Hoffman Amplifiers Tube Amplifier Forum

Amp Stuff => Tube Amp Building - Tweaks - Repairs => Topic started by: kagliostro on September 17, 2012, 03:18:52 pm

Title: A strange circuit I've never seen before - I'm not able to understand it !
Post by: kagliostro on September 17, 2012, 03:18:52 pm

I've never seen a circuit like this, the part that is labeled "Noise Reduction/Flashy Light"

here the complete schematic (a bit unusual)

(http://i.imgur.com/utFtgTN.jpg)

(http://i.imgur.com/q7BAamu.jpg)

(http://i.imgur.com/mSCvw6O.jpg)

Can someone give me info about it ?

Thanks

K

Title: Re: A strange circuit I've never seen before - I'm not able to understand it !
Post by: PRR on September 17, 2012, 07:56:53 pm

> Can someone give me info about it ?

No.

Well, the 1816 lamp is 13V 0.33A. So it is 40 ohms hot and around 4 ohms cold. This in shunt with 4/8/16 ohm speaker will load-down the amp when there is no real signal, only stray hiss. When slammed to 6V (4 Watts in 8 ohms) the lamp will come up over 20 ohms and add very little loading, you get nearly full loud-sounds.

As for the 0.68uFd..... it shunts sounds above 30KHz. In combination with a cheap OT, maybe 10KHz.

Title: Re: A strange circuit I've never seen before - I'm not able to understand it !
Post by: kagliostro on September 18, 2012, 12:04:17 am

Many Thanks for explanation PRR

K

Title: Re: A strange circuit I've never seen before - I'm not able to understand it !
Post by: thelonious on September 18, 2012, 10:05:13 am

Quote from: PRR on September 17, 2012, 07:56:53 pm

This in shunt with 4/8/16 ohm speaker will load-down the amp when there is no real signal, only stray hiss.

Out of curiosity - if there were no speaker attached, would it be enough protect the OT? Or would the bulb just fry?

Title: Re: A strange circuit I've never seen before - I'm not able to understand it !
Post by: jazbo8 on September 18, 2012, 06:35:58 pm

Quote from: drgonzonm on September 18, 2012, 02:19:03 pm

Forty some odd years ago, when I was in college, one of my dorm mates had light panels hooked up into his stereo system.  Different colored lights for different frequencies, Just maybe this was the method those lights were made. 

You are thinking about the color organ, they were very popular basic electronic kits back in the day...

http://www.freeinfosociety.com/electronics/schemview.php?id=1526 (http://www.freeinfosociety.com/electronics/schemview.php?id=1526)

Jaz