Simple Killer Amp - Listening impressions

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#401
Re: Re: BOLD STATEMENT

KLe said:
Hi mikelm
This is the FB to Gnd cap. Do you think that the cap can be removed without any DC problems arising?
:cheers:
Click to expand...

you could try with speakers disconnected & measure - if too high greg has dc trimming instructions an email should do it.

if you work out the power dissipated with different amounts of DC you will see that even 500mV offset will probably do no harm but you will have measure the DC resistance of your speakers to do the calculation

P = V x I

I = V / R

so for 6 ohm ( dc ) speaker I = 0.5Volts / 6 ohms = 0.0833Amps

0.0833Amps x 0.5 volts = 0.0416 watts

you will have to do this for you own speaker DC res & offset measurement

So even though it's good to aim for a low value you can see from my typical example that even quite high values are not harmful.

mike
 
#405
mastertech said:
film caps

Mastertech😎
Click to expand...

Yes, if caps can't be avoided in a practical way (like on the output of a single voltage delta-sigma dac), styroflex caps are the best (IMO and IME) that can be used on the signal path.

Just today in the morning I went to order some PCBs on one of the local parts stores around here.
This store is old, and sometimes I find amazing things there, talking with the guy.
Just bought today these 0,3uF/63V (+/-2%) styroflex caps.
Oh glory, oh joy... 0.4 € each. 😎
 

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#410
PauSim said:
Nice caps, Carlos. What´s the name of that old store? Is it Minitron or Radiolux?

Thanks.
Click to expand...

Total, near Areeiro in Lisbon.
Hey Paulo, you are not going there and buy the full stock, are you? 😀

They had 0.36uF, but only 6 caps... the man told me he used to have these ones on values up to 1.2uF. 😱
When I need small values, in the pF range, I go to this store, they always have styroflex caps (the transparent ones), while on other places they only have ceramics. :dead:
Today I asked what was the highest values he had for styroflexes, and he showed me these 0.3uF and 0.36uF (which he only had a few).

Jacco, these must be old stock, as he told me that this 40 cent price is while he has them, because (his words) "these caps must cost much more these days"...
 
#411
Oh, I know that store for some time. I´ve bought a few things there. Friendly people (and patient) 🙂 .

Well, thanks anyway.

Edit: Don´t worry, I won´t buy the caps full stock 😀

BTW, when you´re looking for custom inductors and transformers for a very low price go to Retralinhas. The old man also rewires loudspeaker drivers (just remember him to wire both drivers in phase and to not use any varnish).

Cheers

Apologies for hijacking this thread.
 
#412
Today I replaced the C9 47 uf green electro with a Panasonic FC series 220 uf 35 volt electro.

I tried BC N series 10uf in place of C 4 and C5 but without 100 hour burn in it was inconclusive so I removed them entirely for the time being.

I have listened to it and it sounds more neutral than previously and is now similar to my PSS 600 (Pro A/B 150/150 Bjt).

I suspect C 4 and C5 effect is subtle and need to be carefully selected

Macka
 
#413
Hi Macka

Have you tried the Blackgates yet?

I fitted some 100uf standard types to C4 and C5 that were left over from a mod to my 55N+. I've also fitted a 47uf Blackgate N type at C9.

I've been listening to them this weekend and think that I can hear some definite improvement to the overall sound and especially with the lower end. I've also got two modules that don't have the mod so I'll be comparing them later today hopefully but I've got to drill and attach these modules to the heatsinks and then wire everything up. Once I've done a direct comparison of standard vs. with blackgates I can offer something more conclusive.
 
#415
KLe said:
Hi all
My friend, Ian, has since emailed me and reported the following criticism

'I do have one criticism in that I felt it lacked some "sparkle" in the top end.'

As good as the amp is, it would appear there is still more that can be done, to extract absolutely everything from this amp.
Click to expand...

I feel that the 1nF cap from input to ground is (at least in part) responsible for this.
Those of you who are :smash: with the amp, try reducing this cap for something around 200pF.
No ceramics, please.
 
#417
Macka,

I suspect you could achieve what you are after by using a 0.22uF film cap as the LTP bootstraps, and cross coupling them to the emitter of the OPPOSITE emitter follower. It should be rated to at least 125V.

Used in this way, the bootstrap capacitance is over 2000 times more effective than the present configuration. Thus, 47uF need only be replaced by 0.022uF, so that from a charge storage POV 0.22uF would in fact be the equivalent of 470uF in the present arrangement.

The high surge currents on the larger bootstrap are possibly overloading and destroying the emitter followers.

It's just an educated guess, as I've not seen the schemat and am surmising from the conceptual diagram only.

Cheers,

Hugh
 
#418
macka said:
Do not use larger bootstapping capacitors than specificed.

I did and I think it is broken..at least for the time being.:bawling: :bawling: :bawling: :bawling: :bawling: :bawling: :bawling: :bawling: :bawling: :bawling: :bawling: :bawling:
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Sorry to hear about that Macka. I'm sure you'll have it back up and running in no time with the help of Greg and other helpful folks.

It may or may not be relevant but I'm using 100uf's for C4 and 5 which are the bootstrap C's. No incidents as of running in this config for several hours. You've got me a little paranoid though now and I'd like to hear from Greg or others before continuing with them just in case.

How did your's fail? Was it working one minute and not the next or did it simply fail as soon as you turned it on?
 
#419
AKSA said:


I suspect you could achieve what you are after by using a 0.22uF film cap as the LTP bootstraps, and cross coupling them to the emitter of the OPPOSITE emitter follower. It should be rated to at least 125V.

Used in this way, the bootstrap capacitance is over 2000 times more effective than the present configuration. Thus, 47uF need only be replaced by 0.022uF, so that from a charge storage POV 0.22uF would in fact be the equivalent of 470uF in the present arrangement.
Click to expand...

If you couple the bootstrap to the opposite emitter of the emitter follower , you will not producing any bootstrapped efect anymore , actually quite the opposite, because the signal in the opposite emitter will be in phase opposition with the signal at the base of the emitter follower.

So the increase in gain that can be achieved by the bootstrap , is completely lost!
 
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