A House Jam Combo

[Phil Starr]

Hi All this has been stimulated by two (thanks for the impetus @Pea Turgh )of us having the same need, for a tiny combo for 'quiet jamming'. Most of us will have had the same problem, even an acoustic bass just isn't loud enough when someone else starts playing a guitar and singing and maybe those wall are just too thin so any deep bass goes through them as a deep and annoying thud for the neighbours. In my case it was a stay in a rented holiday flat. I grabbed a tiny 10W guitar Combo I'd bought for my son about 20 years ago which had never been used. It did the job in that he could hear me but it sounded awful, it didn't have very little bass it had no bass at all and it was only loud enough because of the nasal tone. I wanted something just a bit better but in the same fomat, really tiny and something that would plug and play.

Here's what I started with.

 

Edited November 16, 2020 by Phil Starr

[Phil Starr]

As you can see it was an open backed guitar cab just about 30cm tall. Ignore the speaker inside it had something much smaller which looked like a car speaker from the 1970's and not in any good way.

Here's the speaker next to it's replacement, as you can see the original speaker had a tiny magnet and what you can't see is the flimsy cone. It was rated at 20W handling and 4ohms. the replacement was a Fane 6-100 rated at 100W but crucially with a heavier cone, good excursion limits and a proper magnet. Despite the slight loss of power this was going to be a little louder due to the larger magnet driving it harder.

 

[Phil Starr]

As a first step I cut a piece of ply to be a tight friction fit in the open back, I knew from previous experiments and from theory that you wouldn't get any bass when the sound from the back arrived and cancelled the sound from the front of the speaker. Actually sealing the cab made the original speaker sound a little better but I found that I could just drop the new speaker in so i did, total time so far was about 20 mins. this was getting there but was still bass light. Off to Win ISD to model the speaker in it's new cab. I used a hole saw to cut a hole in the ply and a hacksaw to cut 93mm of plastic drainpipe.

 

[Phil Starr]

That's it really, I'm using it with the mains lead going in through the port at the moment. Let's not carried away, it sounds OK but there is almost no deep bass, a little warmth above 100 Hz helps but that is the point really, it doesn't annoy the neighbours as normal house structures are fairly good at containing the higher frequencies. It keeps up with two of us singing and my duo partners unamplified but enthusiastic acoustic guitar, it takes up very little space and it is plug and play. All the donor guitar combo provides is the amp and a ready made cab. Surprisingly the 10Watts advertised is actually 18W into the new 8 Ohm speaker and that is plenty. I'm contemplating replacing the power amp section with something that runs on a car battery and i need to move the IEC mains socket on to the rear panel but i'm happy that this was an experiment worth doing. Total time was about 90 mins over a couple of evenings

Edited November 16, 2020 by Phil Starr

[Pea Turgh]

Oh, I’m definitely doing mine now!

[Phil Starr]

The Fane 6-100 is on offer at Blue Aran at the moment £28 + a few pence. Another alternative might be the Beyma 606CMV http://www.bluearan.co.uk/index.php?id=BMA606CVM28&browsemode=category

If you want I can model the speaker in your cab and give you some port dimensions.

[Chienmortbb]

I am tempted to mod my Peavy Rage 158 but need to finish the After Eighty first.#

 

[Jus Lukin]

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Edited March 10, 2022 by Jus Lukin

[Phil Starr]

2 hours ago, Chienmortbb said:

I am tempted to mod my Peavy Rage 158 but need to finish the After Eighty first.#

 

I wonder what's next, should we design something from scratch, use one of the cheaper pocket amps or just persist with simple mods like this? I'm thinking of having a look at my Hartke Kickback, It's been a really useful thing but weighs a ton for it's size bangs your legs when you carry it and falls over in anything but kickback mode. 

[Passinwind]

On 17/11/2020 at 06:12, Phil Starr said:

I wonder what's next, should we design something from scratch, use one of the cheaper pocket amps or just persist with simple mods like this? I'm thinking of having a look at my Hartke Kickback, It's been a really useful thing but weighs a ton for it's size bangs your legs when you carry it and falls over in anything but kickback mode. 

You just know I'm going to vote for a bespoke build. I'm still finishing up my all consuming100 watt tube amp build but a small combo is very much on my radar as a winter project. Before lockdown here so much of my playing was without drums and with just a handful of mostly acoustic instruments, and I expect it may be even more so once we get off this roller coaster. Nice job Phil, as usual.

[Phil Starr]

2 hours ago, Passinwind said:

You just know I'm going to vote for a bespoke build. I'm still finishing up my all consuming100 watt tube amp build but a small combo is very much on my radar as a winter project. Before lockdown here so much of my playing was without drums and with just a handful of mostly acoustic instruments, and I expect it may be even more so once we get off this roller coaster. Nice job Phil, as usual.

Coming from you that's a welcome comment. I know you re helping John (Chienmortbb) with his After Eighty project. I'm using this with my Zoom B1ON and I'm thinking of maybe something with little more than simple volume bass and treble and taking advantage of some of the high power chips they make for car audio. I want something simple enough for others to build so if I can use widely available ready assembled boards for the amp that would be good.

[Pea Turgh]

I was going to build a minimalist cube amp a few years ago (I like to sketch when I’m bored).  I wanted to round the edges off and paint it a nice sky blue.  Dug my notepad out and took a snap for you.  Input & power at the back, volume & power switch on the front.

 

[durhamboy]

I know next to nothing about building amp, but have a Gen 3 Epiphone 5w valve Junior that rarely gets an outing these days. perhaps a candidate for an at home practice/jam along bass amp? 

Anyone ever tried that already? Or the thought just occurred to me, as it has a line out for a cab, perhaps a bass cab build to suit would be worth considering?

 

[Pea Turgh]

Or what sized cab would get the best out of that Fane driver?

I’ve got a small amp module (20w) that I put together from a kit in the house somewhere.  It worked on a 9v battery.  I was going to put it in a pedal housing to use as a tiny amp and also separately to drive some spring reverb tanks.  Damned if I can find it now though!

[Phil Starr]

On 19/11/2020 at 13:53, Pea Turgh said:

Or what sized cab would get the best out of that Fane driver?

I’ve got a small amp module (20w) that I put together from a kit in the house somewhere.  It worked on a 9v battery.  I was going to put it in a pedal housing to use as a tiny amp and also separately to drive some spring reverb tanks.  Damned if I can find it now though!

about 9litres the same size as the cab I used though that was luck rather than judgement.

I've been wondering about something similar, you can buy an amp based on the TPA3116D2 for around a fiver which will run on a car battery or the TDA2030 if you don't want Class D on eBay TDA2030A Mono 15W Audio Power Amplifier Board AC/DC 12V Assembled Nice UKO FG | eBay

[Chienmortbb]

1 hour ago, Phil Starr said:

about 9litres the same size as the cab I used though that was luck rather than judgement.

I've been wondering about something similar, you can buy an amp based on the TPA3116D2 for around a fiver which will run on a car battery or the TDA2030 if you don't want Class D on eBay TDA2030A Mono 15W Audio Power Amplifier Board AC/DC 12V Assembled Nice UKO FG | eBay

The TDA 2000 series such as TDA2020/30/50 are dual supply and although they can be used single supply, I would not recommend it especially as the quiescent current will br quite big, running down your battery faster. 

Thr TPA series are very efficient and will run cooler so I would stick with them. 

[Phil Starr]

16 minutes ago, Chienmortbb said:

The TDA 2000 series such as TDA2020/30/50 are dual supply and although they can be used single supply, I would not recommend it especially as the quiescent current will br quite big, running down your battery faster. 

Thr TPA series are very efficient and will run cooler so I would stick with them. 

I agree John, I wouldn't personally look past the TPA series at the moment and you can get ready wired boards for all sorts of applications, so you need to do little other than make a case for them. the other issue is heat dissipation which is so much less for class D. 

[Phil Starr]

On 19/11/2020 at 00:51, durhamboy said:

I know next to nothing about building amp, but have a Gen 3 Epiphone 5w valve Junior that rarely gets an outing these days. perhaps a candidate for an at home practice/jam along bass amp? 

Anyone ever tried that already? Or the thought just occurred to me, as it has a line out for a cab, perhaps a bass cab build to suit would be worth considering?

 

I had to look that up  

To be honest it looks too nice to mod in the way I did, though everything I've done is reversible. On the plus side a single EL84 should sound fine through a little speaker for this sort of use. The problem with mine is amp distortion when you push too hard, you can't really over-drive an amp this size without it sounding nasty. I reckon this little amp will sound sweet. I'd go for building something the same size and finish as your little epiphone, something it will sit on and look right. If you give me the measurements I can suggest a speaker that might work

[durhamboy]

Sorry for the delay in acknowledging you most informative post, (I went in for bypass surgery on the 24th. got home yesterday, so I have plenty of time for planning before I can get into the workshop. About 3 months! That's going to hurt....)

Yes, I was thinking more along the lines of just building a bass cab to be driven by the Epi head as it already has the facility to unplug the inbuilt speaker and plug into a separate cab. I will contact you with some specs in the near future, but at the moment it's more than my life's worth to be seen with a ruler or tape measure in hand, my wife is making sure I stick with the hospital and rehab guidelines. for now...😉

[SpondonBassed]

Wishing you a successful recovery.

[durhamboy]

Thanks, all looking good at this stage.

[Phil Starr]

Good luck with the recovery, there will come a time when a nice relaxing project will be just the thing .

You might find it fun to do some internet research whilst you are laid up. I've designed stuff for someone in Australia before and sourcing drive units was an issue. A lot of the stuff available here wasn't available over there at the time and the exchange rate was appalling. That's bound to have changed in the last ten years but we did find an Australian manufacturer and some lovely drivers.

[lemmywinks]

If anybody wants a small amp section for a project like this I have a Kinsman 10w bass head (of sorts) going spare, one of those BB10BS cheapies from a knackered combo, I used it in a makeshift acrylic case for a while until I got a better amp for around the house. Left the lid and black plastic wrap on but had to take the speakon and IEC connectors out. Has the handle and screws etc which might be handy.

Can post it out for free to anybody who wants to rescue it from the bin, furloughed at the moment but will post as soon as I'm back in work. 

 

 

[Phil Starr]

ignore this

Edited January 27, 2021 by Phil Starr

[Phil Starr]

 

 

Just thought I'd finish off this little project. I left it with leads coming out of the port, good enough for testing and sitting in the corner but not very practical, not least because the mains switch was only available by reaching through the port.

First thing I decided was to have the possibility of adding another 8ohm speaker, 20W would be better with an 8x10

Then I added a new switched IEC socket. I wanted to be able to remove my mods in the future so I wired up the IEC plug cut off from one of those Thomann euro plug jobbies

 

This and the spade connectors can just be unplugged to return the amp to original.

Bit of black paint and the job is done

Edited January 27, 2021 by Phil Starr