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jmillerdoc 10th January 2010 06:42 AM

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

Jaap 10th January 2010 10:39 AM

1 Attachment(s)
So you changed your mind :D

Triode Dick's Page

pauldune 10th January 2010 10:47 AM

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

pauldune 10th January 2010 10:52 AM

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".

rcdaniel 10th January 2010 11:12 AM

Quote:

Originally Posted by jmillerdoc (Post 2041811)
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

Jaap 10th January 2010 11:28 AM

Quote:

Originally Posted by pauldune (Post 2041920)
Ha ha Jaap,

I think he wants to use the d3a as an amplifier, not a CCS/Mu stage tube.

I don't think that the D3a is doing anything else than amplifying here :D:D

edit: sorry mistake, I thought he was using a triode strapped D3a as amplifier and an other pentode on top (is an option of course)

Jaap 10th January 2010 11:34 AM

Quote:

Originally Posted by rcdaniel (Post 2041936)
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.

rcdaniel 10th January 2010 12:00 PM

Quote:

Originally Posted by Jaap (Post 2041953)
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

Jaap 10th January 2010 12:34 PM

Quote:

Originally Posted by rcdaniel (Post 2041967)

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) :o

Shoog 10th January 2010 12:50 PM

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


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