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Author Topic: Help with Foreplay II gain part 2  (Read 2548 times)

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Offline Rollie

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Help with Foreplay II gain part 2
« on: January 12, 2010, 06:26:52 AM »
Thanks for the help on my original posting re: Dynaco st70 and Foreplay:
 
 "My only problem is that the Foreplay volume controls are unbelievably sensitive. I have them set almost to nothing, If I move them a 1/16 of an inch the volume goes up a great deal. I called and ordered the sweetest whispers hoping this would help. My question is will this reduce the gain issue, or will I need to do something else?  On the Carver it had its own volume controls so I guess I just kept them very low and didn't notice the gain issue."

lgranger 49 replied:
"A search of the old forum will yield a hundred or so posts on the FP 2 hair trigger.  The answer is generally to pad the input of your amp.  A voltage divider of 2:1 will be a big help.  The ST-70 has an input resistor of 470k ohms.  Buy two more and put them in series with the input resistor.  Take the input to the tube from the junction between the two resistors.  If that isn't clear I can make it clear in another post."

I had wanted to post a picture of the 470kb input resistors in the Dynaco showing what I thought I needed to do but I couldn't load a 45kb folder. (the upload folder was full) . I sure would appreciate a further clarification.

My hum issue is very minor and only audible within a foot of the speakers. I tried grounding the 10 ohm resistor and it made no noticeable difference.

I am still waiting for the sweetest whispers upgrade I will put it in before I modify the Dynaco

Offline Doc B.

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Re: Help with Foreplay II gain part 2
« Reply #1 on: January 12, 2010, 06:38:44 AM »
Quote
I had wanted to post a picture of the 470kb input resistors in the Dynaco showing what I thought I needed to do but I couldn't load a 45kb folder. (the upload folder was full) . I sure would appreciate a further clarification.

Curious. I just checked and we only have 10MB of images in the attachments folder, with a 2GB limit. When you say 45kb folder, were you attaching the images individually?
Dan "Doc B." Schmalle
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Bottlehead Corp.

Offline Rollie

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Re: Help with Foreplay II gain part 2
« Reply #2 on: January 12, 2010, 10:40:18 AM »
Hi Doc,

I originally tried to attach 2 files but got  "input folder full" so I reduced the file sizes and only loaded one at 45kb, it still wouldn't load same error.

I used the additional options, Attach, then added file.

I will try to upload the file to this posting to see if it works now. If there is a picture on this posting things are working, if no picture I assume there is some sort of problem.

Tried loading got the same reply "input folder full" maybe I did something wrong.

Thanks

Offline Paul Birkeland

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Re: Help with Foreplay II gain part 2
« Reply #3 on: January 12, 2010, 12:09:29 PM »
If you still have the stock 100k pair of pots on your Foreplay II, here is what you can do:

Remove each wire that goes from the selector switch center terminals to the volume pots.  Replace them with 100-500k resistors (use the same value for both channels).  Now all your inputs will be padded down, and you can get more range out of the pair of pots.  From what you describe, I would start with 470k resistors in place of those wires.
Paul "PB" Birkeland

Bottlehead Grunt & The Repro Man

Offline Paul Joppa

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Re: Help with Foreplay II gain part 2
« Reply #4 on: January 12, 2010, 12:11:10 PM »
I have teh same photo upload problem - just tried it now.
Paul Joppa