B1 with Korg Triode

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#3,184
Ok, as it seems acceptable to post links, and as some asked for it, that's where I got my Tocos Cosmos from (again, not advertising)

[url]https://www.ebay.com/itm/1pc-COSMOS-TOCOS-Potentiometer-RV24YG-20S-15A503-x2-A50k-x2-A50K-50K-24mm-Japan/142161428668?hash=item21197b40bc:g:qS0AAOSw5ZBWF-PV[/URL]

I hope that helps those who asked...

Bullit, if you go the trouble to test different pots in the B1 Korg, then for little money it might perhaps be of interest to you to try that one aswell. Who knows: if it works well you could end up keeping it (little money) while selling the expensives ones 🙂

Good chase anyway and let us know your findings, after all this is all about sharing DIY experience

Claude
 
#3,185
Hi Nash

Posts 2609 and 2611 might give you ideas about what caps to go for (values and type), what benefits to expect, what adaptation is required...

These posts are in fact a follow up of Zenmod's post which was a reply to my initial question... and in my case inspirational for the realisation of this tweak.

Have fun

Claude
 
#3,187
Been offered an integrated four source selector and 64 step attenuator with remote in one package for $200 from Khozomos. Just talking shipping now. Rotory Encoder for volume. I have a Galaxy 2U Chassis on order so have some room to play with. Looks like i'll need 5v for this board. What's the best way to reduce 24v down to 5 in this situation?

Khozomo Integrated.jpg
 
#3,190
Just asked for an invoice now. Apparently you push the knob to change the sources. $225 inc UPS is a great price for a remote volume set up. I run movies through my system so I like the convenience of that idea.

It's close to what you could pay for a motorised Alps blue and a decent Elma source switch. See how we go 🙂
 
#3,191
Can anyone tell me what resistance the ALPS blue in the kit is? My speakers are good for 106db per watt I'm thinking I should take what ever is in the standard kit and double it! Previously i've added resistors on each channel to a valve amp to get the volume knob a bit more manageable.

Thanks in advance

Steve
 
#3,192
Steve Luck said:
Been offered an integrated four source selector and 64 step attenuator with remote in one package for $200 from Khozomos. Just talking shipping now. Rotory Encoder for volume. I have a Galaxy 2U Chassis on order so have some room to play with. Looks like i'll need 5v for this board. What's the best way to reduce 24v down to 5 in this situation?

View attachment 783903
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Do you have a link for this one?
 
#3,194
I'm not sure if this is the correct place to post this question, but after having completed the Whammy headphone amp (well, it's up and running, but not in an enclosure yet) and loving it, I've gone ahead and purchased all the parts for a B1 Nutube pre-amp and the M2x power amp. My question is, is there any reason I cannot/should not put both the B1 and M2X circuit boards in the same enclosure? My intention was to put the power supplies for both into a separate box.

Thanks for any help/guidance.
Gary
 
#3,195
48804244258_82e8964f31_k_d.jpg


Here's another one. Built into a Naim 42.5 case/chassis for a friend. The chassis is now a bit 'over worked' many previous projects have been housed in this.

For the eagle eyed, I have only fixed (via stand offs) one side of the Korg board. This helps with the ringing in my opinion (not good practice I know) this particular B1 Korg build is super quiet.
 
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#3,196
stablgr said:
My question is, is there any reason I cannot/should not put both the B1 and M2X circuit boards in the same enclosure?
Click to expand...

You could do it, but if you build them as separate components, you'll be able to use these pieces with other amplifiers and preamps you build in the future. And you will build more, this hobby works like that... 🙂 🙂 🙂
 
#3,198
Steve Luck said:
Can anyone tell me what resistance the ALPS blue in the kit is? My speakers are good for 106db per watt I'm thinking I should take what ever is in the standard kit and double it! Previously i've added resistors on each channel to a valve amp to get the volume knob a bit more manageable.
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The efficiency of you speakers isn't relevant for determining the pot value. The pot loads the source and contributes to noise. It's a balancing act between a value high enough for your source to drive without problems but not so high as the add unnecessary noise. 50K is often a good compromise (as seen by the value recommended in the B1K article).

In addition, the source can load the pot if your source impedance is high. A rule of thumb is that the pot value should be at least 10x the source impedance. This usually isn't an issue unless you have a high impedance source.

Finally, the pot itself is subject to loading from the following stage. What the pot is driving should ideally have a high input impedance or it may load the pot in a way that adversely affects it's taper (Hence the B1 buffer in this design after the pot and before the Nutube).

Assuming your pot is a audio or log taper, you'd ideally want you typically listening position to be in the middle third of the rotation. With your high efficiency speakers, you may find you have too much gain and end up with a pot position in the lower third of the attenuation band which may be too sensitive. If this is the case, you'll want to adjust your gain structure somewhere.

You can add a voltage divider to adjust the gain, just be aware of the loading affects it may have on the pot (as discussed above). Another buffer stage may help.

Rod Elliott has a great article on this: Beginners' Guide to Potentiometers
 
#3,200
Zen Mod said:
L pad cells for attenuating excessive signals are robbing signal energy , issues in that department needs to be addressed differently
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Are you referring the lower leg of the pot reducing the current available to the stage that follows? If so that makes sense. If that is the case, this would be a scenario where a JFET stage following the pot would eliminate this as a concern (i.e. the B1 buffer). Is that correct?
 
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