Krell KSA 50 PCB

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#2,861
Re: Aaron,

Stuart Easson said:
So do you have your amps biased for 4ohm loads now?

Reason I ask, I was wondering if you noticed a big difference in the sound character of the amp as the bias was increasing...

I have about ~1A idle current in the big amp, I am thinking of increasing it further, but only just finished the assembly of the last half of the output stage. Don't want anything to pop unexpectedly.

Stuart
Click to expand...

Yes, they are fully biased for 4 ohm load... works out about 133wrms @ 4 ohm full class A 🙂

I noticed a change in sound, IMHO a definate change, it's much smoother sounding.... I'm running a fair bit of bias though!!! I can't listen to crap amps any more the Krell clone sounds too good 🙂

How's the high power one going??? How much power?

Aaron
 
#2,862
power...

Aaron,

Last time it was all together, I was getting 800w RMS into 4 ohms, but the goal is >1000w into 4, 2000 into 2. I'm gonna let the 4000 into 1ohm slide, can't afford the outputs and power supply it needs...probably time for a 'real' protection circuit...though at this level it is probably beyond the capabilities of a 110v circuit...might not need anything more than the breaker in the fuse box...

So I am reassembling the power supply with a pair of 1.4kva xfrmrs, adding another 6 pairs of outputs, to a total of 16 pairs, should be able to retest soon...I'm a little concerned that 16 pairs is marginal for a 2ohm load, but once I test into 4 and measure the operating conditions I'll have a better idea...

Stuart
 
#2,864
Re: power...

Stuart Easson said:
Aaron,

Last time it was all together, I was getting 800w RMS into 4 ohms, but the goal is >1000w into 4, 2000 into 2. I'm gonna let the 4000 into 1ohm slide, can't afford the outputs and power supply it needs...probably time for a 'real' protection circuit...though at this level it is probably beyond the capabilities of a 110v circuit...might not need anything more than the breaker in the fuse box...

So I am reassembling the power supply with a pair of 1.4kva xfrmrs, adding another 6 pairs of outputs, to a total of 16 pairs, should be able to retest soon...I'm a little concerned that 16 pairs is marginal for a 2ohm load, but once I test into 4 and measure the operating conditions I'll have a better idea...

Stuart
Click to expand...

Hey Stuart, are you making a high power welding machine of some sort? or what do you intend to drive with these power plants? gosh...


:bigeyes: 😱 :bigeyes: :bigeyes:
 
#2,866
more power...

Initially the 'recreation' of the amp as a kilowatt monster was more an academic exercise for me... That is until one of the other guys (k-amps) here decided he really wanted one. Since he also had some spare examples of the big power supply components and I had the inclination to do the 'work' it started in earnest...I think he has detailed what he wants to drive in an earlier posting, but basically it is a big(!) set of woofers...

The mechanical assembly is the slowest part for me, I think my paranoia makes me slower, I really don't want any nasty surprises with >200v rail to rail...when starting this thing up, my variac is my best friend...

Stuart
 
#2,867
Re: Re: power...

lgreen said:



Stuart, if you need any outputs (output devices?) email me and I would be happy to send many pairs your way.

Terry- you look pschyed! Are you a rocker?
Click to expand...



I use to be a rocker years ago. I'm more of an old blues hack now on guitar. I do pretty much all Gospel now. I'm mainly a vocalist.

You can here some of my stuff
here if you are so inclined. Don't expect too much. 😀

Blessings, Terry
 
#2,870
lgreen said:



WHOA! I see that the feedback circuit connects to a number of circ componets. I think you need to use the feedback circ even with no protection (300 series numbered components) installed.

Have I got this right or is FB not necessary with no protection components installed?
Click to expand...

I don't think I got an answer-- do you need to connect the output to the FB point on the driver board if you don't use any of the protection components?
 
#2,873
lgreen said:
do you need to connect the output to the FB point on the driver board if you don't use any of the protection components?
Click to expand...

Of course you do !

This point is not only the feedback connection from the output, it is also the output of the drivers.
The driver emitter resistors are 25 Ohms, this is a low value for drivers.
The drivers deliver part of the music signal too, and they are better at it than the output devices, one of the reasons why Dan the Man picked such low values.

The other half of the entrance of the amplifier needs a reference voltage from the output.
If there is 1 volt on the input of the amplifier there is 1 volt on Q101/Q102.
If the amplification works ideal there is 1 volt on Q103/Q104 too , coming from the voltage feedback.
Suppose the amplifying job is bad, then there will be a higher or lower voltage on the base of Q103/Q104, again because of the feedback.
This leads to Q103/Q104 opening/closing, because of it Q101/Q102 will have more/less current, and amplification changes, in result the output signal is forced to follow the right path.
Without making the connection there wil be no feedback, without feedback the Krell will be a true alien ! :clown:
 
#2,877
Al, have a look at the picture. Isn't that plane not a bit to close to the transistor pins?
 

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