SCA-35 Dynaco - Page 3 - diyAudio
Go Back   Home > Forums > Amplifiers > Tubes / Valves

Tubes / Valves All about our sweet vacuum tubes :) Threads about Musical Instrument Amps of all kinds should be in the Instruments & Amps forum

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 18th December 2006, 01:51 AM   #21
diyAudio Member
 
Join Date: Apr 2004
Location: Monroe Township, NJ
Quote:
Originally posted by stokessd
If you don't need the tone and balance controls, bypass them, the unit will sound a whole lot better without them.

Sheldon,

If the tone control circuitry goes, wouldn't the owner/thread originator be better off switching the 7199s out and 12DW7s, ala ST35, in? The extra gain the 7199's pentode section provides is no longer needed.

The power trafo has 2X 6.3 V./2.5 heater windings. Phase up the heater windings and connect them as 12.6 VCT/2.5 A. 4X EL84s as series connected pairs draw 1.52 A. A pair of 12DW7s draw 0.3 A. That adds up to 1.82 A., leaving 680 mA. on each side of the CT. That's plenty to full wave CT rectify with a MBR20200CT twin Schottky diode, cap. filter, and low drop out regulate into the 6.3 V./600 mA. of DC needed by the 12AX7 phono section tubes. I DETEST AC on phono section heaters.
__________________
Eli D.
  Reply With Quote
Old 19th December 2006, 06:48 PM   #22
diyAudio Member
 
stokessd's Avatar
 
Join Date: Nov 2002
Location: Grantham, NH
Good point Eli, the one advantage to just bypassing the tone and balance control is that the mod is easy to do and easy to reverse without any other significant changes to the amp.


Sheldon
  Reply With Quote
Old 19th December 2006, 08:46 PM   #23
diyAudio Member
 
Join Date: Jun 2004
Location: Wylie, Texas
One thing that may have been overlooked is the preamp for the cartridge.... unless the turntable has one built in.

On speakers, tube amps tend to have lighter sounding bass than transistor. For that reason and the power, it's good to use larger 2-ways or 3-ways. Vintage AR or Advents (or others) with 8 inch or larger woofers usually have enough efficiency and bass. I used to have the Advent 10" 2-way.... wish I had never got rid of it!
  Reply With Quote
Old 19th December 2006, 08:47 PM   #24
SY is offline SY  United States
diyAudio Moderator
 
SY's Avatar
 
Join Date: Oct 2002
Location: Chicagoland
Blog Entries: 1
The SCA35 has a phono stage. It's not a great one, but it does work.
__________________
You might be screaming "No, no, no" and all they hear is "Who wants cake?" Let me tell you something: They all do. They all want cake.- Wilford Brimley
  Reply With Quote
Old 19th December 2006, 11:51 PM   #25
diyAudio Member
 
Join Date: Apr 2004
Location: Monroe Township, NJ
Quote:
Originally posted by SY
The SCA35 has a phono stage. It's not a great one, but it does work.

SY,

What say you about replacing the Dyna circuit with the "classic" circuit found in RCA Receiving tube manuals?
__________________
Eli D.
  Reply With Quote
Old 20th December 2006, 12:47 AM   #26
SY is offline SY  United States
diyAudio Moderator
 
SY's Avatar
 
Join Date: Oct 2002
Location: Chicagoland
Blog Entries: 1
That's a step up. Still not particularly good, but not as actively bad.
__________________
You might be screaming "No, no, no" and all they hear is "Who wants cake?" Let me tell you something: They all do. They all want cake.- Wilford Brimley
  Reply With Quote
Old 1st November 2009, 07:21 PM   #27
bulgin is offline bulgin  South Africa
diyAudio Member
 
Join Date: May 2006
Hey Guys

Look wot Santa brought

I got this sweet little SCA-35 last Saturday from a local flea market. About US$20 is all it cost.

I spent last weekend cleaning pots and chassis, tubes and sockets and input jacks and when everything was sparkling clean again, fed it some 220V through 40, 60 and 100W lightbulbs and have been listening to it now for a couple of days - right now with my Troughline 11 tuner.

I've had to replace the fuseholder as it had no cap, as well as fitting some new, slightly taller chassis feet.

Its long slumber seems not to have affected it too bad but I'll have to start thinking about renewing some vitals soon.

bulgin
Attached Images
File Type: jpg IMG_0005.JPG (79.8 KB, 463 views)
File Type: jpg IMG_0007.JPG (103.9 KB, 447 views)
  Reply With Quote
Old 1st November 2009, 07:27 PM   #28
bulgin is offline bulgin  South Africa
diyAudio Member
 
Join Date: May 2006
Another pic of my pretty one

bulgin
Attached Images
File Type: jpg IMG_0005.JPG (95.3 KB, 448 views)
  Reply With Quote
Old 1st November 2009, 11:45 PM   #29
kevinkr is offline kevinkr  United States
diyAudio Moderator
 
kevinkr's Avatar
 
Join Date: Sep 2004
Location: Boston, Massachusetts
Blog Entries: 6
Looks pretty clean.. Nice,, I would definitely look into replacing the electrolytics in your baby soon. Should be available from dynakits here: Dynakitparts.com amongst others.
__________________
"Extraordinary claims require extraordinary evidence." - Carl Sagan
  Reply With Quote
Old 2nd November 2009, 12:32 AM   #30
frugal-phile(tm)
diyAudio Moderator
 
planet10's Avatar
 
Join Date: Oct 2001
Location: Victoria, BC, NA, Sol III
Blog Entries: 5
Bulgin,

What a steal... good on you.

dave
__________________
community sites t-linespeakers.org, frugal-horn.com, frugal-phile.com ........ commercial site planet10-HiFi
p10-hifi forum here at diyA
  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


Similar Threads
Thread Thread Starter Forum Replies Last Post
Dynaco ST-120 botrytis Solid State 21 18th August 2012 03:30 AM
preamp suitable for Dynaco st-70- OTHER than dynaco namatjira Tubes / Valves 3 22nd December 2011 01:21 AM
Dynaco ST-410 Amp Creelove Solid State 7 22nd July 2010 05:08 AM
Dynaco A10 XO wising Multi-Way 0 24th March 2009 03:16 PM
dynaco st 70 c3 dcb50 Introductions 1 30th September 2008 11:20 PM


New To Site? Need Help?

All times are GMT. The time now is 01:24 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