A DIY Bass Head Build

[Passinwind]

After a brief flirtation with 1/2 rack width format builds I recently decided to try my hand at building a more compact integrated bass amp. Just to bump the degree of difficulty a bit further I decided to commission a fully custom enclosure for this one as well. I'm hoping to be making noise within the next week or so, and here are the major bits:

Preamp and high pass filter / parametric equalizer circuit boards:



ICEpower 700ASC module w/ ~3.3 pounds of added heat sinking, as this will be convection cooled due to my extreme aversion to fans.



Test fitting of controls in case:



As always, I should reiterate that "Passinwind Electronics" is still just a vanity name for my hobby builds, not an actual commercial entity at this time.

[Merton]

Oooh, nice

[Beer of the Bass]

Looks good! The HPF and parametric seem like useful things to have. Do you include any sort of limiter to protect against overloading the module on peaks, or does the module have that covered?

[Passinwind]

[quote name='Beer of the Bass' timestamp='1459015015' post='3012915']
Looks good! The HPF and parametric seem like useful things to have. Do you include any sort of limiter to protect against overloading the module on peaks, or does the module have that covered?
[/quote]

Thanks guys.

The module has a pretty good soft clipping circuit built in. It can be bypassed if desired though and eventually I will probably take a stab at rolling my own.

Since I play electric upright a lot, the HPF and PEQ come in very handy for facilitating switching between EUB and fretless bass guitar. This will be my third build using the same basic preamp format, but I've done at least a few revisions to the circuit boards each time.

[machinehead]

I'm thinking about building my own amp in the near future . If I get to half as professional looking as yours I'll be very happy.

Impending redundancy will give me more time to pursue such things. I'm looking forward to it.

Excellent work.

Frank

[Wolverinebass]

Superb work there! Will you be open for business and custom orders soon?

[silverfoxnik]

[quote name='Wolverinebass' timestamp='1459072121' post='3013236']
Superb work there! Will you be open for business and custom orders soon?
[/quote]

+1

Great to see something like this; really makes you realise what alternatives there are, instead of always just buying what's already out there in the marketplace.

[Bill Fitzmaurice]

[quote name='Passinwind' timestamp='1459012016' post='3012868'] I should reiterate that "Passinwind Electronics" is still just a vanity name for my hobby builds, not an actual commercial entity at this time.
[/quote]Good thing, one would not want bass gear to have a name which implies that it will fart out.

[ahpook]

Looks fantastic - what kind of preamp design are you using ?

[Passinwind]

[quote name='ahpook' timestamp='1459166765' post='3013999']
Looks fantastic - what kind of preamp design are you using ?
[/quote]

It's my own design which I've been refining for a few years now in LTspice, using somewhat "uptown" opamps. I do circuit board layouts in KiCad, which is open source freeware.

Bass and mids are active, then comes the one band fully parametric EQ, followed by the passive treble stack, EFX/Aux send/return, variable high pass filter (2nd order fixed plus 2nd order variable), and a final gain stage/line driver. The power amp has a Jensen input transformer added at the input as well. Signal/noise measures at better than 100dB and THD at around .001%.

[Passinwind]

[quote name='Bill Fitzmaurice' timestamp='1459165910' post='3013985']
Good thing, one would not want bass gear to have a name which implies that it will fart out.
[/quote]

My real feelings about all MI gear would have been better served by "Entropy Electronics", but that's already taken.

[ahpook]

[quote name='Passinwind' timestamp='1459174584' post='3014097']
It's my own design which I've been refining for a few years now in LTspice, using somewhat "uptown" opamps. I do circuit board layouts in KiCad, which is open source freeware.

Bass and mids are active, then comes the one band fully parametric EQ, followed by the passive treble stack, EFX/Aux send/return, variable high pass filter (2nd order fixed plus 2nd order variable), and a final gain stage/line driver. The power amp has a Jensen input transformer added at the input as well. Signal/noise measures at better than 100dB and THD at around .001%.
[/quote]

Very impressive indeed.

Your attention to detail is second-to-none, a job very well done - I like the transformer coupling.

[Guest bassman7755]

So ... how did you manage to acquire the ICE module ? what with them only being available to OEMs at least officially.

[Passinwind]

[quote name='bassman7755' timestamp='1459178528' post='3014161']
So ... how did you manage to acquire the ICE module ? what with them only being available to OEMs at least officially.
[/quote]

OEMs all have to start somewhere. In my old day job I became fairly proficient at writing things like evaluation sample requests, but as always, a lot comes down to [i]who you know[/i]. In this case I didn't even actively solicit, go figure.

There is also a substantial gray market these days though, and there are also factory blessed closeouts on some of the older modules, at Parts Express in the US for example. Although one of the most attractive features of the 700ASC module is that it has a good quality +/- 15 volt regulated power supply onboard, which potentially saves a lot of hassle and expense.

[Passinwind]

[quote name='Wolverinebass' timestamp='1459072121' post='3013236']
Superb work there! Will you be open for business and custom orders soon?
[/quote]

I worked in the music business for many years, time to do something more respectable in my old age!

But seriously, economy of scale, regulatory and liability issues, and a general disdain for marketing and answering the phone would make forging a workable business building "boutique" bass amps pretty difficult. Doesn't mean it can't still be a dream or goal though, of course. For now I'm just trying to refine my craft a bit more. I'm really just a tech, not an engineer, and to a tech everything is pretty much either broken or about to be.

[Passinwind]

This week's progress:

Mounted power amp module and tested thermal properties of my convection cooling scheme, no problems observed.

Preamp and HPF/PEQ circuit boards stuffed:



Surface mount format opamps installed on DIP-8 adapter daughter cards and tested before installation:



Interface between power amp module and preamp section ready for installation on heatsink hanger bolts:



All connections will be broken out to quick disconnect terminals to facilitate modifications or service work. Hope to be making noise within a few days now.

[Bottle]

[quote name='Passinwind' timestamp='1459444207' post='3016690']
All connections will be broken out to quick disconnect terminals to facilitate modifications or service work.
[/quote]
As someone who spends a living doing this 9 -5 every day, I can testify to the need for everything to be disconnect-able, especially with prototypes

We use Molex connectors for the vast majority of inter-board and wire-to-board connections. KK-100 system for low voltage / low current and Mini-Fit Junior for anything power related as it can handle 10A per pin at 250VAC. Anything else requires a specialised connector.

Downside is the investment in tooling which can be considerable. It is worth it in the long run.

HTH,
Ian

[Passinwind]

[quote name='Bottle' timestamp='1459515627' post='3017322']
As someone who spends a living doing this 9 -5 every day, I can testify to the need for everything to be disconnect-able, especially with prototypes

We use Molex connectors for the vast majority of inter-board and wire-to-board connections. KK-100 system for low voltage / low current and Mini-Fit Junior for anything power related as it can handle 10A per pin at 250VAC. Anything else requires a specialised connector.

Downside is the investment in tooling which can be considerable. It is worth it in the long run.

[/quote]

The power amp side uses JST connectors. ICE do not provide cable harnesses with OEM modules, and the pair of crimpers needed run ~$950. That's for the basic manual ones, the trick ones are considerably more expensive. I bought a couple of perfectly decent cable harnesses from a vendor in the ROC at $18 ea., shipped. But I agree, good tooling is generally worth whatever it costs.

[Bottle]

[quote name='Passinwind' timestamp='1459520570' post='3017381']
The power amp side uses JST connectors. ICE do not provide cable harnesses with OEM modules, and the pair of crimpers needed run ~$950. That's for the basic manual ones, the trick ones are considerably more expensive. I bought a couple of perfectly decent cable harnesses from a vendor in the ROC at $18 ea., shipped. But I agree, good tooling is generally worth whatever it costs.
[/quote]
That's the shape of things to come - it's far cheaper to have the harnesses made by a third party vendor. We do that a lot now with our volume production, especially PCB assemblies and cable harnesses. We have a good working relationship with a local sub-contract electronics manufacturer, and they've started sending our SMT boards overseas now. Yields are far better and any faulty boards now get binned rather than reworked.

YMMV

Ian

[Passinwind]

And after another week of burnt fingers and colorful language, today just might afford a first listen. I spent pretty much all day yesterday troubleshooting omissions and wiring errors, but at least I now have a test jig and a method for doing mods or repairs in the future. There are a few odds and ends in this pic that will need cleaning up eventually, but of course that's a never ending thing with DIY builds anyway.

Edited April 7, 2016 by Passinwind

[RandomBass]

I'm extremely impressed with this. At the age of 14 I built my first variable voltage power supply. Soon after it was 555 counters with led displays. That was 36 years ago mind you lol. Now I stick to fixing my heavy old Trace amps when they fail, which is very rare.
Looking forward to the finished product.
Cheers
Geoff

Edited April 7, 2016 by RandomBass

[Chienmortbb]

[quote name='Passinwind' timestamp='1460045841' post='3022077']
And after another week of burnt fingers and colorful language, today just might afford a first listen. I spent pretty much all day yesterday troubleshooting omissions and wiring errors, but at least I now have a test jig and a method for doing mods or repairs in the future. There are a few odds and ends in this pic that will need cleaning up eventually, but of course that's a never ending thing with DIY builds anyway.


[/quote] Since I first tried those blue Powercon I loved them. They just feel professional.

Are you only using one speakon?

[Bottle]

[quote name='Passinwind' timestamp='1460045841' post='3022077']
And after another week of burnt fingers and colorful language, today just might afford a first listen. I spent pretty much all day yesterday troubleshooting omissions and wiring errors, but at least I now have a test jig and a method for doing mods or repairs in the future. There are a few odds and ends in this pic that will need cleaning up eventually, but of course that's a never ending thing with DIY builds anyway.


[/quote]
That is looking extremely tidy nice thing about the Powercon, Speakon and XLR jack is they all use the same cutout profile

[lowhand_mike]

love it, looks very pro and nice to be able to have your own built stuff
still as much as i like seeing this stuff it does make me realise just how thick i am

[Passinwind]

[quote name='Chienmortbb' timestamp='1460055831' post='3022234']
Are you only using one speakon?
[/quote]

Since I'm only using one cab these days, yes. I could always add another one if needed though. I haven;t really done anything about the DI output either, but I do have a spare Jensen transformer I can throw in there if I feel too lazy to work up a solid state DI. A few people have asked me about doing a headphone output as well, but that's something I've never used myself, so it's not a high priority.

[quote name='Bottle' timestamp='1460113416' post='3022680']
That is looking extremely tidy nice thing about the Powercon, Speakon and XLR jack is they all use the same cutout profile
[/quote]

Yep, they all use the D connector format, but in this case the cutouts are laser cut, so the vendor doesn't require a tooling change charge for dissimilar cutouts. The switch holes on the front even all have the little keyway locator included, which is a real luxury when it comes time to install the switches. No alignment hassles and no spinning as you tighten the retaining nut.