Go Back   Home > Forums > Amplifiers > Solid State

Solid State Talk all about solid state amplification.

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 15th October 2013, 04:07 PM   #11
Bigun is offline Bigun  Canada
diyAudio Member
 
Bigun's Avatar
 
Join Date: Jan 2009
Blog Entries: 2
Hi Richie - both my TGM7 and Hugh's NAKSA use vertical MOSFETs.

Nelson Pass doesn't advocate dc protection for his amps either from what I remember(?)
__________________
"The test of the machine is the satisfaction it gives you. There isn't any other test. If the machine produces tranquility it's right. If it disturbs you it's wrong until either the machine or your mind is changed." Robert M Pirsig.
  Reply With Quote
Old 15th October 2013, 09:28 PM   #12
diyAudio Member
 
Join Date: Apr 2010
Location: Coffs Harbour, on the east coast
I haven't fitted relays to my own amplifiers since the first, way back when AC coupling was normal. However, now that we have several designs for Mosfet output relays, I'm seriously considering using that in my next full-sized project. With the right super-low Rds Fets, it seems close to an ideal solution.

I have had several problems recently with those enormous, too closely spaced speaker connectors now fitted to commercial and DIY amplifiers. No matter whether plain wire, spade, pins, bananas etc, when any sort of "audiophile" terminal is used, there are just too many ways to short the speaker leads, given the cramped, precarious and uncertain way the connections are made.

I always fit relay protection to amplifiers sold to others because not only do customers misunderstand the dangers of shorting speaker leads or overdriving the amp, they seem always to have other family members who (ab)use the amplifier when no one is about. Sure, some relays can sound poor but that's less a problem than irate clients who expect modern equipment to always work, whatever happens.

It comes down to who sets up and uses the equipment. If you are the builder and user, you still may never have a problem without any form of protection. I'm starting to be a little clumsy or hasty myself, so perhaps it's time for me to build that better mousetrap?
__________________
regards
  Reply With Quote
Old 15th October 2013, 09:31 PM   #13
diyAudio Member
 
KatieandDad's Avatar
 
Join Date: Nov 2011
Location: UK
I agree with Bigun. Running Pass amps here, none of them have any output protection, they rely on their rugged construction for reliability.
  Reply With Quote
Old 15th October 2013, 09:43 PM   #14
diyAudio Member
 
lanchile's Avatar
 
Join Date: Sep 2008
Location: AREA 51
I do not use relays in my amps, beside they are not so safe as people think
if you have a well designed amp you can get away without relays to avoid thumps on the turn on/off or stop any Dc voltages to speakers also as mentioned before, if amp is well build...there is not worries
__________________
Make it simple...Make it better!
  Reply With Quote
Old 15th October 2013, 09:47 PM   #15
sreten is offline sreten  United Kingdom
diyAudio Member
 
Join Date: Nov 2003
Location: Brighton UK
Hi,

Its an easy thing to add to the specification if output relays
are used and near impossible to add without relays unless
a fully active regulated power supply is used, not cheap.

rgds, sreten.
__________________
There is nothing so practical as a really good theory - Ludwig Boltzmann
When your only tool is a hammer, every problem looks like a nail - Abraham Maslow
  Reply With Quote
Old 19th October 2013, 08:00 PM   #16
diyAudio Member
 
indianajo's Avatar
 
Join Date: Jan 2010
Location: Jeffersonville, Indiana USA
I've just read all 48 pages of post 191449 about diy solid state relays, particularly the design Michael Bean came up with with two FET's and a photovoltaic optocoupler driver. I'll post comments here rather than mess up that classic thread.
Yes, you need speaker protection if you are driving Black Widow 15" costing $139 each plus freight, plus a $100 tweeter, IMHO. Particularly on a PA amp with a lot of inebrieted musicians wandering around in the dark on stage sticking random phone plugs into random holes. Bonsai's suggestion that you should switch the ground and forget the extra expense of switching the speaker, and be careful with speaker wires, has no applicability to my world, or that of the average bar band. Among the three pieces of PA gear I've bought and repaired so far, the PV-1.3k had 18 of 20 output transistors totally shorted and 89 other parts blown including two crowbar triacs that totally melted the lands leading to them off the board, without blowing the main breakers. The CS800s amp had input caps so vaporized by the wrong phone plug in the hole, that I had to download several schematics to find out what they ever were, caps or resistors. The Unity 2002-12RQ mixer has blown main out op amps, probably another case of the guitar amp output going in the wrong hole on stage, although it could have been just a phone plug pulled partially out by someone tripping over it. And don't forget about whiskers on bare wires touching the grounded chassis in the home, or the tip of any phone plug touching anything grounded on stage in the dark.
Actually building Michael Bean's design is problematic for me. Among the usual USA suspects, newark.com, mouser.com digikey.com alliedelec.com, nobody stocks the PV15013 optocoupler IC, now an International Rectifier product. Nobody stocks or lists the Toshiba TLP191 that Bonsai used on his design with PWB layout. I don't like Toshiba anyway, I've had the datasheet for a year and just now figured out after three days reading that it wasn't a regular optocoupler but instead generated 7 vdc into a tiny capacitor (NMOS gate). Nobody but digitech even lists the Avago ASSR-V622, and they predict they can buy them in batches of 350 with 106 day lead time at $4 each. Mouser only stocks the Panasonic APV1122 with through hole design. Among other photovoltaic optocouplers, only digitech separates them out as a catagory, and the ASSR-V622 is not in the catagory. Unsuitable optocouplers include the IXYS LOC-110, the Vishay IL300, and the Avago HNCR201. Those three are some sort of linear coupler used for telephony, apparently, and are readily in stock. Don't bother downloading the datasheet for those.
After reading thread 191449 output relays, I've decided after 6 months of wrangling with triacs and snubbers tiny 15 VAC transformers, triac opto drivers, 5 W power resistors, 120 VAC wiring, etc that even free 4 pole 22 Amp ac 600 VAC rated relays outside the feedback loop, on the 4 power supply rails, are likely to 1. weld themselves closed in a fault 2. cause a big pow or thump on turn-on 3. cause AC hum from the coil, 4. possibly mess up 1.5 V music with distortion, which is the level where I typically listen to an amp in the home. This is even with the Peavey internal driver board silencing circuit after the rail relays. I don't even want to put relays after the output transistors, I know how relays except for rhodium plated ones corrode, and how unsuitable rhodium plate is for breaking 70 amp DC currents. I had planned to plate the tungsten contact relays I had with silver solder, but I find the plumbing "silver solder" is 90% something else. Stainless steel welding wire is an unsuitable plating material, it contains chrome which has a hard oxygen layer and is totally unsuitable for low voltage contacts. And 90% nickel 10% silver wire for plating tungsten with a torch probably only comes in 2 lb rolls for the price of 6 months entertainment budget.
One other comment on the 191449 output relays thread. Pavel Macura's design, looks competent to shut off the AC coming out of the output transistors only before they blow up. He has a regular phototransistor optocoupler controlling the NFET gate , subject to a zener diode to establish the gate voltage, powered by +- rail voltages from the outside. He doesn't mention that the rail voltages coming in need to come off a separate winding of the transformer, 7 v higher than the rails going to the output transistors. As long as the output transistors are normal the music will be about 1/2 the rail voltage, so there is plenty of headroom to power the fets. As soon as an output transistor shorts to the rail, the speaker voltage goes to the rail (+170 v in the case of the PV-1.3k) and there is no headroom to power an nfet. Please explain anybody, I don't see a voltage doubler inside PMA's circuit design, although I'm not sure I can figure out a voltage doubler for a design using no center taps and a bridge rectifier, anyway.
Another fact I found in thread 191449 is a casual reference to bridgable amps. The PV-1.3k I'm trying to make safe for speakers, is bridgeable, and has "flying rail" which means the power supplys have the music riding on them and drive the OT collectors, the emitters drive the speaker, and speaker return is case ground. Is flying rail usual in "bridgeable" amps or just a Peavey design? This means my nfets have to be rated 200 v, and I can't figure if the current in nfets in the rail switch position (after filter cap, before collector common) flows "backwards" in the fet usually, or not. I like the rail switch position instead of the speaker terminal position because it has a possibility of saving $36 of output transistors that are really hot from damage after the first transistor shorts and puts DC out to the speaker.
Six months ago, I came up with $100 as the price of 4 suitable nfets for my 22.5 amp RMS @ 170 v application. This week I found some FDP52n20 52 amp 200 V fets for $1.70 each, I hope they are not rejects. These have .05 ohm max over temperature, which may be marginally acceptable. You can buy .015 ohm nfets, they appear to run $8 to $10 apiece, which is beyond my budget right now, and that low distortion is probably not needed on a PA amp driving bass mostly.
I haven't even ordered the APV1122's yet, I've blown the months entertainment budget already.
I can't deal with smc, I can barely keep solder from bridging pins on DIPs with a fiber barrier between pins. Surface mount is totally beyond my capability. As is making PWB's, I don't have a fancy computer to run layout software, don't have the money to buy PWBs from a supplier, and can't find hair bleach peroxide locally to etch them even if I laid out a mask with a marksalot and transferred to photo paper at the local service copy machine. I build on perf board, drilled by myself mostly out of bulk stock.
Thanks for listening. Hope the list of unsuitable photovoltaic drivers saves you some time. any other suitable commonly stocked numbers, please update me, newark, mouser, digikey, alliedelec are no help on this weird little part.
__________________
Dynakit ST70, ST120, PAS2,Hammond H182(2 ea),H112,A100,10-82TC,Peavey CS800S,1.3K, SP2-XT's, T-300 HF Proj's, Steinway console, Herald RA88a mixer, Wurlitzer 4500, 4300

Last edited by indianajo; 19th October 2013 at 08:08 PM.
  Reply With Quote
Old 19th October 2013, 08:09 PM   #17
Bigun is offline Bigun  Canada
diyAudio Member
 
Bigun's Avatar
 
Join Date: Jan 2009
Blog Entries: 2
Interesting to read your experiences - those are some serious amplifiers you play with. You are saying the Triac crowbars failed to protect the PV1.3k amplifier because they vaporized their contacts before the main breaker blew. WOW . I guess the crow bar should be soldered point to point with substantial wiring to ensure it works until the lights go out.

By the way, the TLP190 and TLP191 are available from Digikey -which is where I got mine from when I build a set of solid state relays for the output of my TGM5 amplifier. They are SMD though........
__________________
"The test of the machine is the satisfaction it gives you. There isn't any other test. If the machine produces tranquility it's right. If it disturbs you it's wrong until either the machine or your mind is changed." Robert M Pirsig.

Last edited by Bigun; 19th October 2013 at 08:13 PM.
  Reply With Quote
Old 19th October 2013, 08:22 PM   #18
diyAudio Member
 
nigelwright7557's Avatar
 
Join Date: Apr 2008
Location: Carlisle, England
I have always used DC protection with a relay but I use my amplifiers for on the road use where cables are always getting plugged in and out and tripped over so they can get damaged.
__________________
http://www.murtonpikesystems.co.uk PCBCAD50 pcb design software.
  Reply With Quote
Old 19th October 2013, 08:47 PM   #19
diyAudio Member
 
indianajo's Avatar
 
Join Date: Jan 2010
Location: Jeffersonville, Indiana USA
Thanks for the digitec tip. Maybe I could bend the TLP191 leads down or something to stick them through the holes. No pick & place machine, here.
Yes, the replacement crowbar triac melted an 18 ga bus wire PWB patch in front of my eyes when one of the output transistors that passed the DVM diode test twice, blew the die through the case after 30 seconds: without the breaker blowing. (You've got to sort old damaged transistors with a Iceo test, I use 17 VDC for that now with the base shorted to emitter). It could be a replacement 14A breaker with 11x overcurrent capability suitable for air conditioners and unsuitable for amps, I don't know. This PV-1.3k should nuisance trip any breaker as delivered, the turn on surge when I bought it was bad enough to dim the room lights for 1 second. I've since put in a CL101 NTC ahead of the transformer to soften the turnon surge, but prefer some better solution to DC on speaker terminal than a crowbar triac and a softer main breaker. At $55 the PV-1.3k was worth it just for the heat sinks case fan and transformer, and I have learned a bunch of things trying to repair and tame it. Maybe I've have a band someday that needs one. With a 330 lb Hammond organ as my main instrument, hefting a 55 lb amp around with a transformer power supply instead of a switcher would be a snap.
__________________
Dynakit ST70, ST120, PAS2,Hammond H182(2 ea),H112,A100,10-82TC,Peavey CS800S,1.3K, SP2-XT's, T-300 HF Proj's, Steinway console, Herald RA88a mixer, Wurlitzer 4500, 4300
  Reply With Quote
Old 19th October 2013, 10:00 PM   #20
diyAudio Member
 
KatieandDad's Avatar
 
Join Date: Nov 2011
Location: UK
A lot of valid points there, with two distinctly different environments.

1. On the Road - Quality is not paramount but reliability is.

2. At Home - The opposite.

If the equipment is going to be regularly disturbed then protection is acceptable.

I hate anything in the signal path but at home that ceases to be an issue.
  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
Difficulties with DC/DC converter 12V to +/-40V, 8 amps vena2a Power Supplies 16 18th June 2013 01:35 PM
Crown, Rane, DBX, Chip-amps, DC to DC converters, etc! techbiker Swap Meet 1 22nd March 2013 05:15 AM
Combined DC protection and tweeter protection? CopperTop Solid State 10 13th January 2011 07:52 AM
DC speaker protection for Sure class-D amps?.. OzOnE_2k3 Class D 23 12th April 2010 02:43 AM
Chip Amps with no DC PROTECTION fine? commstech Chip Amps 9 27th November 2007 02:24 PM


New To Site? Need Help?

All times are GMT. The time now is 03:53 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