Sun SV-2A3 mod - JKT - Tube DIY Asylum

Sun SV-2A3 mod

Posted by JKT (A) on September 8, 2010 at 16:58:43

Hi, I thought some here might be interested in some mods that I recently performed on my Sun SV-2A3 amp. I built the amp several years ago and in that time it has mostly sat on it's shelf. The sound was a little too polite for me. This spring I proposed building a SET 300b amp for a friend. He wanted to know what it would sound like. I suggested that as a proof of concept, I could rebuild my Sun with the front end that I had proposed to him. I ordered a pair of Lundahl 1690 input transformers, a pair of Kevin's stepped attenuators and four CCS kits from K&K Audio (making Kevin happy) and got started. The input stage now consists of the input trannies, tantalum series resistors and the attenuators connected with OCC silver wire to the grids of the 6SN7. I changed the operating point of the input tube to 120V plate/4.5mA bias per side using a pair of red LEDs for the bias voltage and CSS plate loads. The input is still direct coupled to the driver, but the driver is now a 6BX7GT. The driver tube is operated at a lower voltage than I would normally run a 6BX7, ~125V plate to cathode to allow for enough swing for the output tubes and headroom for the CCS. A bias current of 19.5mA/side yields a plate voltage of ~260V with 6.49K cathode resistors bypassed with Blackgates. The lower Rp of the 6BX7 allowed for decreasing the output tube grid leak resistor to 75K. That should make for a happier output tube. As with the input stage, the driver stage uses a CCS as a plate load. With a heavier filament current draw, I thought it prudent to add a separate filament transformer the 6BX7. This also allowed me to bias the filament up 150V. The change in the amp's character was dramatic. This amp now gets up and boogies. No longer the polite Japanese amp. If anyone is interested in pictures there are some posted here: http://www.raleighaudio.com/tracy.htm

"It is better to remain silent and thought a fool, then speak and remove all doubt." A. Lincoln

This post is made possible by the generous support of people like you and our sponsors:

Topic - Sun SV-2A3 mod - JKT 16:58:43 09/8/10 (2)

RE: Sun SV-2A3 mod - Palustris 12:25:07 09/9/10 (1)

RE: Sun SV-2A3 mod - JKT 15:38:40 09/10/10 (0)

FAQ

Post a Message!

Forgot Password?

Moniker (Username):
Password (Optional):
	Remember my Moniker & Password (What's this?) Eat Me
E-Mail (Optional):
Subject:

Message:	(Posts are subject to Content Rules)

Optional Link URL:
Optional Link Title:
Optional Image URL:
Upload Image:
E-mail Replies:	Automagically notify you when someone responds.

To view your new posting or follow-up, click on the RELOAD or REFRESH button on your browser.