Converting a Threshold S300 to SA/3?

Redwingnine · 25th January 2012, 08:30 PM

I would like to be able to convert a Threshold S300 to a SA3. From looking at the manuals, it looks like the amps are very similar.

Was looking for input as to if this is possibe? The speakers I'm using seem to work fine with a SA/3 I tried out on them (loves the high current).

Thanks for any help.

seng · 26th January 2012, 02:56 AM

I just convert my SA3 to S300 , if you want convert S300 to SA3, it only need to changed the supply voltage from +- 62 V to +- 34V (the original transformer had this wiring) and adjust the VR5K to the proper bias for the out put transistors (totat 2.2A for each channel).

analog_sa · 26th January 2012, 06:10 AM

Don't think all S300 transformers have this option though.

Redwingnine · 26th January 2012, 09:59 PM

Thanks much for the feedback. My S300s are optical bias types, so the trasformers should support this.

Curious as to why you converted to S300? Do you need the extra voltage for your speakers? I have found that the Class A output to sound better overall with my speakers.

seng · 27th January 2012, 07:11 AM

Yes, class A is better, so I had Threshold SA3 & T100, but SA3 can converted to S300 to drive my Dynaudio Speakers.
Besides,please replaced the 4pcs rail fuse to 8A after you converted to SA3.

Redwingnine · 5th February 2012, 12:32 PM

Completed the conversion of the first of two S300 to SA/3. Also changed out the emitter resistors.

The bias was a bit tricky, but it did stay at the new setting after a couple of tries.

I continue to be amazed at just how different (and better) tha amp sounds runnig in class A. It seems that most speakers are quite happy with 50 watts in class A. The speakers seem to have more bass heft running class A, and the reduced distortion is audible, no question.

This is one my favorite amps from Nelson. It just sounds like music.

Zen Mod · 5th February 2012, 12:48 PM

just be sure that that Graetz cooling plate on top of caps isn't too hot

everything above hand temp is too much for caps

relocate Graetz on back plate , if needed

Redwingnine · 5th February 2012, 03:48 PM

Quote:

Originally Posted by Zen Mod

just be sure that that Graetz cooling plate on top of caps isn't too hot

everything above hand temp is too much for caps

relocate Graetz on back plate , if needed

The chassis, plate, and internel layout of the S300 and SA/3 iis identical, so no worries there.

Class A is definately the way to go if the speakes support it.

PKI · 5th February 2012, 11:19 PM

and can S200 be converted in to class A amp SA/something? Thanks.

Redwingnine · 6th February 2012, 02:36 AM

Quote:

Originally Posted by PKI

and can S200 be converted in to class A amp SA/something? Thanks.

The short answer is, no, do not think so. The trnsformer in S200 is only 400VA, and I am not sure what other rails are on it.

You could check with Jon S. ay Vintage Amp Repair to ask.

25th January 2012, 08:30 PM	#1
Redwingnine diyAudio Member Join Date: Apr 2010	Converting a Threshold S300 to SA/3? I would like to be able to convert a Threshold S300 to a SA3. From looking at the manuals, it looks like the amps are very similar. Was looking for input as to if this is possibe? The speakers I'm using seem to work fine with a SA/3 I tried out on them (loves the high current). Thanks for any help.

5th February 2012, 12:48 PM	#7
Zen Mod diyAudio Member Join Date: Jan 2003 Location: ancient Batsch , behind Iron Curtain	just be sure that that Graetz cooling plate on top of caps isn't too hot everything above hand temp is too much for caps relocate Graetz on back plate , if needed __________________ my Papa is smarter than your Nelson ! tnx to clean thread ; Cook Book ; PSM LS Cook Book ; Baby Diyaudio FORUM ; BAF Forum & Gallery;I'm dumb

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

Similar Threads
Thread	Thread Starter	Forum	Replies	Last Post
Upgrade and restore Threshold S300	aspiens	Pass Labs	5	4th October 2011 08:25 AM
Threshold s300 Amp Power on Thud	nellson	Pass Labs	16	30th August 2010 05:57 PM
Threshold SA/ and SA/e series monoblocks	gigi.vassallo	Pass Labs	0	6th January 2010 07:07 PM
Threshold S300 offset issues	FootFungus	Pass Labs	5	15th December 2009 12:58 AM
Threshold S300 output transistors help	jewilson	Pass Labs	12	24th June 2002 07:44 AM

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

26th January 2012, 06:10 AM	#3
analog_sa diyAudio Member Join Date: Aug 2002 Location: Sofia	Don't think all S300 transformers have this option though.

26th January 2012, 09:59 PM	#4
Redwingnine diyAudio Member Join Date: Apr 2010	Thanks much for the feedback. My S300s are optical bias types, so the trasformers should support this. Curious as to why you converted to S300? Do you need the extra voltage for your speakers? I have found that the Class A output to sound better overall with my speakers.

5th February 2012, 11:19 PM	#9
PKI diyAudio Member Join Date: Aug 2011	and can S200 be converted in to class A amp SA/something? Thanks.

Currently Active Users Viewing This Thread: 1 (0 members and 1 guests)