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PostPosted: Wed Nov 08, 2006 4:06 pm 
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Hen

Joined: Tue Nov 07, 2006 2:54 pm
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Hi Greg!

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Welcome to DIYHiFi!


Thanks!

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Yes I have it now on my website.


O.K. I found it!

Greets:

Tyimo


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PostPosted: Wed Nov 08, 2006 8:50 pm 
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Hi Pasi P,

You have many choices -

1. My simple OPA2134 VolBuf kit as you use the same chip in your Orion active crossovers and the reg supply would be a +.
2. The SKpre but this will give 12dB gain and is probably overkill with it's onboard regs....
3. A simple FET buffer from one of the circuits discussed on "A simple FET Buffer" thread.

Hi Tyimo,

The VolBuf is very compact, simple and reasonable. The Simple FET Buffer using 1 FET and 2BJT's requires only offset adjustment for DC coupling, otherwise no adjustment.

Cheers,
Greg


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PostPosted: Wed Nov 08, 2006 9:37 pm 
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Sheep

Joined: Sun Mar 12, 2006 9:36 am
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Greg,

Sorry, i meant OPA2134 VolBuf, not FET buffer that i said by mistake.

I will try these :tonqe:

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PostPosted: Thu Nov 09, 2006 8:35 pm 
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Sheep

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I ordered VolBuffers. I will use only one channel each to improve crosstalk. When i have good quality +/-15VDC available, i think zeners can be left out. How about filter caps, is it better to left these out also?

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PostPosted: Thu Nov 09, 2006 9:30 pm 
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Goat

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Location: Scottish Borders
Hi,
the regulators will have their own filter caps.
The best place for the regs are directly over the load.
If the connections are very short (5 to 10mm) the load will not need any more filtering or impedance reduction.
You may find that decoupling can also be dispensed with except at the opamp pins.

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Andrew T.


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PostPosted: Thu Nov 16, 2006 9:17 am 
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Hi Pasi P,

Yes you are quite right, the zeners can be omitted. Depending on the loading limits of your regulators, we can adapt the circuit.

Cheers, Greg


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PostPosted: Wed Nov 29, 2006 10:13 pm 
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First orders for the SKpre have now been shipped and some have started assembly, awaiting results...


more detail here -

http://www.diyhifi.org/amplifierguru/guru_008.htm

Applications as linestage and DAC I/V are already under way.

Cheers,
Greg


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PostPosted: Fri Dec 29, 2006 9:25 pm 
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I'm almost at the stage of panellising for another run of (double-sided thru hole plated PCBs) and am considering a trimmable+/-50V regulator PCB for use with the GB150D's allowing the IRFP9140's to be used without power loss due to demand sag.

Any views? I was thinking either a MOSFET boosted LM317/37 simple design or a more complex discrete design. I'm thinking a spec -

PSRR 80dB and < 0.01ohm Z out would seem a worthwhile improvement on a C smoothed supply partic < 1KHz.

Something new.
Greg


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PostPosted: Sat Dec 30, 2006 5:48 pm 
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Jones (R.I.P.)
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Let me get this straight... you are going to add a regulated supply to get rid of power loss do to demand sag of the power supply....

You now have even more power loss in the regulators! Plus with the same amount of raw power supply capacitance (that will have to be higher voltage most likely to allow for the regulator voltage drop) the input voltage to regulator will droop. There is no such thing as a free lunch. Doesn't sound very green :mrgreen: If you want the supply to sag less, use more filter capacitance. If you want improved sonics from a regulated supply without wasting as much energy, Use a topology for which you can regulate the amplifier's front end power supply without having to regulated the output stage supply. No charge.

Oh, if you proceed with your initial idea.... definitely go with the Mosfet asisited three terminal regulators. :drinkers:

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PostPosted: Sat Dec 30, 2006 8:37 pm 
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Hi Fred,

What you say. :mrgreen:

The SKA topology is markedly superior to current alternatives and we can't throw out the baby... I would love to do a SMPS for +/-49V and 100V-250V input but that won't happen overnight, so, how else to have <0.01 ohm at 100Hz PSU.

I could achieve this spec in a simple CS MOSFET discrete low drop reg similar to the SKA topo. Way to go? A CS output reg? Not your dream but The GB150D does DF > 500 for 8ohms so why not? Add the losses for a boosted LM317 for comparison of green. :rolleyes:

I have had interest from a few DIY audiophiles who are happy to sacrifice some power in their quest for audio nirvana... and this would be a simple add-on between PSU and amp.

Cheers,
Greg


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 Post subject: regulating the supplies
PostPosted: Sun Dec 31, 2006 11:05 am 
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Goat

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Location: Scottish Borders
Hi,
someone is missing the point.
the GB150 was originally built to put out 150W into 8r from +-55Vrails.

The modification to using 240 & 9140 as the output pairs forces a reduction in Vrail to some lower value.

Regulating the original +-55Vdc down to +-49Vdc or +-50Vdc does not involve any extra energy loss.

The original PSU probably fell to something around +-47Vdc to +-50Vdc when heavily loaded.

It seems to me that the addition of the regulators looses nothing and potentially gains some of that lost power with the attendant advantages of 9140 pair matching and lower supply impedance.

Let's see/hear what could come out of this.

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Andrew T.


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PostPosted: Sun Dec 31, 2006 9:35 pm 
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Hi Andrew,

Exactly.

If I've got it in the repertoire and it's an easy add in, and reasonable then it's a worthwhile plus to DIYers who want to experiment.

A simple discrete source follower bootstrapped low noise BJT arrangement seems like the way to go. Simple and effective. I'll lash it up.

Maybe also a reasonable no-hype reg for the Squeezebox and Orion XO's. Some are asking $300 for them. Can you believe it? :rolleyes:

Cheers,
Greg


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PostPosted: Mon Jan 08, 2007 9:23 pm 
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With the SKpre I now have the optional Alps blue dual gang pots.

As dual gang pots for volume introduce some measure of interchannel crosstalk depending on the closeness of the gangs and the shielding between. It is highest at high frequencies and high impedances and worst case is the electrical half way where wiper impedance is highest.

For this reason I use a 10K Alps blue and have measured worst case crosstalk at 15KHz at -66dB. With the simple copper box fitted and grounded, the improvement is ~ 8dB to -74dB. Worthwhile for little outlay!

The copper is supplied with the Alps pot option to SKpre buyers.


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PostPosted: Sat Jan 20, 2007 9:20 am 
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Here, attached, is a stunning build of my BassXt kit just sent from an Aussie DIYer. The unit is unity gain except in the low < 100Hz bass where a tunable 6dB of peaking bass boost is available.

Fully ground planed with 80dB discrete regs onboard and subsonic filtering of -40dB at 0.1 Fpeak unitially 15dB/octave tames room modes and vibration while controlling cone 'unloading'.

Greg


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PostPosted: Wed Jan 24, 2007 8:13 pm 
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And here is his assessment -

..."I was looking for something to add some lower bass to a large pair of bookshelf speakers (Peerless 850122 woofers) that's used secondary system. The idea was to have extra extension when playing some DVD's with good musical soundtracks (not action flicks as there's a HT setup for those). The system does not warrant a small sub, even though it had one in the past that was rarely used, so this seemed a good solution. Bass extenders I have heard in the past tended to sound like a bad loudness button.

The BassXt was first tested with a small loudspeaker that's in an undersized box where the F3 is 62Hz but 48Hz in the correct size box. The woofer is the PAE 14WG08 (Vifa BC14WG49-08) which has limited power handling so would be a good candidate to see if there would be any over driving. Not only did the BassXt restore the lower end bass, it improved on the larger box extension as well as controlling the woofer better. There were no crazy excursions and it was very well controlled. So the bass went lower and the power handling capabilities went up. The tonal quality of the bass was very good (depends on the driver of course) and natural with no boom or one note qualities. The same happened when tried with the Peerless 850122 woofer design and the F3 went from 47Hz down to well below 40Hz which is enough to enhance the selected movies where I wanted better bass from the soundtrack. This speaker now sounds more like a floorstander with a fuller sound in the bass.

In these speakers, it was not implemented to replace a subwoofer, but to extend and enhance the bass capabilities that were already there. I'm sure that port tuning (lower Fb) to give a under damped response would have even more gains but no port re-tuning was done during my tests and final use.

The circuit and layout is extremely simple with a 12VAC (plug pack) in, power switch, in RCA and out RCA. In the final application it's placed in the tape circuit so hitting a monitor button on the amp will put it in or out of the signal path. In the first test it was placed between the CD player and the pre amp but one will be built into the pre amp so it can be switched in as required.

I am not affiliated with the designer but I got quite excited with the results so thought this could be a great solution for those looking for a bit of extra bass extension. It worked out cheaper than a small woofer and the box was built from scrap material.... woohoo."...

for more -

http://www.rzaudio.com/rz52/bassxt.htm

Cheers,
greg


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