Troels Gravesen SBA-761 Project Build

[DavidH71]

I had to make another version of the clipping indicator PCB's (clipping_ind_V2) , I changed the resistors that will dissipate heat to standard size through hole resistors except for R9 which I made a 5W through hole resistor , R4 and R5 can't be 0402 surface mount size as I discovered because of heat , I have tested it and it works well now.

 

I now have the SMPS from Connex so I have everything to rebuild my amp , should be in the next week or so .

 

I am still awaiting the Textreme tweeters to try.

Edited March 11, 2021 by DavidH71

[DavidH71]

I feel like such a dick.

 

When I rebuilt my subwoofer amp from mono to stereo for dual subs I used a Connex IRS2092 class d stereo amp module , you need to wire it so 1 channel is out of phase with the other channel to avoid bus pumping (class d thing).

I had done this but when I was fitting my clipping indicator I discovered I had misread the labelling on the outputs of the amp module and didn't have the inverted channel output swapped around so I actually had one subwoofer out of phase with the other.

I had not picked this up as I also fitted the second sub at the same time as doing the amp mods and the outcome sounded different but I had expected it too because of the second sub.

 

I fixed the amp speaker terminal wiring and holy crap it all made sense now as I was a bit underwhelmed with the addition of the second sub and expected more but now I am finally getting what I expected from my 2 subs , huge difference , I almost have too much bass (is that possible?)

 

My house doesn't like it much , bloody walls/windows rattle like crazy , not sure what I can do about that.

 

The sub I have also had a bit of EQ boosted down low using an active filter setup that I made a PCB for and fitted to the amp years ago but because I upgraded the internals of the amp recently I decided to change that function to a 2 x 4 Minidsp HD which I had laying around.

 

What I hadn't realized by just making the exact same filters in the minidsp as my PCB version was that I also had a low pass on the sub which is not necessary because the AVR should be controlling the crossover frequencies from sub to mains , with it like this I was missing upper bass as the subs low pass and the AVR low pass were adding and giving me double the slope so instead of 24db slope it would have been more like 48db which means the sub wasn't blending correctly with the mains and missing upper bass. 

I removed this low pass filter at the same time as discovering the wiring out of phase on my sub amp so these 2 changes happened at the same time.

 

The result is my bass is on another level and I am currently going back through listening to my old bass heavy favorite tracks again as it just sounds so damn good now.

 

I am so disappointed in myself for having it this way since I built the second sub months ago and because of my mistakes not getting the full potential out of them.

 

I am slowly assembling my stereo amp with the Holton amp modules.

 

Because I have already pulled apart my Playmaster Pro series 3 amp I had to wire the SBA-761 speakers to my Denon X3700 AVR

and could tell instantly the drop in sound quality , AVR amps are no good for quality music amplification as I have now clearly proven to myself.

 

Still waiting on the Textreme tweets.

 

Cheers

 

David

Edited March 17, 2021 by DavidH71

[RoHo]

Don't knock yourself out over a dumb mistake.

If I started a thread titled "I'm a DIYer and I've never stuffed up" it would be a very, very short thread 

Who hasn't blown up their share of semiconductors?  Or wired output transformers out of phase?  Guilty on both counts here!

[RankStranger]

@DavidH71 It’s not even just DIY. When I was working at a hifi shop 15 years ago, we had a visit from the head engineer of an Italian manufacturer to demonstrate some of their new high-end kit. He set it up himself and spent the better part of an hour trying to tune it in, getting increasingly irate, swearing in Italian and blaming the terrible room and filthy power and whatever else came to mind, for the lacklustre sound. 

 

Turns out, he had one speaker wired out of phase the whole time ¯\_(ツ)_/¯ 

[DavidH71]

I spent yesterday listening to the Holton amp modules.

 

I think I am going to fit the Playmaster pro series 3 modules back as they sounded better to me.

 

I'll give it another week before I decide for sure.

 

The things I liked when I first set up the Playmaster were gone with the Holton modules , the clarity wasn't there compared to the Playmaster , there was no sparkle or excitement to the sound , very boring , maybe good for really bright speakers , oh well only way to find out was to try.

 

Still waiting for the Textreme Tweeters.

 

Cheers

[DavidH71]

Well I have fitted the Playmaster Pro series 3 modules back with the Connex SMPS power supplies and it works very well , no noise and very quiet and weighs quite a bit less.

 

While I was at it I also changed the amp modules input transistors Q3 Q4 (BC556) to KSA992 (different pin out so you need to bend the legs to match) and matched their Beta and Vf , I also cable tied them together with some thermal paste so their thermal properties stay the same.

 

I am now back to the sound I am very happy with , the Holton modules never did it for me and were just very boring to listen too.

 

I think I will be keeping the Playmaster Pro series 3 amp for a while , I really like it.

 

I guess audio is a personal thing with personal preferences as everyone doesn't hear the same. 

 

I queried my tweeters with WES and was just told there are production issues with them and they have been delayed until the end of April , bummer.

 

Cheers

Edited March 26, 2021 by DavidH71

[Janus77]

I'm waiting on a tweeter surround ring for mine (cracked the surround ring screwing it down on install) from WES, is taking ages..

Are your tweeters SBA?

[DavidH71]

Yes , SB Acoustics TW29TXN-B-8 Textreme tweeters are what I am waiting for from WES components.

[Janus77]

Ok, sounds like i'm in for a bit of a wait too.  I ordered 20th January and was told around 6 weeks.

[DavidH71]

I also wanted to try some SOT-23 surface mount PNP transistors in my Playmaster amp (Q3,Q4) , as the Playmaster PCB is configured for TO-92 through hole , I needed some adapters so I knocked up a PCB , the gerber files for the PCB are on my google drive. 

 

Out of curiosity I am also building the Silicon Chip SC200 low distortion amp modules and will give them a try too.

[kiwilistener]

 

Quote

 

Oh and one other thing i only discovered after mounting the drivers was that i need to blacken the MDF behind the drivers as on certain angles you can just see the yellowish MDF , which on a dark cabinet stands out.

 

Cheers

 

David

 

 

Snap, happened to me as well on a pair of speakers I made a few years back. Not terribly noticeable but I knew about it, a source of irritation every-time I had the grills off.

Edited April 12, 2021 by kiwilistener

[Janus77]

FYI, my SBA parts arrived at Wagner.  

[DavidH71]

Yeah , finally my Sb Acoustic Textreme tweeters will be delivered today from Wes , hopefully I will get a chance to fit them this weekend also I should have the SC200 amp ready to test as well , I will report back in a week or two on the outcome.

[DavidH71]

I fitted the Textreme tweeters on the weekend , I also changed the tweeter level resistor from the 4.7 ohm I previously fitted to a 6.9 ohm as the sensitivity of the new tweeter was higher.

 

Wow , these are impressive tweeters , the airiness has improved a lot as well as percussive higher frequencies and also the stereo imaging has also gone up another level which I didn't expect.

 

I think my main problem with the original tweeter response I was getting was that I came from listening to the Vifa D25AG metal dome tweeter for the last 20 years and was very much used to the metal dome tweeter sound so when I built these I was a bit underwhelmed by the tweeters and was after more edginess.

 

The Textreme tweeters seem to give me that sound but without harshness which the D25AG could suffer from on certain material.

 

Overall I am very very happy with the outcome and can highly recommend these tweeters.

 

I am still slowly assembling the SC200 amp to test as well , hopefully sooner than later.

[Janus77]

Awesome, keen to see some pics of the installed tweeters.

[DavidH71]

Yes I will get some pictures and I just realized I don't have a finished picture of my subwoofers , I will get some of those as well.

[DavidH71]

[Janus77]

How's the sub go?  Was it a DIY plan or you designed yourself?

Cool setup, that upward firing speaker on top, are you running an atmos setup or something?

[DavidH71]

Yes , the speakers on top are for Atmos.

 

This is the link for my subwoofer http://mainkas.tripod.com/page/audio/allmighty/tangen_sub2r.htm

 

I stumbled across this sub over 20 years ago and built one then , that's the one in the photo and I have another one in the opposite corner of the room that I built a few months back.

 

The subwoofer is the cleanest / lowest sub I have heard , I have been to a few live concerts and I think mine sounds better.

 

It shakes the crap out of my house , very good for movies as well.

 

It actually looks a lot like the marty subs with a bit higher tuning (24hz) but this was designed in the 90's long before the marty subs.

 

I love my subwoofers , I am a bass head.

[Janus77]

Bass is addictive

 

My TG 3wc's have excellent bass, but i've wondered if a sub running 20-40hz to complement the speakers might not round the system out.  I reckon I miss the very lowest notes.  A good example is Kendrick Lamar's "Loyalty", the bass line drops very low around 30-40 seconds in, and goes lower and lower, the very lowest note i'm just getting, but not strongly.  A mate's Duntech Princess (new model) tickled my ears at the lowest notes.

 

 

 

 

[DavidH71]

My subs are flat down to 20Hz in room so I get all the good stuff down low including what you can't hear but feel , you don't know what you are missing out on if your system doesn't reproduce the lowest notes with authority , for me it's almost the most important aspect of my sound system.

Edited May 6, 2021 by DavidH71

[Janus77]

My wife's been very understanding to this point.  If i try to install additional "furniture" in the living room,  hard to say how she'll react.  I guess you don't know unless you try.

 

What amplification are you using for the system?

[DavidH71]

Ha , I don't have the wife factor to worry about.

 

I built up a subwoofer amp with a 2400w smps power supply with stereo irs2092 class d amp modules , about 400wrms each channel 8 ohm and for the mains I am using my Playmaster Pro Series 3 amp which I bought from Jaycar (when they had audio stuff) and built about 20 years ago , I recently tried some Holton amp modules https://holtonprecisionaudio.com/collections/diy-audio-amplifier-modules/products/hpa-nxv200l-r4-balanced-xlr-input-amplifier-module  but I found I preferred the sound of my Playmaster amp so that's what I have been using.

 

I am still experimenting with amps , I am currently building the Silicon chip SC200 Ultra low distortion amp modules to try out as well and hopefully should be firing it up this weekend.

[DavidH71]

Well I fitted the SC200 amp modules on the weekend and spent yesterday listening to them. 

 

It is a little bit clearer mid/top but the biggest difference which I didn't expect was the improvement it made to the bass.

 

The bass just sounds so much better , more of it to begin with but also the quality of it is very good.

 

And it wasn't just the very low notes , it was all bass frequencies that improved.

 

I ended up half of my listening session without the subs going and just the SBA-761's because the bass sounded so good and it was surprising me at the amount and quality of the bass.

 

With the subs running it now has much better blending with the mains because there is more bass from them.

 

So I will be keeping these modules as my main amps .

 

Cheers

 

 

[DavidH71]

Argh , now I have a niggling question in the back of my mind , does it ever end ?

 

Now I have installed the Textreme tweeters , it has brightened up the speakers so now I am thinking of trying the Holton amp modules again as that's what I was missing most was the sparkle , it just disappeared with the Holton modules.

 

Well actually also I am now really curious how the bass compares to the SC200 modules as the SC200 modules are so damn impressive in the bass department.

 

Looks like more playtime to come.