LM3875 (Audio sector) + Aikido 12VAC or Aikido ACF-2? - diyAudio
Go Back   Home > Forums > Amplifiers > Chip Amps

Chip Amps Amplifiers based on integrated circuits

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 22nd August 2013, 12:30 PM   #1
diyAudio Member
 
Sodacose's Avatar
 
Join Date: Feb 2006
Location: mke, wi
Default LM3875 (Audio sector) + Aikido 12VAC or Aikido ACF-2?

Does anyone have any opinions (ha, that's a silly way to start this question, isn't it?) on the use of Aikido preamps with Gainclone amps?

Long story short, I need to downsize my living room setup and I've been burning to try both of these designs for some time. I'd like to put both the GC and Aikido in the same enclosure (approx 12" x x 8"), so space is somewhat of an issue. Reading through the documentation, I'm confident with my ability to construct these designs, though I may need advice in picking out ACF values/tubes if going that direction.

Any experience with Aikido designs feeding a Gainclone here? Would it be better to go with the buffer ACF-2 or the preamp 12VAC. I will be playing mostly vinyl through this system (with an appropriate phono pre, of course).

Last edited by Sodacose; 22nd August 2013 at 12:35 PM.
  Reply With Quote
Old 22nd August 2013, 12:43 PM   #2
Einric is offline Einric  United States
diyAudio Member
 
Einric's Avatar
 
Join Date: Feb 2011
Location: Bozeman, MT
ACF-2 Buffer, I had the same problem, I built the Aikido 9-Pin All In One and I built an AudioSector LM4780.
Problem is that the LM4780 design has all the gain you need built in.
So.....What you really need is a buffer.
My Aikido with my LM4780 has WAAAAAYY too much gain.
Go with 6SN7's and the factory values that John recommends in the build manual, it will work very well I'm sure.
  Reply With Quote
Old 22nd August 2013, 01:24 PM   #3
diyAudio Member
 
Sodacose's Avatar
 
Join Date: Feb 2006
Location: mke, wi
Thanks, Einric! Reading through Gainclone posts, I suspected that may be the case.

The ACF-2 board is a little larger, and it requires a transformer, but I'm sure I can make do. Looks like JB recommends an Edcor here, which will save some space inside the enclosure vs a toroidal with the 12VAC.

Unfortunately, the ACF-2 board is out of stock and the link to the ACF pdf manual is busted. Anyone know if JB is still producing this kit?
  Reply With Quote
Old 22nd August 2013, 10:16 PM   #4
diyAudio Member
 
Sodacose's Avatar
 
Join Date: Feb 2006
Location: mke, wi
Hmm, did some more research after seeing the ACF2 is out of stock and I'm reconsidering the 12VAC and thinking 3886 instead of 3875 (supposedly more stable into 4 ohms?).

For one thing, it's available; for another, it's a simple and fairly small preamp that I might want to use elsewhere in my DIY adventures.

So here's the slightly modified proposal:
-Go with a chipamp.com LM3886 kit and set the gain fairly low (maybe R3 of 1.5k for 15db?)
-Stick with the Aikido 12VAC, 6DJ8 for gain of 15db
-Total gain of 30db

Any thoughts? Warnings?
  Reply With Quote
Old 25th August 2013, 05:41 AM   #5
diyAudio Member
 
danielwritesbac's Avatar
 
Join Date: Nov 2007
See Decibel Dungeon for inverting mode gainclones that can be set for lower gain.
The Decibel Dungeon Gainclone index page with links to all chip amp articles.
The stability is high on both the t-network and ordinary inverting designs, and that's just the sort of thing that you can set to lower gain.

Also the TDA7293 has a power buffer (aka "slave") mode that disables its internal voltage amp: TDA7293 single, bridge, parallel In that way it may be possible to do Aikido with Fet (tda7293) outputs. However, it is possible that discrete parts output buffer might be easier. Surely someone has published an Aikido hybrid already?
__________________
Tools, Models & Software for DIYClipNipper boostLM1875 TurboPowerful TDA7293 kitTDA7294 pt2pt ♦ My post has opinion.
  Reply With Quote
Old 25th August 2013, 05:03 PM   #6
diyAudio Member
 
Sodacose's Avatar
 
Join Date: Feb 2006
Location: mke, wi
Hi Daniel-

Thank you for the info. I haven't seen any Aikido hybrids around the net, but maybe someone else chimes in? There were some Tubecad articles that touched on it, but they're so far over my head that I decided to ask here as well.

I'm open to ideas about how to tackle the post-Aikido portion of this project. The chassis I have to work with is very small (12" x 8") though and that's what lead me down the chipamp path.

I realize this is probably a very basic question, but could anyone briefly explain the hypothetical advantage of having the Aikido handle the voltage gain and the chip handle the current gain (hopefully I have that straight)? Is it just playing off the strengths of tubes vs chips?
  Reply With Quote
Old 26th August 2013, 12:14 AM   #7
Einric is offline Einric  United States
diyAudio Member
 
Einric's Avatar
 
Join Date: Feb 2011
Location: Bozeman, MT
My Aikido Drives a DIY store F4 and it is phenomenal.
In my application the F4 provides FAR superior experience across the board V.S. my LM4780 Parallel amp.
I understand this is apples and oranges, but If I could find a way to lower my 4780 gain I would.
However the idea of having a tube "front end" with a chip "output" is a great idea that the TDA7293 may be able to pull off for you.
Daniel probably has a picture of the 7293 on perfboard for P2P wiring.
This would make for a pretty straight forward application.
12x8 will barely be big enough since your transformer will take up 50% of your useable 8".
This will lead to the possibility of HUMMMMM that everybody hates.
  Reply With Quote
Old 26th August 2013, 01:30 AM   #8
diyAudio Member
 
Sodacose's Avatar
 
Join Date: Feb 2006
Location: mke, wi
After reading about the 41hz and GC amps, it's become fairly clear that something like the F4 is what I really should be building with the Aikido 12VAC (ie voltage follower buffer). Of course, that's going to be too big for my enclosure (and my wife's tastes)!

I'm going to have to either wait for the ACF2 to come back into stock, build the original ACF with a separate power supply (pushing size constraints again), or give up integrating a tube pre into this project. Sigh, nothing ever comes easy in DIY audio, does it?
  Reply With Quote
Old 26th August 2013, 01:15 PM   #9
diyAudio Member
 
danielwritesbac's Avatar
 
Join Date: Nov 2007
The only thing I can think of is to look at this: Tube Gainclone for DIY Buffs And then ask Joe Rasmussen.
__________________
Tools, Models & Software for DIYClipNipper boostLM1875 TurboPowerful TDA7293 kitTDA7294 pt2pt ♦ My post has opinion.
  Reply With Quote
Old 26th August 2013, 05:13 PM   #10
diyAudio Member
 
Sodacose's Avatar
 
Join Date: Feb 2006
Location: mke, wi
Nice find, Daniel! Looks very promising and I will read through it.

At first glance, it appears that the LM3875 in the schematic is at 26db gain (before what's added by the 6922). Wouldn't this not be much different than running the 3886 kit at lower gain, say around 15db, and using the Aikido 12VAC kit to drive it at around another 15db for a total of 30db?

I'm open to PTP wiring from a schematic, but the tinkerer in me says boards will be easier to swap and play with in the future

Edit: Ah, nevermind. I read through the article and looks like the 6922 is used as a unity gain buffer, like the ACF (not the 12VAC).

Last edited by Sodacose; 26th August 2013 at 05:23 PM.
  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
Aikido 12Vac yakusa Tubes / Valves 33 22nd October 2013 12:28 PM
Integrating Bugle2 PSU into preamp design (also Aikido 12VAC and Gainclone) Sodacose Analogue Source 5 27th August 2013 03:08 AM
FS: Aikido ACF + Bas PSU kit Bengali Swap Meet 2 9th August 2013 08:10 PM
FS: Aikido ACF Tube Buffer w/6DJ8 Bengali Swap Meet 2 1st August 2012 04:35 AM
Coupling Caps for Aikido ACF Buffer Bengali Tubes / Valves 0 19th November 2010 05:09 AM


New To Site? Need Help?

All times are GMT. The time now is 12:26 PM.


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