Quickie as a line amp

[dtroise@bellsouth.net]

Hi
I was wondering if the quickie could be used as a line amp and how it would function in that capacity,
I also would like to know how much gain that it has.

Thanks
Don

 

[Chris65]

Do you mean a 'line stage'? aka a pre-amplifier.
Thread about the Quickie's gain: http://bottlehead.com/smf/index.php?topic=7325.msg70730#msg70730

 

[dtroise@bellsouth.net]

No
I mean a line amp to boost the signal over distance
Don

 

[Doc B]

Typically you want a device with very low output impedance to drive a long cable run. That is not the Quickie. Gain is about 6dB. The Crack could do what you want, its output impedance is a lot lower. Gain is somewhat higher, but of course there is a level control.

 

[dtroise@bellsouth.net]

Thanks Doc
I never thought about the crack, I just built one for my little Brother and really loved it while I broke it in, very quiet and musical, he is ecstatic.  If I use the crack could I drop the coupling capacitors down in value to a much lower uf, I used 68 uf Polypropylene  in his and had to fit them to the side panels as they were quite large.

Don

 

[Doc B]

The load impedance is the determining factor for the minimum cap value. If you can tell us what the input impedance of the gear you are driving with the Crack is, we can suggest a value.

 

[dtroise@bellsouth.net]

It is an Akido pre amp and I believe that it is 10,000

Don

 

[Paul Birkeland]

What's the value of the volume pot on that preamp?

 

[dtroise@bellsouth.net]

The pot is 50000 that is what I chose when I built it because it runs 4 6sn 7 tubes, it is feeding all tube amplifiers as well, I am not really positive as to what the input imp. is for this circuit

Don

 

[Paul Birkeland]

If the pot at the input of the preamp is 50K, and there aren't super high gain triodes like 12AX7's or 6SL7's sitting right after the pot or absurdly low plate voltages on the tubes (not an issue with the Akido), then the input impedance is 50K.

 

[dtroise@bellsouth.net]

O K,  so what size can I drop the crack caps down too, I want to use jupiter wax but I want them as small as possible , I already have an aikido line amplifier that I have .47 caps in.

Thanks
Don

 

[Paul Birkeland]

I would use at least 1.5uF.  You could just use paralleled .47uF caps to get there.  If you use a Crack as the line driver, the voltage rating on these caps can be anything at or above 160V. That makes something like the V-cap OIMP 2uF/250V an affordable choice.  The 100V rated Jupiters aren't a good choice unfortunately without reworking the circuit a little bit.

-PB

 

[dtroise@bellsouth.net]

Thanks for that info, the Jupiters are 600 volt, they are the copper version and I think they sound better than V-caps,shouldn't they be OK,  or is the heat an issue ?

Don

 

[Paul Birkeland]

I don't believe heat will be an issue.  Long, long ago Jupiter caps were somewhat sensitive to heat, but that's more of a non-issue these days.  The key to keeping your kit running at thermal equilibrium so to speak is to install the supplied rubber feet on the base to allow for proper air flow.