Is single ended Class A better than push-pull? - 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 26th August 2005, 05:37 AM   #21
arnoldc is offline arnoldc  Philippines
diyAudio Member
 
Join Date: Apr 2003
Location: Makati
Send a message via Yahoo to arnoldc
30 watts per channel
  Reply With Quote
Old 26th August 2005, 07:20 AM   #22
EC8010 is offline EC8010  United Kingdom
diyAudio Moderator Emeritus
 
EC8010's Avatar
 
Join Date: Jan 2003
Location: Near London. UK
If you're looking for 30W PP, then you're entering a different ball game. You're slightly out of the range of EL34 (although in practice you'd never notice the power deficiency), 6550 would probably be about right. You'd have a 450-500V HT. Alternatively, 845 and 211 could easily achieve the power, but the HT would be far higher. Time for some choices about what you feel competent to make.

Oh, and as to the original question, I'm with Johan Potgieter and SY; I'd like the amplifier to be engineered so that distortion is as inaudible as possible. That usually means PP triode or UL. I can accept the use of SET with loudspeakers that are so efficient that a 4W amplifier is barely ticking over.
__________________
The loudspeaker: The only commercial Hi-Fi item where a disproportionate part of the budget isn't spent on the box. And the one where it would make a difference...
  Reply With Quote
Old 26th August 2005, 10:47 AM   #23
arnoldc is offline arnoldc  Philippines
diyAudio Member
 
Join Date: Apr 2003
Location: Makati
Send a message via Yahoo to arnoldc
Hi EC8010,

I'm no designer, and can no way make a well-engineered amp given your specs.

The 6550 is ok with me, so can you point me to a well engineered 6550 amp?

Sy, I'd still like to hear from you.

Maybe you mods can split these posts of mine into a new topic "A well-engineered amp" or something like that?
  Reply With Quote
Old 26th August 2005, 11:35 AM   #24
SY is offline SY  United States
diyAudio Moderator
 
SY's Avatar
 
Join Date: Oct 2002
Location: Chicagoland
Blog Entries: 1
Arnold, if you don't want to do a from-scratch design, one good candidate would be a UL-connected version of the Joe Curcio Stereo 70 mod. It was published in an early issue of Glass Audio and was a popular project. Full power supply regulation, constant current cascode diff amp input stage using an ECC88, EL34 output. Probably good for 25 watts, close to your target. With a slightly heftier power supply and KT88/6550 outputs, you could do 50 watts easily with the same 4300 ohm load. The only circuit change would be adjusting the bias string to give a bit higher grid bias.
__________________
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 26th August 2005, 12:03 PM   #25
EC8010 is offline EC8010  United Kingdom
diyAudio Moderator Emeritus
 
EC8010's Avatar
 
Join Date: Jan 2003
Location: Near London. UK
I'd second the Curcio suggestion. Realistically, most of the 6550 designs are based on the classic designs of the 50s and 60s, athough the Curcio design adds a certain amount of silicon support circuitry. Provided that the design is based on one of these classic designs, you really can't go far wrong. A more adventurous modern design will probably require more experience to build. The key issue, as always, is the quality of the output transformer...
__________________
The loudspeaker: The only commercial Hi-Fi item where a disproportionate part of the budget isn't spent on the box. And the one where it would make a difference...
  Reply With Quote
Old 27th August 2005, 01:28 AM   #26
amperex is offline amperex  United States
diyAudio Member
 
Join Date: Feb 2005
Location: MI
Default Depends.....

SE is best for high-efficiency speakers where PP does not quite produce the quality sonics. (why? I have no idea after building a few high quality amps). SE needs a better power supply and careful attention to the output transformer.

On the other hand, PP is great for lower efficiency speakers and does produce more power using the same tubes in same Class of operation. From an engineering stand-point, I like PP better. Best PP to date was a set of 6P5 driving a 6SN7 to 45 tubes. Sonics are wide open, relaxed without any fatigue, huge soundstage, powerful & tightly controlled bass, detailed & just wonderful sounding.
  Reply With Quote
Old 27th August 2005, 02:34 AM   #27
amperex is offline amperex  United States
diyAudio Member
 
Join Date: Feb 2005
Location: MI
Default Oh, 6550?

I should read all posts before posting.

I am almost finished building a 6550 PP amp. UL means Un-Linear to me. Triode does yeild 30 watts with 400 volts plate to cathode. Remember 450 volts is needed with cathode bias.

My design is a 1/2 a direct couple 6SN7 (other 1/2 is for other channel) driving a 6SN7 twin-tail phase splitter. I much prefer Sylvania 'T' plate design from the 1940s & early '50s. I also understand the Wing C Svetlana 6550C is a good tube, but stay away from the older design with the round holes in the plates. It is reported the slotted plate holes are the good tubes.

The screen power supply is critical. I use a pair of 0A2 with a .1uF cap across both tubes to reduce noise. Then, the output is routed to a 12 HY choke with a 35uF polyproplyene cap on the choke output to the screen. This is unusual, but the choke isolates any 0A2 regulator noise & the 7ma to 38ma screen current does not effect regulation.

Use good iron such as MQ 465. In a pinch, the Dynaco ST70 audio iron can be used with a limit of 75- 80ma per tube idle current for about 40 watts output.

If you go triode connected 6550, bias voltage is much higher. However, the 6SN7 to 6SN7 will drive the 6550s.

A better tube especially for triode connected is the EI KT90 type I or II.
  Reply With Quote
Old 27th August 2005, 02:47 AM   #28
SY is offline SY  United States
diyAudio Moderator
 
SY's Avatar
 
Join Date: Oct 2002
Location: Chicagoland
Blog Entries: 1
I've never had a KT90 in my hands. Roger Modjeski has asserted loudly that it has some "funny" characteristics connected as a pentode. Is that actually so? And is it a problem in triode and UL?
__________________
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 27th August 2005, 03:56 AM   #29
diyAudio Member
 
Miles Prower's Avatar
 
Join Date: May 2005
Location: USA
Blog Entries: 6
Best PP to date was a set of 6P5 driving a 6SN7 to 45 tubes. Sonics are wide open, relaxed without any fatigue, huge soundstage, powerful & tightly controlled bass, detailed & just wonderful sounding.

With or without global feedback?
__________________
There are no foxes in atheistholes
www.dolphin-hsl.com
  Reply With Quote
Old 27th August 2005, 04:25 AM   #30
amperex is offline amperex  United States
diyAudio Member
 
Join Date: Feb 2005
Location: MI
I designed with 0, 3 & 6dB feedback. Was best with most recording using zero feedback. 6dB was not ever best.
  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
push pull Vs single ended class A amp space2000 Solid State 25 23rd August 2008 03:31 PM
Single-ended OR push-pull? kacernator Tubes / Valves 48 31st March 2008 02:50 PM
Single ended amp from class A push-pull Wavebourn Tubes / Valves 2 12th October 2007 09:14 PM
Parallel single ended or push-pull? Jeffy74 Tubes / Valves 6 12th February 2004 06:04 AM


New To Site? Need Help?

All times are GMT. The time now is 05:25 AM.


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