Hoffman Amplifiers Tube Amplifier Forum

Amp Stuff => Tube Amp Building - Tweaks - Repairs => Topic started by: tubenit on July 12, 2015, 06:07:45 pm

Title: Another OD tone stack idea?
Post by: tubenit on July 12, 2015, 06:07:45 pm: I have wondered about shaping/contouring the OD channel by using a James Tone stack which can be dialed to a "pseudo mid-boost" or mid scooped almost similar to Fender. * see attached screen shots demo'ing this.

I'm wondering if the ability to add or lessen mids in relation to treble and bass might allow someone to dial in more smooth and/or more crunch? I think it could be cool to have sort of an overdrive contour one knob pot.

I was thinking about building this on to a dual gang 250ka pot & trying it out? I am aware of the loss of gain using a James tone stack. However, I usually use 5751's in the OD and hardly ever have the 100ka pots dialed beyond 5-7.

Anybody try anything like this? Thoughts??

with respect, Tubenit
Title: Re: Another OD tone stack idea?
Post by: Fresh_Start on July 12, 2015, 10:46:55 pm: My first question is what happens if you reduce the value of R4 (180K)? It's the "upper" half of two voltage dividers AFAICT?

Second, you haven't been afraid of MOSFETs before so why not use one as a cathode follower to drive your OD tone stack?

Cheers,

Chip

P.S. Don't have access to Duncan's TSC right now or I'd answer the first question myself.
Title: Re: Another OD tone stack idea?
Post by: John on July 13, 2015, 05:52:29 am: Quote
I am aware of the loss of gain using a James tone stack.

I think the James stack is actually much less lossy that the standard FMV?
Title: Re: Another OD tone stack idea?
Post by: kagliostro on July 13, 2015, 06:53:25 am: Quote
My first question is what happens if you reduce the value of R4 (180K)?

I think this can give an answer to your question

(http://i.imgur.com/Au9V6W8.jpg)

(http://i.imgur.com/JU0eG5f.jpg)

Franco
Title: Re: Another OD tone stack idea?
Post by: tubenit on July 13, 2015, 08:27:45 am: Gentlemen,

Thanks for the responses! I have tried the James tone stack after cathode followers several times and didn't care for it too much. It seems to work well directly off of a plate though. It seemed sort of sterile/hi-fi off a CF for some reason but had warmth directly off a plate. When I tried it after a CF, I would eventually end up with a FMV type tone stack instead.

Parameters are that it has to be done with a dual gang 250ka pot and get the mid boost and mid scooped tone.

I hope to try this sometime this week or this coming wkend and will report back.

With respect, Tubenit
Title: Re: Another OD tone stack idea?
Post by: kagliostro on July 13, 2015, 11:26:04 am: Quote
I hope to try this sometime this week or this coming wkend and will report back.

waiting for your report with interest

Franco
Title: Re: Another OD tone stack idea?
Post by: jjasilli on July 14, 2015, 10:47:28 am: Here's some info, though focused on pedals: http://www.mylespaul.com/forums/pedals/108296-eq-your-distortion-tips.html (http://www.mylespaul.com/forums/pedals/108296-eq-your-distortion-tips.html)

The general consensus seems to be that too much mid or bass > overdrive tends toward muddiness. Afterwards, Overdrive adds harmonics so it's good to tame hi's after the OD circuit. It seems your idea accomplishes this. I suspect a James stack should work well after an OD circuit.

But, 2 complete tonestacks in the signal path may require a lot of fiddling, especially if different tone settings are required when switching between Clean / OD. Meanwhile, on a pedal board the [OD pedal along with its chain of pre & post eq pedals, compression, etc.] can be entirely looped in & out of the signal path in one-fell-swoop without fiddling.
Title: Re: Another OD tone stack idea?
Post by: jjasilli on July 15, 2015, 11:32:49 am: I guess I'm re-stating the old argument in favor of a true two-channel amp, with separate tone controls for ea channel.
Title: Re: Another OD tone stack idea?
Post by: tubenit on July 18, 2015, 05:51:44 pm: Didn't work. Yes, it was versatile but there are other approaches that are "smoother" in tone without the insertion loss. A "cut" control or the pseudo 5E3 tone stack still seems to be the best,IMO

With respect, Tubenit
Title: Re: Another OD tone stack idea?
Post by: kagliostro on July 21, 2015, 05:46:57 am: Just curious

someone tried this ?

(http://3.bp.blogspot.com/-TPVVms8B0JI/T7eVRb9Fl0I/AAAAAAAABVw/YaPxTm_sIfU/s1600/blackstr_isf.gif)

http://el34world.com/Forum/index.php?topic=17379.msg174016#msg174016 (http://el34world.com/Forum/index.php?topic=17379.msg174016#msg174016)

Franco
Title: Re: Another OD tone stack idea?
Post by: stevehoover on August 08, 2015, 11:52:54 am: +1 on the 5e3 control, I added a bass shelving control after that and was pretty happy with it in a plate loaded circuit.
Title: Re: Another OD tone stack idea?
Post by: jojokeo on August 10, 2015, 11:09:50 pm: tubenit,

This may not be your cup of tea but it works real well for me. I don't have room on the faceplate for a mid pot but this Mid Shift switch ends up working better actually. Having the Mid switch really has it's benefits. As you know the loading effect changes as well as the frequency response with a different Mid value/setting and with a pot it varies all over the place when combined with various Treb & Bass settings. Having a Mid pot makes it difficult to consistently find your sweet spot but getting used to the switch really helps find it again and again on your favorite settings in it's 3 different positions. This can be a big time saver depending on your uses (gigging vs recording). Your values may vary...