Go Back   Home > Forums > >

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

What tube amp to build.
What tube amp to build.
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
Old 12th January 2021, 08:37 AM   #11
OldHector is offline OldHector  Sweden
diyAudio Member
 
Join Date: Jun 2018
Location: Tšby, Sweden
I heartily recommend the Tubelab offerings. He has his own vendor forum here, and the support from George and the community is second to none.

You have three entry points, depending on your ambition.

I use the Simple Single Ended (SSE) all the time, and have never had power issues driving my medium sensitivity bookshelf speakers. With transformers from Toroidy, frequency range is excellent, and if you take the transformers without the fancy covers, all transformers can be had for £200, which will be your single biggest outlay for a tube amp.
  Reply With Quote
Old 12th January 2021, 08:46 AM   #12
Bas Horneman is offline Bas Horneman  Netherlands
diyAudio Moderator Emeritus
 
Bas Horneman's Avatar
 
Join Date: Apr 2002
Location: The Netherlands
I'm with Eli here. What speakers will be used? But also, what size is the room they will be used in?
__________________
http://basaudio.wordpress.com
  Reply With Quote
Old 12th January 2021, 12:03 PM   #13
Jeff429 is offline Jeff429
diyAudio Member
 
Join Date: Jan 2021
Room is small say 10x12. Have not picked speakers yet.
Was thinking about PSB X1T or X2T or KEF Q750.
Will a class A drive these? How low db speakers would I need?
I don't want to get into the engineering side of this. I would like to find some proven prints to build from. I am open to any speaker suggestions.
I have never listened to a 5 watt amp before, is that enough power to to have some volume out?
A kit would be OK or prints with a BOM. The small parts are no problem. I would need advice on transformers.
Would you use a design that used tubes in the power supply or a SS power supply?
  Reply With Quote
Old 12th January 2021, 01:05 PM   #14
evanc is offline evanc  United States
diyAudio Member
 
Join Date: Sep 2009
Location: New Jersey. About 1 hour from NYC and 1 min. from the beach
What tube amp to build.
Iím going to agree with the earlier advice to build a simple single ended amp. Get a copy of Morgan jones book valve amplifiers and gain a true understanding of whatís happening. It will give you building and theoretical expertise while still leaving room for some experimentation. I wish I had started this way.
__________________
http://www.evancotler.com
  Reply With Quote
Old 12th January 2021, 03:18 PM   #15
Eli Duttman is offline Eli Duttman  United States
diyAudio Member
 
Join Date: Apr 2004
Location: Monroe Township, NJ
Quote:
Originally Posted by Jeff429 View Post
Room is small say 10x12. Have not picked speakers yet.
Was thinking about PSB X1T or X2T or KEF Q750.
Will a class A drive these? How low db speakers would I need?
I don't want to get into the engineering side of this. I would like to find some proven prints to build from. I am open to any speaker suggestions.
I have never listened to a 5 watt amp before, is that enough power to to have some volume out?
A kit would be OK or prints with a BOM. The small parts are no problem. I would need advice on transformers.
Would you use a design that used tubes in the power supply or a SS power supply?
If you want some volume out, apply Paul Joppa's 102 dB. rule, which states that an amp/speaker combo should be capable of a 102 dB. SPL at a 1 M. distance. Speakers whose sensitivity is upwards of 96 dB. are in order with a 5 WPC amp. Also, the speakers must exhibit a reasonably flat impedance curve. You can use nominal 8 Ω speakers, with impedance dips, on 4 Ω O/P transformer taps. However, you have to derate the claimed sensitivity by 3 dB.

Let's examine the KEF Q750. Its nominal impedance is 8 Ω and the claimed sensitivity is 88 dB., but it dips down to 3.2 Ω. Therefore, when mating KEF Q750s to a tube amp its impedance is 4 Ω and the sensitivity is 85 dB. Joppa's Rule indicates that (sic) upwards of 50 WPC are in order. That's push/pull KT88 pair "territory".

Most, but not all, commercial speaker designs are not suitable for mating to low power tube amps, either SE or PP. Klipsch "Heresy" and "Forte" speakers will be fine with 5 WPC, provided a decent damping factor is present.
__________________
Eli D.
  Reply With Quote
Old 12th January 2021, 05:44 PM   #16
Tom Kamphuys is offline Tom Kamphuys  Netherlands
diyAudio Member
 
Join Date: Aug 2020
Location: Den Ham
Are there any other speakers, more 'El Cheapo', you could advise?
  Reply With Quote
Old 12th January 2021, 05:57 PM   #17
cogitech is offline cogitech  Canada
diyAudio Member
 
cogitech's Avatar
 
Join Date: Jan 2011
Location: Kamloops, BC
What tube amp to build.
In a 10 x 12 room a 5-7w amp will create plenty of volume with speakers as low as 88-89dB efficiency.

Hell, even in my much larger room, my Tubelab SSE has no problem hitting over 95dB peaks with my two 88-89dB speakers at a distance of 2 meters. Way too loud to have a conversation, and loud enough to cause cumulative hearing loss.
  Reply With Quote
Old 12th January 2021, 06:11 PM   #18
Eli Duttman is offline Eli Duttman  United States
diyAudio Member
 
Join Date: Apr 2004
Location: Monroe Township, NJ
Quote:
Originally Posted by Tom Kamphuys View Post
Are there any other speakers, more 'El Cheapo', you could advise?
High sensitivity and low cost seem to be incompatible. The "sweet spot" may be mid 90s sensitivity and 8 or so WPC. Low 90s sensitivity and a "knock off" of the Sherwood S5000's power section (20 WPC) could be attractive too. 7189 equivalents are needed by the S5000 and the nice Russian 6Π14Π-EB (6p14p-ev), AKA EL84M, affordably meets the requirement.

It's a stone cold fact that in any power handling range SE O/P "iron" costs more than the PP stuff. Like it or not, "iron" is a major expense in building tube amps.
Attached Images
File Type: jpg Sherwood S5000 Schematic.jpg (1.04 MB, 130 views)
__________________
Eli D.
  Reply With Quote
Old 12th January 2021, 06:28 PM   #19
Steve Morley is offline Steve Morley  Canada
diyAudio Member
 
Join Date: Jan 2015
Location: Georgian Bay
Jeff,
A straight forward and fairly simple amp is the Tubelab SPP (Tubelab forum on this site and circuit board available from Tubelab.com). ~15wpc from one 5AR4, four EL84s and two 12AT7s. If you are in the USA a complete set of "iron" is available from Edcor for about 200 bucks.

Steve
  Reply With Quote
Old 12th January 2021, 08:46 PM   #20
Jeff429 is offline Jeff429
diyAudio Member
 
Join Date: Jan 2021
Thanks for all the info. I will research the tube labs.
  Reply With Quote

Reply


What tube amp to build.Hide this!Advertise here!
Thread Tools

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

Forum Jump

Similar Threads
Thread Thread Starter Forum Replies Last Post
Tube rolling for my Tube T1 tube preamp gasolin75 Tubes / Valves 2 13th September 2020 03:21 AM
F5 Turbo v2 Stereo Amp Illustrated Build (my first amp build) chuckd Pass Labs 16 27th August 2020 11:45 PM
Super Squirrel Monkey - First from-scratch tube amp build, first guitar amp build ericj Instruments and Amps 33 22nd June 2020 07:26 AM
FS: Yaqin CD-1 Tube Buffer w/Mullard 6DJ8 Tube. Adds tube warmth to any system. matevana Swap Meet 2 15th June 2013 12:35 PM
WE 300B Vs &&&& Trout Tubes / Valves 22 20th December 2004 08:57 AM


New To Site? Need Help?

All times are GMT. The time now is 01:28 AM.


Search Engine Optimisation provided by DragonByte SEO (Pro) - vBulletin Mods & Addons Copyright © 2021 DragonByte Technologies Ltd.
Resources saved on this page: MySQL 15.00%
vBulletin Optimisation provided by vB Optimise (Pro) - vBulletin Mods & Addons Copyright © 2021 DragonByte Technologies Ltd.
Copyright ©1999-2021 diyAudio
Wiki