15W SS amp build

Keefy

My gigging amps are a Matchless Lightning 15 Reverb and a DIY 5E3 Deluxe clone. They're both all-valve, and valves can and do die in service.  I used to take out a complete set of spare valves in case of problems, but who wants to be farting around fault-finding on a gig? I have a spare bass head, a MarkBass Nano 300, but that amount of power could easily fry a guitar speaker. So my plan is to build a small emergency head.

The various sections:
[rear] Eddystone aluminium box picked up cheap from Maplin when they were closing down. I'm hoping this will be an adequate heatsink on its own.
[centre left] 15W power amp module based on a TDA2030A chip, bought as a kit from eBay. I have used these before when refurbing a friend's shonky home jukebox. I meant to photograph the parts but I've just built it so that's not going to happen!
[front right] FuzzDog Acti-Boost Type R kit i.e. RC Boost clone - this will be the preamp. If you saw Jim Lill's recent video, you'll recall there were some of these in his 'tackle box' amp.
[front left] Some of the other bits that I'll need - power switch, knobs (my final choice of knobs may differ).
[not pictured] Trust Notebook Power Adaptor, capable of providing 24V DC at 3A.

ICBM

How far up do you turn the Matchless?

If it’s a long way, I’m unconvinced that a 2030-based amp will be loud enough, even through good speakers.

Keefy

ICBM said:

How far up do you turn the Matchless?

If it’s a long way, I’m unconvinced that a 2030-based amp will be loud enough, even through good speakers.

Generally not that far - gain and master both 3/10, and feed to the PA via mic or speaker-emulated DI box. The speaker in the Matchless combo is a Vintage 30 that I understand has been partially de-doped.

It has occurred to me that it might be underpowered but the 2030 kit cost less than £4! I have thought about getting a second one, sending it an inverted signal, and bridging the outputs, but the circuit has a Zobel network so I'm guessing that wouldn't work. I'm also open to alternative, more powerful, monolithic amps.

ICBM

If you’re not cranking the Matchless it will probably be fine.

Keefy

ICBM said:

If you’re not cranking the Matchless it will probably be fine.

Cheers, well we'll see! I've looked around for other power amp chips but heftier ones tend to need a split-rail power supply and/or much higher voltages.

I should also mention it's a bit of a fun project. Total outlay (i.e stuff I didn't have already) is £30 to date. If it's a complete failure I can always turn the RC Boost board into a pedal.

ICBM

Keefy said:

Cheers, well we'll see! I've looked around for other power amp chips but heftier ones tend to need a split-rail power supply and/or much higher voltages.

Yes, using the offboard DC supply does limit you a fair bit.

If it matters, a friend has the new Soldano SLO-Mini which uses a 30W Class D power module driven from a similar power supply, and it's loud enough - just - to use with the band, through a 2x12" with G12H-30s. He normally uses a Laney LA30BL, and although the Soldano clearly isn't as loud and has much less headroom so it's a lot dirtier at maximum volume, it's probably about equivalent to 15W on the same scale. I also modded the crunch mode to 'SLO clean', as it was just too gainy and compressed before.

The Class D module inside is hilariously tiny too - the chip doesn't even have a heatsink other than the ground plane on the PCB - Class D is so efficient it doesn't need one, amazingly!

Keefy

ICBM said:

Keefy said:

Cheers, well we'll see! I've looked around for other power amp chips but heftier ones tend to need a split-rail power supply and/or much higher voltages.

Yes, using the offboard DC supply does limit you a fair bit.

If it matters, a friend has the new Soldano SLO-Mini which uses a 30W Class D power module driven from a similar power supply, and it's loud enough - just - to use with the band, through a 2x12" with G12H-30s. He normally uses a Laney LA30BL, and although the Soldano clearly isn't as loud and has much less headroom so it's a lot dirtier at maximum volume, it's probably about equivalent to 15W on the same scale. I also modded the crunch mode to 'SLO clean', as it was just too gainy and compressed before.

The Class D module inside is hilariously tiny too - the chip doesn't even have a heatsink other than the ground plane on the PCB - Class D is so efficient it doesn't need one, amazingly!

Interesting, might look at some Class D options too. What's the name/number of the module in the Soldano?

ICBM

Keefy said:

Interesting, might look at some Class D options too. What's the name/number of the module in the Soldano?

It appears to be labelled PM-30(Synergy)_V03, but I can't find any information about it online at all.



The actual power IC is the square one with 8 pins along each edge - it's smaller than an 8-pin DIL op-amp!

Keefy

ICBM said:

Keefy said:

Interesting, might look at some Class D options too. What's the name/number of the module in the Soldano?

It appears to be labelled PM-30(Synergy)_V03, but I can't find any information about it online at all.



The actual power IC is the square one with 8 pins along each edge - it's smaller than an 8-pin DIL op-amp!

Thanks! I’ve found a 30W Class D module on eBay called OEP30W but it’s only 15W into 8ohm. I’ll breadboard my build first to see how it performs before taking a drill to the enclosure.

victorludorum

Would you have a link to that 15w kit that you bought on ebay please?

Keefy

victorludorum said:

Would you have a link to that 15w kit that you bought on ebay please?

Here you go: https://www.ebay.co.uk/itm/184177220388

Make sure you attach the chip to a heatsink!

victorludorum

@Keefy ; Cheers for that

hollywoodrox

Keefy said:

My gigging amps are a Matchless Lightning 15 Reverb and a DIY 5E3 Deluxe clone. They're both all-valve, and valves can and do die in service.  I used to take out a complete set of spare valves in case of problems, but who wants to be farting around fault-finding on a gig? I have a spare bass head, a MarkBass Nano 300, but that amount of power could easily fry a guitar speaker. So my plan is to build a small emergency head.

The various sections:
[rear] Eddystone aluminium box picked up cheap from Maplin when they were closing down. I'm hoping this will be an adequate heatsink on its own.
[centre left] 15W power amp module based on a TDA2030A chip, bought as a kit from eBay. I have used these before when refurbing a friend's shonky home jukebox. I meant to photograph the parts but I've just built it so that's not going to happen!
[front right] FuzzDog Acti-Boost Type R kit i.e. RC Boost clone - this will be the preamp. If you saw Jim Lill's recent video, you'll recall there were some of these in his 'tackle box' amp.
[front left] Some of the other bits that I'll need - power switch, knobs (my final choice of knobs may differ).
[not pictured] Trust Notebook Power Adaptor, capable of providing 24V DC at 3A.

Ace good luck in your project ,sounds like it will be brilliant 

Keefy

hollywoodrox said:

Keefy said:

My gigging amps are a Matchless Lightning 15 Reverb and a DIY 5E3 Deluxe clone. They're both all-valve, and valves can and do die in service.  I used to take out a complete set of spare valves in case of problems, but who wants to be farting around fault-finding on a gig? I have a spare bass head, a MarkBass Nano 300, but that amount of power could easily fry a guitar speaker. So my plan is to build a small emergency head.

The various sections:
[rear] Eddystone aluminium box picked up cheap from Maplin when they were closing down. I'm hoping this will be an adequate heatsink on its own.
[centre left] 15W power amp module based on a TDA2030A chip, bought as a kit from eBay. I have used these before when refurbing a friend's shonky home jukebox. I meant to photograph the parts but I've just built it so that's not going to happen!
[front right] FuzzDog Acti-Boost Type R kit i.e. RC Boost clone - this will be the preamp. If you saw Jim Lill's recent video, you'll recall there were some of these in his 'tackle box' amp.
[front left] Some of the other bits that I'll need - power switch, knobs (my final choice of knobs may differ).
[not pictured] Trust Notebook Power Adaptor, capable of providing 24V DC at 3A.

Ace good luck in your project ,sounds like it will be brilliant 

I don't know about brilliant, I'm shooting for functional and free of extraneous noise!

Keefy

Started on the pre-amp board - that's all the resistors and diodes, plus the IC socket. Where they can be swapped to convert from RC Boost to AC Boost, I've left them standing on legs rather than flush to the board.

Keefy

Finished the preamp board a while ago but haven't had time to do any more yet.

Keefy

It's finished and it works. I never did breadboard it! But...

(1) It's not that loud through a Neo Creamback in a cab. The power amp module does break up quite nicely when it's pushed though. I've yet to try it through the speaker in my Matchless.

(2) It sounds pretty dull unless you crank the bass a bit, and the treble a lot. Not a problem, just an observation.

(2) It buzzes unless you earth it. The SMPS I'm using has no earth connection, so I had to fudge one using a croc-clip lead to exposed metalwork on a rack unit nearby. I'm pondering how to implement this in a non-fudgey way.

All is not lost, there's not much here for which I can't find an application elsewhere at some point. I went on eBay and found a loaded Marshall MG30DFX chassis so I plan to convert that into a compact head.