Go Back   Home > Forums > >
Home Forums Rules Articles diyAudio Store Blogs Gallery Wiki Register Donations FAQ Calendar Search Today's Posts Mark Forums Read

Power limitations for LLC-smps for amplifier
Power limitations for LLC-smps for amplifier
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 8th November 2017, 06:44 PM   #1
TroelsM is offline TroelsM  Denmark
diyAudio Member
 
TroelsM's Avatar
 
Join Date: May 2003
Location: AARHUS. DK
Default Power limitations for LLC-smps for amplifier

Hi.

I'm a newbie at SMPS and LLC in particular, but with the aid of the app-note An1160 I have managed to get a simple LLC prototype running. I don´t claim to understand every calculation in the PDF, but I put it all into a spreadsheet and it puts out values that are similar to the values calculated in the example.

https://www.infineon.com/dgdl/an-116...53559a85df1115

The target is to power a bridged amp with +/-30V driving a single 8Ohm speaker to around 150W (100Vpp).
So peak-current is around 7A, and average is like 1A for music

I'm using a L6599 controller in a standard setup, IRFP450 (overkill, but I had them), and a ATX-transformer-core with a airgap in the center-leg.
Transformer x-section is around 1cm2 and prim-sec windings are side-by-side to integrate all magnetics into one. I have tried dual, triple and littze-wire for primary and although it changed the internal heating a little it does not affect the output power

The LLC works great up until approx 60V into a 22Ohm dummy-load (60^2/22 = 160W).

But when its loaded with 12Ohm (60V/12Ohm = 5A) for just 10mS the voltage drops to around 40-45V and it struggles to maintain soft switching.

Now the ATX-core and the windings will probably never supply 60V@7A for more than short pulses before the heat rises, but it needs to supply the peaks in the sine.

I have tried different resonant-caps and different airgaps. This result in different minimum switch-freq to maintain soft-switching, but it dos not affect maximum output current by much. Also tried to add more sc-windings with little luck.

Depending on the airgap the prim inductance is around 500uH (250uH with shorted sec). Prim-inductance can go from 1500uH to 250uH with airgaps from 0.1 to 1mm with around 50 prim turns.

So, any ideas?

Kind regards TroelsM
__________________
Need more time...
  Reply With Quote
Old 9th November 2017, 09:10 AM   #2
TroelsM is offline TroelsM  Denmark
diyAudio Member
 
TroelsM's Avatar
 
Join Date: May 2003
Location: AARHUS. DK
small update.

Maybe part of the problem was that I had placed the AUX-winding (psu for the L6599) over the primary winding. The AUX-voltage rose way too high during high loads on the sec.

With the AUX winding over the sec winding the voltage on the AUX should be semi-regulated as well.

Problem is that the isolation-distances are much better when AUX is placed over prim.

Whats the normal here?

Kind regards TroelsM
__________________
Need more time...
  Reply With Quote
Old 9th November 2017, 02:25 PM   #3
TroelsM is offline TroelsM  Denmark
diyAudio Member
 
TroelsM's Avatar
 
Join Date: May 2003
Location: AARHUS. DK
well I found a app-note that deals a little more with the actual construction of the LLC transformer:
https://www.onsemi.com/pub/Collateral/AND8460-D.PDF

See page 17 to 21.

PLacing the gap under the primary makes construction a little harder as one have to cut and glue the ATX-psu transformer-core, but I think it can be done.
I have had some luck with cutting ferrite with a small ebay diamond-disc in a dremmel.

Kind regards TroelsM
__________________
Need more time...
  Reply With Quote
Old 13th November 2017, 11:22 AM   #4
MorbidFractal is offline MorbidFractal
diyAudio Member
 
Join Date: Nov 2017
Magnetics design is hard. LLC magnetics design is evil. LLC operation and feedback compensation is critical in respect of the magnetics design.

If your transformer parameters do not match your design parameters then things will fall over and it is very hard to get the transformer to match. You might notice mention is often made of 'cut and try'...

You might want to try using an external inductor with a tightly coupled 'transformer' rather than integrating it into the transformer itself. The method is suggested in many application notes but people wish to play hardball and save money...

Otherwise you might care to look at,

http://www.ti.com/lit/ml/slup105/slup105.pdf
http://www.ti.com/lit/ml/slup103/slup103.pdf

Just in case I am not allowed to post links yet search Google for "sepic Lloyd Dixon" and "coupled inductor Lloyd Dixon".

to get some idea as to what is going on. I really know nothing myself but basically leakage inductance is uncoupled energy between windings. With the caveat that I know nothing then I would be slightly dubious about location of the gap.

I do not doubt that it will have an effect but as to how it might be quantified is another issue... 'cut and try'. Stray flux can be dealt with by the use of an external shield foil. However rather than trying to chop things to move the gap it would be easier to make the primary winding longer than the secondary so the primary overlaps the gap and the secondary misses it.

In respect of isolation of your primary auxiliary whilst maintaining some concept of regulation you might consider triple insulated wire. Otherwise given the primary auxiliary is likely to be low power waste the overvoltage in a resistor and zener diode regulator.

You mention that you are using an ATX transformer core which suggests that you have taken something from a junked computer power supply. That could/will be a source of grief because you do not know what the core parameters really are.

This might actually work in your favour assuming it is already an LLC transformer. Someone has already designed the transformer with 12V windings. Take it to bits, identify the 12V windings and put them back in place with three times as many turns.

Unfortunately now you have to match your proposed control circuitry to that used by the supply.

Looking back at the Lloyd Dixon application note he suggests a target of 2mH/200uH or 10% leakage inductance. Your On Semi application note suggests 750uH/130uH or about 17%.

If you read about LLC and try to get your head about things the the ratios determine the range of regulation and peak currents along with other things. Again I am no expert but going for a wide range results in greater circulating currents and higher losses.

However the difference between what Dixon achieves and what On Semi imply to be a suitable solution is not excessive. Basically, assuming 'like for like', you can just double the space between the windings and you should/might be close.

One thing that has always bothered me is that in the description of coupled inductors it is apparent that positioning of the leakage inductance is important in order to achieve the required ripple current steering.

I am not sure how that might apply to a transformer but would guess that either you assume that in that case it is symmetrical
or, just to be safe, place it in series with the primary. That seems to go against what On Semi suggests in respect of location of the gap... Whatever.

You are still going to get problems if you are using 'any old core'. It, it's gap and the windings have to be designed to hit your specification. That may or may not work with 'any old core' but, for the moment, that's another story.
  Reply With Quote
Old 18th November 2017, 08:25 PM   #5
TroelsM is offline TroelsM  Denmark
diyAudio Member
 
TroelsM's Avatar
 
Join Date: May 2003
Location: AARHUS. DK
Hi. Thank you for the long answer. I really appreciate it.

My findings so far: With the ATX-core, a 3mm seperator in the middle of the bobbin and a 1-2mm gap in the center-leg the inductance-ratio between becomes approx 1:2.

The app-notes and design-calculators I looked at suggest that the primary-inductance shall be lower for higher output. This puzzled me in the beginning, but now I'm thinking that the inductance needs to be low in order for the primary-current to rise enough?

The calculators suggest that the primary-windings shall be calculated like for an un-gapped Xformer based on the voltage the windings will see. This gives approx 50-60 windings for a core with 1cm2 cross-section. But that drives the inductance way up.
So I tried with fewer windings and a gap of 1,5mm. 30 windings appears to e good compromise. -iddle heat is low. Heat at 60W output is luke-warm and it will do peaks of 500W without sagging in output voltage.

Inductance is approx:
Click the image to open in full size.

I have not calculated or simulated the entire feedback-loop. From what I have seen it looks very complicated, so I just copied the feedback-loop from a similar design.
So far it handles all, load-changes I tested with.

Kind regards TroelsM
__________________
Need more time...
  Reply With Quote
Old 19th November 2017, 02:43 PM   #6
MorbidFractal is offline MorbidFractal
diyAudio Member
 
Join Date: Nov 2017
Data is a good thing to have. One of the best in respect of ferrites would be,

https://en.tdk.eu/download/519704/06...-db-130501.pdf

Siemens -> Epcos -> TDK

Rather than using a Junk core think about buying one that fits your requirements.

I have already mentioned I do not know enough but I have looked at LLC converters in the past using LTSpice. If I try to recreate it, this for the moment is incomplete...

Code:
Version 4
SHEET 1 1128 932
WIRE -64 32 -416 32
WIRE 16 32 -64 32
WIRE 112 32 16 32
WIRE 240 32 208 32
WIRE 352 32 320 32
WIRE 544 32 432 32
WIRE 672 32 608 32
WIRE 736 32 672 32
WIRE 848 32 736 32
WIRE 880 32 848 32
WIRE -64 96 -64 32
WIRE 16 96 16 32
WIRE 112 96 112 32
WIRE -112 112 -192 112
WIRE 432 112 432 32
WIRE 544 112 432 112
WIRE 640 112 608 112
WIRE 352 144 352 32
WIRE 432 144 432 112
WIRE -112 160 -160 160
WIRE -416 192 -416 32
WIRE -64 224 -64 176
WIRE 16 224 16 160
WIRE 16 224 -64 224
WIRE 112 224 112 160
WIRE 112 224 16 224
WIRE 208 224 208 32
WIRE 208 224 112 224
WIRE 352 256 352 224
WIRE 432 256 432 224
WIRE 544 256 432 256
WIRE 640 256 640 112
WIRE 640 256 608 256
WIRE 736 256 736 32
WIRE 848 256 848 32
WIRE -64 272 -64 224
WIRE 16 272 16 224
WIRE 112 272 112 224
WIRE -112 288 -192 288
WIRE -160 336 -160 160
WIRE -112 336 -160 336
WIRE 432 336 432 256
WIRE 544 336 432 336
WIRE 672 336 672 32
WIRE 672 336 608 336
WIRE -416 400 -416 272
WIRE -160 400 -160 336
WIRE -160 400 -416 400
WIRE -64 400 -64 352
WIRE -64 400 -160 400
WIRE 16 400 16 336
WIRE 16 400 -64 400
WIRE 112 400 112 336
WIRE 112 400 16 400
WIRE 352 400 352 320
WIRE 352 400 112 400
WIRE 640 400 640 256
WIRE 640 400 352 400
WIRE 736 400 736 320
WIRE 736 400 640 400
WIRE 848 400 848 336
WIRE 848 400 736 400
WIRE -416 432 -416 400
WIRE 160 432 -80 432
WIRE -208 464 -240 464
WIRE -304 480 -336 480
WIRE -208 480 -208 464
WIRE -208 480 -240 480
WIRE -208 496 -208 480
WIRE -208 496 -240 496
WIRE -208 512 -208 496
WIRE -208 512 -240 512
WIRE -32 528 -240 528
WIRE 160 528 160 432
WIRE 160 528 128 528
WIRE 368 544 336 544
WIRE 400 544 368 544
WIRE 496 544 464 544
WIRE 608 544 576 544
WIRE 640 544 608 544
WIRE 736 544 704 544
WIRE 848 544 816 544
WIRE 880 544 848 544
WIRE -80 576 -80 432
WIRE -80 576 -240 576
WIRE -48 576 -80 576
WIRE 160 576 128 576
WIRE 192 576 160 576
WIRE -304 592 -336 592
WIRE -208 592 -208 512
WIRE -208 592 -240 592
WIRE -208 608 -208 592
WIRE -208 608 -240 608
WIRE -208 624 -208 608
WIRE -208 624 -240 624
WIRE 368 624 368 544
WIRE 400 624 368 624
WIRE 608 624 608 544
WIRE 608 624 464 624
WIRE -208 640 -208 624
WIRE -208 640 -240 640
WIRE 32 672 0 672
WIRE 160 672 160 576
WIRE 160 672 32 672
WIRE 608 672 608 624
WIRE 608 672 576 672
WIRE 672 672 608 672
WIRE 736 672 672 672
WIRE 848 672 848 544
WIRE 848 672 816 672
WIRE -208 688 -208 640
WIRE -64 688 -208 688
WIRE 32 688 32 672
WIRE 32 688 0 688
WIRE 368 688 368 624
WIRE 512 688 368 688
WIRE 32 704 32 688
WIRE 32 704 0 704
WIRE 608 704 576 704
WIRE 32 720 32 704
WIRE 32 720 0 720
WIRE 32 736 0 736
WIRE 160 736 160 672
WIRE 160 736 96 736
WIRE 368 736 368 688
WIRE 400 736 368 736
WIRE 608 736 608 704
WIRE 672 736 672 672
WIRE -32 848 -32 736
WIRE 96 848 96 752
WIRE 96 848 -32 848
WIRE 128 848 128 624
WIRE 128 848 96 848
WIRE 336 848 336 640
WIRE 336 848 128 848
WIRE 608 848 608 816
WIRE 608 848 336 848
WIRE 672 848 672 816
WIRE 672 848 608 848
WIRE 672 880 672 848
FLAG -416 432 0
FLAG 880 32 VOUT
IOPIN 880 32 Out
FLAG -192 112 DRVA
IOPIN -192 112 In
FLAG -192 288 DRVB
IOPIN -192 288 In
FLAG 880 544 VOUT
IOPIN 880 544 In
FLAG 400 736 VERR
IOPIN 400 736 Out
FLAG 672 880 0
FLAG 48 480 0
FLAG 48 624 0
FLAG -336 480 DRVA
IOPIN -336 480 Out
FLAG -336 592 DRVB
IOPIN -336 592 Out
FLAG -256 528 0
FLAG -256 640 0
SYMBOL ind2 336 128 R0
WINDOW 0 -64 44 Left 2
WINDOW 3 -65 70 Left 2
SYMATTR InstName LP
SYMATTR Value 750µ
SYMATTR Type ind
SYMBOL ind 224 48 R270
WINDOW 0 59 60 VTop 2
WINDOW 3 62 59 VBottom 2
SYMATTR InstName LLeak
SYMATTR Value 130µ
SYMBOL cap 336 256 R0
WINDOW 0 -65 12 Left 2
WINDOW 3 -66 37 Left 2
SYMATTR InstName CRes
SYMATTR Value 100n
SYMBOL ind2 448 240 R180
WINDOW 0 -45 68 Left 2
WINDOW 3 -56 43 Left 2
SYMATTR InstName LS
SYMATTR Value 30µ
SYMATTR Type ind
SYMBOL diode 544 48 R270
WINDOW 0 32 32 VTop 2
WINDOW 3 0 32 VBottom 2
SYMATTR InstName DR1
SYMATTR Value DID
SYMBOL diode 608 96 R90
WINDOW 0 0 32 VBottom 2
WINDOW 3 32 32 VTop 2
SYMATTR InstName DR2
SYMATTR Value DID
SYMBOL diode 608 240 R90
WINDOW 0 0 32 VBottom 2
WINDOW 3 32 32 VTop 2
SYMATTR InstName DR3
SYMATTR Value DID
SYMBOL diode 544 352 R270
WINDOW 0 32 32 VTop 2
WINDOW 3 0 32 VBottom 2
SYMATTR InstName DR4
SYMATTR Value DID
SYMBOL cap 720 256 R0
WINDOW 0 36 19 Left 2
WINDOW 3 39 43 Left 2
SYMATTR InstName CF
SYMATTR Value 100µ
SYMBOL res 832 240 R0
WINDOW 0 38 35 Left 2
WINDOW 3 38 59 Left 2
SYMATTR InstName RL
SYMATTR Value 10R
SYMBOL sw -64 192 M180
WINDOW 0 -78 122 Left 2
WINDOW 3 -77 97 Left 2
SYMATTR InstName S1
SYMATTR Value MSW
SYMBOL sw -64 368 M180
WINDOW 0 -75 129 Left 2
WINDOW 3 -75 103 Left 2
SYMATTR InstName S2
SYMATTR Value MSW
SYMBOL diode 32 160 R180
WINDOW 0 -57 43 Left 2
WINDOW 3 -49 21 Left 2
SYMATTR InstName DB1
SYMATTR Value DID
SYMBOL diode 32 336 R180
WINDOW 0 -57 46 Left 2
WINDOW 3 -50 22 Left 2
SYMATTR InstName DB2
SYMATTR Value DID
SYMBOL cap 96 96 R0
WINDOW 0 39 19 Left 2
WINDOW 3 40 45 Left 2
SYMATTR InstName CP1
SYMATTR Value 1n
SYMBOL cap 96 272 R0
WINDOW 0 36 18 Left 2
WINDOW 3 38 43 Left 2
SYMATTR InstName CP2
SYMATTR Value 1n
SYMBOL voltage -416 176 R0
WINDOW 0 36 43 Left 2
WINDOW 3 38 69 Left 2
SYMATTR InstName VBUS
SYMATTR Value 311V
SYMBOL Opamps\\opamp 544 624 M0
WINDOW 0 9 95 Left 2
SYMATTR InstName U1
SYMBOL voltage 608 720 R0
WINDOW 0 -101 45 Left 2
WINDOW 3 -101 66 Left 2
SYMATTR InstName VRef
SYMATTR Value 5V
SYMBOL res 832 528 R90
WINDOW 0 0 56 VBottom 2
WINDOW 3 32 56 VTop 2
SYMATTR InstName R1
SYMBOL res 832 656 R90
WINDOW 0 0 56 VBottom 2
WINDOW 3 32 56 VTop 2
SYMATTR InstName R2
SYMBOL cap 704 528 R90
WINDOW 0 0 32 VBottom 2
WINDOW 3 32 32 VTop 2
SYMATTR InstName C1
SYMBOL cap 464 528 R90
WINDOW 0 0 32 VBottom 2
WINDOW 3 32 32 VTop 2
SYMATTR InstName C2
SYMBOL res 592 528 R90
WINDOW 0 0 56 VBottom 2
WINDOW 3 32 56 VTop 2
SYMATTR InstName R3
SYMBOL cap 464 608 R90
WINDOW 0 0 32 VBottom 2
WINDOW 3 32 32 VTop 2
SYMATTR InstName C3
SYMBOL res 656 720 R0
SYMATTR InstName R4
SYMBOL SpecialFunctions\\modulate 336 544 M0
SYMATTR InstName A1
SYMBOL Digital\\dflop 48 480 M0
WINDOW 0 48 -19 Left 2
SYMATTR InstName A2
SYMBOL Digital\\and -272 432 M0
SYMATTR InstName A5
SYMBOL Digital\\and -272 544 M0
SYMATTR InstName A6
SYMBOL Digital\\buf1 96 672 M0
SYMATTR InstName A3
SYMBOL Digital\\xor -48 640 M0
SYMATTR InstName A4
TEXT -416 -80 Left 2 !K1 LP LS 1
TEXT -416 -32 Left 2 !.MODEL DID D(Ron=10m Roff=1E7)
TEXT -416 -56 Left 2 !.MODEL MSW SW(Ron=10m Roff=1E7 Vt=5)
TEXT -416 -8 Left 2 !.LIB OPAMP.SUB
LINE Normal 384 224 384 144 2
LINE Normal 400 224 400 144 2
Copy the text and save it as an .asc file. LTSpice should open it.

Might look like the attached picture and I think you will be able to guess as to what is going on.
Attached Images
File Type: png Screenshot at 2017-11-19 15:32:11.png (64.7 KB, 193 views)
  Reply With Quote
Old 19th November 2017, 05:01 PM   #7
voltwide is offline voltwide  Ireland
diyAudio Member
 
Join Date: Jan 2010
Some remarks for your basic understanding of LLC.

The primary inductance is of minor importance.
Under full load conditions you have to consider the series resonant tank consisting from primary stray inductance and primary series capacitor.

It is a good idea to approach the LLC with a fixed frequency between 50 ~ 100khz with no regulation at all.
Tune your clock to the primary series resonant frequency.
This is the "sweetspot" operating point yielding lowest total loss.
This can be done by monitoring primary current under full load, adjusting the shape to a sinewave.

Now you can use your unregulated LLC to power your amp like you used to power with an unregelated toroidal supply in the past.

Primary inductance is controlled by the air gap. It should be low enough to allow sufficient primary magnetizing flowing to enable zero-voltage-switching during dead time. This significantly reduces heat up of your primary power MOSFETs.

You can simulate LLC basically with a square wave generator feeding the LCC circuit with the primary loaded by a resistor.
This helps to find matching Ls and Cprim.

A typical Lstray/Lprim ratio is 1/5.

I am constructing LLC-smps just for fun, achieving 500W with ETD39 core at 120kHz . With secondary synchronous rectification efficiency peaks at 97%.

Last edited by voltwide; 19th November 2017 at 05:04 PM.
  Reply With Quote
Old 22nd November 2017, 12:12 PM   #8
TroelsM is offline TroelsM  Denmark
diyAudio Member
 
TroelsM's Avatar
 
Join Date: May 2003
Location: AARHUS. DK
@Voltwide: Thank you for the input. I did think about running it un-regulated, but dropped it because: 1) I would like to power a Class-D chip that cannot tolerate voltage peaks. 2)To th ebest of my understanding the resonant-freq will change when the load changes. (please correct me if I'm wrong).

Could you maybe share some pictures or other detail of the transformer you use that have a 1:5 ratio?

Kind regards TroelsM
__________________
Need more time...
  Reply With Quote
Old 24th November 2017, 04:01 PM   #9
TroelsM is offline TroelsM  Denmark
diyAudio Member
 
TroelsM's Avatar
 
Join Date: May 2003
Location: AARHUS. DK
OK. So I had i 5 minutes break and tried to load the LLC with 6Ohm across the 60V. With short pulses in order not to blow it up...

Both mosfets (IRFP450, To247-case, with a 50cm2 heatsink) blew, and main fuse blew. Instantly.
I'm pretty sure that the freq was way above the res-point so I guess the mosfets was soft-switching and even if they entered hard-swicting I guess it would take a few seconds for them to heat up and blow?

I could not understand what happened that could cause a rugged mosfet like that to D-S-short in a split-second. Then I started thinking about what happens during hard loading and i remembered that the primary-current in a LLC will go very high.

I'm using a X-former core that only has 1cm2 area and I tried to measure at what current the core saturates with this setup that half-way down this page. Flyback Converters for Dummies

With open secondaries the core saturates around 18A. With shorted secondaries the core saturates around 9A.

Would I be correct in assuming that a big step-load will make the secondary appear to be shorted as seen from the primary side?

In that case this may be why the mosfets blew. The current got so high that the core saturated and the current sky-rocketed from there?

Thats a thing I did not think about in the design. I had hoped that for big, short current-pulses i would only have to deal with the thermal issue.

Does it makes sense? -if so, I guess I need a bigger airgap to make sure that the core dont saturate.

Kind regards TroelsM
__________________
Need more time...
  Reply With Quote
Old 25th November 2017, 12:47 PM   #10
MorbidFractal is offline MorbidFractal
diyAudio Member
 
Join Date: Nov 2017
Going back to your OnSemi App Note,

I have had a go at putting the equations into a FreePascal/Lazarus application. It's not pretty but... Attached.

The results do not exactly agree with the App Note but, assuming its equations are right, look at EQ27-29. Their calculations are wrong.

Also have a look at Page 15)

Quote:
The difference between the LLC design with external
resonant inductance and the design that uses a transformer
with high leakage inductance can be determined with
simulations. The integrated resonant tank gain differs from
the inversed transformer turns ratio when operated in series
resonant frequency. This phenomenon is related to the fact
that the leakage inductance is physically not located in series with the primary winding like in the external resonant coil solution.
I think that might be fairly telling. Look back at my previous post and the Notes by Lloyd Dixon where he explains how to position/associate the Leakage Inductance with a particular winding and also estimate its value.

Also notice that some of the equations in the OnSemi App Note include the number 8. I am used to dealing with voltage fed square wave converters whereby minimum primary turns kind of work out to be,

NPmin = VIN.TON/Bpeak.Ae

It's the integral volt-seconds applied to the primary. When you see 8 then someone is looking at a sinusoidal voltage drive rather than a square wave voltage drive. The sums are a bit incestuous but there may be another way of working things out...

You mentioned a flyback converter and that might be worth pursuing.

Later.
Attached Images
File Type: png Screenshot at 2017-11-25 13:17:59.png (27.1 KB, 163 views)
File Type: png Screenshot at 2017-11-25 13:22:52.png (31.7 KB, 163 views)
  Reply With Quote

Reply


Power limitations for LLC-smps for amplifierHide 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

Forum Jump

Similar Threads
Thread Thread Starter Forum Replies Last Post
amplifier TDA7294 + power supply smps cmeletronica Solid State 4 9th August 2015 04:55 AM
SMPS for DAC and small power amplifier twest820 Power Supplies 2 24th December 2013 01:08 AM
Power Transformer Limitations howe0168 Tubes / Valves 11 16th March 2012 10:20 PM
Amplifier 3000 Wats Rms Power + Smps Higcht Power Bestiality MARAVILLASAUDIO Class D 1 5th November 2004 04:06 PM


New To Site? Need Help?

All times are GMT. The time now is 04:19 PM.


Search Engine Optimisation provided by DragonByte SEO (Pro) - vBulletin Mods & Addons Copyright © 2018 DragonByte Technologies Ltd.
Resources saved on this page: MySQL 15.00%
vBulletin Optimisation provided by vB Optimise (Pro) - vBulletin Mods & Addons Copyright © 2018 DragonByte Technologies Ltd.
Copyright ©1999-2018 diyAudio
Wiki