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Topics - exztinct01

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Amplifier Discussion / My Lead 12 Pre Clone Squeals at High Gain
« on: December 10, 2016, 01:18:48 AM »
Is this natural? or can I do something to remove it? Squeal starts at about 90% rotation I think
I used 5k, 3 x 20k, 1M all linear as of now. I added a switch to choose between 100pF or 220pF for C5.
Here's the layout I made but there were some slight changes in the actual build

Here's the build ;) And I'm hoping being unshielded's not the reason for the squeal.

Maybe the layout's the main problem?
Anyway, those red colored pads indicate tracks cut. It was some kind of stripboard something but tracks are customized by the store I bought it from

Amplifier Discussion / Darker Sounding Preamp?
« on: November 17, 2016, 10:53:59 AM »
I've been using my P27 preamp with a silicon fuzz face clone in front and is not quite satisfied with the results. I love the cleans of the P27 alone, although not amazed by the sound produced by those clipping diodes. I might just remove those in the future.
However, I also want some darker sounds for other kinds of music. What preamp can I build to achieve this?
My speaker only adds to the brightness of the P27 and adding that FF clone resulted in harsh and unpleasant sound IMO. I need some dark distorted sounds from some gears, be it a complete preamp, a distortion pedal, that will balance the brightness of my speaker.

PS: I was considering the Lead 12 Pre as it already earned some praise from people more experienced than me but I don't know if it's what I need. Is it?

I found a spreadsheet containing some values for LM3886 design. Can anyone of you please confirm it?
It already contains data that can be used to determine proper VA for traffo and proper heatsink, and independent variables like VCC, speaker impedance and crest factor can be changed values.

Here's the site
and the spreadsheet

Amplifier Discussion / Should I buy this kit?
« on: September 04, 2016, 08:19:03 PM »
I was planning to buy a board from ESP but was still hesitant because of the cost.
Then, I found this kit. It is being sold here in the Philippines and costs only Php457 (about US$ 9.5). Reason for considering a kit is because I think it is easier to work with professionally made boards and that kit is so affordable.
Problem is, it says the Zobel network which is supposed to make it stable does the opposite so it removed those. Also, supply bypass caps are both 3300 uF (is this too large or any values will do?). Luckily, the board still has the holes for the Zobel RC.
Any comment on this kit?
Link is

Amplifier Discussion / Help Me Connect Two Preamps to One Power Amp
« on: August 12, 2016, 12:24:00 PM »

Above is ESP Project 115.
I want my guitar amp (P27 Preamp and P19 Power Amp) to have an MP3 Input but since my player (smartphone) has low gain, I decided to add a preamp for the mp3 player inside the guitar amp.
Now, can I please ask for guidance what kind of circuit should I put in between the mp3 preamp to power amp, and guitar preamp to power amp. I think it might be better if it's illustrated but a clear explanation and guide is enough.

Also, I don't need that many resistors and the relay for the preamp since I'll only be using it for the mp3 player so I need it simplified too.

Amplifier Discussion / LA4601 amp help
« on: July 23, 2016, 12:56:16 AM »
i removed the la4601 chip from my old yamaha psr keyboard and built a small amp based on its datasheet. (i can't attach datasheet since its in my laptop).
Anyway, the amp worked but it always produces this sound like when a message is coming to my phone near an amp. Of course, I tested the amp uncased so maybe shielding it will help. Or maybe you can recommend some mods to the datasheet schem to help remove those sounds. I will always be playing it with my phone.
Also, I think my phone's output level is too much for the amp coz most mp3's sound too distorted when my phone's volume is more than 10/30.
Does the LA4601 expect line/headphone level or not?
Sorry for posting this here. I know there are many forums where this topic is more suited but I'm at home in this forum. (more than any other)

Amplifier Discussion / Need help analyzing a part of a circuit
« on: July 17, 2016, 04:23:10 PM »
I opened a small amp circuit out of curiosity as how these things are designed. Also, I want to see how it separated the signal to use for the low end driver. Speakers are only 3W stereo and 8W for the low end. Below is the schematic I drew from it. From preamp, it goes to volume then treble then goes to Con2 (Red & White). I don't understand how from Conn2, it passes through a dual opamp then to the bridged TEA2025. Can someone explain what's the purpose of that opamp circuit?

Amplifier Discussion / Heatsink for LM3886 Guitar Amp
« on: July 04, 2016, 03:46:45 AM »
Is this enough for a mono LM3886 (two for stereo) guitar power amp?
I'm planning to build a stereo amp using two LM3886 now that I'm finished with my LM1875 one. If placing the heatsink fins outside amp chassis would help for better dissipation, then I'm willing to do it with that heatsink.

If not, how 'bout one of these for stereo?
I know they show their thermal resistances were given but I still need your advice.

is it okay to play distorted and compressed guitar sound through speaker box that has both woofer and tweeter? Won't it damage tweeters?
How about in PA?

As the title speaks, can you recommend a power amp project for my 42-0-42 300watts traffo? I remember I scavenged it from a powered mixer with 2 pairs of 2SC5200 and 2SA1943 but I'm prepared to use better power trannies for the amp. I prefer it to be versatile enough for use as guitar or hifi power amp, something in the middle I think. I don't have any ideas as to how many watts it will put out but doesn't matter for me right now. Traffo must be put to use  ;)

Amplifier Discussion / Need some answers
« on: May 31, 2016, 09:35:46 PM »
A friend just bought a Sakura AV5023 amp. It is considered a home theatre amp and is made in China, I think. But company is local here in the Phil. I've seen people connect too many speakers in the outputs of this amp, about 4 woofers, 4 tweeters and 2 midrange drivers to build a karaoke system. Are they doing it right? I mean, it's not a high powered amp. It claims 500W+500W in its main outputs but I don't believe them of course. Plus, the impedance thing. What can you say about the outputs of this amp and its capabilities?

Schematic is in attached pdf, PrtSc function would excessively reduce the quality of the image.

Amplifier Discussion / Bi-amping/ Tri-amping
« on: May 02, 2016, 08:14:43 PM »
I built an LM1875 mono amp for guitar and for testing purposes, I connected it first to a 4 ohms 5 watts speaker, next to an 8 ohms 150 watts woofer with eff 93db. The signal source was my smartphone so there was no other preamp, no crossover. The only signal is a mono from the phone to LM1875 amp.

Now, I noticed that it can't give the woofer enough power to make it thump (not really great at english so I just picked the word thump  :lmao:)
What amp power, specific amp, can make a woofer with that spec sound good, assuming I have an active crossover? Of course subs will give more bassy sounds but woofers are still capable of some low Hz I think.

I am not really into building crossovers and biamped or triamped systems as of now simce I am only a beginner but there's nothing wrong with studying every aspect of amp building. Plus, my father-in-law is "obsessed" with audio systems, he owns 3 karaoke systems being rented, and he plans to buy a PA system. He's a good carpenter so I think if I gain enough knowledge to build crossovers and high powered amps, coupled with his skill at building speaker cabs, we could assemble a good PA system in the not so near future. It's very ambitious of me but nothing is wrong at aiming high  ;)

The Newcomer's Forum / Have doubts on transformer rating
« on: April 25, 2016, 10:04:06 AM »
I just bought a transformer made here in the Philippines. It's 220vac to 18-0-18vac and rated at 2 amperes. (i don't know why they don't use va for transformers rating here)
 I'll be using it for a power amp (Rod Elliott's Project 72) which asks for at least 50VA. Problem is I don't trust its rating since it's on the small side. Photos below shows the laminations' dimensions. Can anyone confirm if it really is 2 amperes (72VA for 18-0-18)?

I'm building this as preamp for an LM1875 power amp.
Since I don't think this preamp will require current above 1 Ampere, can I use LM7815/7915 voltage regulators instead of the zener diodes?
Also, what other things do I have to change to match the output of the preamp to the input of the LM1875 power amp?

I'm in a country (Philippines) where our wall outlets only has the LIVE and the NEUTRAL conductors. So, obvious question is where does my amplifier's ground go?

If I want to avoid shock, should the ground just remain inside the chassis and NOT CONNECTED to the chassis?
Or should I find a way to bring that Ground Connections to Earth? Question is how?

Any suggestions that would not ELECTROCUTE me is appreciated  :cheesy:

PS: I was actually starting the build, but then that part crossed my mind.

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