Compound Power Amplifiers - Page 4 - diyAudio
Go Back   Home > Forums > Amplifiers > Pass Labs
Home Forums Rules Articles diyAudio Store Gallery Wiki Blogs Register Donations FAQ Calendar Search Today's Posts Mark Forums Read

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 5th November 2012, 09:45 PM   #31
diyAudio Member
 
Join Date: Jan 2012
Location: Pennsylvania
Blog Entries: 1
The attached file: CompoundAmp A7.pdf shows another schematic/diagram of a Compound Power Amplifier [CPA] whereby its VSA and TCA are electrically isolated. In this application the VSA [one channel of THRESHOLD S/150] drives one voice coil of a woofer/subwoofer, and a diy TCA drives the second and independent voice coil of the same woofer/subwoofer. The amplifiers drive the voice coils in phase. This experiment is in progress. I'll report results for these 2 unique cases:
  • A free hanging 10" dual voice coil woofer driver.
  • An enclosed 10" dual voice coil woofer in a commercial box designed for subwoofer duty. The voice coils are preceeded by a crossover network.
Attached Files
File Type: pdf CompoundAmp A7.pdf (37.7 KB, 51 views)
  Reply With Quote
Old 6th November 2012, 12:08 AM   #32
diyAudio Member
 
Join Date: Jan 2012
Location: Pennsylvania
Blog Entries: 1
Quote:
Originally Posted by Antoinel View Post
The attached file: CompoundAmp A7.pdf shows another schematic/diagram of a Compound Power Amplifier [CPA] whereby its VSA and TCA are electrically isolated. In this application the VSA [one channel of THRESHOLD S/150] drives one voice coil of a woofer/subwoofer, and a diy TCA drives the second and independent voice coil of the same woofer/subwoofer. The amplifiers drive the voice coils in phase. This experiment is in progress. I'll report results for these 2 unique cases:
  • A free hanging 10" dual voice coil woofer driver.
  • An enclosed 10" dual voice coil woofer in a commercial box designed for subwoofer duty. The voice coils are preceeded by a crossover network.
I may add that one coil of the two maybe a stationary field coil instead of a moving voice coil like in the new Lowther [BAF 2012] or Supravox drivers.
  Reply With Quote
Old 25th November 2012, 08:59 PM   #33
diyAudio Member
 
Join Date: Jan 2012
Location: Pennsylvania
Blog Entries: 1
Default A Mini Compound Power Amp Using the LM386 Chip

The above posts taught using powerful amps [e.g Threshold S/150] to implement compounding. The attached schematic shows a Mini Compound Power Amplifier [MCPA] which uses two LM386 IC chip amps as a starting model for this application.
  • The upper LM386 is wired as recommended by its maker. Its output port must have a Zobel for stability. It simultaneously functions as the output port of the MCPA and the [+Vs] port for the lower LM386.
  • The lower LM386 is thereafter connected as recommended by its maker. Curiously, its output port [pin 5] must be connected via a capacitor [0.1 uF film to 1000 uf electrolytic] to + 12 VDC so as to make the net MCPA work right.
  • Note the phasing on the secondaries of the transformer driving the inputs of both LM386 chips.
  • Vo/Vi = 15 or ~24 dB at 1 KHz. A 1.5 Vp-p energized an ADS L730 loudspeaker of 6 Ohm impedance for this voltage gain test.
  • Sound of music was fully satisfactory within the milliwatts capability of MCPA.
The NPN output transistor of the upper LM386 works as a voltage source amp [common collector]. The NPN output transistor of the lower LM386 works as a current source amp [common emitter]. Its output emanates from its collector node which is at its +Vs pin. This is the same topology like that in the Classic parent of Mr. Pass's F6; but with localized loop feedback in the output stage of the chips.
Attached Images
File Type: jpg CompoundAmp B.jpg (554.1 KB, 233 views)
  Reply With Quote
Old 26th November 2012, 07:47 PM   #34
diyAudio Member
 
Join Date: Jan 2012
Location: Pennsylvania
Blog Entries: 1
I have an error in the lower LM386 diagram of the above schematic. The top lead of its transformer's secondary winding goes to the [+] or non inverting input at pin 3. The grounded bottom lead of the winding goes to the [-] or inverting input at pin 2.

Note that LM380 has a similar circuit topology like LM386; but with a higher output capability. It is highly likely to operate well in my schematic of the previous post. LM380 requires additional heat sinks to work properly.
  Reply With Quote
Old 10th December 2016, 09:31 PM   #35
diyAudio Member
 
Join Date: Jan 2012
Location: Pennsylvania
Blog Entries: 1
The schematic of the Compound Amp [CA] is attached. It can be readily assembled and its subjective performance assessed. Here are its broad-brush details:

1. U1 and U2 are high fidelity power amps I have. They are found in the working stereo receiver [Kenwood KR-6050] and the stereo power amp [Threshold S/150].
2. The 1:1 transformer is a power toroid made by Triad Magnetics.
3. By example, the input signal Vin [say 100 Hz] is offered to the Right and Left inputs of Threshold S/150. Its R and L power outputs [Vout] fed the power toroid as shown. Their Vouts are highly matched or equal in value as best I can measure their values with a digital voltmeter.
4. By a second example, the input signal Vin is offered to the R and L Aux inputs of the Kenwood receiver. Its tone controls were intially bypassed or set flat. Its power Vouts were adjusted with its volume control to the same values measured for S/150. The 2 Vouts from Kenwood were different in value driving the same power toroid. They were almost made equal by using its Balance Control which is stepped, and not smooth turning.

Some analysis;
1. With the power amps' signals equal in magnitude and of identical phase [depicted], neither one can dump power into the other. Thus the inter reflected impedance is large. May remind of the term common mode.
2. Suppose the stand alone left amp has a higher intrinsic THD than the right amp. Its harmonic signals [error] are wiped out by the right amp in the CA before they appear. This CA assembly does not allow the extra THD signals to be present on the right side of the traffo. May remind of a differential signal.
3. Both power amps drive power through the windings of the toroid. If one winding generates more common distortion than the other, this extra distortion is also wiped out before it emerges as explained in point 2 above.
4. It follows that CA is highly symmetric, and the toroid moves in the direction of ideality [~distortionless], as both amps clean it up , and take care of each other.
Attached Images
File Type: png CompA.png (28.1 KB, 170 views)
  Reply With Quote
Old 14th December 2016, 11:01 PM   #36
diyAudio Member
 
Join Date: Jan 2012
Location: Pennsylvania
Blog Entries: 1
The complete schematic of the compound amp [CA] is attached and shows the following:
1. The 4 windings of the AC power toroid were interconnected as suggested by Triad Magnetics so as to give a 1:1 isolation transformer. Two additional options are available to interconnect the coils.
2. The loudspeaker loads the left power amp U1. It may be physically moved to load the right power amp instead of the left. This option is slightly different, and its effect probably irrelevant.
3. It follows that U1 does most of the work in the loudspeaker [R1 Load] , while the right amp is lightly loaded by the primary coils of the toroid [L1 and L3].

During operation using music input signals [Vin], I thought the following points explain the great sound of this CA.

1. The electrical conditions [voltage and phase] at the secondary [Vload], are essentially similar to the electrical conditions at Vout. Said otherwise, the electrical status [Vload] defaults to and/or closely tracks Vout. The objective and subjective performance on both sides of the toroid are similar. This result is sonically valuable.
2. Both amps see each other through the transformer. The right amp readily corrects any electrical imperfections it sees on the loudspeaker side.
3. [Vout] from the right amp is inherently very low distortion; because this amp is doing little work in the primary coils, and is doing some error correction work on the loudspeaker side.
4. The damping factor [DF] of the left amp is expected to be like that of the right amp which is inherently high due to the high value of its load. The DF of both amps can be argued to be ~equal and high; because Vload is ~ equal to Vout.
5. [CA] is electrically stable against oscillation.

More...
Attached Images
File Type: png CompB.png (35.1 KB, 134 views)
  Reply With Quote
Old 18th December 2016, 06:24 PM   #37
diyAudio Member
 
Join Date: Jan 2012
Location: Pennsylvania
Blog Entries: 1
The attached pictures show an assembled stereo compound power amp. Each channel subscribes to the attached schematic on the right which is the same one I discussed in the previous post. Please note the detail for the far left picture:

1. The small/short block on the left of the view is a dual channel Class T [digital] amp made by Stellar Labs and was sourced from MCM Electronics. It is a hi-fi unit rated to give 15W/ch into 4+ Ohms load. Both of its power outputs drive the power toroid per the schematic/interconnection diagram. Only one of its amps which is connected to the toroid's secondary drives the Right channel loudspeaker.
2. The block on the right of the view is a dual channel Class AB analog power amp made by SONY, and is part of Mini HiFi Compact system. Its power outputs are rated to give 15 W/Ch [1% THD] when driving a 6+Ohms load. One of its power amps which is connected to the secondary of the power toroid, drives the Left channel loudspeaker.

The middle picture of this stereo compound amp system shows that each of the "monoblocks" has a volume control. The volume control of the digital amp was maxed, and the one on the SONY was adjusted during music play so as balance the acoustic outputs of the loudspeakers.

Surprisingly, it sounds great.
Attached Images
File Type: jpg IMG_3236.jpg (394.0 KB, 86 views)
File Type: jpg IMG_3238.jpg (307.1 KB, 86 views)
File Type: png CompB.png (35.1 KB, 39 views)
  Reply With Quote
Old 20th December 2016, 11:06 PM   #38
diyAudio Member
 
Join Date: Jan 2012
Location: Pennsylvania
Blog Entries: 1
The Threshold S150, and Kenwood KR-6050 I have are ~1983 productions [33 years old]. Their power supply capacitors are original. Both products work fine after each was idled for 72 hours so as to rejuvenate their caps.

In the previous post, I showed the use of a 1:1 isolation toroid transformer. The resistance via Ohmmeter of its primary and secondary coils are 20 Ohms, and 23 Ohms respectively. The resultant current flowing through the coils at 60Hz is low noting that I measured 5-10 Vp-p [Vout] music voltage driving each loudspeaker. The S150 and KR-6050 performed quite well with this transformer; but they are high peformers to begin with as stand alone or without the transformer. So I used another power toroid which allowed each power amp in S150 and KR-6050 to dissipate more power in its primary and secondary coils.

The attached schematic on the left view shows how I did that using the indicated Triad transformer. One 115 Vac primary coil was paralleled with a 12 Vac secondary coil. The other 115 Vac primary coil was likewise paralleled with the other 12 Vac secondary. Here are the findings for the stereo system; with S150 and one toroid driving the Left loudspeaker, and KR-6050 and a second toroid driving the Right loudspeaker. The attached picture shows the assembly with S150.

1. The sound of this system is superb.
2. I give it a definite subjective step above the system using the first 115Vac:115Vac toroid.
3. The toroids warmed up slighly after prolonged music play.
4. I used a light bulb fuse [1 Ohm cold] in series with each power output of S150 and played music. Got a pulsating light show in both fuses for mostly bass information; maybe allowing ~0.3 A to pass through.
5. There's adequate power dissipated in the toroid by either amp so to impact favorably the other if needed.

Triad offers other 25 VA toroids which have two separate secondaries of 12 [in use; highest power use], 15, 18, 24, and 115Vac [lowest power use by amps]. The toroid VPT48-520 [two 24 Vac secondaries] maybe the best compromise in this application for power dissipation and favorable influence on subjective performace of one amp on its twin.
Attached Images
File Type: png CompC.png (35.7 KB, 20 views)
File Type: jpg IMG_3244.jpg (422.8 KB, 23 views)
  Reply With Quote
Old 21st December 2016, 09:27 PM   #39
diyAudio Member
 
Join Date: Jan 2012
Location: Pennsylvania
Blog Entries: 1
Two high quality power amps of similar objective performance have a probability to sound different [subjectively] to a listener playing through the same loudspeaker. Many variables are at work in this A/B comparison. This differing subjective outcome suggests that the power output of music presented to the loudspeaker from Amp A is different from that of Amp B. I may even conclude that the power output from either power amp to the loudspeaker is different [in phase, harmonic content..]from that offered to a dummy load resistor which is the expected exact/accurate replica. Thus, this sound system is deficient.

This compound amp in the attached schematic suggests that the aforementioned deficiency [by the left amp/loudspeaker] can be remedied by using the right side power amp which is not directly connected to the loudspeaker. Both power amps are in constant signal communication via the power transformer which enables this timely correction. The resultant performance on the secondary side is the same as that on the primay side; because the right amp is continuously correcting any arising imperfection on the loudspeaker side.
Attached Images
File Type: png CompC.png (35.7 KB, 13 views)
  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
Choke power supplies for Class AB Power Amplifiers - which Rules for Calculating ?? tiefbassuebertr Solid State 12 3rd November 2011 09:47 AM
Compound Lateral FET for higher power Class AB amp. Mooly Solid State 17 22nd August 2010 03:13 PM
Balanced compound-IGBT power amp idea revintage Solid State 10 21st January 2008 05:27 PM
Can i use a computer power supply to power audio amplifiers? destroyer X Solid State 91 25th September 2006 05:36 AM


New To Site? Need Help?

All times are GMT. The time now is 03:07 PM.


vBulletin Optimisation provided by vB Optimise (Pro) - vBulletin Mods & Addons Copyright © 2017 DragonByte Technologies Ltd.
Copyright 1999-2017 diyAudio

Content Relevant URLs by vBSEO 3.3.2
Wiki