i want to mess around and see if i can get the power of a 225hcca(digital reference) to be made at a higher ohm.
i saw a picture of a 275sx pcb and noticed it was the exact same pcb, (pics at www.ampguts.com)
i have a few 225hcca's that ive rebuilt (with alot of help from perry babin) and i want to see if i can take it one step further and see if i can turn it into a 275sx and make power at a higher ohm load.
i noticed there are more windings on the 275sx's core, but is this all that is needed to make power at a higher load? higher rail voltage?
i know that somewhere along the line i would probably have to lower the voltage/current going to a few of the circuits, as well as swapping out a few capacitors for a higher voltage rating.
anyone have any ideas? think i would have to lower the voltage to the opamps also?
oh, just to make it clear, im not trying to make more power, i just want the rated power to be delivered at a higher ohm...
i saw a picture of a 275sx pcb and noticed it was the exact same pcb, (pics at www.ampguts.com)
i have a few 225hcca's that ive rebuilt (with alot of help from perry babin) and i want to see if i can take it one step further and see if i can turn it into a 275sx and make power at a higher ohm load.
i noticed there are more windings on the 275sx's core, but is this all that is needed to make power at a higher load? higher rail voltage?
i know that somewhere along the line i would probably have to lower the voltage/current going to a few of the circuits, as well as swapping out a few capacitors for a higher voltage rating.
anyone have any ideas? think i would have to lower the voltage to the opamps also?
oh, just to make it clear, im not trying to make more power, i just want the rated power to be delivered at a higher ohm...
If you want to make more power into ligher loads, you need more rail voltage.
The main difference is going to be the transformer. The 225 has a transformer wound with a 1.83:1 ratio (6:11 actual turns). The 275 has something like 2.83:1 (6:17 actual turns). If you don't need a fully regulated supply a 3:1 ratio should be a good starting point. If you want a 'fully' regulated supply (never goes to maximum gate drive no matter the load), you would have to go with a higher ratio. These numbers are for a rail voltage of ~±35 volts. The amp would require other mods for higher rail voltage. Most of the transistors used in the audio section are limited to 80 volts. If you go with more than 80 volts rail to rail, you'll have to use different outputs which will be rated for lower current.
The regulator is very simple. It uses a Zener diode to determine the rail voltage. When the rail voltage is high enough to cause the zener to conduct, it switches on a 2n6488 transistor which pulls down the voltage feeding the gate drive circuit of the FETs (this was also used in pre-FET amps). Changing the Zener to a value just below the rating of the rail caps will provide the proper regulation. In the attached photo, the Zener just to the right of the TO-220 transistor (standing up) is the regulator diode.
The low voltage reg for the op-amps is discrete and should work without modification.
The main difference is going to be the transformer. The 225 has a transformer wound with a 1.83:1 ratio (6:11 actual turns). The 275 has something like 2.83:1 (6:17 actual turns). If you don't need a fully regulated supply a 3:1 ratio should be a good starting point. If you want a 'fully' regulated supply (never goes to maximum gate drive no matter the load), you would have to go with a higher ratio. These numbers are for a rail voltage of ~±35 volts. The amp would require other mods for higher rail voltage. Most of the transistors used in the audio section are limited to 80 volts. If you go with more than 80 volts rail to rail, you'll have to use different outputs which will be rated for lower current.
The regulator is very simple. It uses a Zener diode to determine the rail voltage. When the rail voltage is high enough to cause the zener to conduct, it switches on a 2n6488 transistor which pulls down the voltage feeding the gate drive circuit of the FETs (this was also used in pre-FET amps). Changing the Zener to a value just below the rating of the rail caps will provide the proper regulation. In the attached photo, the Zener just to the right of the TO-220 transistor (standing up) is the regulator diode.
The low voltage reg for the op-amps is discrete and should work without modification.
Attachments
will the amp blow if i go below 2 ohms mono/1 ohm stereo after the mod? or will it just get really hot?
right now i have IRFZ44N in the power supply, if i change to IRFZ48, think it would make any difference?
also i have STmicro BD911/912 for the outputs, is there anything stronger i can put in there place...kinda limited on knowledge concerning bipolar outputs.
thanx
right now i have IRFZ44N in the power supply, if i change to IRFZ48, think it would make any difference?
also i have STmicro BD911/912 for the outputs, is there anything stronger i can put in there place...kinda limited on knowledge concerning bipolar outputs.
thanx
Whether the amp survives depends on how hard you drive it. With 35 volt rails, 2 ohms mono would probably be OK. It would get hot (just as it would when running at the minimum load before the mods). If you fan cool it, it's going to be more likely to survive.
I would use IRF3205s in the supply if you are going to replace the FETs. I wouldn't change them unless they fail. Orion uses FAR more FETs than needed.
The 911/912 are probably as good as you'll get. I don't know of any TO-220 case BJTs that can handle more current for the voltage that they can handle.
I would use IRF3205s in the supply if you are going to replace the FETs. I wouldn't change them unless they fail. Orion uses FAR more FETs than needed.
The 911/912 are probably as good as you'll get. I don't know of any TO-220 case BJTs that can handle more current for the voltage that they can handle.
Clipped said:alright then , im gonna give it a shot...just have to decide which one is going to be my victim...i have 3- 225's, everytime i see one i buy it....
agreed on the 911/912 i cant seem to find a better substitute.
thanx !
That would be me with 275or 2125SX's...
Mr Erath and Mr Gerald made a servo unit that "mates" with the amp using the +/- 15 and matches the gain of the Orion amps. Kicks major boottie and now I can pick up these incredible amps dirt cheap.
Clipped said:Mr Erath and Mr Gerald ? who are they?
tell me more of this servo unit, a sub, processor, another amp, what the heck is it ?
gotta link? now you have me wondering
Mr. Erath designed a servo controller for amplifiers back in the 60's and made a loudspeaker that was the Ferrari of it's time called the LWE-1A. He has continuously refined the servo over the years as technology improved and is now making a new version of the loudspeaker.
I have both his home and car units. In this case the car unit is an external box that plugs into the DIN port of the Orion.
You run the full range RCA's into his box, it electronically cross' over the signal, sends the high pass out a pair of RCA's and bridges the low pass and sends them via the 5 pin DIN to the Orion amp.
The Servo does input to amp and output from amp comparison and adjust accordingly to compensate for amp irregularities and to compensate for a KNOWN reduction in woofer box volume.
His 15" woofers use a 1.23 cubic ft box; I run a pair of 10" woofers in a 1.0 cubic foot box. Both are flat from 20 to 80 Hz where mine are crossed and TIGHT as can be since the volume is reduced.
As for a web site, he does not have one other than his cheap Cable modem service. Look at the last page (contact us) and you will see a picture of him in his "younger" days.
http://www.lweloudspeakers.com/index.html
Keep in mind I have a TON of respect for the mans work, but his personal life I have issues with.
Mr. Gerald was / is his "partner". He is a great man to work with and probably the better one to deal with but he just "retired" and closed his company (Marquis Electronics). However he is still building some stuff for me now so he is still around and available.
thanx perry!
btw, i found something weird between 1 of the 3 amps i have...i'll have to scan a pic of the pcb.... for some reason there are diodes, where a resistor should be...(the 2 grey resistors by the bridged output speaker wires on each side of the amp)
on this amp, it uses a cheaper potentiometer...with black optocouplers
the other 2 amps have the sealed black pots...with white optocouplers
well i'll have to get around to scanning a pic for ya, im just wondering why they are different and if one design is better than the other..ever see this before?
btw, i found something weird between 1 of the 3 amps i have...i'll have to scan a pic of the pcb.... for some reason there are diodes, where a resistor should be...(the 2 grey resistors by the bridged output speaker wires on each side of the amp)
on this amp, it uses a cheaper potentiometer...with black optocouplers
the other 2 amps have the sealed black pots...with white optocouplers
well i'll have to get around to scanning a pic for ya, im just wondering why they are different and if one design is better than the other..ever see this before?
troystg said:
i just saw his pic ....im kinda interested in that crossover module, think he has anymore left?
i always wanted the accessories that plug into the din plug, but could never find them...can they be made for hi into amp/ sub out to rca too?
that would be cool if i could hook up 2 hcca's to it... do you know how much he sells them for?
"think he has anymore left?"
I'll write Mr. Gerald and ask.
"that would be cool if i could hook up 2 hcca's to it."
Nope one module, one amp. Need more power, get a bigger amp.
"do you know how much he sells them for?"
I paid 3-4 hundred for mine.. But this is NOT mass market crap. This is an audiophile grade, purpose built device.
I'll write Mr. Gerald and ask.
"that would be cool if i could hook up 2 hcca's to it."
Nope one module, one amp. Need more power, get a bigger amp.
"do you know how much he sells them for?"
I paid 3-4 hundred for mine.. But this is NOT mass market crap. This is an audiophile grade, purpose built device.
Clipped said:definately interested, but how would i go about acquiring it...?
im working over seas now, so my options are kinda grim...in thailand
should i contact him myself?
thanks for your help, really appreciate it!
I can take a picture of mine and if your still intrested in one you can either mail or PayPal me the money and I will pick it up and ship it to you.
Mr. Gerald has closed his buisness and is "retired" so that is why it is cheaper now.
Actually I have always wondered that myself. I do know that it was designed around the Orion, and has a "matching gain" from output to input for the feedback circuit, but I have always seen those amps as VERY similar.
I will ask.
Where are you located? I'm in Dallas and would love to try it out if you're near.
I will ask.
Where are you located? I'm in Dallas and would love to try it out if you're near.
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