be the same, but missing one pair of Power Darlingtons (TIP102 & TIP107) in the Stinger 20.


5
Amplifier Discussion / Re: Lab Series L3
« on: July 11, 2019, 09:33:15 PM »
Try this: 
https://mega.nz/#!1ph3CSrY!44oxSuZl6oZOZnnXJ12ikMNFncLJ2-AqZqEFzqUrnKg

Interesting schematic, that L3; it uses a CD4007 strung up to use the top half of it's 3 inverters as P-MOSFETs running the tone controls and another for the reverb driver/master out.
I don't see anywhere that counts as adjustable bias, but I could be wrong...

6
Amplifier Discussion / Re: Another Randall RG100ES question
« on: May 27, 2019, 03:24:05 PM »
Schematic says it's a 2K linear.


EDIT: Ooops... 5 days too late... Have you fixed it yet?

7
Schematics and Layouts / Re: Dual or Split supply Audio amps
« on: May 04, 2019, 01:51:24 AM »
According to the datasheet, full power on a LM1875 requires a power supply of +/- 30 volts.   That's 60 volts across peaks.  Are you using a 60 volt power supply? Your schematic calls for a 30V supply, which is not going to give you full power.
Also Single-supply requires a virtual ground made by the junction of two equal resistors that only the amplifier component uses (this is an OLD stompbox trick when using op-amps with a 9V power supply).  On the circuit you provided, this is found at the junction of R24 and R25.  Here they are designated as 10k resistors, which I think possibly puts a bit of load on the power supply (but I could be totally wrong about that). I would try changing those to 47k or 100k to see if you can get a stiffer output.

8
Amplifier Discussion / Re: EBay TDA2050 boards
« on: May 04, 2019, 01:01:31 AM »
Congrats, 2 years is a long time to take on a project, but I'm not one to talk (took me 2+ years to finish building my guitar...  :loco)

The reason your TDA2050s sounded so bad could be because they are cheap knock-offs; the TDA2050 has been discontinued for a few years now, and new ones are just as likely to be filled with wet sawdust as silicon.

Quote
Counterfeit VS. Authentic TDA2050 audio amplifier ic test
Counterfeit parts have been a problem for many years. Let's do a comparison test of the TDA2050 audio IC to see the difference in performance.
https://youtu.be/R2J5xrSiNrI

Glad to hear that your Class D amplifier sounds good.  I may be going that way eventually, but haven't taken the plunge yet.

9
Amplifier Discussion / Re: Etching your own boards
« on: January 04, 2019, 12:23:58 AM »
I've used some thinned-down model paint and a dip pen with very good results.  Speedball "B" series or Cartographer nibs.  Sharpies always drove me nuts, though my first Big Muff box was done with a sharpie.  I drew the circuit, waited for it to dry, and drew over it to get better coverage.  Sometimes, drawing over it would erase the original, so I'd have to re-draw the trace and do a second coat with a lighter hand. 
With the dip pen and paint, I never had to re-draw any, and the traces were solid.  Depending on the nib size, I could do thick, thin, or medium lines as needed.  I used two different sizes of pencil eraser as a "stamp" to make off-board wiring pads; big pads for pots, small pads for other wires.

10
Amplifier Discussion / Re: Biasing opamps in a Marshall Lead 12
« on: November 25, 2018, 04:01:41 PM »
...

So someone suggested a charge pump chip to produce the symmetric supply (an LT1054 or ICL7660(S)), but I decided against it because for all I know, the result is not really symmetric, being the negative rail weaker (my LTSpice simulations show that with a 10mA load it's more like +17V/-16V) and I fear that might induce asymmetrical clipping. Are my concerns here justified or am I simply talking nonsense?
...

Many, many, many distortion circuits utilize asymmetrical clipping as a desired feature, so I think you're OK there.  As far as clean headroom, I think you're still OK as long your preamp isn't overloading the front end of the power stage.  Even the venerable TDA2050 had a maximum input voltage of ±15v, and for most real-world situations, it was probably much less than that.

11
Tubes and Hybrids / Re: Vox hybrid project
« on: November 25, 2018, 04:38:25 AM »
Be sure to read the datasheet docs very carefully.  Class D amplifiers can be somewhat different beasts from 'normal' ones, and I don't have any personal experience with them; I just noted what is on the datasheet.  I also noticed that the input pins are supposed to be differential.  Does that mean the INN pins can be grounded and the INP pins carry signal?  I don't know, and it would probably be worth it to find out.  Read the docs and do a little searching around.  It may turn out that you'll need a phase split circuit between the preamp and power amp.

12
Tubes and Hybrids / Re: Vox hybrid project
« on: November 24, 2018, 11:33:10 PM »
You should be able to simply hook it right in.  Make sure you have a large-ish decoupling capacitor at the power amp input.  I see from the datasheet they recommend 1uf caps at both INPR/L and INNR/L pins.  That should be a good start. 

13
Amplifier Discussion / Re: Sunn Beta Lead Input Switching Issues
« on: November 16, 2018, 12:59:21 AM »
Interesting... if you look at the "Footswitch Circuit" part of the manual (page 5), it says that the voltage drop across the LEDs is what actuates the switching functions.  Maybe check the LEDs and their respective resistors (R140 and R141) for  flaky operation.  Sure they light up, but is the voltage drop still on-spec?

14
Preamps and Effects / Re: Strange pedal issue
« on: November 10, 2018, 11:56:49 PM »
Yes the plug that won't work is TRS and it's the same with my other pedals. Explain?

Sent from my SM-G935F using Tapatalk

In a lot of pedals, the input is a stereo jack that has the (-) lead from the battery or adapter on the R lug, so that when you plug in a TS, it shorts to ground and you have power.  Your cable's TRS end obviously doesn't have any wire connected to the R lug, so the power never makes contact in the pedal.  Sounds like the cable is a home-build?  If so, simply open up the TRS plug and solder a wire from R to S.

15
I fried a Crate Mini-stack yeeeeeeeeaaaaaaars ago by accidentally plugging the speaker outs into each other.  Smoke smell and buzz were the result.  I'll hazard a guess that it's the same thing here.  If you open it up, you'll most likely find a chip-amp handling the speaker output, and the smoke will have escaped.  First thing I'd do is replace the chipamp and the output capacitor, then work backwards from there if that doesn't cure it.  I couldn't find any schematics or specs to suss out what variety of chipamp is loaded in there, but talk around the 'net says contact Crate and they can advise you on that detail.

Are you handy with tools and a soldering iron?

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