Pré amplifier is not needed!.... thread to discussion

Status
This old topic is closed. If you want to reopen this topic, contact a moderator using the "Report Post" button.
João@AltheaMusica... thank you...here is an image from Brasil and to you

The place i have born...Rio de Janeiro city.

regards,

Carlos
 

Attachments

  • Olá João.jpg
    Olá João.jpg
    956.3 KB · Views: 170
Please, dear moderators, increase editing time to at least 30 minutes.

Post 30 should be deleted, was made once again and published as post 32.

Also we cannot correct the post tittle...this is also needed...or we cannot, or i could not make it.


I have fixed post 30 and have brought these other issues up with the webmaster. This is a busy and difficult time as we weed through some of the bugs with the new software. Your patience is appreciated. Also Carlos, it is better if you report these issues using the report a post button (red triangle at the lower left of the window) as we don't necessarily see each and every posts.

Thank you,
Cal
 
Last edited:
Hi,

@destroyer.
My network shows an input impedance that varies from ~4kOhms to 47kOhms between 0 and -63dB and ~1Mohms for -64dBto -99dB, but the Output impedance is sufficiently low (1.2kOhms, input impedance of the load should therefore be 10k<Z<100k). Every modern stage nowadays is able to drive the 4kOhms min. without any problems at all and its normally a short piece of cable from source to Pre. The high Zin for values below -63dB is rather of low interest, since normal listening will take place in a range between 0dB and -40dB.
The network uses 7stages and allows for 127 precise -1dB steps of which I use the first 100. To get really highly precise -1dB steps the resistors (BMF-types!) are manufactured to the 4 digit in tolerance. The relais are first class types speced for low level switching and the contacts are even paralleled. This way the VC performs on a level of precision, quality and sonics, that´ll be hard to equal.
After the design of this VC I designed the active stages and minimized the sonic differences when switching between passive and active. But they are hardly ever switched into the signal path. I use quite simple structured SE-JFET stages without global feedback (and no, they are not SK170 or SK389 ;) but some other verylownoise JFETs and very tightly tolerated parts).
And so it looks alike
An externally hosted image should be here but it was not working when we last tested it.


jauu
Calvin
 
Last edited:
hi all,
i have been using a John L Hood :worship: power amp design for 12 years, this is the 80watt mosfet.
this unit has a higher gain than normal (AV= 122) this gives a sensitivity at the input of 230mV, volume pot connected directly at the input, great for some of my sources, the cd output has to be attenuated.
i keep coming back to this amp i like the sound. although i have plans to do a few mods i have not got around to.

my experience with more 'normal' sensitivity input power amps, they just seem to sound that much more detailed with a preamp of 100R (or less) output impeadance, gain of 4 or so. as opposed to just passive pot.

im not convinced that this may be an effect due to the different positioning on the volume control 'feel' etc and or psycho-acoustic feedback :).

i have or thought i have had this on many different amps and setups.
 
Administrator
Joined 2004
Paid Member
Hi Carlos,
Easily changing a thread title by members is not possible for obvious reasons. As it has always been, just ask nicely and if you are the originator of the thread, your request is normally granted.

The edit time is 30 minutes, extended from the old software. If this is still not enough (and I think this is excessive), then write your reply out in a word processor or email window. Then after you have checked it out, cut 'n paste your response as a post.

We are here to help, and also to try and safeguard the integrity of the posts. After a short time that you have to check your post, it becomes locked in order to assure any responses to that post remain valid. If the post had been changed, the integrity of the site falls into question.

-Chris
 
@ burbeck
Your amplifier is very sensitive and maybe it will be overloaded with the input signal.
So I’d recommend to use a TVC as external preamp and play with the position of your amp’s volume control. I’m sure you’ll find a proper solution.

@ Calvin
You’re located in South Germany near Basel: I live in Konstanz and maybe we can have a nice conversation by phone? If you like please let me know.


Joao
 
para Carlos...

Caro Carlos


obrigado pelo quadro bonitinho do Rio … o meu segundo pais, e tenho muito saudade!!! Contente de ler o fato que você nasceu lá. Em que distrito do Rio? Os meus amigos estão vivendo em Gavea e Jardim Botanico.
Se você tiver alguma pergunta sobre o TVC você pode contatar comigo por da tarde ou o e-mail também.


Um abraco
Joao



English:


Thank you for the nice picture from Rio … my second home, and I have very much. Glad to read the fact that you were born there. In which district of Rio? My friends are living in Gavea and Jardim Botanico.
If you have any questions about the TVC you can contact me by PM or e-Mail as well.


Kind regards
Joao
 

Attachments

  • kn11.jpg
    kn11.jpg
    53.9 KB · Views: 173
I intended to change the post title... alike these words i am writing now

not the thread title.

about the edit time, it normally fit our needs.... 30 minutes use to be fine.

To use the word is not fine to me, as my word is not well adjusted and
lines results out of alignment when i paste it here...well...my own problem for sure, as i do not
know how to use word text editor.

thanks,

Carlos
 
Last edited:
Interesting Debate.

I have had a Sony XA7ES for many years now. It has extensive power supplies,variable unbalanced and fixed balanced outputs and an excellent output stage.

I have now tried 7 different good quality preamps including 2 valve pres with this player feeding AKSA 100N+ and more recently completed Aussie Amps nxV300 monoblock power amps. I have also tried a passive approach.

In every case after extensive listening I have ended up preferring the SQ via direct connection of the CDP to the amps. I now only use a pre for phono when using the turntable (Project Perspective).

A switching box would be handy and I suspect that many prefer preamps because of the quality/drive ability of CDP outputs are not up the standards of the rest of their system. I eagerly await Aussie Amps new DAC to try with the Sony. I also gather Audio Note DAC kits are good (but quite expensive). The latest issue of Aus Silicon Chip magazine also has an interesting DAC Project.
 
I have born in Copacabana..and lived there for 40 years long

Copacabana is my place.... Rua Miguel Lemos 51 was my adress..... very nice place...the best in Brazil i think.

here you have a picture from satelite....the yellow dots are the places i have lived and the hospital i have born.... i was inside the Copacabana fortification for 2 years long together my grandfather that was a civil responsable by the 305 milimeters Krupp cannon maintenance and hidraulical repair.

I am glad you like Brasil, caro João

regards,

Carlos
 

Attachments

  • Rio - Copacabana.jpg
    Rio - Copacabana.jpg
    565.9 KB · Views: 145
hi joao
i'm sorry if i did not make things clear, the amp does not have a problem its designed that way, it has a balance and a volume control, it is just a power amp.
the rated input sensitivity is 230mVfor full output, this is great for old tape machines and tuners they will drive it directly no preamp, some sources need attenuation ie cd player.
the reason i mentioned this amp is that this is unusual \ interesting, and designed by the great man John L Hood. and like i said before i keep coming back to it, sounds nice.
 
Status
This old topic is closed. If you want to reopen this topic, contact a moderator using the "Report Post" button.