New tubeamp - 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 14th November 2008, 01:12 PM   #1
Banned
 
Join Date: Jan 2005
Default New tubeamp

Its been 3 years and now ive just finished a new tubeamp i started earlier this week.

Im not sure about output power but it can play insanely loud, it uses two EL38 in ULPP with an ECC83 as input stage and phase splitter.

Here are some pics: http://s136.photobucket.com/albums/q...eamp/diy/mono/
  Reply With Quote
Old 14th November 2008, 02:48 PM   #2
kevinkr is offline kevinkr  United States
diyAudio Moderator
 
kevinkr's Avatar
 
Join Date: Sep 2004
Location: Boston, Massachusetts
Blog Entries: 6
Interesting design, but please put a cage on it or otherwise protect the plate caps and tag strip on the output transformer primary tag switch from accidental contact. As shown it is more than a bit hazardous..

How about a description of circuit topology and what dictated the choice of an ECC83 as the driver?

I am assuming you used a concertina style phase splitter. Cathode bias in output stage?

Building a second for stereo?

A schematic and some description of how it sounds beyond "insanely loud" would be cool too..


__________________
"Extraordinary claims require extraordinary evidence." - Carl Sagan
  Reply With Quote
Old 14th November 2008, 04:45 PM   #3
Banned
 
Join Date: Jan 2005
I was thinking about a cage, tho the chassi is not connected to the amp ground, however this should not be relied on.

Ill have to make a full schemo of this design. Why i chose ECC83 was simply because i have a pile of them, im not building a second one, however i am modding a tube radio to go with this amp.

The sound is comparable to a ss amp in the same power range, which to my ears is very good.
  Reply With Quote
Old 15th November 2008, 01:59 PM   #4
Banned
 
Join Date: Jan 2005
So heres the schematic of this amp:
Click the image to open in full size.
  Reply With Quote
Old 15th November 2008, 03:21 PM   #5
diyAudio Member
 
Join Date: Apr 2003
Location: Portland,Oregon
Blog Entries: 4
Send a message via AIM to DigitalJunkie
Cool,but C2 is backwards.
  Reply With Quote
Old 15th November 2008, 03:42 PM   #6
Banned
 
Join Date: Jan 2005
I know, i forgot to flip it, atleast its the right way in the amp.
  Reply With Quote
Old 15th November 2008, 04:13 PM   #7
Banned
 
Join Date: Jan 2005
Corrected schematic: http://s136.photobucket.com/albums/q...ntcomplete.png
  Reply With Quote
Old 1st April 2010, 09:28 PM   #8
Banned
 
Join Date: Jan 2005
alittle more than a year have passed and ive done a few mods to this amp, before it was a 10W peak amp that liked to distort at moderate volume.

The mods that have been done is a new gain stage using a 12AX7, however i came up with a filament supply pinout switch to enable using a 6DJ8 as well without having to rewire the socket.

I also moved the volume control from after the gain stage to before the gain stage, as well as adding an additional transformer to the plate supply, raising the the VA from 80 to 160 and raising the plate voltage around 33 volts, just these simple mods made a big difference.

Now the amp can play insanely loud before clipping, of cource the distortion at low freqs caused by the opt is unavoidable, especially since this is a 60 year old opt from an old philips EL6411 PA amp.

Also the EL38s left life on earth last spring/summer after for some reason the little pumpdown tube broke and let air into one of the tubes. The replacement tubes i got was a pair of Red Bank 6889s for around 69 bucks on ebay.

However measurements and calculations on the opt shows that EL519 would be better suited for this plate to plate impedance, 3226ohms with a 4ohm load and around 6450ohms with a 8ohm load, which actually happen to be just right for EL34 or 6L6 tho.

Aight enuf talking, heres the schematic as the amp stands today:
Click the image to open in full size.

Ill make a video tomorrow.
  Reply With Quote
Old 2nd April 2010, 08:46 AM   #9
diyAudio Member
 
Globulator's Avatar
 
Join Date: Aug 2004
Location: Cambridge, England.
Can't see the photos now but:

How do you manage the filament to cathode voltage on V2B?
Also R21, does that make much difference?
  Reply With Quote
Old 2nd April 2010, 09:30 AM   #10
diyAudio Member
 
Join Date: Sep 2009
Location: Aarhus, Denmark
Quote:
Originally Posted by Tekko View Post
...The mods that have been done is a new gain stage using a 12AX7, however i came up with a filament supply pinout switch to enable using a 6DJ8 as well without having to rewire the socket...
Rewire you circuit into the PP1C and add a CCS at the output and get rid of those bias potentiometers and you'll have one of the best PP-amps available.

If you build the PP1C and send Allen a photo and your comments you can get the PP1CS schematic for free. I've used the PP1CS for years and it's an outstanding amplifier and outperforms about everything I had put against it. Instead of EL34 I use the JJ KT77. I can't really recommend the JJ tubes as they are not very reliable but do sound better than the EL34 I tried so far.
I'll upgrade the PP1CS to near the DPA300B using 6H30 & 300B tubes this year. FYI: the schematic for the DPA300B is not available.
__________________
"People can't do what they should: room acoustics and speaker design - so they do what they can: new amps, cables etc." (Lidia)
  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
tubeamp kits arhi45 Tubes / Valves 0 5th December 2007 12:22 PM
philips el6400 tubeamp Tekko Tubes / Valves 7 25th June 2005 04:33 PM
se tubeamp with px4 sonix Tubes / Valves 1 10th July 2004 09:14 PM
Speakers for tubeamp? chrille Tubes / Valves 5 7th August 2002 03:14 AM
Tubeamp for tube-newbie joensd Tubes / Valves 3 8th June 2002 10:50 AM


New To Site? Need Help?

All times are GMT. The time now is 08:06 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