rod elliott's P27/M27 or P03 + preamp?

[yoyoy_kun]

hi im planning on building R. Elliott's 100watt amp, but im thinking twice...
can you suggest something similar build, but better...
or what can i sub for the pre amp..

thanks in advance...

[Roly]

In what way "better"?

Rod's design is about as good as you are going to get, streets ahead of many other "designs" on the web that won't actually work, so you need to be more specific about what you mean by "better".

You can substitute just about anything for the preamp, but again, why?  In what way does Rod's design fall short of your needs?

[yoyoy_kun]

i have been reading about the project 27 of Rod's, and there are some that were saying that the pre amp could be better...
i was wanting to build this amp, but i was searching for a bass amp, i dont think this preamp is what im searching for...
could you suggest any preamp, that like this that is easy to build....

[Roly]

there are some that were saying that the pre amp could be better...

There are "some" people (not specified) who say Rod's preamp could be "better" (in ways not specified).


There are two sorts of people who offer circuits and technical opinions on the net - those who use their real names and have known backgrounds and expertise, who have been doing this *s!!t* for years, the likes of Doug Self, R.G.Keen, Steve Bench, J.C.Mailett, J.M.Fahey, Rod Elliott, ...

This also includes a bunch of people who only go by their first names, but who have established across time and many forums that they actually know what they are talking about.

Then there are people like "snot99", "dribbledumpling", and just plain "anon" who are a totally unknown quantity and who's opinions are generally not worth a burnt crumpet.


I have (for example) been highly critical of a preamp "design" that is published by Anon on runoffgroove.com.  I have been specific about what I (as a retired professional circuit designer) see as wrong with it, and offered up an alternative of my own which I think is a better design (which you will find discussed here).

Rod himself says of Project 27...

the tone controls as shown have sufficient range to cover almost anything from an electrified violin to a bass guitar - The response can be limited if you wish (by experimenting with the tone control capacitor values)
...
As shown, the preamp is just as usable for bass or electric piano as for rhythm or lead guitar.
http://sound.westhost.com/project27.htm

In fact Rod not only discusses this preamp for use with bass guitar, he even suggests few mods to tweek that application, and tweeking circuits like preamps to your taste is a large part of the reason for building your own over buying somebody else's compromises. (e.g. see here).

So on one hand we have a known experienced designer with a track record and a design suitable for bass guitar, and on the other some unknown schmuck who say "it could be better".

Well I can tell you one way that a preamp could be better suited to bass guitar, and that is to include some form of signal compression, and if we look in Rod's index, what do we find?

Ultra Simple Bass Guitar Compressor

You see, Rod has a very good idea of what he is talking about.  He's not some opinionated teen dweeb wannabe who doesn't know a FET from a poke in the eye.

Unless and until you can come up with some specifics about a "better" preamp his advice is entirely reasonable;

I suggest that you try it "as is" before making any changes.

[yoyoy_kun]

im sorry if i may seem to be unreasonable, for the fact that you advising that this is a pretty good amp, ill stick to the project 27...
another thing about p27 is that i cant find the specs of the parts...
ill try to read more... then maybe if i find the parts here in our country ill start with right away, if not, ill research more about substituting the parts... 

regards

[Roly]

"Better" is a very elastic concept and can mean all sorts of things in the context of guitar amps.

This design isn't fancy and should be fairly tolerant of component substitution provided the replacements meet or exceed the required specs.

When it come to building an amp you can go on "window shopping" designs forever, but at some point you need to take hold of something that looks reasonable, and can be modified without too much trouble.  Project 27 fits that bill, but whatever it is, once it is built and going you can move on to the next stage of tweeking and refinement.

In the case of bass guitar that particularly means getting your speaker and cabinet right because they tend to have a much larger influence on bass than tenor guitar, the amp normally being less of a problem as long as it has ample "grunt".

Where are you?

[phatt]

Maybe if I come at this from a players perspective it might help the penny drop.

There is a mindset out in Amp land that assumes the mojo is inside the Rig, usually the big fancy ones with the slick panels that claim all manner of tones can be got by the press of a pedal.

And all seems fine until you realize that the very sounds/tones you really need most are not in the 99 presets. :grr :grr :grr
If you buy one like that,, make damned sure it does Exactly what you want otherwise You WILL regret it,,and likely sooner than you think. 

Rod's preamp design is middle of the road and that is the best way to come at it.
In all the years I've spent creating land fill circuits I've come to see the merit of having a simple basic Amplifier. All the other stuff can be done with pedals or outboard preamps.

If I had a dollar for every player I've asked about how they like there new $$$$ multi channel rig and got this answer I'd be rich.
More often than not the Answer is;

"Well I ended up just using the clean channel and used pedals for all the other sounds."  Under my breath I say, Durh?

Now if you go back a few years to when some of the greatest sounds to ever be recorded where done with *Single Channel Amps* you realize they where basic simple circuits that did the job and any enhancements where done with Outboard gear. HINT!!!

One big advantage to this is the Amps often gave little trouble and some amps both SS and Glass powered made in the ~70's are likely still running today.

Sadly the same can't be said about a lot of these late model rigs with more dials and circuitry than a 747. IME, due to the sheer complexity by design they are far more prone to problems and often end up as scrap due to mass production techniques.

I personally use a crappy old SS Keyboard amp which has bass and treble knobs and about the only fancy builtin asset is a spring reverb.

I ended up building my own dedicated floor preamp to do a few tricks and I've never looked back. :dbtu:

OK obviously I'm an old bugga and Overweight Metal playing is not my favorite tone BUT a while back I had a couple of young lads turn up, one armed with a rather expensive evil looking pointy headstock Axe and he was blown away by the fact that my pile of bits produced a far more convincing Metal tone than his latest $$Brandname$$ killer machine rig.

I then turned a couple of dials on my pedal and played Sleepwalker for them. So from a fat hard scooped sound distortion to Hank Marvin sweet singing melody tone.
All done with a non guitar dedicated basic Amplifier.

The Amp market industry runs on fads but if you block your ears to it all and read between the lines you can achieve a lot of great sounds without the expense,, Hence Rod's idea is a darn good way to start.  :dbtu:

I did test out ESP preamp long time back and did find the distortion section was not much use but as should be obvious now You don't really need it if you use pedals wisely.

cheers ,, Phil.

[Roly]

Great post Phil.  :tup

And all seems fine until you realize that the very sounds/tones you really need most are not in the 99 presets. :grr :grr :grr

Between my synths and rack boxes I have perhaps 300-odd voices to chose from, but not one in ten would be of any practical use, only about half a dozen doing almost all the work.  Playing guitar is similar; I don't often use Fx at all, and when I do it's likely to be a touch of chorus, or a bit of fuzz when the number specifically calls for it, which isn't often.

In my observation bass players need a lot of clean power, a pre with a good selection of EQ, and perhaps some compression ... and a really suitable speaker system.

IMO at the bottom line it comes down to how you play.  I've busked a lot of acoustic and the only Fx you can get is from how you play, and you can get quite a palette without having a single knob.

[yoyoy_kun]

im planning to substitute mje340/mje350 from bd139/bd140 and BC559/BC549 from BC557/BC547...
which is better to use MJ3055/MJ2955, TIP35C/TIP36C...

IS THIS OK?

[phatt]

Hi Yoyo,
           Maybe just read it all again 

http://sound.westhost.com/project27.htm

Lifted from above page,, just below the PwrAmp Schematic;

""As shown, the power transistors will have an easy time driving any load down to 4 ohms. If you don't use the PCB (or are happy to mount power transistors off the board), you can use TO3 transistors for the output stage. MJ15003/4 transistors are very high power, and will run cooler because of the TO-3 casing (lower thermal resistance). Beware of counterfeits though! There are many other high power transistors that can be used, and the amp is quite tolerant of substitutes (as long as their ratings are at least equal to the devices shown). The PCB can accommodate Toshiba or Motorola 150W flat-pack power transistors with relative ease - if you wanted to go that way. TIP3055/2966 or MJE3055/2955 can also be used for light or ordinary duty.""

I think that is all fairly clear.
From memory... BC559/549 have a lower working voltage than BC557/547 so it should work ok.

Look up the specs and compare them,, I would think Breakdown Voltage ratings and Current ratings is what you are looking for.
MJE might be overkill,,, but others here will know more detail.

If you do go TO3 case make those wires as short as possible.
Frankly unless you are going to gig this thing full bore in very hot climate I'd stick to what is given.
Rod has done all the hard work for you and built to a reasonable standard the amp will last a very long time and give faithful service 8|

If you are having trouble sourcing parts then you can always purchase a kit. Hint.
Then you can ask him directly for any tips or mods. 
Phil.

[yoyoy_kun]

thanks phil. what you said was all i needed... i dont really know what specs to look for, i know now..
ill buy the parts this week, and change the pcb for TO-3, by next week ill start building...
the only left is to find a heatsink and casing...

can i use a galvanize plate steel?

thanks again phil...

regards

[Roly]

can i use a galvanize plate steel?

As a heatsink?  Definitely not.  An amp producing 100W output will need to get rid of a similar amount of waste heat, so a proper black anodised aluminium heatsink is a must, and it must also have a low thermal resistance to air (ºC/W) so that the rated operating temperature of the transistors are not exceeded.  This normally means a pretty substantial heatsink with large vertically mounted fins.

IMO getting rid of this waste heat, on stage in a hot venue under hot lights, is a key issue with solid-state guitar amp reliability.

As a general rule you find you end up needing more heatsink than you initially think.  You need to keep in mind that a heatsink is actually a heat coupler, and needs a good flow of free air to carry the heat away.

[phatt]

Roly got up before me today, :cheesy:

Anyway Rod covers a heck of a lot of fine detail but you have to search the place and it's likely bigger than even Roly's junk yard collection.

http://sound.westhost.com/heatsinks.htm
Phil.

[yoyoy_kun]

i will only use this for practice, but i ill use the biggest i can find here...
i will also put a fan or two, with LED to ensure air flow...

is there a proper way to install the fan...?

and im planning to use galvanized steel sheet as casing, what do you think?

http://image.made-in-china.com/2f0j00SCmawchtSZqo/Galvanized-Steel-Coil.jpg

[phatt]

Well IMHO I've never had need for a fan on SS amps.  up to you
If I see a fan on an Amplifier I automatically think ,, maybe it's got some design flaws.

I've run hundreds of functions, weddings, discos, shopping centre promos with power amps that have never had fans and I've still got my old faithful Yamy 2050 power brick still running after 20 years and it's never shown any sign of heat issue. It was already years old When I found it.
adding I live in Nambour = Hot and Humid in summer,, and no fan needed.

If a well built and designed power section ever fails,, ask for the clown who keeps joining speaker boxes on the output so you can thump him and bill him for the cost of repair.

I have a dead 200 watts per side power amp here with blown outputs all because some idiot got sick of changing the 4 x 3 Amp fuses on the rails. He installed 30 Amp car fuses :duh :duh :duh :duh
and of course he destroyed a perfectly good power amp by chaining to many speaker boxes on the outputs. At SIX power mosfets per channel it's not worth fixing now.

Oh yeah,,,, and it was a Perreux 2000 which has a big monster fan.
So don't rely on a fan is my advice,, rely instead on a well designed heat sink.

Re the case;
you need around 1.2mm or even 1.6mm,, as below 0.9mm the case becomes rather flimsy.
Sure below 1mm it's easy to bend by hand but it is worth the extra cost of building with thicker gauge steel.

cheers mate, Phil.