Simplistic NJFET RIAA - Page 750 - diyAudio
Go Back   Home > Forums > Source & Line > Analogue Source

Analogue Source Turntables, Tonearms, Cartridges, Phono Stages, Tuners, Tape Recorders, etc.

Please consider donating to help us continue to serve you.

Ads on/off / Custom Title / More PMs / More album space / Advanced printing & mass image saving
Reply
 
Thread Tools Search this Thread
Old 6th April 2012, 04:11 PM   #7491
Salas is offline Salas  Greece
diyAudio Chief Moderator
 
Salas's Avatar
 
Join Date: Oct 2002
Location: Athens-Greece
Yours are Philips, Teabag's are Fairchild with unusually high Hfe median. Your parts are normal.
  Reply With Quote
Old 7th April 2012, 01:36 AM   #7492
Djinn is offline Djinn  Norway
diyAudio Member
 
Join Date: Mar 2010
Default A thousand and one questions and ideas

I can always use these Philips BC550C then, but is it worth it to one time later change them in to Fairchild? I have seen one distributor that has them, and they are slightly more expensive than On Semi's that I have also found. Well if I am going to do it good why not take it all the way?


And I will use this riaa with a Denon DL-160 on a Rega Planar 3 together with a Shure V15III and SME series III tonearm on a heavily modified Lenco L75 that I am still working on.


PS! I am still wondering about the 1M resistor in the Riaa, and what to put in, and what works best together? The metal vs. carbon and low ppm. I have all the resistors in Shinkoh and in matched pairs except the 1M one and the 1.2K and the 47K is not matched and these are in 1W. I have alot of the values and in matched pairs in PRP and Takman REX and REY + Amtrans AMRG 1M and the Vishay Z-foil in 6.8K and in 47K.

The pictured capacitors are the ones I had in mind for the riaa, and they are russian silver mica crM3-5 combined and matched in 0.3% accuracy in 47nF and 15.330nF, it took some time to do I can tell you so I hope it will be worth it.

One of the countlees smart ideas I found here was the post: 7067 and the eylets that made it easier to change resistors. I will try to imitate this by using some copper sleeves made for crimping on wire ends (good quality ones). I am thinking of using these "tubes" through the board permanetly so I think they have to be of copper and not brass does anyone have any thoughts on this?


My main loudspeakers I use together with a chinese tube amp ( Music Angel KT 88) are currently under a rebuild I found here: http://www.troelsgravesen.dk/Dali800.htm so I have to use a headset evaluating the progress with the riaa.

PS! the crossover in the speaker modification will bee slightly modified in regards to capacitors (some russian teflon and obbligato premium) the coils are the same as in Mr. Gravesens modification.
Attached Images
File Type: jpg Riaa caps.jpg (120.0 KB, 226 views)

Last edited by Djinn; 7th April 2012 at 02:05 AM.
  Reply With Quote
Old 7th April 2012, 03:10 AM   #7493
Salas is offline Salas  Greece
diyAudio Chief Moderator
 
Salas's Avatar
 
Join Date: Oct 2002
Location: Athens-Greece
Headphones are a trusty evaluation tool. But they have to be the neutral kind to judge well. Use AMTRANS 1M. If you want good hfe, lowest base spread resistance and noise, higher Early voltage, although not critical in the common base BJT part of the cascode (BC550's role) locate a Japanese exotic.Like Hitachi 2SC2545,6,7 E or F.
  Reply With Quote
Old 7th April 2012, 05:01 PM   #7494
Djinn is offline Djinn  Norway
diyAudio Member
 
Join Date: Mar 2010
Default Amtrams it is then

I will use the Amtrans 1M thanks for the input. I will try to get the Hitachi 2SC2545,6,7 E or F, but I am thinking that this is most noticable in a Low MC version or am I totally wrong?

I will be building one of the Low MC versions to I expect, so it will be very interesting to hear the difference between the standard BC550C and the Hitachi 2SC2545,6,7 E or F.

With kind regards

Martin
  Reply With Quote
Old 7th April 2012, 05:55 PM   #7495
Salas is offline Salas  Greece
diyAudio Chief Moderator
 
Salas's Avatar
 
Join Date: Oct 2002
Location: Athens-Greece
You will let us know if you can pick up any difference, as I said its not that critical there, regardless the version. I just let you know what is highest spec since you put an expensive build effort and you ask about BJTs anyway. If you can't locate any of those special transistors, 2SC2240BL Toshiba is easier to get, still ~1/3 Rbb' than BC550. The Japanese ones got their pins different, remember to check out if exchanging types.
  Reply With Quote
Old 7th April 2012, 06:48 PM   #7496
diyAudio Member
 
keantoken's Avatar
 
Join Date: Aug 2006
Location: Texas
Blog Entries: 2
The BC550C will do better at low Vce and may have better PSRR. This is because the C2545 is a high-voltage transistor so C-B leakage increases.
  Reply With Quote
Old 7th April 2012, 06:51 PM   #7497
Salas is offline Salas  Greece
diyAudio Chief Moderator
 
Salas's Avatar
 
Join Date: Oct 2002
Location: Athens-Greece
What about 2SC1815 in your opinion? Same low Rbb as 2SC2240, but 50V Vce.
  Reply With Quote
Old 7th April 2012, 06:54 PM   #7498
Salas is offline Salas  Greece
diyAudio Chief Moderator
 
Salas's Avatar
 
Join Date: Oct 2002
Location: Athens-Greece
2545 noise figure is given @ 6V Vce by the way.
  Reply With Quote
Old 7th April 2012, 07:07 PM   #7499
diyAudio Member
 
keantoken's Avatar
 
Join Date: Aug 2006
Location: Texas
Blog Entries: 2
The 2SC1815 has better Vcesat parameters. What I'm looking at is the Ic vs Vce curves. For the C2240 the curves straighten out before .5V Vce, this is very good. For the C2545, they straighten only after about 4V; I wouldn't use it in a current mirror. These don't have much to do with the Early voltage at above 4V Vce, which will determine PSRR as long as you don't go too low. It is not necessarily possible to tell which will have less leakage above these voltages from the datasheets. Whichever has the least slanted lines...
  Reply With Quote
Old 7th April 2012, 08:25 PM   #7500
Djinn is offline Djinn  Norway
diyAudio Member
 
Join Date: Mar 2010
Default BC550C Alternative.

Is it so then that the Toshiba 2SC2240BL alternative that you give here Salas is the better one and even better than the 2SC1815BL if I get all this the correct way?

And do you all think the difference against the BC550C will be noticeable in the high gain MC version 56/60 db, and maybe even with the 43db I am starting with now?


I can at least say that the Hitachi 2SC2545,6,7 E or F is not so easy to find so these alternatives makes it easier.


“vgeorge” has this quote in his posts that I really do believe in: “ "Without deviations from the norm, progress is not possible" - Frank Zappa”

PS! Vgeorge I will not steal this, it is a one time incident



With kind regards


Martin

Last edited by Djinn; 7th April 2012 at 08:28 PM. Reason: Easier to read.
  Reply With Quote

Reply


Hide this!Advertise here!
Thread Tools Search this Thread
Search this Thread:

Advanced Search

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Trackbacks are Off
Pingbacks are Off
Refbacks are Off



New To Site? Need Help?

All times are GMT. The time now is 04:54 PM.


vBulletin Optimisation provided by vB Optimise (Pro) - vBulletin Mods & Addons Copyright © 2014 DragonByte Technologies Ltd.
Copyright 1999-2014 diyAudio

Content Relevant URLs by vBSEO 3.3.2