• WARNING: Tube/Valve amplifiers use potentially LETHAL HIGH VOLTAGES.
    Building, troubleshooting and testing of these amplifiers should only be
    performed by someone who is thoroughly familiar with
    the safety precautions around high voltages.

Looking for non-DRD 300B using D3a as driver

Hello,
I was wondering if anybody knew of a great 300B design that uses the D3a as the driver. I have searched this forum and eleswhere but I continue to only come up with a DRD topology.

I recently sourced all the parts to build the JEL 300B and bought an extra set of OPTs from James (6123HS). I was toying with the idea of using this D3a in a 2A3 project I am completing but went a different direction with that one. In the process I picked up 4 of the Siemens D3a drivers and now I am thinking I might try them in a 2 stage D3a/300B amp since I have the parts (some of them at least).

Any suggestions for some designs? I wanted to stay away from the DRD designs b/c my power transformer selection I have won't get me the voltages I see with most of these designs.

Thanks,
Jeff
 

Attachments

  • 300B_6H30_ceasar2_schema_versterker.GIF
    300B_6H30_ceasar2_schema_versterker.GIF
    19.5 KB · Views: 1,498
If you have a centre tapped V+, you can use a full wave rectifier bridge on the outer connections, and leave the centre tap open. 250v-0v-250v becomes 500v; DC voltage will be about 500v x 1.41= 705v: should be enough for the DRD amplifiers.
You probably will have to use solid state diodes.

Or you can just use the schedule talked about for your 2a3 amp. 1e stage a ccs loaded d3a, coupling C, last stage a standard 300b stage.

greetings, Paul
 
Ha ha Jaap,

I think he wants to use the d3a as an amplifier, not a CCS/Mu stage tube.
On the other hand, it is a good schedule, and a good use of the d3a.

On triode dicks page are a number of 300b schedules with d3a and ecc99 or 6n30p.

Triode Dick's Page It is in dutch, but the schematics and pictures are easy to understand. Just click on "projects".
 
Hello,
I was wondering if anybody knew of a great 300B design that uses the D3a as the driver. I have searched this forum and eleswhere but I continue to only come up with a DRD topology.

I think it prudent to ask this question. I don't have time to go into depth now - after my rant in the JEL 300B thread - but Damir's 300B SE Project on the AudioRoundTable Group Build forum may be worth checking out. The project is spread over several sections; I have linked to the pentodes as triodes part. You should be able to find all the sections on that forum - worth a read. Note the CCS on the driver plate - you should be able to simply use your K&K boards here.

Personally, I am thinking of this design - with a few changes - as a basis for my first build.

AudioRoundTable.com: Group Build => 300B SE Project, Part 9 - E180F, E280F, D3a pentodes - triode connected

Cheers
Raymond
 
I think it prudent to ask this question. I don't have time to go into depth now - after my rant in the JEL 300B thread - but Damir's 300B SE Project on the AudioRoundTable Group Build forum may be worth checking out. The project is spread over several sections; I have linked to the pentodes as triodes part. You should be able to find all the sections on that forum - worth a read. Note the CCS on the driver plate - you should be able to simply use your K&K boards here.

Personally, I am thinking of this design - with a few changes - as a basis for my first build.

AudioRoundTable.com: Group Build => 300B SE Project, Part 9 - E180F, E280F, D3a pentodes - triode connected

Cheers
Raymond

When using a CCS on top of the D3a / E810F / E180F / 6H30 / 6N6 / 5842 / or whatever high mu tube/ try to use one or more leds under the cathode. In this way you can get rid of the cathode cap, which is a good thing (to get rid of). Experiment with a small MKP parallel on the led(s) to see if this gives even better sound.
 
When using a CCS on top of the D3a / E810F / E180F / 6H30 / 6N6 / 5842 / or whatever high mu tube/ try to use one or more leds under the cathode. In this way you can get rid of the cathode cap, which is a good thing (to get rid of). Experiment with a small MKP parallel on the led(s) to see if this gives even better sound.

Interesting and helpful suggestion; I will certainly experiment with it. Ultimately, I think my choice will be decided by my sonic preferences, with a few practical requirements for good measure. I have read some threads in which experienced DIYers have tried a range of loading and biasing methods. One DIYer, with much help, used a CCS load with LED bias and initially loved the 'improvement' in many of the usual audio(phile) criteria, yet after some weeks returned to resistor and cap for bias and stayed with it. He felt his amp was simply more musical (this means different things to different people) and enjoyable. Often I have read of old school biasing methods outperforming - in listening tests - more 'modern' approaches.

The moral of my story: if sonic preferences (subjective) are the main basis for one's decision-making, then there is no Only Way. Experimentation, guided by (but not limited to) sound technical info, a little creativity, gut feel, and ones own perception is likely to reward...

Cheers
Raymond
 
The moral of my story: if sonic preferences (subjective) are the main basis for one's decision-making, then there is no Only Way. Experimentation, guided by (but not limited to) sound technical info, a little creativity, gut feel, and ones own perception is likely to reward...

Cheers
Raymond

This adventure is the sole reason we are (I am) in this "business" (and spending too much of the family budget on it) :eek:
 
The biasing I have seen report of wining out against all comers in side by side preamp tests - is a cathode resistor with supplementary CCS current feed to multiply its voltage drop to an appropriate bias point. I suppose in this case the resistor represents a minimum impedance coupled with intrinsic linearity. Rather like a superior LED bias.

Shoog
 
So you changed your mind :D
Hi Jaap, no, not really. I think my last post stated I was going to stick with the original 5687 driver with the CCS on the plate (for that 2A3) and possibly play around with the idea of the D3a later.

I bought 4 James 6123HS and 2 6112HS, I used the 6112's for the 2A3 Hagtech Clarion. I also have the JEL300Bdx started too. I bought a quad of these D3a so I have plenty to play with.

So, I am sticking with my original plans, I think.......although I really don't know what they were when I first started!

It will be a couple of months before I even get around to the amp I am inquiring about here....if I ever do.

I just have read in several places about this D3a being such a great driver for the 300B, etc....but there doesn't appear to be much in terms of designs and schematics out there that I have found aside from the DRD topologies.

I will look at the links others have posted here for sure.
Jeff
 
Ok, this is what I have come up with...

First, Pauldune....I had some errors in the PM I sent you, I think I worked them out here.

This is what I have come up with so far. I dont have a circuit drawing program (yet) so I will write it out.....please tell me what you think.

First the output stage I will leave basically untouched from the JEL300B.

I will be using the 3.5K tap on the primary of the James 6123HS and supply it with a B+ of 435, give or take a few volts.

The 300B cathode resistor will be 880 to 900 and bypassed with a 100uF 160V Elna Cerafine or BG. The grid leak for the 300B will be 220K with a 1K grid stopper.

This is exactly the same as JEL's 300B so far.

For my driver stage I have come up with the following, please let me know what you think and suggestions are very welcome....

I want to use a shunt-mod for volume control with a 50K pot and a 47K pass through resistor for thesunt mod. As I understand the volume control resistances with be my "grid leak" resistor.

The D3a will be wired triode and supplied with a 160V B+ via a resistor off the main B+, I will add an additional RC filter stage here with about 50uF....all to bring my driver B+ to 160v.

The plate load will be my K&K CCS set at 20mA with a cathode resistor of 75-82R bypassed with a 470uF Cerafine or BG.

This stage will then be coupled with a 0.33 PIO Russian K40 type cap.

Thats it......did I leave anything out?

RCDaniel, that is the extent of my experimentation....whether or not it is guilded by sound scientific principals....I will let everyone else be the judge.

Thanks again,
Jeff
 
Hi,

I was wondering if anybody knew of a great 300B design that uses the D3a as the driver.

I build one for a friend that can use E810F & D3a interchangeably.

Operating point is my usual standard. The Schematic pretty much matches my 437A/300B Amp documented here:

300B-SE-Amp von Thorsten Loesch

Only difference is in the cathode of the Driver, I adjusted the cathode resistor to give me 180V/10mA with the E810F, this is not supercritical.

You can replace the anode load choke with a CCS, in that case the 22K resistor supplying the +B to the Anode Load choke becomes 2.2K.

The various original chokes are no longer available to the DIY market, but you can use alternatives.

Another easy to build this whole amplifier is what I call "simple SE" and documented as "bonus schematic" in the Manual for the Film Capacitor Universal Power Supply for diyhifisupply.com.

While using a 6SL7 there (paralleled sections) for reasons of availability, with the CCS set to 10mA and the cathode resistor adjusted you can just drop the D3a in:

Putting It All Together -- Simple 300B Maxed Out With Modules AND No Electrolytics! | Diy HiFi Supply

That Certain Something | Diy HiFi Supply

Of course, this schematic presumes that you use all the fairly expensive (but very convenient and high performance) modules from diyhifisupply.com, which of course I would not advocate though I use them myself quite extensively of course.

Ciao T
 
That Certain Something

A little off topic:

"That Certain Something" is similar to what I would like to do for my first build, though will probably use a different choke-loaded driver, cathode bias on the output, and snub the power transformer B+ secondary (per John Swenson suggestions?).

Driver is not settled: ether E180F or a low mu pre (double as headphone amp) with a med mu driver for the power amp.

Apologies for the diversion - back to the topic at hand.

Cheers
Raymond
 
I'm at work now, so I cant do much now, but i'm going to draw you a schematic this evening. I think its going to be much simpler than you expected. You cant drop the voltage to make the b+ 160v, because then the ccs has no working voltage anymore. With a appropriate heatsink the ccs does everything for you. Just choose the right current, and make shure that your ccs can handle the voltage it has to drop. (about 300v but it should be able to handle 400v(i dont know the k+k modules)) power dissipation in the CCS is then about 20ma x 300v= 6 Watt.

The CCS regulates the dropping voltage to keep the current constant at 20ma. so if the plate swings up, the dropping voltage swings down, just so that the current stays 20 ma. The cathode resistors you have chosen give you a V plate of approx. 180v. I would use the 75 ohms.
 
Hi,

"That Certain Something" is similar to what I would like to do for my first build, though will probably use a different choke-loaded driver, cathode bias on the output, and snub the power transformer B+ secondary (per John Swenson suggestions?).

Then it will be quite far off the "Je Ne Sais Quoi" then.

I suggest you keep the fixed bias on the output. With a sufficiently quiet PSU and high quality caps from +B to Common this sounds unusually good (I have done it both ways often enough by now).

I'd even go fixed bias on driver stage, if it was me...

Ciao T
 
Hi Shoog

I would sure like to read that report - is it possible to link to it?

Cheers
Raymond

It was a shoot out at the Netherlands triode meet I think - a number of years ago. The result was big news with those who follow things like that. Unfortunately it been a number of years ago I haven't got a link to it.
If you are interested it would be a relatively easy mod to try. The CCS can be a simple resistor from the B+ rail, and the rest is just choosing the cathode resistor.
Its not an idea that has been appropriatre for my projects which need high resistance in the cathodes to work best, so I cannot comment personally.

Cheers

Shoog
 
Pauldean,
Thanks....yes I forgot about the need for the voltage swing and the fact the CCS does all the work. I look forward to the schematic.

To everyone else, I have read about the importance of considering the power supply as an integral part of the signal path. I realize there are many ways to "skin the proverbial caat" when it comes to power supplies. I want to do some reading on the in's and out's of proper power supply design beyond the basics (I know how to use PSUD etc....) and was wondering if there are any good threads on power supplies one might suggest reading.

The 2A3 build is coming along well....I just finished the chassis (always the most time consuming part of the build for me).
Jeff