Another Stereomour build

Carbon13 · 3270

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Offline Doc B.

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Reply #15 on: July 22, 2021, 04:51:25 PM
Quote
which has tone controls

Dan "Doc B." Schmalle
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Bottlehead Corp.


Offline Carbon13

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Reply #16 on: July 23, 2021, 07:53:36 AM
Yes, and I agree that is the difference. Tone controls.

When I first looked at the stereomour, I thought it would be a great match with the fortes given they are relatively high sensitivity. When I found the match a bit thin on the bottom, I initially thought it was because it's a low power amp. But it played plenty loud. So that's why got the preamp with tone controls and yes, that seems to work. Only downside is it limits my number of inputs and kinda defeats the purpose of an integrated.

Doc - it's no fault of the stereomour! It's a fantastic amp and I absolutely love how it sounds. It's just been a bit of a mismatch I think with these speakers that requires some additional fine tuning to dial in the sound I'm looking for. If anything, I think people should be reassured that it's plenty of power to drive these large speakers to ear bleeding levels ;)

Paul - The passive shelf filter sounds like an interesting option but I will admit that I'm outta my league on designing something like that. I'll have to research it and see if it makes sense. Alternatively, I may have to try some new speakers ;)



Offline Paul Joppa

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Reply #17 on: July 23, 2021, 08:25:16 AM
I'll work up a circuit for this - it should be possible to build it into the Stereomour.

Paul Joppa


Offline Carbon13

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Reply #18 on: July 24, 2021, 06:30:55 AM
Thanks Paul! That would be amazing! I'll have a custom tuned stereomour;)



Offline Paul Birkeland

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Reply #19 on: July 24, 2021, 07:38:16 AM
I'll work up a circuit for this - it should be possible to build it into the Stereomour.

Tuned cathode bypass on the driver? ;)

Paul "PB" Birkeland

Bottlehead Grunt & The Repro Man


Offline denti alligator

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Reply #20 on: July 24, 2021, 11:26:36 AM
So I have the Forte IIs. Not sure how they compare with the Forte I you have, but mine sound best with the Stereomour set at 4ohms. However, I might still be missing out on something. Here’s the frequency response, though not sure sure to what degree this is altered by the Crites upgrades.

https://community.klipsch.com/index.php?/topic/170785-alk-xover-diy-for-forte-ii-schematic/
« Last Edit: July 24, 2021, 11:39:55 AM by denti alligator »

- Sam

Rega P3-24 (w/AT 150MLX) w/Groovetracer upgrades / Eros II / FLAC >J.River >DSD256 >Gustard X20 / Moreplay > Stereomour II / Klipsch Forte II w/Crites upgrades / C4S S.E.X. 2.0 +Nickel MQ Iron / Speedball Crack / Sennheiser HD600 w/Cardas cable


Offline Paul Joppa

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Reply #21 on: July 26, 2021, 09:29:18 AM
**** Passive bass boosting with Stereomour II ****

Note: This is actually cutting everything above the bass by a few dB, so you will need to increase the volume setting for the same loudness.

The simplest way to do this is with a series RC network, placed across the volume control potentiometer. Connect a 15Kohm resistor to one end of the volume pot, connect 1 0.022uF capacitor to the other end of the pot, and connect the free end of the capacitor to the free end of the resistor. Insulate that connection with heat-shrink tubing or electrical tape so it can't touch the chassis or any other nearby wires or terminals! Repeat for the other channel. This will be a tight fit.

This gives about 5-6dB boost to the bass below about 350Hz. You may want to try some different component values to get the effect you want:

Increase the capacitance to get a lower transition frequency, or decrease the capacitance to get a higher transition frequency.

Increase the resistance to get a smaller boost AND a lower transition frequency. Don't  decrease the resistance, because that will reduce the input impedance and sensitivity of the amp too much.

Paul Joppa


Offline Paul Birkeland

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Reply #22 on: July 26, 2021, 10:36:31 AM
For a much harder way, you could bypass the 365 ohm cathode resistor with a choke, cap, and resistor in series to bring up the gain in the midbass. 

I would start with:
https://www.mouser.com/ProductDetail/Murata-Power-Solutions/13R336C?qs=gLyyx31KZaCXYrPIar3DqA%3D%3D

https://www.mouser.com/ProductDetail/Nichicon/UDB1H6R8MHM?qs=kArNe9LFxXkiWy78BPgsnw%3D%3D

https://www.mouser.com/ProductDetail/Vishay-Dale/RN55D10R0FB14?qs=60NadEv6cQm8bIQ8le8fAg%3D%3D

Those three parts are wired in series, then tacked across each 365 ohm resistor.  Reducing the resistor value increases the effect of the filter, so putting a 100 ohm pot in there is also a reasonable choice as an experiment.  In fact you could probably find a 100 ohm stereo linear pot to just temporarily stick to the chassis, then wire this up from there. 

The L and C can be adjusted to change the shape of the filter and/or the frequency where you get the most boost. 

PJ's circuit is a lot easier to mess with though!


Paul "PB" Birkeland

Bottlehead Grunt & The Repro Man


Offline Carbon13

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Reply #23 on: July 27, 2021, 05:34:17 AM
Thanks guys! PJ, is this doable with the mourquiet upgrade? That's what I currently have in place.



Offline Carbon13

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Reply #24 on: July 27, 2021, 06:10:24 AM
I just found this thread on redesigned crossover for forte 1s, maybe another option?

https://community.klipsch.com/index.php?/topic/106102-developing-a-network-for-the-forte/



Offline Paul Joppa

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Reply #25 on: July 27, 2021, 06:19:06 AM
Thanks guys! PJ, is this doable with the mourquiet upgrade? That's what I currently have in place.
Alas, it is not. I'll ping PB and see if we can come up with something.

We worked on a tone-control preamp a while back. That gave us the initial design ideas for the Moreplay preamp, but the additional stage and controls added too much cost and complexity for what we expected would be a small audience.

Paul Joppa