My Take on an SRPP Output Stage - diyAudio
Go Back   Home > Forums > Source & Line > Digital Source
Home Forums Rules Articles diyAudio Store Gallery Wiki Blogs Register Donations FAQ Calendar Search Today's Posts Mark Forums Read

Digital Source Digital Players and Recorders: CD , SACD , Tape, Memory Card, 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
Thread Tools Search this Thread
Old 26th February 2010, 08:23 AM   #1
amc184 is offline amc184  New Zealand
diyAudio Member
amc184's Avatar
Join Date: May 2007
Location: Christchurch
Default My Take on an SRPP Output Stage

I just finished a major (by my standards) project today, an SRPP (totem pole) triode output stage for a CD player. This idea has been around for a long time, and this has been done before. I was particularly inspired by Lukasz Fikus and his site Lampizator.

I took the core SRPP circuit values from Lukasz's site, and combined it with a straightforward LM1086T-ADJ regulated filament supply and a small signal relay based mute (to replace the functionality of the muting transistors in a player's original output stage). By default it suits a TDA1541A, but it could be adapted to suit almost any DAC. This DAC is still my favourite, not just for it's sound, but for the beautifully made radial arm laser mechanisms it tends to be paired with.

I installed it in my otherwise stock Rotel RCD-855. The sound is pretty good (don't ask me to describe it more than that, airy, shimmery, what?), but not light years from what can be achieved with a carefully designed opamp based stage. It's dead silent when it should be, with a background noise level lower than the integrated amp I tested it with, which I'd credit to the tight layout and good filament supply. I'm really pleased, as this is the first project I have done with tubes, and I really had no idea of what to expect.

The only disappointment would have to be the muting relay, it's not as effective as I'd like it to be. There is still a slight power on crack, and a medium sized power off thump. I don't know if the relay is just a bit slow, or that the mute signal that drives it (which was designed for an opamp stage) just isn't present for long enough to cover the undesirable noises in a tube stage.

The total cost for this project wasn't actually too bad, probably around NZ$200. The PCB and R-core transformer were the biggest costs.

I designed the PCB using DipTrace, a program I would recommend. Some basic specs for the PCB:
- 140 x 50 mm in size
- 101 holes
- 2 layers

As for component choices, my selections were:
- Resistors : Japanese made carbon compositions (unknown brand), mainly for aesthetic reasons (a poor justification), but also because I think they are part of the 'tube sound'.
- Electrolytic capacitors : Nichicon PS and PT, good quality capacitors at a reasonable price. I did have a couple of 'teething problems' (actually small fires) with the PTs in the HV supply, as they weren't very fresh and I ran them pretty close to there ratings (320 V on 400 V rated caps). Forming them by running the whole stage for a while on my 240 V to 120 V stepdown autotransformer solved that problem though.
- Film capacitors : Illinois Capacitor's MKP series, good and cheap!
- Semiconductors : On Semi diodes and a National Semi regulator, I like to stick to brands I know and trust.

Anyway, here's some pictures and a brief write up / notes document I did on it (which make be a little bit out of date in places):
Attached Images
File Type: jpg Side on.jpg (95.0 KB, 424 views)
File Type: jpg From the top.jpg (131.7 KB, 409 views)
File Type: jpg PCBs.jpg (140.7 KB, 404 views)
Attached Files
File Type: pdf TTO Sheet A4.pdf (162.8 KB, 117 views)
  Reply With Quote
Old 26th February 2010, 01:49 PM   #2
Glowbug is offline Glowbug  United States
diyAudio Member
Glowbug's Avatar
Join Date: Feb 2006
Location: Hillsborough, NC
Very cool
The machine does not isolate us from the great problems of nature but plunges us more deeply into them. - Antoine de Saint-Exupéry
  Reply With Quote
Old 27th February 2010, 03:56 AM   #3
amc184 is offline amc184  New Zealand
diyAudio Member
amc184's Avatar
Join Date: May 2007
Location: Christchurch
Thanks Glowbug.

I've had it up and running for a couple of eight hour stretches now, so I'm fairly satisfied that it's going to be reliable. I think the major change I'll make for the next version is adding a jumper so that it can use ECC83 / 12AX7 tubes, instead of just the 6N2P it does at the moment.
  Reply With Quote
Old 27th February 2010, 10:18 PM   #4
NICKEL is offline NICKEL  New Zealand
diyAudio Member
Join Date: Aug 2005
Smile SRPP Output Stage

Great work!
If you are making any more boards, I be interested in a couple of sets.
  Reply With Quote
Old 28th February 2010, 12:09 AM   #5
amc184 is offline amc184  New Zealand
diyAudio Member
amc184's Avatar
Join Date: May 2007
Location: Christchurch
Thanks Nickel.

I haven't really got any spares, since it was a prototype I only ordered a few. However, if there is enough interest I may consider doing a group buy. Boards like this aren't that expensive, around US$4 per single channel PCB if there are a few keen people, or less if there are more than a few.

Whereabouts in New Zealand are you based?
  Reply With Quote
Old 28th February 2010, 07:42 AM   #6
NICKEL is offline NICKEL  New Zealand
diyAudio Member
Join Date: Aug 2005
Default SRPP Output Stage

Hi amc184

Based in Wellington.

I'd be in for a couple of sets. Lets hope there's a bit of interest.


  Reply With Quote
Old 28th February 2010, 09:04 AM   #7
poynton is offline poynton  United Kingdom
diyAudio Member
poynton's Avatar
Join Date: Mar 2005
Location: UK
What is the transformer ??


If it ain't broke, break it !! Then fix it again. It's called DIY !
  Reply With Quote
Old 28th February 2010, 09:16 AM   #8
amc184 is offline amc184  New Zealand
diyAudio Member
amc184's Avatar
Join Date: May 2007
Location: Christchurch
A nice little R-Core from this website: VT4C. Dual 115VAC primaries, dual 220VAC (50mA each) and 6.3VAC (800mA each) secondaries, total power handling 50VA.

They're US$22 each, and shipping to New Zealand was US$9, which I thought was pretty sharp. They're compact as well, which makes fitting the tube output easier.
  Reply With Quote
Old 28th February 2010, 02:50 PM   #9
gabdx is offline gabdx  Canada
diyAudio Member
Join Date: Jan 2008
I want to build a tube SRPP output stage and I need some good regulator,
I seek help in choosing the best regulator , with less ripple and high noise rejection and stability etc ;

1. Janus regulator
2. Aikido solid stage regulator , the da-1 or something on ebay : LS-57, or LS-65
4. Lampizator style with 5U4C diode , CL(C//R)LC --- or CL(C//R)RC
5. Lampizator style with semiconductors diodes like vishay + caps+res
  Reply With Quote
Old 28th February 2010, 04:29 PM   #10
adamus is offline adamus  United Kingdom
diyAudio Member
Join Date: Apr 2008
how about the salas hv shunt as well
  Reply With Quote


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

Similar Threads
Thread Thread Starter Forum Replies Last Post
SRPP with FETS, what output stage? davidallancole Solid State 18 4th January 2008 05:39 PM
srpp input stage nhuwar Tubes / Valves 11 31st July 2007 10:03 PM
6as7 SRPP output stage Molloy Tubes / Valves 4 15th September 2006 05:39 PM
Changing 6DJ8 SRPP stage gain SSassen Tubes / Valves 0 11th April 2006 01:47 PM
Audio Note DAC4 SRPP output stage problems! bbakota2000 Tubes / Valves 5 12th June 2005 12:25 AM

New To Site? Need Help?

All times are GMT. The time now is 06:47 PM.

vBulletin Optimisation provided by vB Optimise (Pro) - vBulletin Mods & Addons Copyright © 2017 DragonByte Technologies Ltd.
Copyright ©1999-2017 diyAudio

Content Relevant URLs by vBSEO 3.3.2