NCD questions

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#121
Bgt said:


Well T, I own them all but I like to try/investigate(and sell them eventually).
I mean its nice people/designers/DIY's have opinions when they test them but I always want proof. Someone else's truth does not need to be mine.
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I already own over 7 different amps Bert😀 I thought about selling most of mine but never bothered, I keep collecting them, something new or a different design comes along.
Its now time for me to trust others opinions😉
 
#122
t. said:


I already own over 7 different amps Bert😀 I thought about selling most of mine but never bothered, I keep collecting them, something new or a different design comes along.
Its now time for me to trust others opinions😉
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T, you're right about trusting others. But I am a designer myself(f.i. HF/UHF RFID+antenna systems)so for me it is easy to do(equipment wise). And above all......I am adicted to sonics(the proper ones)😀
 
#124
Bgt said:
An externally hosted image should be here but it was not working when we last tested it.


UCD 400
0.2V/div 0,2us/div so is about 475khz.(this 1 is the amp. with groundlift resistors, 1 transf. and 2 supply rails, BTW the UCD dual/mono has exactly the same ripple 😀 )

So UCD has 1V ripple and NCD nearly 6V.
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Hi Bgt,

Nice work up till now, keep it up....

But now you have really scared me with measuring the ripple ...I use the Great Heil tweeter and a pair of them will cost me 1,200 Euros if burnt.

And since they are 100dBs sensitive, if the NCD will output such a high ripple, i wouldn't like my tweeters toasted. Any way to get round it please ?

Many thanks,

Nikos:hot:
 
#125
Bgt said:
An externally hosted image should be here but it was not working when we last tested it.



2v/div and 0,5uS/div.
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Hi Nikos

6Vpp = 2,1Vrms

Residual Power P = 2,1 ^ 2 / 8 = 0.57 W

So you will hardly get them 'toasted' 😀

This is for flat impedance response at 500 kHz, which i presume your Heil Air Motion Transformers have. In normal dynamic tweeters the coil inside the tweeter is responsible for a impedance lift above 20 kHz, so at 500 kHz, the residual power is almost zero.

If your tweeters are the original Oskar Heil types, they will be 2.7 Ohms impedance, but in that case the 6Vpp will start to diminish, so power is lowered accordingly.

All the best from

Lars
 
#126
Lars Clausen said:



Hi Nikos

6Vpp = 2,1Vrms

Residual Power P = 2,1 ^ 2 / 8 = 0.57 W

So you will hardly get them 'toasted' 😀

This is for flat impedance response at 500 kHz, which i presume your Heil Air Motion Transformers have. In normal dynamic tweeters the coil inside the tweeter is responsible for a impedance lift above 20 kHz, so at 500 kHz, the residual power is almost zero.

If your tweeters are the original Oskar Heil types, they will be 2.7 Ohms impedance, but in that case the 6Vpp will start to diminish, so power is lowered accordingly.

All the best from

Lars
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Thanks Lars,

Thats comforting...Yes i have the original Great Heils at 4 ohms "nominal" impedance with just a cap at 3.3mF and no kind of protection at all.

I hope to have the amps up and running by the end of the week. The problem is finding a nice cabinet to do them justice...

Regards,

Nikos
:angel:
 
#132
Bgt said:
why should you want to change the freq? After having it playing for about 200 hours I think the amp. sounds absolutely faboulous. No squaeks, plops or whatever. (with prot. relay in output). Also quite an easy load on a 10k stepper volume pot.
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Hi Bgt
That's excellent 😀
Would you nearly be ready to give a review/evaluation of the NCD1 in your system 😎

thanks
KL
 
#133
KLe said:

Hi Bgt
That's excellent 😀
Would you nearly be ready to give a review/evaluation of the NCD1 in your system 😎

thanks
KL
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Hi Kle,

I am still testing but I am not there yet. I want to do justice to the amps. but have very little time at the moment. Put a lot of time in building it and posponed everything else. Time is not always on my side and I do need sleep:angel:
What is very nice about the amps. is the open spacious sense you'll get. Sometimes it looks like it is a bit more present(sonic wise) than the UCD's but than on another bit of music I just wont hear any difference.
 
#138
Hi Kle,

Well, I really don't have any noise issues left. Remember my speakers are 86Db and 92Db/W/m. Looking on the scope shows more noise than the UCD's(but this is marginal) but in reality with normal low efficient speakers it is no problem at all. Humm is gone. So nothing to complain about really, the amps. sound great. Just want to test them with the LM 4562 to see if there is any difference. Can try some AD8620's also.
 
#139
Bgt said:
Hi Kle,
Well, I really don't have any noise issues left. Remember my speakers are 86Db and 92Db/W/m. Looking on the scope shows more noise than the UCD's(but this is marginal) but in reality with normal low efficient speakers it is no problem at all. Humm is gone. So nothing to complain about really, the amps. sound great. Just want to test them with the LM 4562 to see if there is any difference. Can try some AD8620's also.
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Hi Bgt
That's excellent 😀 My speakers are around 91/92db efficient 🙂
Are you using the LM4562 and AD8620 as preamps?

I have reading about Carlos's AD815 preamp and Greg Ball's SKpre. Both look very impressive. An issue with Carlos's pre is a small amount of DC offset. Everyone who builds it simply rave about how good it is 🙂

Having said that, I plan to try Greg's initially. It has DC offset adjust so any DC offset can be set to 0 🙂 Greg's pre is so new that there are no reviews yet. So, I will let you know what's like. It is very quiet, at < -120db noise, and the output impedance is around 50ohms. This should suit Lar's NCD1 nicely 🙂

Then I will try Carlos's design. I am going to do it this way to just to have an initial reference point. 🙂

thanks
KL
 
#140
KLe said:

Hi Bgt
That's excellent 😀 My speakers are around 91/92db efficient 🙂
Are you using the LM4562 and AD8620 as preamps?
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You mean preamps on the poweramps? Because my main pre is passive. The UCD's have 8620's on them and the NCD the LM6172 I believe.
Will have a look at this preamp., Greg Balls SKpre, you mention.
Missed this 1.
 
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