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Old 17th December 2002, 11:25 PM   #1
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Default Adding Treb and Bass adjustment?!

I'm afraid I'm a newbie when it comes to tube ckt design so I'll defer to the experts. Would there be an easy way to add treble and bass controls to this design? It's the one thing keeping me from plowing head-on into soldering bliss

Active? Passive? Your thoughts are appreciated! TIA! -Cory
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Old 18th December 2002, 12:28 AM   #2
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Default GUITAR AMP?

Hi,

No that would be a piece of cake.
Just put the pots at the input of the amp.

Cheers,
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Old 18th December 2002, 12:55 AM   #3
Gunders is offline Gunders  Norway
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Default .....not an answer

Hmmm... I'm just wondering....
It seems like this amplifier is using a voltage doubler in the power supply, is that correct???
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Old 18th December 2002, 01:05 AM   #4
Gunders is offline Gunders  Norway
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Yes there is an easy way to add bass/treble controls, and simplest is to use a passive bass/treble.
I have attached a picture of a bass/treble control, this schematic is taken from a Marshall JCM 800 2210 preamp.
You simply add this control between your first stage and the next.
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Old 18th December 2002, 01:09 AM   #5
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Default NO YOU DON'T!!!!

Hi Gunderz,

No way.
That would require a redraw of the whole circuit.

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Old 18th December 2002, 02:30 AM   #6
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Default Passive is fine but put it in the right place

The original circuit in this thread shows a power amplifier. It is not customary to install any type of tone control within a power amplifier. The overall feedback within this amplifier would get badly out of whack by the addition of a tone control within the feedback loop.

A passive or active bass and treble control can be added at the very input of the amplifier. Care should be taken that the tone control circuit is driven from a low impedance source. Thus some kind of follower to drive it may be required. Personally I prefer the Baxandall tone control circuit, which is a one stage active type and is usually driven from a cathode follower.

John Fassotte
Alaskan Audio
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Old 18th December 2002, 12:24 PM   #7
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Default TONE CONTROLS

Hi Cadman,

Didn't you want a preamp to go with this amp?

Tone controls are much easier to handle at the preamp than on the amp.
And that is where these are usually fitted.

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Old 18th December 2002, 03:47 PM   #8
Joel is offline Joel  United States
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I've had a lot of luck with an active circuit from the RDH. It uses half a 6SN7, or a 6J5 for the treble, and one for the bass. It allows boost AND cut, 6dB per octave.
The problem with most passive controls is that they can only boost, and also that they cannot boost the midrange at all (even Fender circuits that have a midrange control!).
IMHO if you're using it for a hi-fi, you must go with active.
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Old 18th December 2002, 03:53 PM   #9
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Default TONE CONTROLS

Hi,

I agree with you Joel.

Since he already expressed the desire to build a preamp as well I suggest an outboard active box (withe toobs of course).

By doing so all elements (pre and amp) stay intact and the tonecontrols can be brought into service when needed.

I quite like the circuit at headwize with all the CFs.

Cheers,
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Old 18th December 2002, 10:12 PM   #10
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Default A lot of possibility here!

Hmm, that Baxandall circuit http://msswartz.tripod.com/baxandall1.htm looks like quite an elegant solution. Would it be permissable to couple my low-Z preamp to the power amp with such?

I'm still on the fence with whether to go with that, or something like Joel suggested. My previous amp used two halves of a 6SL7 in such a way, but the downside is a parts count of 2 dozen or so. I think the headwize ckt is a little extreme w/ 6 tubes for 2 channels.

With that amp I usually have the Treb control at 95% (I like my highs ) and Bass somewhere between half and full. Do you think I'd be satisfied with the Baxandall? It looks fairly popular.

Gunderz, yep it's a v-doubler circuit. Gotta get the 700v somehow The trans is a 240v toroid at 1 amp!

The plan is to integrate both monoblocks and the preamp into one chassis. Add tone controls (w/bypass switch), IR remote, microprocessor control with LCD and 4 switchable inputs. The EL509 fil's take 2.5A a piece (the fil xformer is 20A!) At 150w per channel it should get the job done!

So what do you think? Will Baxandall cut it? Can I couple my pre to power with it?
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