Dear Kofi
The world community would be very glad if you would buy a kit to make a nice 6BM8 amp. Rik Stoet (Heart) has a nice one: see link above.
It seems that you want to accomplish things you are not yet experienced enough for. You know where that can lead to.
The world community would be very glad if you would buy a kit to make a nice 6BM8 amp. Rik Stoet (Heart) has a nice one: see link above.
It seems that you want to accomplish things you are not yet experienced enough for. You know where that can lead to.
Ah... I see! OK, so this is in pentode mode. That's fine-- never worked with pentodes before. Also, I think getting an OPT with a UL tap is a good idea. I'll certainly do that.
That's what I'm thinking! Any suggestions on a current rating for a single-supply PSU? Also, I'd gladly hear arguments on tube vs. solid state rectified.
Man. I should learn to go with my gut.
Will do. So, I saw what KWW wrote, but I'm not sure about this. So, I would be able to use the ECC83 as a phase splitter and the EL 84 as output, right? Kuei said something about using the ECC83 first as a voltage amplifier then as a phase splitter, but that would imply that I would need an additional stage in the design, I think.
Obviously, I'm wrong about this, but I'd like to make sure I know how I can use the ECC83 and EL84 in lieu of the tubes in the schematic.
Also, I'm figuring I will need to make some alterations to the schematic to accommodate the ECC 83 / EL84 combo, but I don't know what I'd need to do. Help here would be appreciated.
Got it. So this is the additional HT supply needed for a pentode. Do you mean that I will need an actual regulated supply for this or can I get away with a lot of RCRCRCRCRCRCRCRCRC?
Oh yeah-- and anyone know what the output power of this device would be?
I know that I am not experienced yet, but I use these projects to learn, and learning I am, so I don't think I am interested in the kit right now. Besides, I will need to source these parts over several months since the Annans ain't exactly made of money.
Kofi
Kofi Annan said:
The ECC83 used in this schematic performs both functions at the same time. Just like the triode sections in the dual tube.
As far as the schematic goes, the only changes you'd make would be to add a heater connection to the ECC83. Everything else stays the same, because the triode sections are represented by the same symbols. In the actual circuit, you'd just add a socket and the wires go to that one instead of the triode part of the output tube. Some component values might change a bit, but the guys who know both tubes will help you there.
A separate supply portion for the screen is considered by many to be better in pentode connection, so the engineer in SY probably wanted to see it there. Looking more closely it appears to me like the screen is just taken from the B+ via a resistor in that circuit. So that means it's pentode connected, with no separate screen supply. It ain't the highest res document though. That K, or whatever it is, might be just a test point.
Sheldon
If you regulate the screen supply, you'll have better low frequency stability and better PSR. Lower distortion. This stuff is audible.
Tube vs Solid-State Rectifier
I prefer tube as they are very quiet in operation vs switching noise SS can produce. UF series SS diodes are better in this regard.
A 'sleeper' rectifier are the TV damper tubes such as 6DE4. These are half-wave & require a pair for full-wave CT design. NOS is about $2 to $3 each. The cathode is isolated from the filament, thus can share filament supply with other tubes. However, these do draw a fair amount of current. Another benefit is the 6DE4 provides quite slow warm-up that allows other tubes to warm up before B+ is applied.
For lower current applications, I like the Mullard EZ80/6V4 or EZ81/6CA4.
I prefer tube as they are very quiet in operation vs switching noise SS can produce. UF series SS diodes are better in this regard.
A 'sleeper' rectifier are the TV damper tubes such as 6DE4. These are half-wave & require a pair for full-wave CT design. NOS is about $2 to $3 each. The cathode is isolated from the filament, thus can share filament supply with other tubes. However, these do draw a fair amount of current. Another benefit is the 6DE4 provides quite slow warm-up that allows other tubes to warm up before B+ is applied.
For lower current applications, I like the Mullard EZ80/6V4 or EZ81/6CA4.
Re: Tube vs Solid-State Rectifier
This is something I see asserted quite often. When measuring the actual power supply rails (as opposed to measurements internal to the PS), I have been unable to find the slightest difference in switching noise between tube and SS. In some measurements, the SS was even a bit better.
If anyone has contrary data, I'd love to see it.
amperex said:
This is something I see asserted quite often. When measuring the actual power supply rails (as opposed to measurements internal to the PS), I have been unable to find the slightest difference in switching noise between tube and SS. In some measurements, the SS was even a bit better.
If anyone has contrary data, I'd love to see it.
Not sure why tubes sound better, assume some noise effects the sonics down stream. Tubes have a more gentle peak to average current when charging a capacitor, however that should not be an issue when using a choke input design. And, the statement does not include the transformer secondary resistance. Perhaps a separate filament & HV transformer would make a difference?
With a few DIY high quality amps & some high quality preamps, I have tried 1N4007 SS rectifiers vs tube rectifiers during the design phase. The solid state does not sound as good as a great tube rectifier. I understand this is not true in some designs like the 'monkey'.
Even more unexplained is why different manufacture tube rectifiers effects the amplifier sonics. Having many rectifiers on hand, I can tell you when a great rectifier is installed, the amp performs best and the change is not minor. In fact, a poor rectifier can undo the other careful tweaking in an amplifier.
From an engineering standpoint the performance difference should not be nor makes any sense to me. And, I can not tell anyone exactly why it is so. With regard to audio, much more is taking place than explained in engineering books.
One of my favorite questions is why one amplifier tube outperforms other tubes and not necessary so in every circuit.
Is it the meterials inside, degree of vacuum, inter-element alignment and physical demensions? Obviously, all of the above. What is best is beyond me.
I would venture if one can not hear the differences mentioned above, for the most part the audio system must not be of high resolution, crystal clear & neutral.
With a few DIY high quality amps & some high quality preamps, I have tried 1N4007 SS rectifiers vs tube rectifiers during the design phase. The solid state does not sound as good as a great tube rectifier. I understand this is not true in some designs like the 'monkey'.
Even more unexplained is why different manufacture tube rectifiers effects the amplifier sonics. Having many rectifiers on hand, I can tell you when a great rectifier is installed, the amp performs best and the change is not minor. In fact, a poor rectifier can undo the other careful tweaking in an amplifier.
From an engineering standpoint the performance difference should not be nor makes any sense to me. And, I can not tell anyone exactly why it is so. With regard to audio, much more is taking place than explained in engineering books.
One of my favorite questions is why one amplifier tube outperforms other tubes and not necessary so in every circuit.
Is it the meterials inside, degree of vacuum, inter-element alignment and physical demensions? Obviously, all of the above. What is best is beyond me.
I would venture if one can not hear the differences mentioned above, for the most part the audio system must not be of high resolution, crystal clear & neutral.
Kofi, have you decided yet which PP amp to make? There seems to be a Marantz 8B amp circuit in another thread.
Sy, will that circuit get your vote for a well engineered amp worth building?
Sy, will that circuit get your vote for a well engineered amp worth building?
Guys,
I like to complicate the international state affairs a little bit more even at the risk that the current state of peace between diverse factions of tube-topologies becomes unstable. I am throwing in a simple transformer coupled design
the CIA has put here as a lure for Kofi:
http://www.audioasylum.com/forums/tubediy/messages/86291.html
Kofi cannot go wrong on this and I would say nobody can.
I like to complicate the international state affairs a little bit more even at the risk that the current state of peace between diverse factions of tube-topologies becomes unstable. I am throwing in a simple transformer coupled design
the CIA has put here as a lure for Kofi:http://www.audioasylum.com/forums/tubediy/messages/86291.html
Kofi cannot go wrong on this and I would say nobody can.
Attachments
The original 8B circuit was a very good one. It's dated and could be improved these days, but no complaints here about the engineering!
Well, I've been working on trying to understand the Sansui 500 ciucuit that KWW posted. I'd kind of like to build that one since I've already started looking at the cost and setting up the schematic in Super Spice.
However, if someone can make a compelling argument for the Marantz 8b, I'd be glad to hear it. I found this article, which is pretty detailed. Could this be an improved version that would please SY?
Looks good. Has anyolne had any experience with this amp? How's the sound?
I'll be working with the Sansui in Super Spice (love saying that) to see if I can get it to work with ECC83 / EL84. Just wanted to mess with this program and see if I can make it work in the virtual world before I screw up in the real one. I'm having a hard time manually adding the EL84 model to the program, but once I work that out it should be cake.
Kofi
It will work OK, but it's not optimal. Using a 12AU7 in the first slot is a major compromise- it is not a very linear tube. The long tailed pair has a not terribly long tail, and the designer does the 1950s work-around by unbalancing the plate resistors. Let's not even talk about how expensive those toroidal output transformers are...
There's a question I should have asked earlier, but in my haste to cash the Oil For Food checks, I forgot. What's your goal? Is it to make a decent sounding p-p amp and then stop? Or is it to learn how the thing really works? If it's the latter, I would still recommend the Bevois Valley simply because MJ dissects every detail of the design. If the former, then you've got a much wider range of options, including the Sansui.
There's a question I should have asked earlier, but in my haste to cash the Oil For Food checks, I forgot. What's your goal? Is it to make a decent sounding p-p amp and then stop? Or is it to learn how the thing really works? If it's the latter, I would still recommend the Bevois Valley simply because MJ dissects every detail of the design. If the former, then you've got a much wider range of options, including the Sansui.
SY said:
Well, I'm kinda hoping my goal is to do a little of both. I really do want to learn how the thing works and I think I've got a good idea based on what Morgan Jones has put forth on the Bevois Valley. If you think that this will better contribute to learning, then that's what I'll do. On the other hand, if the Sansui is far and away the better sounding of the two, then I may be compelled to try it.
Any tie in this scenario will likely go to the Bevois Valley. Its well-documented and I could probably get some recommendations on how to improve the sound as I believe that more than a few people have built it.
I'm not sure which one will work our for the cheaper, but I'm willing to believe that it will be about the same in cost for either design. So really, what it boils down to is I want a design where I can learn something that also has some wow associated with it.
Too tall an order?
Kofi
If that's the case, then I think I'll give the Bevois Valley a try. I'll start re-reviewing the design this week. Any advice on this one before I order any parts would be much appreciated. Any parts in particular I should get well-matched (I'd imagine the tubes and the resistors related to the splitting would need to be closely matched)?
Kofi
FWIW, I've built a similar circuit, but using a novel bias scheme and a 12AT7 instead of the ECC88. I'm very happy with it.
I'd recommend following the MJ design though. I had excellent results with JJ EL84s; I got a matched quad from Triode Electronics. I believe that they can ship to New York. You want to match the resistors in the phase splitter AND the resistors on the EL84 grids. Output iron is the first deteminant in amplifier quality- don't skimp here. I used some UTC LS iron, but there are certainly easier-to-get alternatives.
Other than that, it's a simple, classic, non-tweaky design.
I'd recommend following the MJ design though. I had excellent results with JJ EL84s; I got a matched quad from Triode Electronics. I believe that they can ship to New York. You want to match the resistors in the phase splitter AND the resistors on the EL84 grids. Output iron is the first deteminant in amplifier quality- don't skimp here. I used some UTC LS iron, but there are certainly easier-to-get alternatives.
Other than that, it's a simple, classic, non-tweaky design.
Well, since Morgan Jones advocates thinking about tube amps from the output in, what would you recommend for decent output iron that won't break the bank? Will a Hammond do or would you recommend something better for more cash?
Kofi
Kofi
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