oh sorry, I missed attaching the image in my last post.
Here it is

this is my amp layout, let's say it's high current amp. Which connection should I cut?
Power amp's pcb has signal common and supply common directly connected, same with preamp. I already found some errors like my center tap terminates after filter caps. Another, loops. May I also say that I don't have true earth there so grounds' floating. I can't make any fix yet for that floating ground since it will require redesigning my house's electrical system.

in a power amp pcb (e.g. P27 power amp), is the signal common connected to its supply common? Mr. Fahey stated in his post they should return to star ground in different paths. P27 power amp have only one return path and I think both signal and supply commons pass there since preamp is isolated by a 10 ohms resistor from the common point.

In a system composed of a preamp, power amp, them sharing a power supply, which is better? Isolating preamp from power amp or isolating preamp from direct connection to power supply which means its ground connection would pass through power amp first before going to star ground?

I don't even know if I'm asking the right question  :lmao:

I thought maybe if both preamp's and power amp's common are connected directly to PS, and also with each other, there will be a loop and it will do no good for the system if power amp's return will pass through preamp. Am I getting it right? Please help me fix my brain.  :loco

i hope all those components are not shorted  :loco

mine still squeals when I add a distortion pedal in front of the preamp. I'll try putting the distortion after the preamp and see if it minimizes noise.
Did you reduce the gain of your preamp from Rod's original 27db?

Quote from: No6h on June 04, 2016, 03:12:09 AM
am getting perfect continuity from the input jack to the speaker terminals.

why should they have perfect continuity?
Ground, yes. But signal path?

but if the drill will only be used for precise drilling into aluminum or other metals, which of the other two drills, gbm350 & gbm10RE, would suffice or is convenient in terms of power and weight

both have max diameter of 10 mm for steel (also for aluminum I think). gbm350 is 350 watts, gbm10re is 600 watts. gbm10re is a bit heavier and of course more pricey.

So is the 350 enough for the precision drilling in aluminum job?

oh okay. I'm still trying to cut the cost here. So how bout this
http://www.bosch-pt.com.my/my/en/drill-gbm-350-131436-06011a95l0.html
or this http://www.bosch-pt.com.my/my/en/drill-gbm-10-re-131436-06014735l0.html
is 600w also overkill and 350w good enough for aluminum drilling?
I may have to use the drill for concrete sometimes so it's better to have a drill that's versatile. If these two are not enough, I may have to choose the impact drill from my last post.

another question unrelated to the first one.
I'm trying to buy a power drill. Is this good enough for drilling into aluminum say 10mm thick with, maybe, a 3mm bit?
http://www.lazada.com.ph/bosch-contractors-choice-06011a15k0-gsb-550-impact-drill-1541338.html
bit can be used with adapter or holder. I'm asking if this drill has the power to do it.

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.

Quote from: J M Fahey on May 23, 2016, 03:23:14 AM
Go for some commercial kit or clone some commercial well made amp and you'll be miles ahead, or worst case, use the datasheet/handbook example.

By the way, that's what Leo and Jim did themselves ...I don't think they didn't succeed !!!!!

I love that idea of cloning well made commercial amps  :dbtu:
Guess not being an EE is not much of a disadvantage after all 
Learning while building, awesome.

Anyway, I was told by a new friend (I just found him in a forum and discovered he lives a few hours drive away from me) that he'd help me build a P3A. He has the tools and skill to build the chassis, and that's what I lack now. But to minimize the cost, I thought , what if I just use an available toroidal transformer I have now. Problem is the toroid's secondary is 42-0-42 and rated at 300 watts. It also has other secondaries, 17-0-17 and 0-12. Is there any mod that I can do to the P3A to be able to use that traffo, like maybe adding more pairs of output trannies? I don't mind you scolding me if such ideas are stupid  :loco

BSIAB II, I'll definitely try that 

oh I know you're still way better than me at this  :lmao:
I don't think I'll be integrating a drive in the amp. If he wants distortion, then I'll build him a TS808 or a Big Muff Pi aside from my Distortion Plus. Or like you said, I may build an AMZ Booster.

I find it a bit bassy though, the preamp. How about you?

first, thanks to all your help for finishing my first guitar amp. It's not yet in a chassis since I don't have the tools  for building it but when I get some money, I will immediately go to a metalwork shop to order a custom build one.

My take on my first build (again, it consists of P27 preamp using TL072 connected via shielded wire to LM1875 single channel where the shield connects only to the power amp, common connection is through the PS)
- Noise is very low, I barely hear it when not playing, even when both Volume and Master Volume are at maximum.
- We actually used it (uncased) in a praise and worship setting since our guitarist was so excited about the amp. Honestly, our drummer plays so loud that our soundman finds it hard to bring the vocals and keyboard up to its level, but the guitar in my DIY amp sounded so clear throughout the hall, with leads singing 
- After about 45 minutes of playing (our guitarist was not using any effect pedals that time, just the amp and guitar at maximum volume both), I touched the heatsink and the IC and HONESTLY, it did not even get warm (being out in the open air of course helped).
- Our guitarist even asks me why there is no gain pot and I don't know what to answer him. All I know is that the preamp already has two volume controls and the Master Volume at max produces a little bit distortion. But he asks for more, I don't know how to add a circuit that will integrate a gain control there.
- After our service concluded, I put my DIY MXR Distortion Plus in front of the preamp, set it with maximum gain and Volume at about 3 then played a song with distorted guitar. Turning the pedal on makes a dramatic increase in volume compared with the pedal off so I don't know how to make the transition from clean to distorted using the DS+ sound good. Some suggested that I try different diodes than the 1N4148's.
- Also, when I tried to increase the pedal's volume (I think it was at 7 and above), the speaker suddenly squealed. That high pitch sound disappears when I lowered the volume. So, how do I remove that squeal? Should I maintain my pedal at low gain or low volume? I avoid having my pedal at low gain and volume coz I don't think I hear distortion at those settings. I believe I hear those distorted sounds clearer at high volume.
- Also, after playing with the pedal, my LM1875 IC and heatsink got warm. Not too hot, just warm. 

Any suggestions, opinions, recommendations, mad reactions are accepted  :trouble