Hoffman Amplifiers Tube Amplifier Forum
Amp Stuff => Tube Amp Building - Tweaks - Repairs => Topic started by: hesamadman on August 06, 2017, 04:15:38 pm
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Working on my first bass amp. Would like to install a 4 band EQ. Is there a schematic that anyone knows of for this kind of tone control?
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here's a couple to chew on :laugh:
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Some time ago Tubenit opened a similar thread and some schematics were posted, but I'm not able to find that old thread
on my archive I've something that may be interesting to be seen
Old Equalizer
(http://i.imgur.com/87JJj6C.jpg)
Old Stuff
(http://i.imgur.com/pb7VSAb.jpg)
Blackstar ISF
(http://i.imgur.com/pQHXnpq.gif)
Engl 530
(http://i.imgur.com/EgsUE70.png)
Modified FMV
(http://i.imgur.com/Bk4gkKu.jpg)
Modified FMV
(http://i.imgur.com/bSew36z.jpg)
Franco
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Thanks guys. That Engl 530 looks like exactly what I want. As for bass, I could just double the cap value correct?
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Tweaking that cap will adjust where the frequency is changed. There's a mathematical formula for calculating the frequency response of an RC or LC filter, but you could also just download and install Duncan's Tone Stack Calculator and enter in the exact circuit and try the different cap values until you find the graph you like:
http://www.duncanamps.com/tsc/ (http://www.duncanamps.com/tsc/)
~Phil
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here's a couple to chew on :laugh:
You might have a mean streak in you. But if you were really mean, doesn't RDH have a 16 band equalizer?
I actually like the idea of an active equalizer, So what do you you do, toss out every other tube, using tube 1, 3, 5, 7?
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You might have a mean streak in you
Mean, NO, smart A :cussing: maybe :icon_biggrin:
I believe Franco dug up the 7band awhile back, I'm just sharing :laugh:
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I meant the cab values in general. I was under the impression that doubling cap value makes it suitable for bass guitar application. I am aware that this is probably mostly leaning towards coupling capacitors, however I assumed a similar method here would apply to the tone control. In addition would need to adjust resistor values as well for the RC network to coincide.
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But I do have Duncan's calculator. Great tool. But it doesn't allow for 4 band EQ. At least the version I have doesn't.
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But I do have Duncan's calculator. Great tool. But it doesn't allow for 4 band EQ. At least the version I have doesn't.
Understood, but you can change one of the capacitors to the range you want to try and see how that changes the bass range ;)
~Phil
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I think RE6a gives a treble boost, and RE6B a bass, so closing 6b doubles the cap making your thought/logic the same as mine
As for bass, I could just double the cap value correct?
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Do you want a passive 4 band equalizer, or an active equalizer? SS or tube based? I found a three band equalizer CF based active, with a +150-0-(-150) setup, that could be converted to four band (I would recommend 5 band, to utilize 12a_7 tubes). a sch based schematic (untested). download and modify the drawing, probably could elevate the heaters and eliminate need for negative B rail.
I believe with some work, Shooter's seven band equalizer can be converted to a 4 band equalizer, including bass and treble boost. It would be the time to take out the old slip stick, a sharp pencil and engineering pad.
As stated earlier I like the idea of an active tone stack rather than the subtractive FMV tone stack.
Ampbooks has a discussion, and an evaluation method of the 5f6a tonestack. I believe you and use the technique presented to evaluate and split the mid tone.
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For some reason, Shooters schematic he posted didnt show up on my phone at all. I just logged in on my computer and saw it. HOLY GEEZE. No thanks on that.
I would like to stay with a passive EQ. The Engl schematic is perfect. Simple. Will just have to play with values I guess.
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HOLY GEEZE. No thanks
aaah, my feelings are hurt :icon_biggrin:
I do find myself trying to convince myself, this would be an awesome build :think1: :BangHead:
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aaah, my feelings are hurt :icon_biggrin:
I do find myself trying to convince myself, this would be an awesome build :think1: :BangHead:
I do agree. But too many tubes for this particular project. :laugh:
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I've find one 10 Band Equalizer, but in fact it uses a lot of triodes :icon_biggrin:
(http://i.imgur.com/eUeHSHI.jpg)
May be this 5 Band Equalizer is more adequate to the request
Marshall 9001
(http://i.imgur.com/qxF5Ast.png)
(Note that the 9001 is a SS amp preamp, this bring to think about different values to be used in a Tube circuit)
Franco
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HOLY GEEZE. No thanks
aaah, my feelings are hurt :icon_biggrin:
I do find myself trying to convince myself, this would be an awesome build :think1: :BangHead:
Its a perfect preamp for a rack, ptp :icon_biggrin: ; plus its not a CF. I would use a ss rectifier :dontknow:
Franco's 9001, tone stack is from a preamp,
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ptp :icon_biggrin:
nice
I've been saved from the abyiss!, my car broke, I have just spent the equivalent of "that build" on car parts :cussing:
kar-ma sucks :icon_biggrin:
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To be honest I would like to have something like the 9001 EQ plan disposable for a Tube Bass amp (I want to build in the future)
but, despite the fact that I've find the schematic as is (with the indication "From Tube" - "To Tube"), I don't remember the reason
but I'm sure I know (remember) that Tone Controls planned for SS circuits must change the components values to be used on
a Tube Circuit
Where I've find the schematic seems the guy who posted it used it in a tube amp, but he didn't say anything about component values
Franco
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Sounds like a bread board job. I like that 5 band EQ but honestly I think I'm gonna stay with the Engl 4 band. To start with anyway.
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The Engl has the advantage (and it isn't a small advantage), to be planned for a Tube Circuit and used on commercial amps (you don't want someting of ugly on your product...)
So I'm with you
Franco
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I looked into this for a while and basically the idea of using something other than the basic FMV tone controls is an academic exercise. Worthwhile to the learning process but personally I don't believe there is any advantage in shaping the tone. The improvement in clarity is lost on the audience and how much of a range benefit do you end up with? But, like I said, worthwhile to the learning process. I've found the best EQ circuit for me is to put a Mixer in the Effects Loop. You get, depending on the mixer, 3 EQ and a Mid shift as well as a compressor in many cases. A 4 chan. Mixer is under $100. From this you can determine how much of an advantage you will get by departing from the usual designs.
silverfox.
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You know, another thing I've thought about on this, isn't a foot pedal eq just as good at shaping tone in this kind of way? I'd wager you'd do better that way no?
~Phil
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improvement in clarity is lost on the audience
I use that card a lot with musicians, it falls on deaf ears :think1:
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@kagliostro: That 10 band vacuum tube eq article is very intriguing! (for hi-fi)
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I've find one 10 Band Equalizer, but in fact it uses a lot of triodes :icon_biggrin:
(http://i.imgur.com/eUeHSHI.jpg)
May be this 5 Band Equalizer is more adequate to the request
Marshall 9001
(http://i.imgur.com/qxF5Ast.png)
(Note that the 9001 is a SS amp preamp, this bring to think about different values to be used in a Tube circuit)
Franco
Could you upload this schematoc again please?
opacheco.
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Ciao Opacheco
Could you upload this schematoc again please?
I don't understand ... which schematic are you asking for ?
You linked an old post with two schemarics and I see them well, so I don't understand what are you asking for
Please specify
Franco