Comments on 71a PP Pre-amp - Page 3 - diyAudio
Go Back   Home > Forums > Amplifiers > Tubes / Valves

Tubes / Valves All about our sweet vacuum tubes :) Threads about Musical Instrument Amps of all kinds should be in the Instruments & Amps forum

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 10th April 2003, 07:06 PM   #21
Joel is offline Joel  United States
diyAudio Member
 
Joel's Avatar
 
Join Date: Oct 2002
Location: Brooklyn, NY
Richard, is 1k a low enough output impedance? Perhaps we can get that lower.
  Reply With Quote
Old 10th April 2003, 07:06 PM   #22
diyAudio Senior Member
 
fdegrove's Avatar
 
Join Date: Aug 2002
Location: Belgium
Default BACK ON TRACK.

Hi,

Well you could do something similar to the 6B4G amp, namely a low mu triode followed by a phase splitter IS and that's all there is to it.

The triode could be any low mu triode you like, you're loosing some gain in the IS but that's no big deal.
Tack a pot on the front and bingo, you now have a preamp, and headphone amp and a miniwatt amp all in one box.

Cheers,
__________________
Frank
  Reply With Quote
Old 10th April 2003, 07:11 PM   #23
diyAudio Senior Member
 
fdegrove's Avatar
 
Join Date: Aug 2002
Location: Belgium
Hi,
Quote:
Richard, is 1k a low enough output impedance?
For the inputstage you mean?

Cheers,
__________________
Frank
  Reply With Quote
Old 10th April 2003, 07:16 PM   #24
diyAudio Member
 
Join Date: Jan 2002
1K or less is fine.

How about a 12B4 into a IT, with 71a PP on the outputs?

I kinda liked the idea of a balanced PP design... the PS gets a lot easier.

what would the gain be of the above? Assuming a 1/1:1 IT and say a 8K p-p into 1K output tranny.

any other ideas???
  Reply With Quote
Old 10th April 2003, 08:12 PM   #25
Joel is offline Joel  United States
diyAudio Member
 
Joel's Avatar
 
Join Date: Oct 2002
Location: Brooklyn, NY
Quote:
Originally posted by RichardJones
...the PS gets a lot easier...
How so?
  Reply With Quote
Old 10th April 2003, 08:25 PM   #26
316a is offline 316a  England
diyAudio Member
 
316a's Avatar
 
Join Date: Dec 2002
Location: West London
Default power supply

Joel ,
The very nature of push pull means most of the PS crud is cancelled in the output stage . Simple as that

316a
  Reply With Quote
Old 10th April 2003, 08:27 PM   #27
diyAudio Member
 
Join Date: Jan 2002
Well I can just use a simple LC supply (any other ripple theoretically gets cancelled in OPT).

Perhaps an LC stage (10H with 47uF cap) with a voltage regulator tube on the output.

thats why...
  Reply With Quote
Old 10th April 2003, 08:31 PM   #28
diyAudio Member
 
Join Date: Jan 2002
Default parafeed?

Or can get 2 100H chokes.... a really good OPT... and do parafeed PP output stage....

won't my PSRR be even better then?

But would the parafeed cap go from the midpoint of the output tranny to B+ or the cathodes of the 71a's?



or is this way too much complexity for a pre?
  Reply With Quote
Old 10th April 2003, 08:39 PM   #29
mig-ru is offline mig-ru  Russian Federation
diyAudio Member
 
Join Date: Jul 2002
Location: Boulder, CO
Richard,

i amcurious as to why you need 5v on the output when your amp goes up to 4v? wouldnt the full 5v input drive the power amp out of A class operation, into AB and B? im also curious why you're using output tubes for a preamp, especially when youre going to be running it through a solid state amp after that anyway? just curious, dont mean to sound harsh.
  Reply With Quote
Old 10th April 2003, 08:45 PM   #30
diyAudio Member
 
Join Date: Jan 2002
well... i'll probably end up just using my 6B4G PP amps instead....

I kinda like some headroom on my pre-amp... and thats why I have said voltage gain of around 5.

Are there any good higher mu / lower plate resistance DHT out there??? If I go with 46's then mu increases, but plate resistance increases....

txs!
  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
psu comments! lanchile07 Chip Amps 15 27th August 2008 12:20 AM
Comments please on this I/V amp georgehifi Digital Source 9 11th April 2008 02:12 PM
X-over Comments & Help GOWA Multi-Way 23 20th March 2008 01:09 AM
Would appreciate comments... TonyDasilva Digital Source 2 11th August 2005 06:50 PM
my new amp (comments?) LennyK Solid State 16 11th December 2002 04:05 PM


New To Site? Need Help?

All times are GMT. The time now is 01:58 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