Welcome to Solid State Guitar Amp Forum | DIY Guitar Amplifiers. Please login or sign up.

April 19, 2024, 09:10:52 AM

Login with username, password and session length

Recent Posts

 

Super Basic Question for a noob

Started by megatrav, December 28, 2023, 03:02:36 PM

Previous topic - Next topic

megatrav

Hey all,

I just joined the forum and I'm happy to be here. 

I am relatively new to electronics.  I have built a few guitar and bass pedals from PCBs offered by PedalPCB, AionFX, PCB Guitar Mania, and a few others.  I have also done a couple tag board builds which were a lot of fun.

I am interested in learning more about amplifiers (tube and solid state).

I have always wondered something that might be a fairly basic question:

Is there a different between HiFi power amps and the power amp section of a transistor guitar/bass amp?

I understand the importance of a preamp and using the correct speakers and cabinet for bass/guitar, but I never knew if the power amp had different filtering or if it was all pretty much the same?
Also, if they are different, has anyone spent time building and modifying any of the HiFi power amps available?

Thanks and I look forward to explanations!

phatt

Hello and welcome,
Yes you can use a HiFi amp for guitar, some will work better than others.
If you have a line input then try it. Even CD input may work.
Of course obviously you use a guitar speaker NOT hifi speakers.

If the signal distorts early then the incoming signal will need to be reduced.

The older the hifi the more basic the design which may well work better for guitar.
The Digital Pwr amp designs used now may not work as well but suck it and see.

Just keep in mind that the tone controls on hifi gear are not ideal for guitar, again try it let your ears make the judgement.
Midrange for guitar is around 400hZ while hifi is centered around 1khZ.
Phil.

Loudthud

Hifi amps are OK for casual use, but will likely fail under heavy duty stage use. It would be best to operate the Hifi amps below clipping and below the maximum load.

Tassieviking

If you are wondering if you can use a hifi power amp in a guitar amp build then I would say yes, but you would be advised to use bigger heatsinks and cooling.
A larger power supply might be good as well.

If you want to use a stereo to play guitar through then build one of the many Pre-Amp pedals out there and run it into the line in on the stereo, it will sound a lot better if you have a dedicated guitar cab connected up to the stereo as well.

Just remember to only use half of the power available on the stereo as a safety margin.

If you start to look at many modern solid state guitar amp schematics you will find a lot of them use the same type of power amp chip that gets used in stereos as well.

There are also some nice schematics around you can build for speaker emulators, it makes the combo amp sound more like other cabs Ie like a 4x12 Marshall cab with Greenback speakers in it.
From memory Bajaman made a schematic and veroboard layout over on the Freestompboxes site, https://www.freestompboxes.org/viewtopic.php?p=226100&hilit=Baja+cab+emulator#p226100
"Phatt" has posted his Phabbtone here somewhere for us to use (Thanks Phil)

Can I ask why you are asking ? Are you looking at any specific amp design ?

Cheers
Mick


There are no stupid questions.
There are only stupid mistakes.

megatrav

Thank you everyone for the responses!

I currently have 2 TPA3118 modules. I plan to pickup a couple power supply modules for them.

They aren't very powerful, so I was looking at some higher wattage modules. I found one that is rated at 500 watts which I think could work as a bass power amp with the right preamp in front and into the right cabinet.

Should I look into modifying it for lower frequency response?

Tassieviking

If you are looking at that much power I would like to suggest you only look at the ICE power modules, the ICE power modules can be found in several professional Bass amplifiers.
I can't remember if it was the ASX models or the AS models you can find inside several brands of Bass Amps, but I am 99% sure it is one of them.
If you get Chinese made ones of Ebay then I would de-rate them by at least 50% to be safe, bass amps need to be very well made.
https://shop.icepoweraudio.com/
There are no stupid questions.
There are only stupid mistakes.

megatrav

I have looked at those ICEPower modules and they do look nice.
They are a little pricey though.

I think it's a little strange that there aren't more DIY high wattage Class D PCBs or kits available.

I recently read a thread on another forum about Straight Ahead Amplification power amps. I got his email from Facebook and reached out to him.

He said that he offers a standard and a bass model. The Bass model handles lower frequencies better.
He mentioned modifying modules.

Does anyone know what would be modified?


The truth is, I don't really want "change this resistor and capacitor" but more so I would like the ability to test/breadboard/socket components on a PCB so that I could see what sounds best.

I would also really like to learn more about the general operation compared to a tube amp.

For instance, the ability to adjust negative feedback and response.

Does Class D work like that? I think I've seen Class AB solid state amps that do but maybe it was just simulating that.


Tassieviking

The ICE power modules are well priced for what you get, you can get cheaper modules from China but often you have to buy a power supply and an amplifier and put them together.(And most likely not run them anywhere near the advertised power without dropping out from overheating)

The  Straight Ahead Amplification power amps seems like someone is just putting pre-bought modules into a cheap box and selling them from home, I could be wrong but I would not buy one unless they have been fully certified for public use like that.

If you want and need a really powerful amp then it is best to buy a good quality made one as it will be certified with all the various agencies required nowadays.
I don't think that it would be worth the effort to build an amp from scratch if you want to truly be able to gig with it, I believe some venues might not allow non-certified gear to be used due to insurance reasons.
If an arena was to burn down because of a musos homemade amp caught fire there could be serious problems with the insurance companies as well as with the legal implications if someone got hurt or worse.

If you want your own sound then build a preamp in a stomp-box and run that into the return jack on a commercial amplifier, proper Class-D Bass amps are not that expensive and deliver a lot of power. Certification  can cost $20,000-$50,000 to get through for a single amplifier model and that has to be included in the final cost of a proper amp you can buy in the shop.

If you just want it for home use then get/make whatever you want and go for it.
Have you read Teemu Kyttälä's Book about solid-state guitar amplifiers ?
There is more in it then most people will ever need.

https://www.ssguitar.com/index.php?topic=711.0
There are no stupid questions.
There are only stupid mistakes.

megatrav

Quote from: Tassieviking on January 10, 2024, 04:55:37 AMThe ICE power modules are well priced for what you get, you can get cheaper modules from China but often you have to buy a power supply and an amplifier and put them together.(And most likely not run them anywhere near the advertised power without dropping out from overheating)

The  Straight Ahead Amplification power amps seems like someone is just putting pre-bought modules into a cheap box and selling them from home, I could be wrong but I would not buy one unless they have been fully certified for public use like that.

If you want and need a really powerful amp then it is best to buy a good quality made one as it will be certified with all the various agencies required nowadays.
I don't think that it would be worth the effort to build an amp from scratch if you want to truly be able to gig with it, I believe some venues might not allow non-certified gear to be used due to insurance reasons.
If an arena was to burn down because of a musos homemade amp caught fire there could be serious problems with the insurance companies as well as with the legal implications if someone got hurt or worse.

If you want your own sound then build a preamp in a stomp-box and run that into the return jack on a commercial amplifier, proper Class-D Bass amps are not that expensive and deliver a lot of power. Certification  can cost $20,000-$50,000 to get through for a single amplifier model and that has to be included in the final cost of a proper amp you can buy in the shop.

If you just want it for home use then get/make whatever you want and go for it.
Have you read Teemu Kyttälä's Book about solid-state guitar amplifiers ?
There is more in it then most people will ever need.

https://www.ssguitar.com/index.php?topic=711.0


Thanks for the input.  I hadn't considered all of those factors.

I do understand getting what you pay for and I would definitely rather buy something legit than risk blowing myself up. 

I am wondering something- you mentioned issues with combining a power supply board with an amp board:
I have some TPA3118 boards and I have been looking at some AC to DC power supply boards to use with them. 
The ones I have looked at are minimum 110vac to 24vdc 2-5A. The specs call for minimum 48 watts so I have been looking at ones rated above that.

Would it be a bad idea to use one of those? 

I would prefer a proper power cable instead of a laptop power pack supply.

Thanks for the book link, I have saved it and I will definitely be reading it!

Tassieviking

Personally I would get a MeanWell 24V power supply that is rated around 100VA to get plenty of headroom for one of those modules.

The biggest question would be what size heatsink is sitting on the TPA3118 chips, and are they 3118 or 3118-D2 chips on those modules of yours.

To run at full power the chips should have a heatsink on them, but most often they don't have any installed on the Ebay amps.

I went with the TPA3116-D2 mono 100 watt boards from Ebay a long time ago when I tried them, they had a nice heatsink on the modules so I got them.
I think I used a 24V 120VA MeanWell supply to run one for a home practice amp, it worked fine but it never got run hard.
There are no stupid questions.
There are only stupid mistakes.

megatrav

I will check out those power supplies.

This is basically the board I have https://a.co/d/66I0eA7

There is no heatsink attached. I suppose I thought since it's Class D it wouldn't need a heatsink because of the high efficiency.

Can you recommend one to use with it?

Thank you for all of the information

Tassieviking

You might not need a heatsink for that module unless you are going to run it hard, just try it and see what happens.
You can get stick on heatsinks from a lot of places, you will have to see how much room you have and order one that fits if you want/need one. I think you will just have to peel the tape of and press the heatsink down to attach it, they are really easy to use.
Google stick on heatsink and you will find lots of them, and they are cheap to buy as well.

Read the spec sheet on the 3118 chip and see what it says.

There are no stupid questions.
There are only stupid mistakes.

phatt

Just a note on Digi Amps and SMode supplies.
Ok they are cheap, light weight, and so so convenient.
But keep in mind, Unlike Smode supplies Iron and Copper Transformers have an indefinite life span, if used within spec.
Jezzus Not even god could make a more bullet proof design. 8)

 I doubt that in 50 years from now that these SMPS circuits will still be running as they are far more complex and hence far more prone to failure.
Notice how many Dead computer Power boxes fill bins in repair shops.

Now I'm not up to speed on Digi amps but the few I've had the displeasure of working with leaves me thinking that it's hard to beat a basic old school transistor poweramps.
Well designed unit go for years without issue. Of course Can caps dry out eventually but simple to replace.
with most things now surface mounted and hard to work with it's a throw away item. But by then you find out OH sorry they don't make them anymore. ::)
 and you are left with land fill. :'(  :'(

If it interests you Rod Elliot has a ton of info on Amp design, a lot of which is aimed at muso gear.
Start here;https://www.sound-au.com/

I have found him to be very helpful while trying to build Analog Power Amps.
Phil.

megatrav

Quote from: phatt on January 13, 2024, 04:34:38 PMJust a note on Digi Amps and SMode supplies.
Ok they are cheap, light weight, and so so convenient.
But keep in mind, Unlike Smode supplies Iron and Copper Transformers have an indefinite life span, if used within spec.
Jezzus Not even god could make a more bullet proof design. 8)

 I doubt that in 50 years from now that these SMPS circuits will still be running as they are far more complex and hence far more prone to failure.
Notice how many Dead computer Power boxes fill bins in repair shops.

Now I'm not up to speed on Digi amps but the few I've had the displeasure of working with leaves me thinking that it's hard to beat a basic old school transistor poweramps.
Well designed unit go for years without issue. Of course Can caps dry out eventually but simple to replace.
with most things now surface mounted and hard to work with it's a throw away item. But by then you find out OH sorry they don't make them anymore. ::)
 and you are left with land fill. :'(  :'(

If it interests you Rod Elliot has a ton of info on Amp design, a lot of which is aimed at muso gear.
Start here;https://www.sound-au.com/

I have found him to be very helpful while trying to build Analog Power Amps.
Phil.

Hey Phil,

Thanks a ton for the response.

I agree with you on the idea that building things with the intention of them not lasting is never a good idea. It's wasteful and isn't good for anyone.

I have nothing against transistor amps other than the lack of efficiency.
The most appealing thing about Class D is that if someone wanted to build a high wattage bass amp they could keep the weight lower because they wouldn't need as large of a heat sink.
I've looked into Class H amplifiers but they seem even more complicated and with only slightly more benefit over Class AB.

I actually think that when it comes to building an amplifier, a power transformer is a better idea because it will last longer and probably have less failure (potentially?). This may be a silly question, but can one use a power transformer with a Class D amp?


Lastly, these small SMD modules were sort of my Segway into learning about Class D amps. If I were ever smart enough to build my own, I would want to use through hole components.
That's how I build everything I make now. 

phatt

hi Megatrav,

Wise not to focus on one aspect like Efficiency.
Heck, Valves waste a lot of energy as heat yet they are still considered the holy grail of tone for a lot of guitar players.
There are just so many rabbit holes in this field that are mostly a waste of time.
I have 3 Valve Amps but my main setup is a pedal board which delivers a great sound into an old 70's 80's era Keyboard Amp.

If you research how Valves actually work you will realise that a lot of the magic is due to a very poor Power supply.
Depending on the design With no signal the HT voltage might read 400VDC in a valve amp. Turn up the volume and hit a big power chord hard and that 400V will drop like a brick, You might see it drop by 100V or more, depends on The ability of the PSU design.
As that signal fades away that voltage rises back up.

This is effectively causing compression so the sound level actually drops and limits the absolute SPL and as the Voltage rises back up it gives the impression of more sustain.
But with SS amps the supply voltage is very stiff and hence no magic sustain.
A SS 40 volt supply might only sag 2 or 3 Volts and by then you get into hard clip which is ugly, so hence SS gear gets a bad reputation.

So to recreate that effect with SS gear you will need a compressor.
I do all of that with my pedal board and the Amp just makes it louder.
The Amp adds very little colour to the final sound although it does have a spring Reverb which adds a final touch. I use 3 OD dirt pedals into my Compressor.
the Gain of all 3 dirt pedals are set fairly low and as you turn each one on you get more drive. And the compressor does 2 jobs obviously it adds compression but it also keeps the absolute SPL in a set range so when I play leed parts nothing gets too loud.
I use an optical compressor as they tend to work very well for OD rock guitar sounds.

As for Class D stuff I've noticed that the freq response often goes down way too far and that can be a big problem if you are trying to reproduce the classic sounds.

Understanding and limiting the bandwidth of your gear will help refine your sound.
Too much Low and High freq will just frustrate you and drive you crazy.
There are many ways to great tone and even when you get there you will find that different venues and rooms can give different results. I have built many circuits and thought I had cracked the holy grail only to find that when I played live it sounded like crap.

If it interests you I posted a recording of my gear on here a while back.
This will give you some idea of what can be done with all SS gear.
https://www.ssguitar.com/index.php?topic=5309.msg41595#msg41595
Regards from an old bloke who has spent lots of time down these rabbit holes, Phil