hi i have a audio poweramp that i would like to convert into a guitar power amp and add a preamp, maybe tube based.
well the amp right now is a Yamaha A-320 the transistors are: SK A1104 and SK C2579, i have found a datasheet on the last one its a NPN, my guess is that the first i PNP and its push-pull amp.
i was thinking that maybe its that simple as to put a preamp before the volumepot, would be nice but propably not.
so... has any onemade a similar convertion or might have an idea that would be usefull.
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.
Quotemaybe its that simple as to put a preamp before the volumepot,
Something like that.
Mount and wire some jack into both Left and Right volume pots , I assume the amp is salvaged from the trash bin or something like that and not used for Hi Fi anymore.
Do not mess with tubes yet, search the Forum for simple preamp ideas.
There's some info on using an LM386 as preamp, which would drive either a small speaker on its own or your Yamaha to neighbourhood upsetting levels.
Quote from: phatt on April 07, 2010, 12:35:44 AM
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.
well i havent yet decided whether it should be a rebuild or an add on but in terms of preamp would there be alot of difference?
I imagine that if i wanted a preamp for the aux input then there should be some buffer thing since i imagine its low impedance compared to a guitars
Quote from: J M Fahey on April 07, 2010, 09:07:43 AM
Quotemaybe its that simple as to put a preamp before the volumepot,
Something like that.
Mount and wire some jack into both Left and Right volume pots , I assume the amp is salvaged from the trash bin or something like that and not used for Hi Fi anymore.
Do not mess with tubes yet, search the Forum for simple preamp ideas.
There's some info on using an LM386 as preamp, which would drive either a small speaker on its own or your Yamaha to neighbourhood upsetting levels.
i have made tube based stop boxes before so its no new and i am aware of the dangers asocieted to the high voltages used.
its a 180 watts/8 ohm so upsetting the neighbourhood is a guaranty
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.
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
by the way... it says to be an 180 w amp 8~16 ohm speakers i guess 180 w a 8 ohms but would this per channel or total? any sugestions? just to get the speakers right dont want to blow em..
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 $8. Who says you can't get great sound from
bit's of junk. :)
Phil.
180 Watts per channel is probably optomitic,, but if it's very heavy
(due to massive transformer) then could be so.
More likely to be 180 Watt *Total* or 90 Watts per channel.
So that 90 Watts into 8 Ohms will be 65-ish Watts into 16 ohms.
Still above average for a HiFiAmp.
If you use a stereo efx processor then you can run the stereo out to both channels and that would rattle the windows I'm sure. :)
Phil.
thanks alot ....again
repetitive questions are only to be shure that ive understood it right
Quote from: phatt on April 09, 2010, 06:47:43 AM
180 Watts per channel is probably optomitic,, but if it's very heavy
(due to massive transformer) then could be so.
More likely to be 180 Watt *Total* or 90 Watts per channel.
So that 90 Watts into 8 Ohms will be 65-ish Watts into 16 ohms.
Still above average for a HiFiAmp.
If you use a stereo efx processor then you can run the stereo out to both channels and that would rattle the windows I'm sure. :)
Phil.
90-70 thats some where around what i thought since it doesnt say watts per channel but i better thought better get a second opinion on it.
about the stereo thing i already thought about it with a dual preamp, one for each power amp with some jack switch thing, example, if only input 1 is used it drives both preamps 1 and 2, but if somethings only conected to input 2 it would only drive preamp 2, if both inputs are used they would each drive their own preamp. preamp 1 would go to left poweramp and preamp 2 would go to right poweramp. or maybe just a flip switch for mono/stereo mode (one preamp driving both power amps or two preamps driving seperate power amp, still dual preamp).
....and yes windows will rattle and neighbours will be annoiyed
this have project has gone a bit on hold due to prblems financing the speakers. :$
Just some curiosity: where does it claim "180W", close to the power cord ot to the speaker outputs?
Quote from: J M Fahey on April 09, 2010, 11:40:57 PM
Just some curiosity: where does it claim "180W", close to the power cord ot to the speaker outputs?
well i cant remember and im not near it at the time but i found this:
Yamaha budget amp
Natural Sound Systems Ltd., Unit 7, Greycaine Road, Watford WD24SB have announced a new budget amplifier. The Yamaha A-320 (8995) has kept costs down (and possibly improved overall quality) by omitting tone controls and filters. Separate Left and Right volume controls combine the functions of gain control and balance, but are friction ganged to work together as required. The amplifier is rated at 30 watts-per-channel into 8 ohms, with a claimed 'dynamic power' of 50 watts into 8, 4 or 2 ohms
here
http://www.gramophone.net/Issue/Page/April%201985/122/851895/
but i dont think its around the speaker connection...havent thought about it before you mentioned it
i wonder how to understand the power rating...dynamic power???? same at 2, 4 and 8 ohm
Truth is: 30W RMS per channel into 8 ohms; loud enough.
Happy with 2 x 10" or 12" guitar speakers, one on each channel.
Those 180W must be the power socket rating then.
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.
Hi
May be a useful tip. I did it this way for my bass guitar amp.
I took a stereo PA amp, which you might consider a 'HIFI' amp. I built a preamplifier with the same width as the PA amp. I built both components in a wooden housing the same way as in a 19" flight case. The box forms a very good protection an can be made as nice as you wish. All cabling between the Pre- and Poweramp can be hidden in the back of the cabinet. It also makes it possible to experiment with different preamps, install effects and so on.
I am very content about this solution.
GG
Hi bassbuddy.
Even better, because PA power amps are beefier and meant to be cranked all night, either by a band or even worse, by a DJ.
Home stereo power amp sections *can* definitely put out the specified power, no doubt, but do not expect 8 straight hours, full tilt, non stop, because that's unrealistic in any home, unless you live in the middle of a desert or forest.
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
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: 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
this is what greg ginn of black flag uses, in the old days he plugged his guitar directly into the PA amp and turned up the volume until he reached enough distortion...
yours is looking very good
Hi guys
Phil, you're speaking right from my heart. When I was younger I spent a lot of effort to make things look good. I quit with that nonsens.
Here is another picture of the interior of my preamp. I built a modular system to be able to use it as a kind of testbed.
From left to right you see the high impedance input amp, the second stage with gain control, a 5 band equalizer, the (optical) compressor and the last amplifier stage with soft clipping.
The DIN plugs are used for interconnection of the stages and power supply connections. This way I can easily replace one of the stages by something else. Apart from the equalizer I developed each stage myself.
UsuallyI use the amp with two of these cabinets.
Friendly greetings from the Netherlands
Geurt
And the picture........
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.
That's quite a professional job, congratulations.
That's the one short coming of bread board.
If you want something to work 100% trouble free, you have to put it in an enclosure with enough room for 100X the amount of circuitry you've actually built.
Great work though, very clean build.
Yeah but at least he can change a component if he needs to 8)
Try that on a double sided suface mount board :P
Wait till you youngens get past 50 and you need glasses. :lmao:
Phil.
Hi folks,
Even worse, I need two pair of glasses for this kind of work. My colleague nicknamed me "Mister Six-Eyes".
A long time ago I took the trouble to design and make PCB's. I quit that because all my designs are one-off product. Breadboards are ideal for this purpose. Reliable, rugged and easy to modify. As said I use the thing as a kind of testbed for my designs. In this case changing a component mostly means changing a module. The cabinet by the way was made of an old cassette-deck I had lying around.
But to come back to the root of this topic: I am sort of kidnapping it. The idea was to give Vitrolin an idea how to solve the issue of converting a HI FI amp to a guitar amplifier.
GG
So a resumè:
Yes you can convert a HIFI amp to a guitar amp.
- My idea is to build a separate preamp with everything inside to:
- Increase the input sensitivity if necessary. Give the guitar input a high impedance.
(Take measures against RF disturbance. This is an issue with sensitive, high impedant inputs.)
- Make the output of the preamp deliver a signal that is suitable to drive the AUX, CD, Radio or whatever input of the HIFI amp you wish.
- If you want to overdrive the amp, do it in the preamp and not in the HIFI amp. This way the HIFI amp will live longer and you can manipulate the character of the overdrive to sound the way you want. Also you can use the overdriven signal at lower volume levels.
- Build the finished preamp and the entire HIFI amp in one cabinet for easy connection, transport and for protection against the rough life on stage. Realise that HIFI amps are mechanically not designed to be dragged about. It also makes it easier to swap the HIFI amp if you decide to use another one.
GG
thank you all for your help, unfortunately ive have no time nor monety to realize this project at the time but it will happend and then ill post the result