ImPasse Preamplifier - Page 2 - diyAudio
Go Back   Home > Forums > Amplifiers > Pass Labs

Pass Labs This forum is dedicated to Pass Labs discussion.

Please consider donating to help us continue to serve you.

Ads on/off / Custom Title / More PMs / More album space / Advanced printing & mass image saving
Reply
 
Thread Tools Search this Thread
Old 19th January 2009, 07:22 PM   #11
diyAudio Member
 
jackinnj's Avatar
 
Join Date: Apr 2002
Location: Llanddewi Brefi, NJ
I can just about decipher the fact that some kind of beer is required to test the device -- the bottle label has what appears to be a bicycle on it, but the specifics didn't make it passed the offset printer.
  Reply With Quote
Old 19th January 2009, 07:34 PM   #12
SY is offline SY  United States
diyAudio Moderator
 
SY's Avatar
 
Join Date: Oct 2002
Location: Chicagoland
Blog Entries: 1
Fat Tire. I've been trying to figure out a way to get a few bottles shipped to England for a good friend of mine who is a tube fiend, beer nut, and cycling enthusiast.
__________________
And while they may not be as strong as apes, don't lock eyes with 'em, don't do it. Puts 'em on edge. They might go into berzerker mode; come at you like a whirling dervish, all fists and elbows.
  Reply With Quote
Old 20th January 2009, 05:08 PM   #13
diyAudio Member
 
jackinnj's Avatar
 
Join Date: Apr 2002
Location: Llanddewi Brefi, NJ
I wonder if I can fit it into a PAS chassis? -- with all those 630V Polypropylene caps:

http://www.tech-diy.com/Preamplifier...ImPasse_3D.gif
  Reply With Quote
Old 20th January 2009, 07:09 PM   #14
SY is offline SY  United States
diyAudio Moderator
 
SY's Avatar
 
Join Date: Oct 2002
Location: Chicagoland
Blog Entries: 1
Should be no problem except for wedging in the power transformer and the height of the 6SN7. If you can get a board to work, I want one!
__________________
And while they may not be as strong as apes, don't lock eyes with 'em, don't do it. Puts 'em on edge. They might go into berzerker mode; come at you like a whirling dervish, all fists and elbows.
  Reply With Quote
Old 20th January 2009, 08:09 PM   #15
diyAudio Member
 
jackinnj's Avatar
 
Join Date: Apr 2002
Location: Llanddewi Brefi, NJ
Here's the silk -- the traces are dimmed down -- I didn't have any PCB mount octal sockets so I ordered some -- the input transformers have to be mounted on the back panel of the chasis:

Click the image to open in full size.
  Reply With Quote
Old 22nd January 2009, 07:10 PM   #16
diyAudio Member
 
kurtbauer's Avatar
 
Join Date: Dec 2006
Default I want, I want

SY,

I was wondering just how I was going to drive the two Burning Amps in the F4 style when I get them finished. And then along came ImPasse. Thanks so much for this! Have in missed both BAFs I had no idea you had this cooking.

The article was really good and I'm psyched to build one of these. If circuit boards are in the offing I'm down.

If you have time I have a couple of questions about the design.

1. Can you elaborate on your choices in getting the signal from the voltage divider to the output stage? I'm unsure how you calculated the values for the voltage divider and it's overall effect on the signal going to the unity gain phase splitter.

2. I may want to add a balance control to the mix and would like to get some guidance on how to figure out the matching the volume/balance/R1/C1 combo with the prima donna input transformer. I don't have any transformers on hand so I'm pretty open.

My apologies if these are lame questions.

KB
  Reply With Quote
Old 22nd January 2009, 07:18 PM   #17
SY is offline SY  United States
diyAudio Moderator
 
SY's Avatar
 
Join Date: Oct 2002
Location: Chicagoland
Blog Entries: 1
I'll have more time to answer in detail later, but here's the basics:

1. Voltage divider was chosen to get the right DC potentials on the ECC88 split load. The bypass cap on the first resistor turns it into a step network, but at a very low frequency so that the divider doesn't cause a gain loss in the audio band.

2. I'm not sure what's commercially available for balance controls, but I have some old Alps balance pots that are zero ohms through half of the rotation, then audio taper for the other half. That way, at midpoint there's no loss on either channel. I'd look for something like that, and use a value that's about the same as the volume pot- this will give you 6dB of adjustment which should be more than enough, and it won't perturb the input transformer.

Jackinnj is designing some boards which will drop into a PAS chassis. If he wants to do a run and sell them, that's fine with me. Otherwise, if someone else wants to get some quotes from a board house and get a group buy together, and it's OK with Jack, I'll certainly take a board myself.
__________________
And while they may not be as strong as apes, don't lock eyes with 'em, don't do it. Puts 'em on edge. They might go into berzerker mode; come at you like a whirling dervish, all fists and elbows.
  Reply With Quote
Old 22nd January 2009, 08:25 PM   #18
diyAudio Member
 
kurtbauer's Avatar
 
Join Date: Dec 2006
Default Thanks!

SY,

Thanks for the quick response. When you get time for more detail I'd be interested to know how you calculated the values, what components contribute, and such.

As for the balance pot, I wasn't clear on the type of pot you were describing and found an interesting set of pot definitions on www.rane.com. For those of you that didn't know about it either (hopefully, I won't be the only one!), here goes...
  • audio taper (aka A-taper): Usually 15% resistance at the 50% rotation point.
  • E-taper Similar to a reversed audio taper but with 25% resistance at the 50% rotation point.
  • linear taper(aka B-taper): Always 50% resistance at the 50% travel point.
  • log taper(aka D-taper): Often used as an audio taper since its 50% rotation point has 10% resistance.
  • MN taper (aka balance pot) Special taper developed for home stereo "Balance" controls. Consists of two sections (one for each channel) operating opposite each other. Exactly one-half of each section is a zero resistance surface (i.e., solid-copper or equivalent), the next 50% of travel is linear taper. Therefore for one channel rotating the slider through the first 50% of travel does not change the level at all, while the other channel is reduce from full to zero, and vice versa, with the middle position (usually featuring a center-detent) always passing full signal to each channel. See balance control.
  • RD-taper A reversed D-taper (see log taper above).

Could the Noble pot A-25 on this page be the item to which we're referring?

Thanks again. BTW, I'm not in any rush. Just excited about it!

K
  Reply With Quote
Old 22nd January 2009, 09:18 PM   #19
DaveM is offline DaveM  United States
diyAudio Member
 
DaveM's Avatar
 
Join Date: Feb 2003
Location: Vermont
Any chance of a scan of the article for those of us without prescriptions and local newsstands that carry it?

Thanks
  Reply With Quote
Old 22nd January 2009, 09:39 PM   #20
Tea-Bag is offline Tea-Bag  United States
not politcally affiliated
diyAudio Member
 
Tea-Bag's Avatar
 
Join Date: Feb 2006
Location: Kennebunk
Blog Entries: 7
Quote:
Originally posted by DaveM
Any chance of a scan of the article for those of us without prescriptions and local newsstands that carry it?

Thanks

Those of you without prescriptions see the world differently
  Reply With Quote

Reply


Hide this!Advertise here!
Thread Tools Search this Thread
Search this Thread:

Advanced Search

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Trackbacks are Off
Pingbacks are Off
Refbacks are Off


Similar Threads
Thread Thread Starter Forum Replies Last Post
Why do you need a preamplifier? globalweb Solid State 54 14th October 2007 05:47 PM
Mic PreAmplifier Ayne Solid State 4 13th April 2007 04:18 AM
Preamplifier aguantesoda Solid State 24 8th September 2006 03:39 PM
Preamplifier DIY Angel Puerto Solid State 13 20th July 2005 09:53 PM


New To Site? Need Help?

All times are GMT. The time now is 09:02 AM.


vBulletin Optimisation provided by vB Optimise (Pro) - vBulletin Mods & Addons Copyright © 2014 DragonByte Technologies Ltd.
Copyright ©1999-2014 diyAudio

Content Relevant URLs by vBSEO 3.3.2