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What would you do differently to this bias supply circuit?
Follow Ups:
that is a series reg. and it will work but they have a sound to them and not everyone likes it. They are also kind of complicated to build.
IMO, the problem with most active regulators is in the error amplifier, and how it affects the Zout of the regulator over frequency.
Before the power transformer burned up, I was using the very simple B+ regulator using a pair of pentode pass tubes (6LW6), a string of three 0D3A regulator tubes, and NO error amplifier. Being a much simpler regulator, the output impedance is much less frequency dependent than a 'conventional' active regulator that includes an error amplifier. This was for a PP 300B amplifier. I'm using an unregulated supply now, for simplicity and reliability. I can't say which supply 'sounds better', because a direct comparison could not be made.
Steve Bench describes the design - see the link below. Look for the heading entitled "A Simple Pentode Regulator with Line and Load Regulation".
Hi Curly,
"Kiss of Death" get reader's attention? :-) Good. Relax, and read on, my simple testimony :
In the 1980s and 1990s, ALL of my DIY triode amps were built with active B+ regulation, both tube and solid state. VERY complex "all-out" circuits. Sometimes DOUBLE regulation, for each stage, two regulators in series with a bleeder resistor in between them. I did shunt and series type regulator schemes.
As time went by, I came to find out that the real regulation started with the choice of my power transformer, and the choice of my inductors.
I found, through careful listening, that no matter what regulators I used, the SOUND of the iron that came before the regulators, and the iron's quality level, would be HEARD through the complex "theoretically perfect" regulation that followed it.
I now am of the opinion, after doing a lifetime of building, that the best possible audio performance in a triode amp, comes from a low DCR totally unregulated supply, and so now, I will not use regulation but rather, concentrate on the magnetics.
**** Properly designed parts, and a minimalist approach, rules the audio performance race. ****
It is easy to make a complex amp, and depend on the electronics to "bail you out". However, for every extra part you add in an amp, there is a sonic cost to pay, (you hear the parts), and the added circuits have their own anomalies. So, "reduce it to the minimum - for the maximum purity and performance".
Want the best possible amp? Start it off with the power supply iron, which needs to be 20 Ohms or less in DCR, and in some designs, I can get 10 Ohms or less DCR. The music won't pull it down.
These products are difficult to source, on a non-custom basis, and very few people have them, so not too many people realize what they do for an audio amp.
Users love the results.
Surely I am not alone in the "low DCR , no active regulation camp".
Advocates, (and detractors with ACTUAL low DCR experience - specifically, under 20 Ohms qualifies you), who have not interacted with me on any business basis, please feel free to post.
I have started the ball rolling - for the powerful low DCR supply fans.
Jeff Medwin
I was doing some research and ran across a design brief by Steve Bench on shunt regulation. What are your thoughts on the information.
Curly, I personally would not use tubes at all for a regulator because they take up unnecessary space, waste power, deteriorate with age and are imprecise. Tube regulators come from an era before the availability of high voltage SS devices. Save yourself some grief and use an SS regulator. You may like to see the Broskie blog at the link below for ideas.Since you're talking about voltage regulation for the input and driver stages (from what I can gather elsewhere in this confusing thread), the current demand will be quite steady and so a shunt regulator should work well. Shunt is normally preferable to a series regulator if the current drawn is not highly variable, because the signal path doesn't go through the regulator's active device, it goes through the final cap following the regulator. That helps keep noise to a minmum (although series regs can also be made to do a proper job with good design and choice of devices).
Edits: 08/25/09
Ray,Again my apologies for posting the wrong section of the schematic.
People that love solid state amplifiers would use your same arguments to make their point on why we should not use tubes as amplification (wasted power, deteriorate with age, heat, wasted space, etc).
I want to build a pair of mono tube amplifiers, with very little to no SS, but using tube regulation, except for the output stage. Its just one of my bucket list things to do in this lifetime. Good or bad, I want to see what can be accomplished, given the limitations of the antiquated and wasteful tube in my applications.
Edits: 08/25/09
Curly, You know, in my experience highly regulated gain stages sometimes lack a bit of dynamics. The first thing I try on pre-amps and DAC's using gas regulators is pull the tubes as see what the unit sounds like. They USUALLY have better transients and headroom.
I agree, a good power supply starting with power tranny and a well-made filter circuit seems to be better than a poorly or under-designed designed PS with regulation stacked on top of it. Analogy is better to have simple direct flow of water downstream to drive the waterwheel, than a circuitous, complicated route. A well built simple PS doesn't need complicated regulation, as long as it is built to fit the needs of the unit. Just my opinion.
I am not disputing your thoughts at all Fender. This has been my own belief for many years. This is my attempt to see which I really prefer.I also want to give the circuit every chance to change my mind, as I have never heard a tube amplifier that was thoroughly "tube regulated", except of course the output stages. The shunt supplies seem to be the way to go, so now I need to find out more about them.
I am just trying to have some fun and hopefully create a nice sounding amplifier with some luck. If not I start over with a new direction.
Edits: 08/25/09
Curly,
Sorry if I seemed to come on a bit too strong. Just my experience with these highly regulated units of the 1980-90's. Don't get me wrong, there are some very good sounding units which are highly regulated.
It very good idea to try all the varieties and form your own opinion. Good luck with your project!
Steve
Why doesnt he just try a quasi regulator like the grommes 260? It doesnt have a reference so its not a true reg but,he could make a couple changes and they are also using an OB2 for the neg bias...
I like that circuit he posted tho.
If the power supply waveform isn't pretty,neither is the sound in most cases.
Mike, I don't know what to say. But, I've yet to hear a circuit that has either regulator tube which sounds better with the gas tube than without. It's just one of my peccadilloes.
Steve
If you can cancel the noise,the gas regulators can be fantastic.My altec 1530s and a friend's webster amps have the gas regs but I don't like the sound of gas reg when the clip beyond their limitations..I may just implement a shunt reg for the 300v screen bias on the 1530s..I am using the TT-21 genelexs which are a top cap kt88 but they take 300v on the SG with 600v on the plate and I just put in OD3s as opposed to the OC3s
If the power supply waveform isn't pretty,neither is the sound in most cases.
Mike,
I thought that gas reg tubes were supposed to be very quiet by nature. Are you saying that the gas reg tubes are the source of the noise that you mentioned?
Curly
When they overload or clip they sometimes make noise or when you go beyond their rating..
If the power supply waveform isn't pretty,neither is the sound in most cases.
Roger that. Thank you Michael.
I did not think that at all. I like people to be passionate, as I know then that they care about what they do :-)
Sorry it was late. Yes this is a regulated supply for the input and driver stages. I used the wrong schematic by mistake, but I am regulating the negative bias supplies also in the same way as this circuit. I have read some of Broskie's stuff on his Janus shunt regulators, but have not seen much other than using tubes like the OD3, etc for shunt regulation otherwise. Could someone point me to a good resource that talks about shunt regulators in detail?
I was looking thru the archives and saw that Frank had created a shunt regulated supply for his Ultimate Preamp PS. Looks interesting. I am a little worried that I will run out of available real estate on the top plate, if the regulation circuit gets too involved.
Edits: 08/25/09 08/25/09 08/25/09
B+ supply for an amplifier? I see the 440v for a plate supply but you easily implement a negative bias supply just using an OB2..Is this just a general power supply or does it have a specific use?
If the power supply waveform isn't pretty,neither is the sound in most cases.
Pardon my ignorance, but this is a regulated B+ power supply, not a bias supply? Bias supply usually have C- VDC voltage output. ALIME.
Thanks!
Maybe I need new prescription glasses, I do not see a (negative) bias supply in the schematics
Hi casouza,
Does it look more like a tube regulated B+ supply to you, 440 VDC B+ out?
Jeff Medwin
Yes, this is certainly a series-regulated B+ or driver power supply.
The series tube's sound carachteristic will dominate the overall sound quality.
I would use a shunt regulator.
Could you give me some ideas on how to implement it? I have no real experience with shunts.
Describe your proposed amplifiers so i can size the SS shunt regulators. After my lifetime of building, shunt regulated for home entertaiment amps is great. But, rarely used. Also wastes some energy in form of heat. I do not do 'green' for my amps though.
Thanks for the offer Neff, but I want an all tube shunt. I have found some good resources that will hopefully allow me to size it for my circuit.
Ok, but tube shunts are a little out of place over the current that a gas regulator tube can supply. I use a low DCR choke right after the SS shunt.
Going to see what can be done with a sweep tube in this circuit. Looking at what Steve Bench did and some other stuff. I may take you up on the offer if i can not get satisfactory results with my idea.
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