Hi radiogaga,
Now we know something about each other. I am very familiar with that amplifier. Go do your thing with it Everything will turn out fine. The only thing with older amps is they are sensitive to output hFE and gain bandwidth product.
I was also trained on tubes to begin with. We probably share similar history. Also, I have St gear as well, I collect old test gear and HP stuff especially. I am using the new 34465A and 34461A. Beware the resistance functions are done differently and they can lie to you. I had to bring out my 34401A's again. Plus the new product takes a million years to boot. The MSOX3104T does, and I have had issues with most of my Keysight gear. Not the HP way!!! The new E36312A response time on input changes is glacial. Not impressed! Great features if you have all day.
Now we know something about each other. I am very familiar with that amplifier. Go do your thing with it Everything will turn out fine. The only thing with older amps is they are sensitive to output hFE and gain bandwidth product.
I was also trained on tubes to begin with. We probably share similar history. Also, I have St gear as well, I collect old test gear and HP stuff especially. I am using the new 34465A and 34461A. Beware the resistance functions are done differently and they can lie to you. I had to bring out my 34401A's again. Plus the new product takes a million years to boot. The MSOX3104T does, and I have had issues with most of my Keysight gear. Not the HP way!!! The new E36312A response time on input changes is glacial. Not impressed! Great features if you have all day.
Hi llwhtt,
The uA739 is a fantastic op amp. Send them my way please! The rest, sure. Not cutting edge at all. Best as parts.
Hi wrenchone,
Mosfets, eh. Properly driven BJTs seem to perform better but have drawbacks. Higher transconductance really helps. But make no mistake, mosfets have drawbacks too and need to be driven properly.
The uA739 is a fantastic op amp. Send them my way please! The rest, sure. Not cutting edge at all. Best as parts.
Hi wrenchone,
Mosfets, eh. Properly driven BJTs seem to perform better but have drawbacks. Higher transconductance really helps. But make no mistake, mosfets have drawbacks too and need to be driven properly.
I have been thinking the same thing buying some more amps to add to the amp empire and looking at some EV Sentry III I always wanted......to round off the 120db level fusion jazz in the personal audio empire while the world come's unwound....the EV's will take the edge off.....................,such.
life has amazing surprises in store for us.
I have been through a lot of hardship over the past 10 years and the high point was 2020 where I lost my last parent, only my brother and I are left in our whole family, it brings back a lot of things in perspective, I see things very differently now.
Yes I have lost friends and that promotes a prospective of infinite analyzation of ones mortality and just what is real in fact and that friend was real........My grounding has been music my whole life and I'am so luck to understand what a fine power amp and or speaker maybe. Where I live I doubt their is a stereo system in this area....like mine which right now I have a anvil road case of amps in my living room. But those amps and pre-amp's are a vehicle for the music in its own right is a amazement. But I'd say those power amps and pre-amp's when I walk by them even if not on I acknowledge them as I see them as a work of ART, a amazement, a wonderment of audio electrical engineering...... I marvel at them..........How many walking around feeling that way, very few .......I'd say everyone on this site probably has the same special feeling or close.....a very lucky and special group of people to know a audio nirvana to borrow from the Buddhist is apropos to what these amps and pre-amps can mean to a few.....as they translate the wonderment of music.. So you maybe get accustomed to such a things, but never let them be seen as nothing less than a audio electrical engineering feat, a wonderment you hold and appreciate it all as a electrical engineering marvel, a piece of ART here......it is a ART with a human attachment.
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My life has been about helping others. I do this through my work, and improving equipment as realistically possible. Music is the real gift. I worked in recording studios, live sound and stage and a lot in music reproduction (home audio).
The woman I met loves music and i've brought a lot of joy to her life, it helps that everything here at home is about music too. She sings and dances, so she really "gets it". She has made me realise that I need to enjoy life as well. I Find tha twith her, I am greatly.
Yes, there is life after age 60!
The woman I met loves music and i've brought a lot of joy to her life, it helps that everything here at home is about music too. She sings and dances, so she really "gets it". She has made me realise that I need to enjoy life as well. I Find tha twith her, I am greatly.
Yes, there is life after age 60!
I'm still absolutely happy with DC300A, no modifications. All original except small electrolytics and bias-supply transistor (they were prone to fail) which I changed. It is very stable and does not drift at all after over a year of continuous use at different heavy loads and heavy punisment, still working as new. Sound quality is flawless.
I cannot recommend any useless modifications for these as they might became unstable. There is no need to make any mods really if the amp is working as it was designed.
I cannot recommend any useless modifications for these as they might became unstable. There is no need to make any mods really if the amp is working as it was designed.
I agree unless its a replacement part is a new part that is not a out of production... makes the 300A
replacement parts off the shelf update list of such parts is a good list., also the board trim pots could be up dated...
Hi anatech,
indeed I am happy that you like the old hp instruments like I do. These were made for eternity. But tech is changing so fast that these old instruments are often only good for vintage work. Good multimeters are a exception, they work still pretty good after 30 years. Having also Keithley multimeters I am pleased with these ones too. Today I finished rework on my DC300A. Rethinking my first idea to renew all restistors and electrolytics I decided to keep the small wattage composition resistors and only replaced the higher wattage ones with MOX types on the main board only. The output boards are OK and I kept all resistors. I kept the two big rail caps, these are still OK. All other electrolytics were replaced. Power is good and THD is almost in specs. So I will use the amp and had not too much time invested. So this stronger one will replace my Crown D150 actual in my stereo system.
Hi radiogaga,
I would replace any older composition resistors that experience substantial varying voltage across them. These change resistance with applied voltage (= distortion), never mind they are noisy if a DC potential exists across them. They are also very heat sensitive.
I own new Keysight 34465A and 34461A meters, plus an MSOX3104T with all software licenses. I have other Keysight equipment also. However for resistance readings I am forced to use an older HP meter like a 34401A (thank goodness I didn't get rid of these meters!). Most new Keysight product takes a while to boot and be ready for service. One really nice thing is that the voltage references are ovenized in these meters!
You know what? The older HP equipment is every bit as effective on new equipment as the new Keysight stuff is. They simply do not have as many functions built in, that's all. Accuracy is similar and the 3458A is still current. Even though the new 'scopes have a spectrum analysis function built in, a purpose built spectrum analyser cannot be beat. Since I have both I can directly compare them. I also have a lot of RF equipment, AC and DC power supplies and there are things Keysight doesn't make anymore - like the 6186C DC current source (I use these all the time). In my view, an analogue scope is still superior to a DSO or MSO for signal detail and fidelity. I do have a 12 bit mode, but eye patterns are much more clear on say a Philips PM 3070 or 3365A (I have both). I do not like Tektronix oscilloscopes, the traces are too fat and any built in measurement functions are agonizingly slow! My 2465B CT really doesn't do as good a job as the Philips 'scopes. Sorry, but this is true for any Tektronix fans out there, Even my ancient 275 MHz HP scope from the 70's is better!
-Chris
I would replace any older composition resistors that experience substantial varying voltage across them. These change resistance with applied voltage (= distortion), never mind they are noisy if a DC potential exists across them. They are also very heat sensitive.
I own new Keysight 34465A and 34461A meters, plus an MSOX3104T with all software licenses. I have other Keysight equipment also. However for resistance readings I am forced to use an older HP meter like a 34401A (thank goodness I didn't get rid of these meters!). Most new Keysight product takes a while to boot and be ready for service. One really nice thing is that the voltage references are ovenized in these meters!
You know what? The older HP equipment is every bit as effective on new equipment as the new Keysight stuff is. They simply do not have as many functions built in, that's all. Accuracy is similar and the 3458A is still current. Even though the new 'scopes have a spectrum analysis function built in, a purpose built spectrum analyser cannot be beat. Since I have both I can directly compare them. I also have a lot of RF equipment, AC and DC power supplies and there are things Keysight doesn't make anymore - like the 6186C DC current source (I use these all the time). In my view, an analogue scope is still superior to a DSO or MSO for signal detail and fidelity. I do have a 12 bit mode, but eye patterns are much more clear on say a Philips PM 3070 or 3365A (I have both). I do not like Tektronix oscilloscopes, the traces are too fat and any built in measurement functions are agonizingly slow! My 2465B CT really doesn't do as good a job as the Philips 'scopes. Sorry, but this is true for any Tektronix fans out there, Even my ancient 275 MHz HP scope from the 70's is better!
-Chris