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Old 25th November 2010, 12:09 AM   #1
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Default Aikido w/ tone controls

So, I'd really like to have some tone controls in front of my amp. I know many consider this blasphemy, but like many people, my listening room isn't ideal, I can't always listen at an ideal volume, my hearing was damaged by Dinosaur Jr. in 1988, etc.

I'm thinking of adding this modified Harmon Kardon circuit (Figure 5). Since it has 20dB attentuation, I've been thinking about trying to incorporate them into a Aikido line stage.

Is it possible to plop the tone controls between the input and output stages in the Aikido, or would I be better off placing them between the Aikido output stage and a cathode follower (perhaps an ACF)? This latter approach is somewhat similar to the Aikido phono preamp, which looks like an RIAA equalizer sandwiched between 2 Aikidos.
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Old 25th November 2010, 12:55 AM   #2
cjkpkg is offline cjkpkg  United States
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Funny thing is that my first amp for the listening room was a vintage Yamaha and I always fussed with the bass and treble controls. Now the system consists of "typically" the Aikido 5687 preamp and an amp. I rotate between an EL84PP, MOSKIDO, PASS F5, and I am at the final stages of a 300bSE amp.

Speakers are CHR70 drivers in a Fonken cabinet. These things put out crazy bass for a 4" driver - larger than any 6.5" bookshelf I have ever heard.

I really dont feel like I NEED to fuss with bass and treble controls. Typical music is chill and old school jazz and at moderate to low listening levels unless I'm home alone.

Have you built the Aikido yet? What is your amp and speakers?

I would say try it without first and if you still feel like you need equalization, put a nice EQ in the mix.
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Old 25th November 2010, 04:06 AM   #3
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I haven't built the Aikido yet. My sources all put out around 2V peak, so I don't really need a linestage. The only reason would be to add the tone controls, and perhaps a balance. It would also be nice to have a stepped attenuator, and not have to re-do it if I change power amps.

My amp (for now) is a K-12G, but I'm thinking I'm going to build an ST-70 next. At some point I'd like to design and build a SE amp, but I'm not there yet. Speakers are Fostex FE-207E in the Quarter-Wave ML TL design.

I understand what you're saying about regarding the tone controls. To be honest, a lot of this is that I just think it would be a fun challenge. If it doesn't come out all that great, I can just drop it, or give it away. The Aikido isn't terribly expensive to build.

Last edited by sneakers563; 25th November 2010 at 04:10 AM.
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Old 25th November 2010, 11:21 AM   #4
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with the Fostex, you will need some kind of baffle step compensation to tame the shout.... probably would be an elegant solution to build it in as a shelving filter/equaliser/tone control in your aikido... you can easily incorporate a bypass switch when you do not want to use the Tone control.

Aikido + F5 + Fe206E system.
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Old 25th November 2010, 12:23 PM   #5
cjkpkg is offline cjkpkg  United States
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Even with 2V p-p you will need more gain for full power output, especially with a SE amp. Even an ST70 would benefit from the addition of a line/gain stage.

I definitely understand the "what if?" and "because I can" - personally for me this hobby has really taken hold. I have found that first I build a circuit as designed and then tweak from there if needed. Many times the original designers chose conservative values for operating points as something that might be produced in volume.

Build the aikido first and then see if tone control is even needed.

quikie22 - I like the idea of some passive equalization at the speakers...
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Old 26th November 2010, 03:09 AM   #6
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Yep, I built the baffle-step correction circuit into the speakers, but it's an interesting idea integrating it into the preamp. When I built the speakers, there was a range of possible values given for the resistor and inductor, so I just kind of took a stab. I think they sound quite good as-is, but I've wondered whether I couldn't tweak them a bit.

As for "needing" the linestage, I wasn't really clear. My primary source are lossless music files stored on a laptop and piped through an AMB gamma2 DAC. The max output is actually 4V p-p, so I get around 1.4V RMS.

I take your point about building the standard circuit first. That's good advice. But, since I've already broached the subject and have your attention, do you have any thoughts about where to place the controls if I do ultimately decide to go that way?

I'm thinking volume control -> aikido -> tone controls -> cathode follower but I don't know if that's overkill, and whether it's permissible / possible to put the tone controls between the two aikido stages without messing the whole thing up.
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Old 26th November 2010, 04:31 AM   #7
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Quote:
Originally Posted by sneakers563 View Post
So, I'd really like to have some tone controls in front of my amp. I know many consider this blasphemy, but like many people, my listening room isn't ideal, I can't always listen at an ideal volume, my hearing was damaged by Dinosaur Jr. in 1988, etc.

I'm thinking of adding this modified Harmon Kardon circuit (Figure 5). Since it has 20dB attentuation, I've been thinking about trying to incorporate them into a Aikido line stage.

Is it possible to plop the tone controls between the input and output stages in the Aikido, or would I be better off placing them between the Aikido output stage and a cathode follower (perhaps an ACF)? This latter approach is somewhat similar to the Aikido phono preamp, which looks like an RIAA equalizer sandwiched between 2 Aikidos.
Hello,
I am a little Skitzoid or beside myself on this one too. I went to the symphony last weekend. Sitting there in my seat I wanted to turn up the volume and make a couple of other adjustments, not possible.
I use an Aikido RIAA, ACF plus the original Aikido stepped attenuator every day. I have often considered a tone control somewhere in there that operates step wise similar to the stepped attenuator a couple of db per stepp. The RIAA may be perfect, the line stage may be perfect but the speakers and room are not. Turn the volume up or down on a perfect system and my not so perfect ears need adjustment too (think Fletcher Munson curves).
Equalization and tone controls are not a crime. I would much rather make adjustments at the line stage than between the amplifier and speakers. For that matter the crossover also belongs at the line stage as well.
DT
All just for fun!
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Old 26th November 2010, 05:42 AM   #8
dsndblm is offline dsndblm  United States
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I used that tone control circuit in a 6AQ5 push pull amp that I made for my son. It works well.
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Old 26th November 2010, 08:20 AM   #9
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I've installed a line level BSC circuit for my Fostex FE207E EBS bass reflex speakers at the input to my 2W Spud amp. Really worthwhile - gives much better bass and doesn't waste the little power from the amp on a lossy passive circuit in front of the speaker.
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Old 26th November 2010, 11:14 AM   #10
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Quote:
Originally Posted by cjkpkg View Post

quikie22 - I like the idea of some passive equalization at the speakers...
Quote:
Originally Posted by sharpi31 View Post
I've installed a line level BSC circuit for my Fostex FE207E EBS bass reflex speakers at the input to my 2W Spud amp. Really worthwhile - gives much better bass and doesn't waste the little power from the amp on a lossy passive circuit in front of the speaker.
I tried the passive equalization and found the dynamics of the music gone. Like sharpi, I find that the line-level solution more elegant and gives better sound with no loss in speaker sensitivity and sound quality.
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