Emerson EM Drive vs. Emerson Paramount

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sliberty
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Post by sliberty »

Last week, I built the Emerson EM Drive. I had originally intended to build the Paramount, but for simplicity, I started with the EM Drive. Initially, I used a 2N5088 which was listed on the diagrams I have for the EM Drive, but it was too overdriven and compressed. I'd read somewhere that the 2N3094 was a lower gain transistor, so I tried one of those (I socket the transistor of course), and, well, it sounded great. Just a hint of grit on low to medium settings, and very transparent. I was really intrigued, so tonight I modded it to be a Paramount. Basically, the difference is the 100nF input capacitor (EM Drive) vs. the tone control with 2.2nF and a 220nF capacitors attached (Paramount). Also, the diagram listed a different transistor, which I don't have on hand. So, initially I left the 2N3904 in place, but all of the grit was gone. I then tried putting the 2N5088 back in, and I got back much of the grit, but I still feel like it lost some gain. The tone control is pretty cool actually, as turning it to the left beefs up the bass, and turning it to the right reduces the bass and increases the treble (a little). You can get some real beef out of this control, but I miss the low gain grittiness.

I am guessing that the loss of gain is due to the fact that the tone pot is introducing a series resistance into the input portion of the circuit - its like having another gain pot, and turning it down some halfway. Is that right?

I've see a mod that adds a tone control to the EM Drive in a different manner, and may try that.

I'll also try the referenced transistor later this week when my parts order arrives.

Any thoughts on this would be appreciated.
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newly
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Post by newly »

Paramount use MPSA13 which is a darlington pair.
Gain vise, darlingtone pair have much higher gain than the common NPN that you are mentioned.
Darlingtone pair easily have hfe around 800 or above.
You may try check out MPSA13.

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sliberty
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Post by sliberty »

Yes, that transistor is what I have on order.
So are you confirming that the addition of the tone control is attenuating the input, and a higher gain transistor is needed?

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