A DIY out board tone control???

[Frederick Petersen]

Gentlemen:
This is my first post to the Bottlehead Forum. So I want to apologize in advance to those who disagree with what I'm about say.
To begin with I sent the following e-mail to Doc B. the other day and got no response. It then occurred to me "that was not the proper way to broach a new subject to the Bottlehead community." What actually prompted me to send the e-mail was reading about the passive volume control on the site. It occurred to me that a Baxandal (bass, mid, treble) circuit might work & if mounted in a box similiar to the Submissive it would look cool. If enough of us are interested maybe a kit could be in the future. You might even want to call it the B&D because it is after all about control. Anyway here's the e-mail I sent. So please read it and let's see what happens.

Hello Doc B:
I know that in most hi/end circles tone controls are frowned upon. However they can be useful for example when listening
at low levels so as not to wake family members. I have been searching for a quality unit but just can't seem to find one.
For me a simple Bass Treble unit isn't sophisticated enough, yet a parametric or octave eq is too much. Would some thing like the parasound unit below be something BottleHead's future. If so I know of at least four audio friends who would be interested.
FYI: There are a few hi/end manufacturers who've gone on the record lamenting the loss of tone adjustment, one example is the ceo of Harbeth.  link ( http://www.harbeth.co.uk/usergroup/showthread.php?466-Tone-controls-equaliser-or-tilt-controls-at-home )
Parasound made one which I admired in the mid nineties. link(http://www.parasound.com/pdfs/vintage/req150om.pdf )
Quad also used a type of tone control tilt circuit.

                                                  ............................. thanks Doc

                                                                   ........................... Fred Petersen
                                                                                       ( www.audiofyle.com )

p.s. I know there are going to be people who disagree with tone control use. Respectfully this post isn't for you.
I'm interested in responses from people who would like to see this kind of kit offered, I know I want one.

[Doc B.]

"The moral ambiguity of pseudo/science as a marketing tool".

On your website you have a photo of my products as a link to the aforementioned article.

[Frederick Petersen]

My Apology Doc:

It was supposed to link to your website. It now does, hopefully no harm done.
I am playing guitar again & love the image of the Tode & will be ordering one soon.
I'd appreciate your thoughts on my post. I was quite impressed with your tone cntrl
solution on the Tode. This was another reason why I am enquiring about a tone cntrl solution
for home audio.

                       .......................... Fred Petersen

p.s. I read on your site that perhaps Blumenstein Audio will be doing the new cabinets for the Tode?

[Doc B.]

Thanks for fixing it Fred. The tone control idea is interesting. Let me take a look at the Parasound you mentioned and see what we might cook up. One potential issue that pops into my head is that doing this as a passive stand alone unit might make its response curve influenced by the load it runs into. I'll kick the idea around with the guys and see what they think.

[adamct]

I'd be interested. If nothing else, it would be fun to play with...

[Frederick Petersen]

One of the things I admire about Bottlehead products is the retro design & especially the wooden enclosures.
If a power supply is needed would that make the cost prohibitive. Again to me a small high quality tone control
or eq ( I believe the Parasound is an EQ ) is for me a necsessity. My fingers & toes are crossed.

                                 ............................ Fred Petersen

[caffeinator]

I don't miss tone controls, generally...but sometimes I do miss that "Loudness" button...not so much at home, but in the office it would be pretty handy...

[Paul Joppa]

The thing about passive tone controls is, they can only be subtractive. The standard circuits (the ones without opamps and feedback) lose about 20dB of signal voltage.

There is only one approach suitable for passive implementation that I am aware of. It's actually a close relative of the "scoop" in the Tode. We'll kick the idea around and see if it squeals.  :^)

[4krow]

 I like the idea of a passive design. I do not care for the Parasound device. Too much going on.      Yamaha had a great idea for a loudness control. It simply lowered part of the midrange instead of boosting the hi's n lo's.         I think that a Bass Mid  Treble unit would suffice, as long as there were turnover frequency adjustments for each control, especially the bass.

[Jim R.]

FWIW, the best tone controls I've heard are the kind that are cut-only -- as in Sam Kim's modified Scott and Heathkit integrateds.  But those aren't exactly passive either.

Greg, I used to have one of those mid-70s Yamaha integrateds -- CR 820 -- it , as I recall, had both a mid control and variable loudness, though it was a long time ago and maybe it was just one but not both.

-- Jim

[Frederick Petersen]

       I think that a Bass Mid  Treble unit would suffice, as long as there were turnover frequency adjustments for each control, especially the bass.

[/quote] Paul Joppa
The thing about passive tone controls is, they can only be subtractive.
[/quote]
In my original post I referred to the Passive volume control (the SUBMISSIVE). I like it's aesthetic design. The initial question wasn't about a passive tone control, just a tone control that would match the appearance of the submissive.  I want an active tone control not a passive. (4KROW Greg Peyton) hit the nail on the head  a Bass/Mid/Treble unit with turnover frequency adjustments for each control, and for my 2 cents "separate controls for each channel in other words left ch bass/mid/treble and turnover. Right ch. Same as left.

thanks guys ........................... fastfred (Fred Petersen)

[Paul Joppa]

Here's an interesting idea:

* A tone control that attenuates the midrange with variable bass and treble turnover frequencies; possibly a variable treble level level as well. *

This is exactly what a "baffle step correction" or BSC circuit does - there is an example in the SEXy Speaker page. Thus it could serve either or both functions. The basic circuit is extremely simple.

It should be much more affordable than the old White Instruments passive RLC notch filters, which were available with up to 24 bands on 1/3 octave centers!

[Paul Joppa]

FastFred was posting at the same time I was, so this post addresses the "active" notion.

Old-style tone controls are a lossy passive control followed by an amplifier to restore the signal level. The more modern designs, which became common about the time that tubes disappeared and transistors or opamps took over, use feedback with equalization inside the loop. Both are called "active" but to my ear the passive eq approach sounds better.

[Frederick Petersen]

Here's an interesting idea:

* A tone control that attenuates the midrange with variable bass and treble turnover frequencies; possibly a variable treble level level as well. *

This is exactly what a "baffle step correction" or BSC circuit does - there is an example in the SEXy Speaker page. Thus it could serve either or both functions. The basic circuit is extremely simple.

It should be much more affordable than the old White Instruments passive RLC notch filters, which were available with up to 24 bands on 1/3 octave centers!

I like the idea of a tone control that attenuates the midrange with variable bass and treble turnover frequencies; and I vote for a variable treble level level as well. * Aother addition I would want to see & that is a complete bypass circuit for those recordings that don't need help.  I think we're getting close, although it's my post its you guys are the ones who are designing it.   
I have 2 main reasons for asking for tone controls I'm sure there are more.
1. to maintain some sense of contrast while listening at low levels.
2. I have a lot of cd's that aren't audiophile grade recordings some are downright terrible, to the point of being unlistenable to be able to give them some sparkle would be a wonderful thing. One more thing Paul I really appreciate your attention to this issue. I'm sure there are others out there as well who can see the value of an intelligently designed tone control.

[4krow]

I would add that while tone controls are sometimes an invasion into perfection, the real world may suggest otherwise. That is to say, as mentioned above, there are those recordings that need help, either in an addition or subtraction of frequency balance. Also, I don't like to admit it, but my ears hear a little different from one another these  days. Lastly, my room has few issues that could be diminished a bit with a little help. Other times, it is just fine to bypass the tone control altogether.