DIY Audio Projects Forum
 NEW  Matt presents bias and operation data for the 6V6 tube in SE operation - 6V6 Single-Ended (SE) Ultra Linear (UL) Bias Optimization.

DIY Audio Projects Forum

Welcome to the DIY Audio Projects Message Forum. Use these forums to discuss Hi-Fi audio and to share your DIY Audio Projects. Registration is free and required to post messages and view the file attachments. Registration will only take a minute and registered users do not see any advertisements. After you have completed the online registration process, check your email (including spam/junk folder) for the verification email to activate your account. New members are under moderation - so your posts will not be visible until approved by a moderator. See the Read Me 1st, Forum RULES and Forum FAQ to get started on the forum.

It is currently 30 Mar 2020, 11:55

All times are UTC - 6 hours [ DST ]




Post new topic Reply to topic  [ 104 posts ]  Go to page Previous  1, 2, 3, 4, 5, 6, 7 ... 11  Next
Author Message
 Post subject: Re: Baxandall circuit
PostPosted: 31 May 2015, 16:52 
Offline
User avatar

Joined: 25 Jan 2015, 11:51
Posts: 54
Location: Netherlands
While digging the Internet on Baxandall i found this:
http://www.angelfire.com/electronic/fun ... 6-A-A-back

Mathieu


Top
 Profile  
 
 Post subject: Re: Baxandall circuit
PostPosted: 31 May 2015, 18:49 
Offline
Project Author
User avatar

Joined: 06 Jun 2008, 18:23
Posts: 5189
Location: Australia
What I like about the defeat switch is it allows and quick and simple A\B between tone settings and flat. On the fly in real time you can switch between a selected tone setting and dead flat.

Or if you like a certain tone setting for some music but not others you are not resetting the controls everytime you change music. This could even lead to two selectable tone stacks but with knobs with a vernier marked on them should allow quick resetting of favourite settings.

If you remember some LPs of old have three small clock like images on the back where you could score your tone and volume settings. This preamp may just bring them back, lol.

_________________
Projects:”Image” - Low Profile 100W Class D amp | ”fiih” - 150W Holton inpsired power amp | "Precision" - 300W Class AB Holton power amp | ”Gothic” - FET Push-Pull headphone amp


Top
 Profile  
 
 Post subject: Re: Baxandall circuit
PostPosted: 31 May 2015, 20:40 
Offline
User avatar

Joined: 08 Aug 2009, 03:11
Posts: 2229
Location: Chilliwack, BC
Tjeu wrote:
While digging the Internet on Baxandall i found this:
http://www.angelfire.com/electronic/fun ... 6-A-A-back

Mathieu


THANKS! :up:

I had lost that bookmark on a fubared backup. Nice to have it again :smoking:

_________________
-= Gregg =-
* Ratings are for transistors - tubes have guidelines*
Home: GeeK ZonE
Work: Classic Valve Design


Top
 Profile  
 
 Post subject: Re: Baxandall circuit
PostPosted: 02 Jun 2015, 08:52 
Offline

Joined: 01 Feb 2015, 13:41
Posts: 144
Location: Athens-Greece
I think that I will put in the production line Matt's proposal. But, my question is the following:

Will the power supply prepared for original 4S pre-amp , be suitable for tone control that has two tubes instead of one? I will stay with 250V but is it ok to use my toroidal transformer 190-0-190 100mA?

And something else to avoid a mistake. My secondary is 3.15-0-3.15 ; how should I connect it in order to get 6.3 Amps? Can I use center tap instead of virtual CT described in 4S power supply?

Thanks for any advice


Top
 Profile  
 
 Post subject: Re: Baxandall circuit
PostPosted: 02 Jun 2015, 19:13 
Offline
Project Author
User avatar

Joined: 06 Apr 2009, 10:08
Posts: 1620
Location: US Pacific Northwest
dimitris1811 wrote:
Will the power supply prepared for original 4S pre-amp , be suitable for tone control that has two tubes instead of one? I will stay with 250V but is it ok to use my toroidal transformer 190-0-190 100mA?
The cathode follower only draws about 1.5mA per channel. The power supply should have no problems with that. As for voltage, the circuit was specifically designed for 300v B+. You can use 250v but the performance won't be quite as good. I don't really see any reason to not use the transformer you have on hand.
dimitris1811 wrote:
My secondary is 3.15-0-3.15 ; how should I connect it in order to get 6.3 Amps? Can I use center tap instead of virtual CT described in 4S power supply?
Just connect the filaments to the 3.15v lines. Use the center tap as the signal ground connection. Then you won't need the virtual center tab with the two 100Ω resistors.

_________________
Matt
It's all about the Glass!
http://www.CascadeTubes.com
Cascade Tubes Blog


Top
 Profile  
 
 Post subject: Re: Baxandall circuit
PostPosted: 03 Jun 2015, 00:59 
Offline

Joined: 01 Feb 2015, 13:41
Posts: 144
Location: Athens-Greece
Thanks Matt. What is the voltage rating of 4DPT switch? I found up to 125 VAC/DC but should it be 300?


Top
 Profile  
 
 Post subject: Re: Baxandall circuit
PostPosted: 03 Jun 2015, 07:50 
Offline

Joined: 01 Feb 2015, 13:41
Posts: 144
Location: Athens-Greece
I saw the drawing attached herewith as proposed by the forum members. My questions are:

1. Could this circuit work same as Matt's proposal? The reason I am asking is that dual gang potentiometers of 250K can be easily found in UK but the 1M proposed by Matt it is not.

2. If above this circuit is followed, where could I place the volume control? Can this circuit be placed before or after 4S pre-amp? My 4S works fine now, and I was thinking to follow Matt's proposal but I can not find a reliable potentiometer 1M!!!


Top
 Profile  
 
 Post subject: Re: Baxandall circuit
PostPosted: 03 Jun 2015, 08:54 
Offline
Project Author
User avatar

Joined: 06 Apr 2009, 10:08
Posts: 1620
Location: US Pacific Northwest
dimitris1811 wrote:
What is the voltage rating of 4DPT switch? I found up to 125 VAC/DC but should it be 300?
The switch only carries AC signal; no dc bias. As such, any switch rated over 20 to 30 volts should be more than sufficient.

_________________
Matt
It's all about the Glass!
http://www.CascadeTubes.com
Cascade Tubes Blog


Top
 Profile  
 
 Post subject: Re: Baxandall circuit
PostPosted: 03 Jun 2015, 20:09 
Offline
Project Author
User avatar

Joined: 06 Apr 2009, 10:08
Posts: 1620
Location: US Pacific Northwest
dimitris1811 wrote:
1. Could this circuit work same as Matt's proposal? The reason I am asking is that dual gang potentiometers of 250K can be easily found in UK but the 1M proposed by Matt it is not.
Well I'm a little confused because the only other circuit I've found of this thread uses 100kΩ and not 250kΩ pots. However, I did slap this circuit from the second post into the Duncan Amps tone stack calculator (b.t.w. I have found this calculator to be a reasonably accurate tool so long as it's drive and load limitations are kept in mind) and the results were less than impressive. There seemed to be about a 10dB loss at high frequency compared to low. There may be an error in values in the posted circuit.

I will say that the circuit I designed was done from first principles with the intended use being in a tube circuit. The simulation shows excellent performance in this role and the points I've spot checked with a prototype (see picture below) seem to bear this out.
Attachment:
TS_front.jpg
Attachment:
TS_inside.jpg

Before using the other one posted I would recommend some careful simulation work or to simply design one from scratch.


This post has a file attachment. Please login or register to access it. Only Registered Members may view attached files.


_________________
Matt
It's all about the Glass!
http://www.CascadeTubes.com
Cascade Tubes Blog


Top
 Profile  
 
 Post subject: Re: Baxandall circuit
PostPosted: 04 Jun 2015, 01:00 
Offline

Joined: 01 Feb 2015, 13:41
Posts: 144
Location: Athens-Greece
I was talking about this Matt. At any case , I finally managed to find 1M potentiometer in Germany but I am not sure for the quality. I will follow your schematics.

I sent you at e-mail some photos from testing (sinus & square signals 1vpp). I will re-run the tests when the new 4S with tone control will be ready. How to understand which results will be better. Sorry to ask but I know a little about oscilloscopes. I will probably get the sinus signal at output; ok they are smooth but should I measure the amplitude in both cases?


This post has a file attachment. Please login or register to access it. Only Registered Members may view attached files.



Top
 Profile  
 
Display posts from previous:  Sort by  
Post new topic Reply to topic  [ 104 posts ]  Go to page Previous  1, 2, 3, 4, 5, 6, 7 ... 11  Next

All times are UTC - 6 hours [ DST ]


Who is online

Users browsing this forum: chow123, fewjr and 16 guests


You cannot post new topics in this forum
You cannot reply to topics in this forum
You cannot edit your posts in this forum
You cannot delete your posts in this forum
You cannot post attachments in this forum

Jump to:  
DIY Tube Projects :: DIY Tube Amp Kits :: DIY Speaker Projects :: DIY Solid State Projects :: DIY IC / Op-amp Projects :: DIY Phono Projects :: DIY Cable Projects :: Hi-Fi Audio Schematics
© diyAudioProjects.com - Terms of Service - Privacy Policy