Bottlehead Forum

Bottlehead Kits => Legacy Kit Products => Quickie => Topic started by: mcandmar on January 11, 2015, 11:09:20 AM

Title: Quickie gain question
Post by: mcandmar on January 11, 2015, 11:09:20 AM

What is the gain and max output voltage a PJCCS Quickie can reasonably be expected to output assuming a 2v rms input?

The product page doesn't list any of the specs for the quickie so i'm having trouble working out its output level vs the Smash and Beepee.

Thanks,

Mark

Title: Re: Quickie gain question
Post by: Paul Birkeland on January 11, 2015, 11:26:40 AM

I actually have taking these measurements on my task list for the near future.  PJ will certainly weigh in with an estimate undoubtedly, but we will update the product pages shortly with some measurements of the stock Quickie and the Quickie with the PJCCS.

-PB

Title: Re: Quickie gain question
Post by: mcandmar on January 11, 2015, 12:14:02 PM

Thanks Paul, care to make a guesstimate?

As i have the Quickie its my reference if you like, so i am interested to know how these two compare. Also is the max output voltage of the Smash higher with the C4S upgrade?

Thanks,

Mark

Smash Gain 10dB, max output 7V rms

BeePree Gain 8.3dB, max output 18v rms

Title: Re: Quickie gain question
Post by: Paul Birkeland on January 11, 2015, 12:49:47 PM

Quote from: mcandmar on January 11, 2015, 12:14:02 PM

Thanks Paul, care to make a guesstimate?

I don't have the triode curves handy, but I'd imagine PJ will have an estimate of the Mu at least.

Quote from: mcandmar on January 11, 2015, 12:14:02 PM

Also is the max output voltage of the Smash higher with the C4S upgrade?

The maximum output voltage of the Smash does go up with the upgrade, both because of the C4S loads, and because of the altered operating point.  At the same time, distortion will also drop significantly at all voltages.

-PB

Title: Re: Quickie gain question
Post by: Paul Joppa on January 11, 2015, 01:50:42 PM

Stock Quickie gain 2.2 (7dB), output impedance  2Kohms, max output 2.3 to 3.5vRMS depending on battery condition. There is some distortion at this maximum output; for clean output I would use about half that.

With the PJCCS or a choke load (Hammond 156C), gain is about 4.4 (13dB) and maximum output is 4.5 to 7 volts RMS depending on battery condition. Output impedance is about 4Kohms. The distortion is lower so you can approach this maximum more closely.

Above are theoretical design calculations, not measurements. And they assume a high impedance load of at least 50K ohms.

Title: Re: Quickie gain question
Post by: mcandmar on January 11, 2015, 02:26:27 PM

Perfect thanks Paul, the amp i am looking to drive has an input impedance of ~50k so that gives me a good starting point to work out what i need.

Somewhat related question, what would happen if i tried to use the S.E.X. as a preamp to drive a 47k input?   I assume the volume control would be pretty much unusable, but would there be any drastic frequency roll off, or increased distortion?

Title: Re: Quickie gain question
Post by: Paul Joppa on January 11, 2015, 04:19:03 PM

No problem, SETs are very happy with high load impedances.