I have an amp that uses 2N3773 output transistors. I want to replace them. Is there a direct equivalent that would make the amp sound better? I'm really a tube guy so I'm used to different sounding tubes. But transistor amps all sound pretty much the same to me.
Some of us noticed that transistors perform better when they are used closed to their limits. 2N3773 is the higher power version of 2N3055. If your power supply voltage is low, a certain 2N3055 could possibly sound better.
That´s a rather adventurous recommendation,
when you exceed their limits you will have no sound at all.
IMHO you should not attempt to do any "transistor rolling" before
you have investigated the schematic.
when you exceed their limits you will have no sound at all.
IMHO you should not attempt to do any "transistor rolling" before
you have investigated the schematic.
It is probably a quasi complementary if using 2n3773 transistors.
These 2n3773 have a very high guaranteed 1.5A @ 100Vce
No other 150W device can match this and few 250W devices can better this.
Do not swap in inferior devices.
If you really want better sound then look at an alternative design and hope it can perform better.
BTW, I love my Crimson CE1704vii, which uses 2n3773
These 2n3773 have a very high guaranteed 1.5A @ 100Vce
No other 150W device can match this and few 250W devices can better this.
Do not swap in inferior devices.
If you really want better sound then look at an alternative design and hope it can perform better.
BTW, I love my Crimson CE1704vii, which uses 2n3773
Hi,
No point changing the output transistors. Transistor "sound"
is all about the overall design / topology not the devices.
rgds, sreten.
No point changing the output transistors. Transistor "sound"
is all about the overall design / topology not the devices.
rgds, sreten.
Details of the design matter.
If your 2n3773 are original from the 1960's, they could be quite slow transistors, a low Ft. Most modern transistors have 2 mhz or better, probably even modern version of these. The ON semi datasheet for 2n3773 doesn't even list Ft. ON semi didn't even exist as a brand until 2000?
A person on here did simulations of a Leak Delta 70 amp from the midsixties, with original 5 digit RCA transistors (2n3055 selected for lower leakage at high voltage), TIP3055, and something else. Every time the output transistors sped up, the harmonic distortion went down.
My dynaco ST120 amp with the same original transistors was reviewed in 1966 as one of the vilest experiences known to man. I never heard the original transistors since I bought it blown up and installed NTE181's; I never played it a low volume where it has crossover distortion by design, and had no idea what they were complaining about.
So maybe if you tried something like MJ15024 it might sound better. You might not even need the soa of 2n3773. if your transformer is too wimpy to put out much current. It may be just that 2n3773 was cheap, they were at one time.
It also may be that faster transistors cause ultrasonic oscillation, since the early designs were not tested with faster transistors. The ST120 design was modified about 1972 to kill oscillations of faster transistors. The famous "TIP mod" detailed on Greg Dunn's website.
Post your design schematic, or list brand and number if it has been looked at already, and we'll examine further. It may be modern 2n3773 instead of 1968 originals would make the amp sound better.
If your 2n3773 are original from the 1960's, they could be quite slow transistors, a low Ft. Most modern transistors have 2 mhz or better, probably even modern version of these. The ON semi datasheet for 2n3773 doesn't even list Ft. ON semi didn't even exist as a brand until 2000?
A person on here did simulations of a Leak Delta 70 amp from the midsixties, with original 5 digit RCA transistors (2n3055 selected for lower leakage at high voltage), TIP3055, and something else. Every time the output transistors sped up, the harmonic distortion went down.
My dynaco ST120 amp with the same original transistors was reviewed in 1966 as one of the vilest experiences known to man. I never heard the original transistors since I bought it blown up and installed NTE181's; I never played it a low volume where it has crossover distortion by design, and had no idea what they were complaining about.
So maybe if you tried something like MJ15024 it might sound better. You might not even need the soa of 2n3773. if your transformer is too wimpy to put out much current. It may be just that 2n3773 was cheap, they were at one time.
It also may be that faster transistors cause ultrasonic oscillation, since the early designs were not tested with faster transistors. The ST120 design was modified about 1972 to kill oscillations of faster transistors. The famous "TIP mod" detailed on Greg Dunn's website.
Post your design schematic, or list brand and number if it has been looked at already, and we'll examine further. It may be modern 2n3773 instead of 1968 originals would make the amp sound better.
As mentioned ft was an issue but also you have to keep in mind that designers at the time didn't explore the limits of the semis but also the limits of their own designs . Obviously Japanese sophisticated test equipment that existed in Japan come over years later.
Result was to make equipment fine tuned by listening tests and that will be kinda limited since not all types of music was available or favorite to the designer and in general play safe better than sorry .
A quick look at the schematic will reveal filtering compensation and feedback that is applied rather safe than correct
Altering these parameters and combine this with modern transistors and you are going to have yourself a brand new and very fast amplifier .
Kind regards
Sakis
Result was to make equipment fine tuned by listening tests and that will be kinda limited since not all types of music was available or favorite to the designer and in general play safe better than sorry .
A quick look at the schematic will reveal filtering compensation and feedback that is applied rather safe than correct
Altering these parameters and combine this with modern transistors and you are going to have yourself a brand new and very fast amplifier .
Kind regards
Sakis
That's very wise. Faster modern transistors *may* sound better, but you'd better be prepared to deal with ultrasonic oscillations, and general instability, as was noted above.
"ON semi didn't even exist as a brand until 2000?"
FWIW, On Semi were MOTOROLA, one of the bigger producers of discrete power devices.
They did make 2N3771 - 2N3773 (Vmax grades) and I still have plenty in my parts bin. Very hard to destroy ....
FWIW, On Semi were MOTOROLA, one of the bigger producers of discrete power devices.
They did make 2N3771 - 2N3773 (Vmax grades) and I still have plenty in my parts bin. Very hard to destroy ....
http://www.onsemi.com/pub/Collateral/2N3773-D.PDF
Looks like the ft is 200kHz min (gain of 4 min at 50kHz, under Dynamic Characteristics).
Looks like the ft is 200kHz min (gain of 4 min at 50kHz, under Dynamic Characteristics).
If it ain't broke... is the most childish approach i have ever listened in this forum obviously from non tech people .
By your logic you may travel with a car that is 30 years old because it is preserved right from looks , engine starts , and no tire is flat ...
well sorry this not enough to take you to Canada if you ever manage it is going to cost you a fortune from gasoline , and the engine will probably fail either from oil , or cooling or any other reason ... suspension and steering is to found not suitable for today's driving speed and roads ...so result is that anything that will go wrong will be at least catastrophic
To your information all vintage amplifier will behave alike and like vintage cars that engine might start after 30 years , and sound might come out of the amplifier but in no case this is enough or correct ....
as about parasitic oscillations and generally oscillations if you use today's practice and semis to make the amplifier better you have to use them wisely and altering the speed of the amp to an astronomical speed will not ensure safety ...like most things the truth lays in the middle .
Kind broken regards
Sakis
By your logic you may travel with a car that is 30 years old because it is preserved right from looks , engine starts , and no tire is flat ...
well sorry this not enough to take you to Canada if you ever manage it is going to cost you a fortune from gasoline , and the engine will probably fail either from oil , or cooling or any other reason ... suspension and steering is to found not suitable for today's driving speed and roads ...so result is that anything that will go wrong will be at least catastrophic
To your information all vintage amplifier will behave alike and like vintage cars that engine might start after 30 years , and sound might come out of the amplifier but in no case this is enough or correct ....
as about parasitic oscillations and generally oscillations if you use today's practice and semis to make the amplifier better you have to use them wisely and altering the speed of the amp to an astronomical speed will not ensure safety ...like most things the truth lays in the middle .
Kind broken regards
Sakis
I'd argue that the "No guts, no glory" approach doesn't make much sense here. This is a vintage amp, and changing just the output transistors alone probably won't make a big difference. The whole circuit would have to be looked at, and everything considered to make it worth doing.
There is just no guarantee that changing the output transistors will make it 'better'. If it has the old RCA hometaxial type in there, probably ANYTHING would be an improvement unless it is a class A amplifier. If it has any Motorola from about 1973 on, changing them with any type from MJ1500X to MJ2119X will probably sound no different at all. Using modern high fT types may or may not be an improvement, and may or may not oscillate.
Possibly changing the drivers, or optimizing the bias circuit may have more impact than changing the output transistors themselves.
Possibly changing the drivers, or optimizing the bias circuit may have more impact than changing the output transistors themselves.
I agree. I have made an amp using old TIP100/105 Darlingtons. These are some of the least desirable devices considered for class AB outputs but I just wanted to experiment and prove that even these ‘crappy’ transistors can be used to make a great sounding amp. The circuit is not a typical LIN or anything similar, yet this amp works and sounds immaculately wonderful. The parameters of the outputs are of little influence in the functionality of the output stage circuit. Any similar part used would make no difference in the ‘sound’ of the amp, it‘s just that the old junk I had cluttering a closet had these within. This is just the way I designed it at the expense of a little complexity, but other amp makers may design the circuit around a specific device. Just dropping in higher Ft devices, just like using a different tube, would change the parameters of the circuit and might be problematic without a redesign of the filters/de-coupling/compensation scheme. Not saying it can’t be done, just pointing out it may not be worth the effort. Tis why I rather prefer to make my own designs. Much more fun.😀😉 The biggest problem with power transistors, particularly BJTs, is that if they are pushed above the limits for even the tiniest amount of time, be it from over-driving, oscillations, or a bias malfunction, the sand crystal melts and the smoke comes out. The old saying goes, the $10 transistor will always blow before the $0.10 fuse.😛
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No, someone with tube amps are well known in device's sound. Tube sound and transistor sound do exist. If it able to replace it with 2N3055 (lower power) it is then ok. Some good sounded for old topology are: 2n3055, TIP3055, 2sc2922, and another least better sounded, 2SC3281, MJ15003. I am never trying many new transistors since I moved to mosfet few years ago.
Look at this thread http://www.diyaudio.com/forums/soli...-70-attempt-diy-overhaul-buy-another-amp.html
especially post 3 by Lineup about his simulation of the Leak Delta 70. "TIP3055 did lower distortion quite a bit compared to 2n3055a"
So a TIP anything transistor is probably modern faster technology, not the old second generation power transistors. I've got a 1975 RCA transistor databook, and the 2n3773 has no Ft spec. By contrast with that quote of the ON semi datasheet. ON semi 2n3773 is probably a different die and process than 1970 RCA transistors.
It is possible the original poster has a 1966-1972 amp with original 2n3773 in it. Particularly since he didn't report a complimentary pair of numbers. If I remember right, dynaco ST120 was delivered at one point with 2n3773. So it is up to the OP to look at what amp he has, or what production date and brand his transistors are. If they are 1970 RCA transistors, an easy fix may be in order. And the fix to accomodate faster transistors for the ST120 is already well documented as the "TIP mod" see Greg Dunn for the document. This included disc caps across b-e of the drivers, and a resistor capacitor network added on the output.
As far as ftpas theory that the driver transistors need to be updated too, I have one channel of my ST120 with NTE49-50 driver transistors and a NTE249 input, and the other side original TO5 RCA 5 digit transistors for input and drivers. With NTE181 output transistors on both sides, the djoffe constant bias circuit mod on both sides, and my Peavey SP2-XT speakers, I can't tell the difference between the channels. Neither is as vile as the 1966 reviews said, and really better sounding than my ST70 tube amp with new electrolytic caps and rectifier and power tubes.
especially post 3 by Lineup about his simulation of the Leak Delta 70. "TIP3055 did lower distortion quite a bit compared to 2n3055a"
So a TIP anything transistor is probably modern faster technology, not the old second generation power transistors. I've got a 1975 RCA transistor databook, and the 2n3773 has no Ft spec. By contrast with that quote of the ON semi datasheet. ON semi 2n3773 is probably a different die and process than 1970 RCA transistors.
It is possible the original poster has a 1966-1972 amp with original 2n3773 in it. Particularly since he didn't report a complimentary pair of numbers. If I remember right, dynaco ST120 was delivered at one point with 2n3773. So it is up to the OP to look at what amp he has, or what production date and brand his transistors are. If they are 1970 RCA transistors, an easy fix may be in order. And the fix to accomodate faster transistors for the ST120 is already well documented as the "TIP mod" see Greg Dunn for the document. This included disc caps across b-e of the drivers, and a resistor capacitor network added on the output.
As far as ftpas theory that the driver transistors need to be updated too, I have one channel of my ST120 with NTE49-50 driver transistors and a NTE249 input, and the other side original TO5 RCA 5 digit transistors for input and drivers. With NTE181 output transistors on both sides, the djoffe constant bias circuit mod on both sides, and my Peavey SP2-XT speakers, I can't tell the difference between the channels. Neither is as vile as the 1966 reviews said, and really better sounding than my ST70 tube amp with new electrolytic caps and rectifier and power tubes.
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Hi,
Well my considered opinion is anyone that thinks changing output
devices in a transistor amplifier can tune its sound is very deluded.
Only changing the wrong devices that are causing problems to
right devices that don't can improve the sonic characteristics,
(or also changing wrong devices to different wrong devices).
Of course a bad design may vary a lot with fitted devices and
may work best with poor devices, that is just bad design.
Its complete nonsense that crappy 2N3055's sound good,
and here used as a replacement will improve the sound.
rgds, sreten.
I've already given up on valve types discussing the sound of
various valves as though the circuit design does not matter.
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It is a single supply amp, so it is a really old desogn. The biggest bang for the buck is to replace all those old electrolytic caps with new ones, as 20 year old caps are sealed with rubber that has turned into historic dirt. Electrolytic caps under 10 uf, buy film dielectric caps, they are a lot smaller than they were in 1970. I'd boost that output cap to 2200 or 3300 uf, to give you some more bass response for $.20 more. Big caps are cheaper now.
As far as how old your transistors are you have to look at them for a maker mark or production date. YYWW was a common production date code, 19YY was 19year. Transistor brand and date may tell us something about the Ft limit of the transistors.
As far as how old your transistors are you have to look at them for a maker mark or production date. YYWW was a common production date code, 19YY was 19year. Transistor brand and date may tell us something about the Ft limit of the transistors.
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