Home DIY HiFi Forum

Welcome! Need support, you got it. Or share your ideas and experiences.

RE: What is it?

Hi,

> Is this module a buffer, similar in general concept to the
> First Watt F4?

Somewhat - Yes. But there is an extra trick that works specifically with amplifiers that already put out some power of their own.

> If it is a buffer would it be possible to create an EML 20A
> spud amp (could use an output transformer with suitable 2ndary
> impedance) and add the buffer for some single-stage DHT goodness
> into moderately efficent speakers?

Yes, this could be done. I think the EML20B would a better choice.

> Also, if it can be used as a buffer, what would be preferred
> 2ndary impedance be? 16 Ohm is mentioned; what would be the
> optimum? Up to what impeadance is workable?

Optimum is something that produces 16V at nominal full power (or 32V is using a bridged output for more power).

If we use Child's law that the maximum output power of a triode is 1/4 of anode dissipation we are likely safe.

Using the 20B at what EML calls medium bias we get 18W Anode dissipation and thus around 4.5 Watt power. Call it 4 Watt to be safe.

Ohms law gives us that with 16V at 4Watt we have 0.25A and thus an impedance of 64 Ohm.

So a custom Transformer with around 5 Watt at 25Hz (20W at 50Hz) would be needed, 10K:64R.

This is 12.5:1, so with the gain of the EML 20B at 20, we need around 10V Input Voltage to make this work at full power. One might use a 1:5 Stepup transformer on the input of the EML 20B to get the needed overall gain for full power at 2V input or an extra tube stage or a Tube Preamp with significant gain (14 - 20dB).

It strikes me that this would probably a better job for a 2A3 with a 3K: 64 Ohm output transformer. Use this with a "normal" 2-Stage DC coupled Amp like the old 1940's DC coupled Amplifier from "101 Radio Hookups" Book (6SF5, 2A3 DC) which in turn has been used in a range of famous Amplifiers out there. This kind of Amplifier would need 0.5V for full output so ideal for use with passive preamplifiers etc.

In fact, I have been thinking about building something like that myself (not too serious), with two chassis, one with the 2A3 DHT Amplifer, the other with the Fusion Modules and matching powersupply.

So far the lack of suitable output transformers has limited this, but, for arguments sake, one might use some Autoformers with a 1:2 stepup from a 16 Ohm Tap (2A3 Amp) or 1:4 from an 8Ohm Tap (2A3 Amp) and the fusion module to make a near "universal" DHT Booster Amplifier that could be used to to give most DHT Amp's major Cojones.

TBH, I have so far not really put major work into this as I am unsure if there is significant interest for this "Solid State Booster Amp after SE Amp" concept.

Ciao T
Thor

At 20 bits, you are on the verge of dynamic range covering fly-farts-at-20-feet to intolerable pain. Really, what more could we need?



Edits: 06/28/10 06/28/10

This post is made possible by the generous support of people like you and our sponsors:
  Schiit Audio  


Follow Ups Full Thread
Follow Ups

FAQ

Post a Message!

Forgot Password?
Moniker (Username):
Password (Optional):
  Remember my Moniker & Password  (What's this?)    Eat Me
E-Mail (Optional):
Subject:
Message:   (Posts are subject to Content Rules)
Optional Link URL:
Optional Link Title:
Optional Image URL:
Upload Image:
E-mail Replies:  Automagically notify you when someone responds.