DIY amp build: Done with the headshell ..now comes the tough part :p

[Phantasmagoria]

Re: DIY amp build: Done with the headshell ..now comes the tough part

..and to think you can find amps around these days that weigh less than a plastic cassette recorder & output the same thing :lmao:. Still, massive iron is massive iron.

But I will confess I'm not missing that thump at all with this amp. It sounds huge

Have you tried the other 700 watt (I guess 350W or so @ 8 ohms) mono board they have up on ebay? It was bigger (about the size of the PS board) & costs about $35-40.

THAT was overkill I thought though ..probably have blown my 4x12's with it :lmao:

 

[GoldenVulture]

Re: DIY amp build: Done with the headshell ..now comes the tough part

..and to think you can find amps around these days that weigh less than a plastic cassette recorder & output the same thing :lmao:. Still, massive iron is massive iron.

But I will confess I'm not missing that thump at all with this amp. It sounds huge

Have you tried the other 700 watt (I guess 350W or so @ 8 ohms) mono board they have up on ebay? It was bigger (about the size of the PS board) & costs about $35-40.

THAT was overkill I thought though ..probably have blown my 4x12's with it :lmao:

No, but I've got a defunct Behringer 900 watt Pa amp that apparently had a board replaced and it still doesn't work.
It's a class D. A Power Amp board , A PS and Mixer board. The PA board has been replaced. I've got the old one too, it's got a burst big cap on it.

 

[Phantasmagoria]

Re: DIY amp build: Done with the headshell ..now comes the tough part

Yeah I mean ..big iron is tried and tested and that's a big plus obviously. I nearly pulled the trigger on a Crown PA amp last year. The only thing that held me back was the fact that it was class D with a switching PS.

Ironically I ended up with a 120W per channel Panasonic from the mid 90's which apparently was one of the first commercial amps to run off a SMPS (weighs in at a mighty 6.5 kgs) & has balls like you would'nt believe

It's also still around/going strong.

That opened my mind to Class D (not sure if the Panasonic is actually class D, but it might be ) / SMPS tech & I'm glad I've actually given it a go with this amp.

In the end I like to try new/different things. This approach is a lot cheaper & a hell of a lot lighter & that's what it's got going for it vs. the usual Class A/B + big tranny. The fact that it sounds as good as it does is the icing on the cake :bigthumb:

I've heard of the reliability issues (why I bought an extra power supply :laugh2 and it's way too early to say anything about those, but I did run a part of my old tube preamp off an SMPS for 3 years or so without a problem at all...& like I said the Panasonic's been going strong for almost three decades now. That gives me hope

 

[Phantasmagoria]

Re: DIY amp build: Done with the headshell ..now comes the tough part

Well I stringed everything together and switched it on this morning... ..nothing..lol..dead!

Turns out of all things to be my IEC inlet. Totally dead. There's nothing coming through/reaching the circuit. Maybe a cold solder joint to one of the terminals Everything looks solid ..but I have'nt tested it.

Anyway things worked fine when I wired another AC power cable to it directly. :bigthumb:




Here's a short test clip with it hooked up to a cheap 10" Line 6 speaker (no cab) . I have'nt hooked the "Mid sweep" circuit up to it yet..

Slight tweak of the settings @ about 2:15 or so (where there's silence) I think I turned up the tube preamp & cut the SS preamp back a little ..but otherwise all the settings are the same. Can't really mess with them since I don't want the pot terminals touching each other or shorting something out by mistake ..it's all a bunch of tangled leads right now :laugh2:.



I think I had the delay &/or chorus on as well..don't remember..





..& here's the test/recording setup..



As you can hear @ 2:15 There's absolutely NO noise/buzz in circuit ...this thing runs dead silent when you are'nt playing/mute your strings..

 

[DankStar]

Re: DIY amp build: Done with the headshell ..now comes the tough part

Cool project - more than I could carry into the end zone before going completely insane

 

[Phantasmagoria]

Re: DIY amp build: Done with the headshell ..now comes the tough part

haha..yeah it's been a bit crazy, can't deny it ..but it's been going according to plan for the most part (so far :lmao & that makes it fun/rewarding :bigthumb:

 

[Hank-]

Re: DIY amp build: Done with the headshell ..now comes the tough part

Nice. I thought the troll pic was mikey(ninja turtle) at first.

If that small board can output 280W at 0.1%THD into an 8ohm cab, then thats amazing really.

 

[Phantasmagoria]

Re: DIY amp build: Done with the headshell ..now comes the tough part

Thanks!

Haha.. Ogre ..not troll..& it's more like an evil Flintstones character






I'll probably never know exactly what the amp outputs ...but it's definitely very LOUD :lmao:

Btw..the amp (model) is the "Powerslave" ..I forgot to Mention that :bigthumb:

 

[Hank-]

Re: DIY amp build: Done with the headshell ..now comes the tough part

oh ogre, like shrek :arms: I remembered Tekken 3 game now too lol

it looks very nice, even in the pics at the moment so in actual it will be nicer still.

The product description gives 280W in 8ohm at +/-65V with 0.1%THD, so thats gonna be very loud & clean tgrough efficient speakers. Be careful with 2x12 cabs, this little beast is a monster :wizard:

 

[Phantasmagoria]

Re: DIY amp build: Done with the headshell ..now comes the tough part

Thanks ..it's turning out nice yeah..I think so too

An evil Shrek? That's sounds about right :laugh2:

I think there's already some sort of onboard volume potentiometer (pic) on the board next to the input. It's a tiny SMD thing like this:

I thought I'd try maxing it out to see exactly how loud this thing gets going into my 4x12 (wife was out :lmao , but it just seemed to go around & around without any effect I could hear..maybe it's maxed already or there's some other way to work it. Can't complain about how loud it got though

 

[DankStar]

Re: DIY amp build: Done with the headshell ..now comes the tough part

Maybe post schematics/drawing of the preamp and buffer if you don’t mind

 

[Phantasmagoria]

Re: DIY amp build: Done with the headshell ..now comes the tough part

What Schematics? :lmao:

Not kidding ..I'm actually feeling my way through stuff/googling like hell/dealing with issues as they pop up :lmao:

..just stringing a bunch of chinese boards I had lying around together..making sure that positive goes to positive, neg to neg & ground to ground

The signal is Input jack -> distortion/delay/chorus PCB's I bought a few years ago to make a pedal but never used (ebay) -> tube preamp (kit I bought and assembled. also a few years ago, for my hi-fi..now converted to mono) -> mid-sweep circuit board (chinese..also bought many moons ago off ebay, but could'nt find a use for it) -> tubey "Sag" circuit I read about/copied (basically a couple of large resistors in-line) -> Volume pot -> power amp & power supply (both chinese boards & the only large components I actually bought for this project).

Most of my 'work' involved making the chassis, tough as hell because of my lack of tools/training :lmao: & moving/extending components (jacks power inputs & tons of pots) off the boards with wire leads which was pretty hellish :laugh2:

I do have a drawing (more like a scribble) that I made with the initial "plan", but it's so bad..I can barely tell what's what myself..

All I can do is post pics of the thing when/if it's finally done, which I'll be happy to do.. :bigthumb:

 

[Phantasmagoria]

Re: DIY amp build: Done with the headshell ..now comes the tough part

This is what I'm going with "schematic" -wise. Sorry, but t's not going to be of much use to anyone..barely of much to me. :laugh2:

...not an electronics whizz ..just a hack with an idea.. :lmao:

Sorry about the crappy pic...my camera sucks..

 

[DankStar]

Re: DIY amp build: Done with the headshell ..now comes the tough part

wow! the fact there's no noise blows me away. (I wouldn't think they'd all play nice together on the same power). How in the heck did you avoid ground loops lol

 

[Phantasmagoria]

Re: DIY amp build: Done with the headshell ..now comes the tough part

Pretty sure it was luck :lmao:

The first time I tried the whole circuit out it buzzed pretty bad when I was'nt playing (whether I touched my strings or not) & I thought "well at least it all works and sounds nice when I'm playing" :laugh2:

Then I remembered that grounding the tube preamp's PCB to the input ground lug of my AC socket had got rid of similar buzz when I used it as a hi-fi-preamp..so that's what I did & the buzz literally just disappeared. It's more quiet than all my other amp's now...beginner's luck? Yep, I think so

I'm a little nervous about the effects loop though...that *might" just cause some problem's again. It's the only thing (besides the master volume & a couple of switches/buttons) I've not yet incorporated into the circuit. I did have the mid-sweep attached for a while and it was all quiet with that as well...no buzz at all :bigthumb:

 

[Hank-]

Re: DIY amp build: Done with the headshell ..now comes the tough part

Ground the input -ve of the power amp input to common ground or you'll get continuous noise if the preamp output ground isnt grounded to common ground. I feel the input/output on the lreamp with be sharing same grounds so in that case yoi wont need to ground the poweramp input. But if ya plug ya guitar straight into the poweramp board then you'll get hum/buzz etc. Never connect the speaker out -ve terminal to common ground though

It will get louder depending on the input gain setting on the class d board. If its preset to a lower range, then you will need a strong preamp signal to pump that 280W out of it And it will be very very loud & clean with almost zero hiss or buzz if everything goes well, like impedance match & stuff, provided the preamp doesnt hiss much. Dont worry, it will work out well, its very simple to connect these board modules together, putting them in the shell is the only major labour involved process, just double check the +&- wires are correctly connected & not crossed over accidentally or something could fry someqhere in the chain.

 

[Phantasmagoria]

Re: DIY amp build: Done with the headshell ..now comes the tough part

Thank you! :beerchug: Those are all important tips & I'll be sure to keep them in mind!

I'm going to try and hook everything up today, throw in the mid-sweep circuit & volume pot and see how the whole thing works

 

[Phantasmagoria]

Re: DIY amp build: Done with the headshell ..now comes the tough part

Good news and bad news..

Good:

It works fine..I've got a 10k pot for volume & it's working perfectly ..ideal volume taper and all.. it's perfect...completely off @ zero, No noise, it's as silent as before. I did have to hook up my power amp's negative input to ground as Hank suggested & the buzz immediately reduced to zero again. Sounds great too.. :bigthumb:

Now for the bad...

It's WAY WAY louder when I activate the mid sweep...like ..10 times louder or more! That thing gives the signal a hell of a gain boost. The tones are great if a bit dryer & gainier ..probably some slight clipping of the amp input going on (it sounds like an old radio dial sweeping through frequencies when you turn the knob haha...HUGE tonal variations possible) but it's way too massive a jump in volume/gain to be useable and I can see my speakers blowing to bits in no time if I ever crank the amp & then activate the mid-sweep/boost :lmao:

Any suggestions from anyone on a simple way (trim-pot? / resistors? if so.. pre/post volume pot?) for reducing input gain/preamp volume from the mid-boost circuit into the volume pot or power amp ..I'd like to avoid the huge jump in volume from tube preamp signal to mid-sweep). Any info/ideas would be much appreciated right about now

 

[GoldenVulture]

Re: DIY amp build: Done with the headshell ..now comes the tough part

What's in the mid boost bit ?

 

[Phantasmagoria]

Re: DIY amp build: Done with the headshell ..now comes the tough part

Board with a rotary pot (C 50k), IC, input, ground, output & +12V DC connections