Simplistic NJFET RIAA - Page 925

Salas · 8th February 2013, 05:46 PM

3-5ma

Salas · 8th February 2013, 05:58 PM

Quote:

Originally Posted by Tea-Bag

I am going to start hoarding K369BL

You are going to enjoy a very noticeable reduction on noise. Not only it refers to ground but uses much less current through the cascode BJT which brings it to better current noise and linearity region. Also 2 K369BL are ideal for LMC since the extra capacitance won't bother the bandwidth with such low coil resistance carts. The penalty is the more defined input overload margin (VPP after first stage gain x100 plus) given the RIAA 20dB rise and vinyl hitting over 0dB modulation its something to know how to handle when matching carts and gain. A 58dB single K369BL with 0.9mV cart did not manage to go clipping with dynamic 45rpm reissues is my harder real life test up to now.

buzzforb · 8th February 2013, 06:03 PM

Salas,
As a side note, the Bf245A is difficult to source, stateside, but the 245C, which is availalble, needs to be degenerated by about 35-40 homs. I have 33 and I think it reduces current to 6-7mA. Might be noteworthy to future builders of the folded version.

Salas · 8th February 2013, 06:21 PM

Its everywhere in EU, I could find it in local stores even, maybe harder in the US? A BF245B can be degenerated with less resistance also. A K117GR is acceptable also. Any low noise low capacitance circa 5mA JFET in other words. See if there is something under 20nVrtHz J series American chopper JFET for there is another guide. Those who gonna make SSLVs for it gonna have K117GR spares nonetheless. Since it only takes shorting s&g pins which are sequential in most pin outs when the IDSS is right unaided by degeneration, using several types should be a breeze.

merlin el mago · 8th February 2013, 06:24 PM

Quote:

Originally Posted by Salas

3-5ma

Yep

buzzforb · 8th February 2013, 07:40 PM

Quote:

Originally Posted by Salas

Its everywhere in EU, I could find it in local stores even, maybe harder in the US? A BF245B can be degenerated with less resistance also. A K117GR is acceptable also. Any low noise low capacitance circa 5mA JFET in other words. See if there is something under 20nVrtHz J series American chopper JFET for there is another guide. Those who gonna make SSLVs for it gonna have K117GR spares nonetheless. Since it only takes shorting s&g pins which are sequential in most pin outs when the IDSS is right unaided by degeneration, using several types should be a breeze.

OK. I was unsure of how important that specific part was to performance. Does the degeneration add noise?

merlin el mago · 08:46 PM

Quote:

Originally Posted by merlin el mago

Sorry, exactly Ricardo have five 7.8mA and four 7.7mA K170, could I use?

Quote:

Originally Posted by Salas

It will not go too far off I suppose.

Wich is the best position for each Idss, or is the same?

Salas · 9th February 2013, 09:36 AM

Quote:

Originally Posted by buzzforb

OK. I was unsure of how important that specific part was to performance. Does the degeneration add noise?

Yes but insignificant when talking low ohms in that position. Mainly the Jfet needs be medium impedance to match the Leds own for better PSRR and their 1mF cap to be good in shorting the noise and hum.

Salas · 9th February 2013, 09:37 AM

Quote:

Originally Posted by merlin el mago

Wich is the best position for each Idss, or is the same?

Same.

buzzforb · 9th February 2013, 09:46 AM

Quote:

Originally Posted by Salas

Yes but insignificant when talking low ohms in that position. Mainly the Jfet needs be medium impedance to match the Leds own for better PSRR and their 1mF cap to be good in shorting the noise and hum.

New version gets fired up today. Got dual 175VA instead of 50VA. It will all be cased up, with seperate psu. Also have some 369 coming for comparison.

One quick question. In main pdf, you spec SSlV 1.5. Does this outperform 1.1 which i am currently usiing?

8th February 2013, 06:03 PM	#9243
buzzforb diyAudio Member Join Date: Oct 2010 Location: Burlington, NC	Salas, As a side note, the Bf245A is difficult to source, stateside, but the 245C, which is availalble, needs to be degenerated by about 35-40 homs. I have 33 and I think it reduces current to 6-7mA. Might be noteworthy to future builders of the folded version. __________________ \|F6 Kit/Trasnformer GB Sign up sheet Closed,\|Primrose GB Sign Up sheetClick Here ...Shape the sound , Man!

Thread Tools	Search this Thread
Show Printable Version Email this Page	Search this Thread: Advanced Search

New To Site?	Need Help?
Register to Participate Search Privacy Statement Contact Us	Frequently Asked Questions Did you forget your password? Mark Forums Read


	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

8th February 2013, 05:46 PM	#9241
Salas diyAudio Chief Moderator Join Date: Oct 2002 Location: Athens-Greece	3-5ma

8th February 2013, 06:21 PM	#9244
Salas diyAudio Chief Moderator Join Date: Oct 2002 Location: Athens-Greece	Its everywhere in EU, I could find it in local stores even, maybe harder in the US? A BF245B can be degenerated with less resistance also. A K117GR is acceptable also. Any low noise low capacitance circa 5mA JFET in other words. See if there is something under 20nVrtHz J series American chopper JFET for there is another guide. Those who gonna make SSLVs for it gonna have K117GR spares nonetheless. Since it only takes shorting s&g pins which are sequential in most pin outs when the IDSS is right unaided by degeneration, using several types should be a breeze.