First build 6V6 based - 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 24th July 2014, 01:49 PM   #1
diyAudio Member
 
Join Date: Jul 2014
Default First build 6V6 based

I have worked on some tube amps in the past. Basic stuff such as recapping and fixing wiring and bad components. I have decided I want to build a little small bookshelf amp that I can use with computer/mp3 player/streaming. I don't have speakers dedicated to this setup yet but will probably located a set of vintage bookshelfs for the project. I am not going for absolute most awesome sound in the universe with this, just a solid little amp as my first scratch build. I understand compromises will have to be made by using what I already have rather than buying everything new. I have several older 70 volt line transformers that I can convert to air gapped outputs pretty easily. Turns ratio appears to be usable when applying low voltage ac to the secondary and measuring the voltage at the primary. If these turn out poorly I will buy something.

I have kind of settled on either the rh84 (built with 6v6 tubes as I have those and I have found the mods to use the 6v6 instead of the EL84) or this little amp:

Five Tube Stereo Amplifier

I like the simplicity of the above amp. Does anyone have any insight as to how good of a first build this would be?

I have a few 6V6GT outputs, and a 5Y3GT rectifier. I have no power transformer, so I realize that I may end up needing to get a more suitable rectifier tube with less vdrop to match up to my power transformer.

I also don't have the 6SQ7 tubes but I think I have found those locally. I know I can replace these with a single 12ax7 since the circuit only uses the triode section of the 6SQ7. But I will probably source the 6SQ7.

The only other real mod I really want to do is incorporate a couple of em84 tubes up front for eye candy. Which is completely irrelevant to the rest of the design except to make sure I have enough overhead in the power transformer to run those.

Planning to build on an aluminum plate set in wood chassis. Transformers across the back, outputs under aluminum RF can enclosures, power exposed if I get a pretty enclosed one, other wise under a can too. Rectifier tube centered in front of the power transformer, 6V6s flanking it in front of the outputs. 6SQ7s and EM84s up front. Few inches between everything. I have been reading a lot about other people building chassis that have things too close, using twisted pair heater wiring and general layout so I think I have a good handle on keeping everything tidy and reducing issues there.

Am I out in left field? Any advice for a first time scratch builder.
  Reply With Quote
Old 26th July 2014, 07:12 PM   #2
AllenB is offline AllenB  Australia
diyAudio Member
 
Join Date: Oct 2008
Sounds good. Layout has a few different angles to it such as cooling, EMI, wiring access. You might want to do some sketches or some cardboard cutouts. Placing the OPT between the rectifiers and output valve, and the power tfmr and driver next at either end and close by, tends to give reasonable results. It is sometimes easier to do the heater wiring early.

I find the 6V6 to be capable of very good sound, biased properly and in triode mode. Power is moderate and plate resistance is not particularly low, so you might be looking for some efficient speakers and an OPT with a fair primary inductance (see how you go with gapping)... otherwise, you could always turn into a mid/treble amp where these issues are easier to accommodate.
  Reply With Quote
Old 28th July 2014, 11:40 AM   #3
diyAudio Member
 
Join Date: Oct 2007
6v6 can sound very good, I wholeheartedly agree with the triode mode suggestion.
i have a 6v6 amp coupled with a home grown speaker with quite low efficiency although with a very easy impedance graph sounding just great (if not capable of going veery loud).
You could try to fins some 12sn7 or likewise as these sound better than the 12ax7 imho.
  Reply With Quote
Old 28th July 2014, 01:32 PM   #4
diyAudio Member
 
Join Date: Jul 2014
I am still collecting pieces for this. I have been surfing ebay looking for a suitable power transformer. Lots of vintage iron out there.

Has anyone used the 6SQ7 in the preamp stage as the schematic shows? Thanks for your input!
  Reply With Quote
Old 2nd August 2014, 10:40 PM   #5
jjman is offline jjman  United States
diyAudio Member
 
Join Date: Jan 2009
How are the 6SQ7's biased? I don't see a cathode or grid leak resistor.
  Reply With Quote
Old 5th August 2014, 01:22 AM   #6
diyAudio Member
 
Join Date: Jul 2014
Thats a great point. I was so focused on the output side even after I asked about the preamp portion. I got sniped over the weekend on ebay for a complete set of silvertone transformers so I am still looking for iron.

I am also starting to consider another build thats even less ambitious. Possibly a headphone amp. I have a largish 120-120 isolation transformer (perhaps its a 120-240...gotta find it again) in my junk box that could provide B+ to a single 6AS7G power stage with a E88CC or such on the front end. I would like a neat little headphone amp.

My search continues. I know I could fork out the cash to Edcore and have nice new transformers. But I enjoy the scrounge.
  Reply With Quote
Old 6th August 2014, 03:30 PM   #7
diyAudio Member
 
Join Date: Jan 2014
Location: Texas transplant from Silicon Valley
For a 1st build I would consider this one. You will have to share the power supply. The 6V6 needs a bit more drive, so I like the 6SL7 for even phono inputs. The 2nd link is a good little OPT & cheap, not much bass however, but effective. I have some hook up notes on this little bugger around here somewhere,,,,

http://www.notecannons.com/schematic...0-11_72dpi.jpg

OPT: 70V 10W Line Matching Transformer
  Reply With Quote
Old 6th August 2014, 04:19 PM   #8
diyAudio Member
 
Join Date: Jul 2014
I already have two of those little 70 volt line transformers. Mine have a common plus taps at 1, 2 ,4 and 8 watts on the primary as well as a common plus 4 and 8 ohms on the secondary. One neat thing about mine is the varnish/resin on the core doesn't seem too tough to disassemble and restack for a proper air gap as I have seen in other articles.

I like that design as well. I will try to drag up a few more details about it. Does the treble control act more as an overall tone control in that design?
  Reply With Quote
Old 6th August 2014, 04:32 PM   #9
diyAudio Member
 
Join Date: Jan 2014
Location: Texas transplant from Silicon Valley
Yes, the tone control works well, but I would say mostly in the treble range, however I can detect more bass with the knob turned to the left. Disclaimer, my ears are not used to hearing bass, more like feeling it ~ It is very responsive.

The schematic is actually a factory schematic of a guitar amp from Valco, circa 1946.
  Reply With Quote
Old 6th August 2014, 08:30 PM   #10
diyAudio Member
 
Join Date: Jul 2014
Does it run clean throughout the voltage range or do things start getting gritty when you lean on it? I would build two for general stereo use, driving bookshelf speakers with a share power section.
  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
New 6V6 Build - Suggestions Needed SandyG Tubes / Valves 111 5th January 2013 12:17 PM
Build guitar amp with 2 6L6 or 4 6V6? TubeTweaker Instruments and Amps 11 15th August 2012 12:01 PM
At Last....First Build Complete...6V6/6SL7 cbj591 Tubes / Valves 9 31st July 2010 01:51 AM
6v6 music machine build help! tubo Tubes / Valves 26 5th November 2009 04:34 PM
6V6 PP-based Baby Huey/Mullard inspired design needed... GordonW Tubes / Valves 13 4th August 2008 08:56 AM


New To Site? Need Help?

All times are GMT. The time now is 06:51 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