Looking for 6AQ5 audio preamp schematic! - diyAudio
Go Back   Home > Forums > Amplifiers > Tubes / Valves
Home Forums Rules Articles diyAudio Store Gallery Wiki Blogs Register Donations FAQ Calendar Search Today's Posts Mark Forums Read

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
Thread Tools Search this Thread
Old 20th January 2009, 10:06 AM   #1
diyAudio Member
Join Date: Jan 2009
Talking Looking for 6AQ5 audio preamp schematic!

I'm new to this forum and only 17 years old. I'm just wondering if anyone has, or can write up a very SIMPLE audio amp schematic using a 6AQ5 tube for a preamp and 1 6CA7 for the power amp. and I mean really simple, im looking for 1 input 1 output, maybe a single pot for Gain.

I have at my dispossle:

1 breadboard.
many assorted wires.
2 6CA7 power tubes.
1 6AQ5 tube
Many assorted resistor's, capacitor's,
switch's and diodes.
1 speaker,
1 microphone.
1 1m pot
1 10k pot
1 100k pot
2 1/4 inch female plug's

Ill be using any and all safety precautions when building this, im just looking for the simplest design for a audio amp curcuit.

I want to start out with just a preamp first and get the curcuit operational before adding in the 6CA7 tube, As I've read a single 6CA7 can produce 11 watts which should be sufficent

Any help with this little project would be GREATLY apreciated!!

Thank You,
  Reply With Quote
Old 20th January 2009, 10:26 AM   #2
SY is offline SY  United States
On Hiatus
SY's Avatar
Join Date: Oct 2002
Location: Chicagoland
Blog Entries: 2
Do you have a power transformer and an output transformer? Those are generally the biggest-ticket items.
"You tell me whar a man gits his corn pone, en I'll tell you what his 'pinions is."
  Reply With Quote
Old 20th January 2009, 10:30 AM   #3
Stuey is offline Stuey  Australia
diyAudio Member
Join Date: Mar 2006
Location: Perth, Western Australia
Not sure how simple you want, but look at the Moebius for a preamp.
  Reply With Quote
Old 20th January 2009, 03:41 PM   #4
diyAudio Member
Join Date: Jan 2007
Location: Central Iowa
You will need more 6AQ5's, but they can be had for a relatively low price. This is the Moebius that was suggested above.


For more 6AQ5's check here:


I would check this tread out too since the 6AQ5 is more or less a 7-pin 6V6.

6V6 line preamp

As for the 6CA7's, may I suggest the Tubelab Simple SE. A simple design with a full PCB available and lots of support from DIY Audio, both from builders and from the designer himself. You would have to invest in a 12AT7 but they are fairly cheap. If you hit surplus and garage sales you can probably find some, I picked some up for $0.25 each not to long ago. The 12AT7 can also be bought new for around $7 to $10. The 5AR4 rectifier is optional as the board also has previsions for SS diodes, but a new stock 5AR4 would run about $10 to $15. The majority of the parts can be ordered from Digikey or Mouser and there is a full build manual with parts list on the Tubelab site. All in all, using Edcor output transformers (the $20 ones, don't let the price fool you, great transformers), this amp can be built for around $200. Check out Allied for the power iron and some of the parts as well. It is also very friendly to tube rolling, with some tweaks it can use just about any octal out there.


Could also go the other way, pick up some more 6AQ5's, and build this:


Great little amp that again would weigh in at around $200 mark, give or take, depends on what you already have.


  Reply With Quote
Old 20th January 2009, 11:57 PM   #5
diyAudio Member
Join Date: Jan 2009
The Moebius looks very inticing, I think I will go for that.
I've changed my plans for this little project, since I own and run a recording studio out of my home I think ill try and make just a preamp for the microphones, no power amp. which means I wont need the 6CA7's. Anyone know where I can get 4 mounts for the 4 6AQ5's?

Oh and before I go for 6AQ5's im wondering if I should go with better tube's? perhaps some 12AX7's? Any suggestions on better preamp tubes?

I'll also need this to have balanced inputs & outputs aswell.
How can I add in transformer balancing to the in's and outs on the moebius schematic? What transformers will I need?

And thank you for helping me out here, I appreciate it!
  Reply With Quote
Old 21st January 2009, 01:48 AM   #6
diyAudio Member
Join Date: Jan 2006
Location: SF Bay area
Hi Lightning,
Is that your sail number?
Thanks, Victoria
  Reply With Quote
Old 21st January 2009, 02:14 AM   #7
diyAudio Member
aardvarkash10's Avatar
Join Date: Mar 2007
Location: Auckland, NZ
Default och the noo...

ummm, with all the little changes you suggest, suddenly you don't have a moebius any more... I think you need to more clearly define your design goals. Either this project is aimed at maximising the use of available parts, or you ar eprepared ot start from scratch. Either it is a pre- for a specific use (a microphone being substantially different to a CDP as a source) or its an integrated for pleasant noodling. Good luck - and welcome to the DIY toobies dillema!
"It may not be easy for some to not hear differences, even if they are not there." - Vacuphile,
  Reply With Quote
Old 21st January 2009, 04:11 AM   #8
diyAudio Member
Join Date: Jan 2007
Location: Central Iowa
I don't know much about mic preamps so can't help you there. However if this will be used for mics I would shy away from the 6AQ5, Poinz (and I am sure others) found them to be microphonic in the Moeb preamp, now he is playing with 6T4's. If this will be used for home audio and you need balanced you could try something like this:


Transformers from Lundahl but Sowter also makes some specifically for this line amp.

Like I said, for mic I can't help much, but I can say you could look to Lundahl for mic iron too. Also Electra-Print, great iron and custom wound to whatever you need; Jack is a great guy too, just an added bonus. If you have 12AX7's great, but they are a "hot" tube so NOS prices are sky high. Luckily they are also still made by lots of tube companies. 12AT7's deserve a look, along with maybe 12AZ7's, 12AY7's, 6SL7's, EF86's, 6J7's...all medium high to high gain triodes and petodes. 6J7 for example was used for years by RCA in high gain low noise photo input sections on theater amps. The EF86 is kind of a continuation of this tube, different specs and 9-pin, but still low noise high gain. NOS EF86's command high price points, but are also still made today. (I may regret saying this, but it seems this tube is fairly undiscovered, or maybe disliked, IDK) NOS 6J7's can still be had on the cheap, the down side is a cap to deal with, but no worries, it is just a grid cap. I would go out on a limb and say that the 6J7's bests the popular 6SJ7.


  Reply With Quote
Old 21st January 2009, 09:55 AM   #9
Stuey is offline Stuey  Australia
diyAudio Member
Join Date: Mar 2006
Location: Perth, Western Australia
Apex Jr has the seven pin sockets for only 0.35c.
  Reply With Quote
Old 22nd January 2009, 06:17 PM   #10
diyAudio Member
Join Date: Jan 2009
Hi, Thanks for all the info everyone!


Sail number? huh?


Well, my design goal did change I was just planning on tinkering iwth some tubes, but i figured if I can manage to build a preamp for $200, I would do that, since I need preamp's in my studio for recording and most preamp's that are 100% tube are anywhere from $500 to $7,000. The "Moebius" looked like a good schematic I just figured that I could add to it and make it have balanced in's and out's since that is a requirment since studios need 100% hum/noise-free conditions. I am more of starting fom scrap parts, I would like to find out what else I need and how much it would cost to build a modified Moebius.


Thanks for the heads up on the 6AQ5's, however the Raven is a bit more complex I dont think im skilled enough to build something like that. and im not sure about using different tubes in the "Moebius"? Not sure about compatibility. Like I said im new to this forum and am fairly new to tube circuit designs.
What would you suggest for a better audio qaulity tube that is compatible with the "Moebius"?


Thank you all for your help!
  Reply With Quote


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
Need schematic for Elevation Audio DX1500.1/Sundown Audio SAZ-1500D jaimegmr Car Audio 0 5th May 2009 06:39 PM
FS/T: Lite Audio Chinese audio preamp PCBs CaliforniaBob Swap Meet 0 26th July 2007 09:36 PM
6aq5.......6v6....... diesel_tech Tubes / Valves 9 23rd February 2007 12:43 AM
Need schematic Cary Audio SLP-70 preamp coolmaster Tubes / Valves 0 19th January 2007 03:05 PM
Which 6AQ5 dstockwell Tubes / Valves 4 12th December 2005 11:05 AM

New To Site? Need Help?

All times are GMT. The time now is 11:35 PM.

vBulletin Optimisation provided by vB Optimise (Pro) - vBulletin Mods & Addons Copyright © 2017 DragonByte Technologies Ltd.
Copyright 1999-2017 diyAudio

Content Relevant URLs by vBSEO 3.3.2