Tone controls?????

[dnm]

Which of the Bottlehead preamps incorporate tone controls:  bass and treble?  If none of them do, then is there a mod that had been successfully built in to the Foreplay, for example?

Thanks!

[Grainger49]

We don't need no stinking tone controls. . .     Seriously, the Bottlehead equipment are all flat, no tone controls.  At the prices they charge you don't usually get tone controls.  

[Paul Joppa]

I just finished the detail design of a custom version of the "Repro" preamp, made for variable phono equalization. Now I REALLY understand why we don't mess with tone controls - what a lot of work!

Angelfire http://www.angelfire.com/electronic/funwithtubes/Amp-Tone-A.html has a good discussion of tone controls. Figure 9 is a passive Baxandall that can go between a preamp and power amp. You lose 20dB of signal level, but if you are among the many with excessively sensitive power amps that could be a blessing in disguise.

[edfallon]

Figure 9 is a passive Baxandall that can go between a preamp and power amp. You lose 20dB of signal level, but if you are among the many with excessively sensitive power amps that could be a blessing in disguise.

The concept of passive tone control seems like it could make a perfect black box accessory kit.  Was that already on the list of future products?  Lot's of folks trying to use Foreplay and hi gain amps might benefit from this.  Plus, a little tone control might be nice too if you can tolerate some phase shift.

[JC]

Boy, that was my first thought, too.  Paul may hate me for suggesting this, but I think adding a midrange control to this might make it viable as a stand-alone passive kit.

Of course, then you could have an optional version that added the lost gain back.

Oh, wait...

I think the phase shiftiness is precisely why tone controls have fallen out of favor.  No clue as to what the solution to that one is.

[Paul Joppa]

Boy, that was my first thought, too.  Paul may hate me for suggesting this, but I think adding a midrange control to this might make it viable as a stand-alone passive kit....

So, like the old Pultec MEQ5? That would be cool, I'd love to do it. It should be possible for only a few grand. Tell you what, as soon as we get 50 orders (50% deposit OK?) I'll start talking to winders for the custom tapped chokes and transformers...  :^)

Seriously, I'd expect a $99 kit to sell better. But Doc B makes those decisions!

[JC]

Hey, as long as you're at it, you may as well throw in a few more bands and call it an Equalizer!

I've actually worked on a couple of vintage Ampeg guitar amps that had that flavor of passive EQ, chokes and all, but I've never seen that class of HiFi equipment...

I do wonder, though, if a stand-alone tone control amp with active tube circuitry would generate any interest.  I was thinking more along the lines of a Foreplay Plus, though!

[ironbut]

Hey hey,.. just stumbled across this thread.
I'm planning on building the Gyraf Pultec PEQ1 clone using the Sowter's one of these days. It's pretty far on the back burners but I want to use it to add some of that midrange goodness to the live recordings I do (strictly amateur hour recordings but fun). I figure that I'll build it according to the Gyraf design and try different combos for the "make up gain".

One idea that might work for a cheap alternative is to buy an old preamp with tone controls and pull the boards of the passive eq in it (or just bypass everything else and just use the chassis and eq). I have an old GAS preamp and IIRC, the 3 freq tone controls on it weren't too bad. The last time I saw a preamp like mine on the used market, it was $50. Of course, I haven't got a clue what it would take to interface it with a couple of tube circuits.

[dnm]

Thanks, everyone so very kindly for responding...     I understand that it is the simplicity and purity of these designs that make them sound good.   With that in mind in this exploration - I have ordered the Foreplay (extended) -- I  look forward to putting it together and enjoying it.   I do think that the concept of adding filtering/tone stages is at war with the purity concept, but I wondered what others think.  One is better off sonically when matching components instead of having a half dozen dials to twist and having the signal travel through all the supporting circuitry.  It ain't just a price point thang.

When I reach break-in, I'll assess where I am.  When there, I presume that others may have pursued a "hotter" or "softer" high-frequency response by tube rolling or capacitor rolling or some such.   

So, when I reach that point, I may have more questions. 

I'll also say that Doc B and the Queen were great when they answered my questions about their pre-amp, and that figured strongly in my decision to pursue this as my venture into the diy pre-amp tube world.

Thanks again!

[Grainger49]

We actually flavor out rigs in more complex ways.  Rolling tubes, changing capacitors, changing resistors, different interconnects, different speaker wire and biggies cartridges and speakers.  All these things tilt and tweak the frequency response.

I don't think anyone here would seriously tell you that if you like using treble and bass you can't.  I know I have some 60s rock that screams out for both.

Get yourself a couple of pair of tubes to roll through when the build is done.  They don't have to be the high dollar tubes, I bought a pair of Toshiba 12AU7s that were interesting for $6.

Enjoy!

[InfernoSTi]

My solution to bass/treble tone control is to bi-amp which allows me to adjust the treble/mid and the bass independently.

I have some DIY Open Baffle speakers with a nice set of Hawthorne Audio Augie "woofers" that begged for a bit more power than any of my sub-five watt tube amps could provide, so I bi-amp such that my tweeter/mid run off my tube amp and I use a pair of Rythmik 370 OB plate amps to drive my Augies in true stereo.

These plate amps have a switchable 12/24 db low pass, a crossover frequency level, and a gain level that can be adjusted depending on preference.  I have a general setting that I like "mostly" but certain recordings beg for a bit of tweaking: adjusting the gain and crossover allows some pretty major tuning, while switching the low pass from 12/24 changes the character by creating more/less of a upper shelf and adds more than a subtle character change.  Combine this with a separate gain on the tube amp for the tweeter/mid and I can adjust the treble/mid quite effectively. 

It can be pretty subtle too.  For example, if I need a bit less high bass/low mid, I can crossover lower than normal, say 50 Hz or so and/or switch to the 24 db shelf to make a hard low pass shelf (or if I need more I crossover higher, say 125 Hz or so and/or switch to the 12 db low pass for a smoother roll off).  With three distinctive adjustments on the bass and a separate gain adjustment on the treble/mid, the variables are numerous and complex indeed.

Bi-amping with the right second amp thus provides fairly detailed tone adjustment for balancing bass and treble/mid without adding any additional "stuff" in the signal path.  I never really thought about it as a set of tone controls until I set it up and started using it that way quite naturally. I was just looking for a bit more punch from the Augies, if you will. 

The adjustments are an enjoyable listening ritual now, particularly with a serious listening session.

Food for thought....

John