Thanks Hugh and Kean. I should say that the Zobel felt less than warm, a wee bit higher than ambient temperature.
Sound is near ideal; not bright, splashy or sibilant. The spectrum is very well balanced tonally. The VAS does have degeneration of 56E. The so called 'majic resistor' is 33E.
Only thermal compensation is a bit overdone. When I set Iq to 150mA, after moderate listening it drops to 130mA and stays there. I'll have to check at higher listening levels.
I'll report more after further listening tests. Thanks again.
Sound is near ideal; not bright, splashy or sibilant. The spectrum is very well balanced tonally. The VAS does have degeneration of 56E. The so called 'majic resistor' is 33E.
Only thermal compensation is a bit overdone. When I set Iq to 150mA, after moderate listening it drops to 130mA and stays there. I'll have to check at higher listening levels.
I'll report more after further listening tests. Thanks again.
Hello Ostripper.
I have great confidence in your amplifier design knowledge.
I find it a bit hard to find out what schematic/amplifier is discussed.
Visiting your Mongrel website did not make easier.
There are AX, BX, CX, GX and god knows what ....
But the current complete schematic of Mongrel I did not find out.
So I comment the schematic in the Topic.
Which was set in first post, as usual.
After looking some minute, there is nothing strange.
What differs from many other is 2 things:
1. The cascoding arragement in input.
2. The bias of drivers using CCS.
I have great confidence in your amplifier design knowledge.
I find it a bit hard to find out what schematic/amplifier is discussed.
Visiting your Mongrel website did not make easier.
There are AX, BX, CX, GX and god knows what ....
But the current complete schematic of Mongrel I did not find out.
So I comment the schematic in the Topic.
Which was set in first post, as usual.
After looking some minute, there is nothing strange.
What differs from many other is 2 things:
1. The cascoding arragement in input.
2. The bias of drivers using CCS.
Lineup , my man... if you read further, I decided to go modular. This can be good for the environment and for the DIY'er. AX,BX, CX , and GX are done. In Fact , I have enough FR-4 and parts to build them all. Then I can do a subjective/objective "shootout" to see what is better/best. (I think GX will win) Mongrel means "mutt" , you can add any of the 4 voltage stages to the 2 power boards to get a custom amp.
Edit , the "CX" is the original "mongrel" , you can take that one (it is in my living room now) and make a little 60watter or go nuclear and make a 8 OP device kickbutt amp.
Below is the madness... you can "plugin" any amp you like!!
OS
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What's wrong with the cascoding arangement?
(I'm thinking about connecting the casodes Zener anode to ground insted connecting it to the tail CCS. Still not sure about this...
)
I'm in "build mode"
Good old board cutting.. some have shears , saws , all sorts of fancy tools. How can we do it without nuthin' .. hmmm?? (hands and a needle punch).
Picture 1 - scribe with a good straight edge (don't slip) using a VERY sharp needle scribe or punch. 2 or 3 passes with straight edge held firm on copper side , use paper so you don't scratch copper.
Picture 2- flip board over , you will see the copper side scribe on the green side (component side) You don't want to scratch this either , use paper. Repeat what you did on the copper side. 12-15 times each side , keep scribing .. using increasing pressure until you are down to half thickness both sides combined, don't slip. With just minor flex board should break strait and clean , flex both directions. lightly file edges down to remove "burrs" , clean with acetone.
Picture 3 - finished with very tight tolerances , just like a shear !!!
I got my 2 PB250's , 2AX's, 2BX's, and 2 GX's out of this.
I did get some "scrap" ... maybe a LED power meter or something.
And the screwup (pix 4). No one is perfect.
OS
Good old board cutting.. some have shears , saws , all sorts of fancy tools. How can we do it without nuthin' .. hmmm?? (hands and a needle punch).
Picture 1 - scribe with a good straight edge (don't slip) using a VERY sharp needle scribe or punch. 2 or 3 passes with straight edge held firm on copper side , use paper so you don't scratch copper.
Picture 2- flip board over , you will see the copper side scribe on the green side (component side) You don't want to scratch this either , use paper. Repeat what you did on the copper side. 12-15 times each side , keep scribing .. using increasing pressure until you are down to half thickness both sides combined, don't slip. With just minor flex board should break strait and clean , flex both directions. lightly file edges down to remove "burrs" , clean with acetone.
Picture 3 - finished with very tight tolerances , just like a shear !!!
I got my 2 PB250's , 2AX's, 2BX's, and 2 GX's out of this.
I did get some "scrap" ... maybe a LED power meter or something.
And the screwup (pix 4). No one is perfect.
OS
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I am a he-man redneck. nail polish...
geezz...A keen eye , Hugh. Someone seen that before and said "dirty nails" . I dig in gardens with bare feet...
I did screw up slightly on mouser order , need 47R and 68R 1/2 watters.. no biggie. Next 3 pictures are rare indeed. (mongrel lab and crazy OS)
Lots of free inductors in my junkpile (PC PS's- 3rd pix)
OS
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Here is the uber expensive toner sealant and modifier films (below) . I hope these will set this project apart from the norm. The toner transfer sheets cost $1.40 APIECE , but are supposed to float off the toner when soaked in water.
They coat the paper in some water soluble starch which dissolves when wet.
The green film combines with the toner to seal any pinholes and create a bulletproof etch resist. The white film combines in the same manner and makes a tough white finish for the silkscreen side. These products are best used with a laminator and are supposed to make "board house" quality work. I hope they don't lie !! I figure 4-5$ for large boards (PB250) and 2$ for all the voltage boards , not too bad .
I await my laminator (UPS tommorrow)
OS
The toner transfer sheets cost $1.40 APIECE , but are supposed to float off the toner when soaked in water.They coat the paper in some water soluble starch which dissolves when wet.
The green film combines with the toner to seal any pinholes and create a bulletproof etch resist. The white film combines in the same manner and makes a tough white finish for the silkscreen side. These products are best used with a laminator and are supposed to make "board house" quality work. I hope they don't lie !! I figure 4-5$ for large boards (PB250) and 2$ for all the voltage boards , not too bad .
I await my laminator (UPS tommorrow)
OS
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Even with hand design I never had pitting or undercut problems. Now , I just want repeatability and the possibilities for finer and more complex designs. This is why I never made contributions in the protection and accessory area's. If this works out , SMD and the BEST protection (power supply monitoring based) will be next.
OS
Ahh , so many free amp parts. Scrapping is the way (free transport below1)Runs on sandwiches and taco's (bike powered ) . Pc's have many multilayer ceramics and polystyrene bypasses. By the time the electrolytic's (2k-10kMTBF) go , most of the other types have 50k-100k hours left.
Most PC PS's and televisions have mostly .1uF @ 250v polystyrene in the AC input section and many 63-100v .01 .22uF everywhere else .. perfect for DIY zobels and PS bypasses. Lots of to-220 mounting hardware on the switching supply too. AND some better scrap PS's have AC input filter networks (below 2-top) just dandy to keep all that modern switching "hash" out of your creations.
Also , can't forget the over rated snubber caps (400v+) that abound in these circuits.
OS
. Pc's have many multilayer ceramics and polystyrene bypasses. By the time the electrolytic's (2k-10kMTBF) go , most of the other types have 50k-100k hours left.Most PC PS's and televisions have mostly .1uF @ 250v polystyrene in the AC input section and many 63-100v .01 .22uF everywhere else .. perfect for DIY zobels and PS bypasses. Lots of to-220 mounting hardware on the switching supply too. AND some better scrap PS's have AC input filter networks (below 2-top) just dandy to keep all that modern switching "hash" out of your creations.
Also , can't forget the over rated snubber caps (400v+) that abound in these circuits.
OS
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You need old CRT pc monitors This is how looks like,already stealed made in china 2000 year monitor ,see below
And some video transistors from it
2sa1370 200v 100ma , 1w ,hfe 40-320, 150mhz, 1,7pf
2sc2229 150v 50ma , 800mw, hfe 70-240, 120mhz, 4pf
2sc4934 120v 0,2A 1,5w, hfe 250-800, 350mhz, 3,5pf
Lots of ceramic caps,200V electrolites and so on...
This is how looks like,already stealed made in china 2000 year monitor ,see belowAnd some video transistors from it
2sa1370 200v 100ma , 1w ,hfe 40-320, 150mhz, 1,7pf
2sc2229 150v 50ma , 800mw, hfe 70-240, 120mhz, 4pf
2sc4934 120v 0,2A 1,5w, hfe 250-800, 350mhz, 3,5pf
Lots of ceramic caps,200V electrolites and so on...
Attachments
You need old CRT pc monitors
And some video transistors from it
2sa1370 200v 100ma , 1w ,hfe 40-320, 150mhz, 1,7pf
2sc2229 150v 50ma , 800mw, hfe 70-240, 120mhz, 4pf
2sc4934 120v 0,2A 1,5w, hfe 250-800, 350mhz, 3,5pf
Lots of ceramic caps,200V electrolites and so on...
Too bulky , shipping would be prohibitive. Many toxic substances. I only collect local waste , smash CRT's ,bury it all at local landfill. PC power supplies are better finds. Wish I could find some old audio receivers ... need test trafo's.
Also , I try not to use recycled semi's , they are far too cheap here in the states ($0.07 for ksa992/ksc1845 $0.27 for ksa1381/ksc3503)
electrolytes, NO ,NO ,NO...they are first to "go"...
OS
How about the switching modules in consumer DVD players?
Attached is a DAC, lots of nice film caps. And don't forget about about radio tuner boards, with all manner caps of the finer sort. Also an assortment of things I've found in old TV equipment. I'm still not sure what that tube thing is. The cylinder cap is an ERO MKC1863, polycarbonate 1.5uF 200V. What am I supposed to do with only one? Tuning cap in the lower right.
- keantoken
Attached is a DAC, lots of nice film caps. And don't forget about about radio tuner boards, with all manner caps of the finer sort. Also an assortment of things I've found in old TV equipment. I'm still not sure what that tube thing is. The cylinder cap is an ERO MKC1863, polycarbonate 1.5uF 200V. What am I supposed to do with only one? Tuning cap in the lower right.
- keantoken
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What's bad about old semi's? For GX i will use sc1845 and sa992 from old amp (best catch).Guarantee to be original... Of course with mouser your can't go wrong.Will order from them some day...
BTW inspired by your experience about PC power supply,took one COBA 400w (good one) and found almost nothing.Even 2x MKT 250v on AC line were different
BTW inspired by your experience about PC power supply,took one COBA 400w (good one) and found almost nothing.Even 2x MKT 250v on AC line were different
What's bad about old semi's? For GX i will use sc1845 and sa992 from old amp (best catch).Guarantee to be original... Of course with mouser your can't go wrong.Will order from them some day...
BTW inspired by your experience about PC power supply,took one COBA 400w (good one) and found almost nothing.Even 2x MKT 250v on AC line were different
yes , some chinese PC PS's are not worth a damn , cheap junk ... many RMA's.
COBA ... ha ha , wouldn't build my enemies PC's with one... FIRE HAZARD!!!
Oh wow.. a sprauge "orange drop" , that brings back memories of old days. Some of them old poly's last forever. Same with old Nichicon electrolytics .. 20 years and they will still be usable or even good. the old 2sc1845/2sa992 will work , but you may only get 2-5 years+ instead of 20 years. BTW , my amps are so over-rated , I expect 15-20 years 24/7 use... MTBF
. Not bragging , but true.OS
Those pix are exactly what I speak of , beautiful film caps , many 10's of K life left in them....
CRT TV's are the same... just stay away from the labored electro's the 15750hz shortens their life considerably.OS
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