I maybe missing something here but at a glance,,, this is the worst possible way to blow up 2 amps.
I think you need to do some research.
You can *Bridge* two outputs and send out of phase to the inputs but then the speaker terminals float from ground.

Sorry to tired to think now.
Phil.

OK, look if you want to believe  in Hi teck then do as they say it's your amp after all.
In all My Years Of Experience I've never had issues with such *TRIPE*

Yes I spose if you wish to disect every last dB from a box you can run a wacky sim on it if you must.
Keep in mind the Marshall Simulation Experiment:)
Jim Marshall designed Built by this amazing bit of computer called the *Brain*.

It's called the economy and cost simulation (and you don't even need a conputter:)

Take x number of boards from a supplier and work out the most amount of boxes you can get out of one sheet of board.

Sounded good emough to make his Amplifiers *World Famous*

Ports only work below 100Hz and can make things rather peaky and thats just with HiFi woffers. Now take a guitar speaker which has freq response all over the place and it's anyones guess as what it will sound like.

The bottom string on your guitar is 82 Hz  and you want extra bass
Then go buy a bass guitar and a bass amp.
The problem with this modern world is everything has to be hi-teck and specialized and made to sound vastly complex and the simple truth is it's NOT.

If you want better Bottom end then tweak the Amp.
Phil.

Yeah but at least he can change a component if he needs to 

Try that on a double sided suface mount board

Wait till you youngens get past 50 and you need glasses. :lmao:
Phil.

Hi Zappacat,
                 You have a 9VDC 500mA adaptor.

Obviously a SMPSU ,, you can tell by the dual AC mains of 110 to 220 V primary.

These suckers can be horrendiously noisey buggas depending on how well they are designed and how prone the circuit it powers is to picking up noise.

IMO play it safe and use a wall wart with a *RealTransformer*.

SMPSU's may work on some gear but may spell trouble when mixing and matching pedals in front of higain amps.

Sounds like you need to get some bedtime reading on the basic's of power supplies. 

Go here; http://evatco.com.au/hamptchoke.htm

Click on transformer *selection guide* halfway down

Direct try this: http://evatco.com.au/ham_files/hampwrselect.jpg

Now ***SAVE IT*** Print it,,, as you progress you will fast come to see how useful it tiss.  :tu:
Should be mostly self explanitory,, oh remember the *I* stands for current.
Cheers Phil.

Quote from: mnturner on April 16, 2010, 04:19:38 AM
Hi phatt,
yeah I saw those kits at Jaycar; I didn't want to buy one to begin with but I've pretty much ended up building an LM3886 gainclone type amp which is basically the same thing, just with a little more power. Thanks for the tips on the preamp!
Hi Fahey,
when I get around to building that thing I'll have to do that. I had it running at really low power on a breadboard and even then T11 and 12 were getting way too hot.

Um?   I think you will find the LM3886 (although reasonable) is no match for pure grunt of SC480.
LM3886 only has 2 driver tr's ,,whereas the SC480 has 4 giving it far greater current ability.

LM3886 is only 40Watts @ 8 Ohms and I believe that is the outer limit.
68 Watts on paper sounds nice until you see the 4 Ohm tagged on the end.
but I'm sure as you have spent the money you will have fun with the chip amp, 40Watts is still loud.
Phil.

Hi mnturner,
                 Another Aussie ay?
might make life much easier if you just purchase the *Jaycar SC480* kit.
$50 for the PCB and all the bits but you supply Heatsink and PSU.
You should get change out $100 all up.

Or go to Rod Elliot's site *ESP* to give you some ideas to ponder.

Also have a look at ; http://www.ssguitar.com/index.php?topic=1609.msg10267;topicseen#new

Bassbuddy's got a nice preamp setup he built.
Cheers Phil.

Hey Bassbuddy,
Very tidy inside, for a home job that would have taken a lot of time and effort.

My Laney rig is just for convenience,, only 35 watts.
I have a massive 120watt Poweramp for bigger stuff but I hardly use it as the gigs I do are only small.
Handy to have more than one piece of gear in case something goes down.
Phil.

Quote from: Bassbuddy on April 12, 2010, 01:05:06 PM
Hi
The idea I meant was not using a PA amp but to build a separate preamp in such a way that it can be combined easily with A power amp to make a nice matched couple. I will attach pictures of my amp to show what I mean.
GG

Plus 1 from me,,, Your's looks a bit neater than mine
Yes at my age you don't give a rats A what it looks like,,, it just has to sound good.
Cheers Phil.

Quote from Vitrolin;
"i wonder how to understand the power rating...dynamic power? same at 2, 4 and 8 ohm"

Just don't wonder,,, it won't make sense anyway
Stick to X amout of watts RMS into a load of 8 Ohms as that keeps everything in perspective.

Hi JM Fahey,,
LOL, Trust you to read between the lines and pick the possible mistake,, good call. wink.
Phil.

180 Watts per channel is probably optomitic,, but if it's very heavy
(due to massive transformer) then could be so.

More likely to be 180 Watt *Total* or 90 Watts per channel.
So that 90 Watts into 8 Ohms will be 65-ish Watts into 16 ohms.
Still above average for a HiFiAmp.

If you use a stereo efx processor then you can run the stereo out to both channels and that would rattle the windows I'm sure.
Phil.

Quote from: Vitrolin on April 08, 2010, 05:34:40 PM
So.. basicly i could just put any preamp infront and just use the aux or cd or tape or whatever input... well propably not tho phono input.

if i insist on the tubepre i should then make a buffer at the output so that imp will be low.

well thanks alot for your help...

pd the sound clip in your link cant be found

Hi again, I'll quote you,

"So.. basicly i could just put any preamp infront and just use the aux or
cd or tape or whatever input... well propably not tho phono input."

>(YES !
I can't promise the earth but there is a very good chance that all will
be ok. (with Aux ok , you will have to suck it 'n see with the other inputs)
NO! don't use the phono circuit,, as they a special circuit to match
magnetic cartrides used for Vinyl records.)<

" if i insist on the tubepre i should then make a buffer at the output so
that imp will be low."

>( Just take a good look at The VTwin circuit and note that the output is
from an opamp so the issue is resolved)<

"well thanks alot for your help...
pd the sound clip in your link cant be found"

>( oh bummer:(  
Ever since this site had an attack A lot of stuff has
gone missing. My computer went down also and I've lost a lot of stuff I'll see what I
can drag up from the bkups.)<

BTW,
The Graphic EQ in the picture is a HiFi Elcheapo S/hand device I picked
up at a gararge sale for $8.  Who says you can't get great sound from
bit's of junk.  
Phil.

Hi Vitrolin,
            Well the aux input will except a line level (or there abouts) and as most preamp circuits often output close to *line level* then it's all matched for you.(close enough)
In general it's only the first stage that needs the high input.

In Valve circuits things can go wonky at interstage places because the signal is often taken from the plate,, unless you employ a cathode follower for low output imp it will be a mismatch.
With a SS opamp circuit the signal out is going to be low imp.

The general rule of thumb in regard to joining multipule stages is they should have high input and low output, the other way round will have net loss.

As to *which preamp circuit* well pick one of the hundreds that exist.
Depends what kind of music you want to play and want you want to achieve.

If you are heading towards a *Seperate preamp unit/box* then at least if you don't like the preamp you can just keep making new circuits until you are happy with the result otherwise you will have holes drilled all over the Yamaha and it won't look pretty.

If you wish to try one of my simple *Well Tested* circuits for a start then go here.  http://www.ssguitar.com/index.php?topic=1136.0

Also Brouse these pages for many more circuits that may deliver the sound you are chasing.
If you want to go crazy with Valve circuits then download the Messa V Twin schematic. Probably one of the better designs that intergrates Valves and Opamps in the same circuit. You only need to build the clean channel and you won't need all the add on cabsim/ line stuff.
I have built a cut down version so I know how well it works.

If you are fussy about tone then I recommend purchasing a small proto board which makes it quick and easy to setup many different circuits until you are happy with what you hear. You also learn a lot more that way.
After close to 30 years of messing with circuits
(I have a bottom draw full of, seemed like a good idea at the time circuit failures to prove it)

I Now use a very modular setup which did not break the $budget$ and pulls some great guitar tones.
signal runs thus;
Tone box > Distortion control unit (exotic fuzz box)> GraphicEQ > PowerAmp > speaker.

My Laney Amp is just a 3 channel *Keyboard Amp* so it's closer to a flat hifi poweramp. (definitly not a guitar amp)
Which proves that by careful selection of preamp setups you can pull some very conviving guitar sounds.
Don't forget to find a decent guitar speaker, try and test drive them before commiting.

With just volume, bass and treble controls on all 3 channels the Laney would be similar in response to your HiFi power amp. Assuming you run the signal into the line input, which should give you access to the onboard tone controls.

If it interests you I will post some circuits for you to play around with.
Meantime if you wish to hear what my elchepo setup can do go here;
http://www.ssguitar.com/index.php?topic=1446.0

Oh and a pic of my rig might give you ideas as to how to approach it.
Have fun with it all, Phil.

Hello rowdy,
               I spose It all depends greatly on your definition of *Clean*?

SRV, Mark Knopfler, Hank Marvin. To a heavy metal freak those 3 sounds would be considered clean,,, But if you care to notice there is still a lot of rattle, Certainly still far removed from SS HiFi clean.

Yes it's easy enough to get big fat distortion from most modern circuits but those in between sweet sounds are very tricky to nail. Frankly ultra clean guitar sounds quite dead.
Sorry if I'm getting off track.
Re the loading;
                     The Plate is always more positive than the Cathode.
I believe the issue has more to do with the control grid and plate.
The internal impedance of the Valve itself,, (Imp is just AC resistance and that changes).
I did read up on this long ago but sadly the wonderful books had to be returned, sadly my brain needed to learn more basic stuff at that time so was not able to fully absorb the complexity involved. At least I sucked up enough to realise that something weird happens under load.
Phil.

A 500k pot can be anywhere from 300k to 550k.
This is called, tolerance window.  most stuff like this is general/ kinda/ about.

Same with caps where you see a value 50nF but the closest you will find on the shelf is 47nF.
don't worry you will catch onto all these little quirks soon enough.
Phil.

Do you want to gut this thing to build a complete amp from scrap or do you just want a preamp that plugs into an aux input?
Phil.