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Author Topic: need advice, noob wanna try to build an amp  (Read 7051 times)

slim_blues_boy

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need advice, noob wanna try to build an amp
« on: October 01, 2009, 06:01:33 AM »
hello,
I play guitar in church service and because my church's amp isn't adequate enough as guitar amp, I used to borrow my friend's amp (Marshall Valvestate VS15R, the one with electrical problem that I mentioned here few months ago).
recently, my service schedule become more and more frequent, and I can't always borrow my friend's amp. so I will need a guitar amp and I'm planning to build one for myself.

problem is, I'm noob in 'diy amp world', so I will need advices from all of you here to find out which amp is suitable for me.
I'm looking for not too complicated amp with nice clean sound, 15-30watt output I think enough.
so any advices which amp should I build?

any advice is greatly appreciated.

iTzALLgoOD

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Re: need advice, noob wanna try to build an amp
« Reply #1 on: October 01, 2009, 03:01:08 PM »
Keep it simple for your first try.  Do you have any experience with electronics i.e. soldering, schematic reading?  A simple preamp and a chipamp should get you started.  What kind of tone control do you need?  It could be as simple as a Fetzer from ROG and a TDA2030 or LM1875 for the power amp.

I've looked at schematics from commercial amps and they usually go above and beyond my ability as a DIY'er.  Good luck on you adventure.  Keep us posted

slim_blues_boy

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Re: need advice, noob wanna try to build an amp
« Reply #2 on: October 02, 2009, 11:09:36 AM »
Keep it simple for your first try.  Do you have any experience with electronics i.e. soldering, schematic reading?  A simple preamp and a chipamp should get you started.  What kind of tone control do you need?  It could be as simple as a Fetzer from ROG and a TDA2030 or LM1875 for the power amp.

I've looked at schematics from commercial amps and they usually go above and beyond my ability as a DIY'er.  Good luck on you adventure.  Keep us posted

I do have experiences and know a little bit about electronics, but it's limited.
I got basic electronics lesson when in junior high and I always make own stompboxes pedals.
to be honest, I'm little bit don't understand with what you said. at this moment I only know how to read schematic, arrange the components as shown on the schematic, and solder them.
I know that amp is constructed by power and preamp, are you saying that using Fetzer as preamp and combined it with a power amp? how I do that?
and tone control? is that same as adding tonestack to stompboxes when you modified stompboxes?
sorry if my question sounds silly, as I said, I'm still noob and I don't have high technical electronics knowledges.


Mark Hammer

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Re: need advice, noob wanna try to build an amp
« Reply #3 on: October 02, 2009, 02:06:01 PM »
Something based on a chip like a TDA2030/2040 or LM1875, and delivering 12-15W can be quite loud enough if you keep the following considerations in mind:

1) Efficiency of the cabinet and speaker can often make a bigger difference than doubling or even tripling the wattage.  A great many lower-cost amps come with speakers that could be larger or more efficient, and/or come in cabinets that are kind of slender or shallow.  Sometimes, something as trivial as closing the back off more, or even just moving the baffle ahead a bit so that it isn't recessed, can elicit higher performance, and especially more of the bass that creates the sense of loudness.  Similarly, trading up from an 8" to a 10" or even 12" speaker will net you more apparent loudness.

2) Your power supply should be robust enough, in terms of current capacity, to support the amp.  Forty watts with a wimpy supply will not sound any better than 10 with a robust supply.

3) Manage your signal levels such that each stage delivers as much signal as it can while still preserving a bit of headroom.

iTzALLgoOD

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Re: need advice, noob wanna try to build an amp
« Reply #4 on: October 02, 2009, 05:16:39 PM »
Quote
I know that amp is constructed by power and preamp, are you saying that using Fetzer as preamp and combined it with a power amp? how I do that?
and tone control? is that same as adding tonestack to stompboxes when you modified stompboxes?

Yeah you've got the idea.  The output of your stompbox/preamp goes to the input of your power amp.  I know the TDA20XX datasheets have schematics and pcb layouts for functioning power amp circuits.  Not sure about the LM1875.  I don't recall offhand but there is a website that sells LM1875 kits fairly inexpensive.  Try a search for LM1875 kit.

I built the PCB layout for the TDA2030 right from the datasheet.  I just redrew it in PCB Express and etched a board.  Then I set up different preamps on the breadboard until I find what I'm looking for.

Teemuk also has a downloadable PDF book with all the info you'll need in the sticky section.

slim_blues_boy

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Re: need advice, noob wanna try to build an amp
« Reply #5 on: October 07, 2009, 02:21:38 PM »
hmm, interesting, will try too build these amp things right away.
I also already download Teemuk book, great book, give deep explanation.
it will take long time to read the whole book, but there are lot of informations there, so it will be worthed to read the whole book.

armstrom

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Re: need advice, noob wanna try to build an amp
« Reply #6 on: October 07, 2009, 05:02:49 PM »
qkits.com has some great prices on chip amp kits (some discrete kits too). I used one of their TDA2030 kits for my first build and couldn't have been happier with it.

To see all of the audio kits they sell browse around here.
http://store.qkits.com/category.cfm/AUDIO

As for the TDA2030 kit I used here's a direct link.
http://store.qkits.com/moreinfo.cfm/FK607

For $9.99 + shipping you really can't beat it. That price even includes a heatsink :)

Just find yourself a 12V 2A DC adapter and you're set. For your first build I would avoid any of the higher voltage kits that require mains wiring and/or bipolar power supplies.

You then have a couple of options, you could build your amp as a power amp only and use one of your stompboxes as the preamp. Some will work better than others, but it generally works out quite well, especially if the stompbox has a tone control. This would be the fastest way to start using your new amp. The other option would be to choose and build a dedicated preamp circuit and integrate it into the enclosure with the power amp. Again, stomp box circuits can work very well here if they produce the type of tone you're after.

If I were in your situation I would build the power amp into an enclosure, adding a 1/4" input, 1/4" output jack and 12V power jack. Then just plug one of your stomp boxes into the input of the power amp, plug an extension cabinet into the output jack (make sure you use a cable that is rated for speaker level signals!!!) and have some fun. The volume control on your stompbox will be your master volume.

Brymus

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Re: need advice, noob wanna try to build an amp
« Reply #7 on: October 07, 2009, 06:23:52 PM »
Hey Armstron thats excellent.
Does it come with everything? except the power supply of course but the IC PCB and caps and resistors are they all there at that price?
If so that would be ideal for Slim Blues Boy

armstrom

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Re: need advice, noob wanna try to build an amp
« Reply #8 on: October 07, 2009, 08:02:50 PM »
Yup, it comes with everything needed... even screws to attach the heat sink to the board and chip.  You will need to pick up some heat sink compound but every local radio shack or computer store will have that.
-Matt

Brymus

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Re: need advice, noob wanna try to build an amp
« Reply #9 on: October 08, 2009, 01:32:15 AM »
Cool this one is 100watts @4ohms they state "ideal for guitar or instrument amp"
http://store.qkits.com/moreinfo.cfm/HSVM100
only 27$ For the heat sink and power supply (from Apex Jr) your looking at another 40$
plus the pre-amp ,spkr and enclosure.
It could be done for less than 150$

They have a 30-40watt amp that around the same price a little cheaper but it includes the heatsink and APexJr has a supply for it for about 10$
That would make it in under 100$ with a homemade enclosure and a decent 12" spkr.

armstrom

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Re: need advice, noob wanna try to build an amp
« Reply #10 on: October 08, 2009, 09:57:19 AM »
the link you posted is to a heat sink with mounting holes for a 100W or 200W kit... I don't see the kit you're referring to. Here's a 100W discrete power amp they sell for $29.. It shows a heat sink but doesn't mention if it's included.. I would hope so, but who knows :)

http://store.qkits.com/moreinfo.cfm/FK666

Some of the kits they sell are from futurekit (any that have a part number starting with FK) so you can actually find rough schematics of the circuits online. Most component values are deleted (resistors, caps, etc..) but you can at least get a feel for the topology of the circuit. Here's the schematic for that 100W kit: http://www.futurekit.com/basic_elec/FK666E-1.pdf

Edit: Ok, I see the amp kit now.. Yeah, that does look like a decent deal. You can even buy it fully assembled and ready to go for $69. It seems the kit has the power supply built right in. While its nice that you don't have to build your own it doesn't appear that there are any DC taps after the rectifiers so you would have to create a separate power supply for your preamp circuit. You could use the same AC taps but would need to rectify the AC and regulate it down to your desired voltage.

Here's the full assembly manual for the kit: http://www.vellemanusa.com/downloads/0/illustrated/illustrated_assembly_manual_k8060_rev1.pdf

I have to say the connection between the darlington output transistors and the board is kind of sketchy... They use a standard .1" pin header and solder the pins of the transistor between the pins of the header... really?? At least the manual includes a full schematic so maybe one of our more experienced readers could comment on the topology of the amp.. if it will deliver the quoted performance.

-Matt

« Last Edit: October 08, 2009, 11:12:26 AM by armstrom »

slim_blues_boy

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Re: need advice, noob wanna try to build an amp
« Reply #11 on: October 12, 2009, 01:44:50 PM »
@armstrom
I'm thinking the same, build a power amp and use my pedal as the preamp.
I'm planning to use my multi effect AX100G.
as for the kit, it also seems interesting. unfortunately I live in the far east and shipping cost would be expensive.
so I think I'm just gonna look schematic for power amp for now.

@Brymus
I saw your "Pedal based practice amp TDA 1519b" on the other forum, it's also seems interesting.
with 12watt output, is it loud enough for small venue with people around 50 persons?
for comparison, I can get enough loudness with 15watt Marshall Valvestate.

Brymus

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Re: need advice, noob wanna try to build an amp
« Reply #12 on: October 12, 2009, 05:14:56 PM »
Thank you,
Its pretty loud with a good spkr (like 2x12" with 99db SPL)
Its just loud enough to jam with my friend on drums,but he can easily play over me with out trying.
I built that for a friend as a practice amp.
But for a small venue I think a 30-40 watt SS amp would be better.Like a single LM3886 for example.
My 40 watt Crate was loud enough but still some heavy handed drummer could still play over it...
If I were to do it over again I would probably use one of the TDA20XX chips.
The tda1519 was only .79 at Apex Jr and I was already ordering stuff for my LM3886 build so I got a few of them as well for 12V supply use.

armstrom

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Re: need advice, noob wanna try to build an amp
« Reply #13 on: October 12, 2009, 06:47:14 PM »
@armstrom
I'm thinking the same, build a power amp and use my pedal as the preamp.
I'm planning to use my multi effect AX100G.
as for the kit, it also seems interesting. unfortunately I live in the far east and shipping cost would be expensive.
so I think I'm just gonna look schematic for power amp for now.
Many of these kit companies are based out of Asia and have local distributors there.  Here's a list of distributors for the FutureKit kits (TDA2030, and others) http://www.futurekit.com/distributor.php

As for the velleman kits, they're a European company but seem to have distributors all over the world too. Find your closest one here: http://www.velleman.eu/ot/en/dealer/search/