first go at design - pp

adamus · 20th October 2009, 07:57 PM

Hi,

I have built other peoples designs, but want a go myself. I have a basic understanding of the theory, but a lot of it is pieced together.

Basically, will the following design work?

The css would be borrowed from morgan jones, the output valves could be css biased ala baby huey.

no feedback shown, but i could work it in.

I am new at this, so constructive criticism is very very welcome. my valve choices are what i have in my box.

aardvarkash10 · 20th October 2009, 08:11 PM

Go to SY's website and read through his desription of the Heretical pre-amp. Sure, its not at all what you are aiming to build, but it is a grerat insight into a detailed design process. I was just blown away by the new to me yet oh-so-obvious considerations that are set out there. It has completely changed how I think about designing ANYTHING...

adamus · 20th October 2009, 08:15 PM

will do mate, cheers.

adamus · 21st October 2009, 12:42 PM

any glaring errors?

Any tips for bias points of the input and splitter?

SY · 21st October 2009, 12:55 PM

It would help if you could number the components so that the design could be discussed. Some stuff on there looks not-quite-right, but I don't have you here to point at the screen.

kavermei · 21st October 2009, 02:14 PM

I don't understand the use of CCS in the cathode of the power valves...?

adamus · 21st October 2009, 02:56 PM

sy. thanks forthe advice. I will number the components tonight.

the css is just a better auto bias.

adamus · 21st October 2009, 06:24 PM

Here is the number schematic

SY · 21st October 2009, 06:32 PM

Brilliant! Let's start with R11. What's it doing in there? You've got a CCS keeping the two sides of the phase splitter balanced- why not return the grid of the bottom side to the upper grid through a large resistor, then bypass that lower grid to ground? This will give you balance limited only by how well you can match R5 and R6. That also allows you to eliminate C2.

Do you have any philosophical objections to getting rid of R2/C1 and replacing with a diode or LED?

Will the rather high source impedance of the output stage without feedback be a problem with your speakers?

I will not be popular for saying this, but an output stage CCS is not generally a good idea, especially if you're going to clip the amp every once in a while (as we all do, at least all of us who don't have 102dB/1W speakers).

adamus · 21st October 2009, 06:48 PM

Sy, how is this looking. Re led bias for the first stage, i like it and will have a play when buiilding.

As for the CSS in the output, I have some bias perfboards that i can take from my baby huey and try. I did try the huey without, and it lost something.

clipping.... not in my flat with my neighbours unfortunately!

Feedback, i will apply some and i have shown how, but just to the first stage. I'll have to keep an eye on oscillations.

20th October 2009, 07:57 PM	#1
adamus diyAudio Member Join Date: Apr 2008	first go at design - pp Hi, I have built other peoples designs, but want a go myself. I have a basic understanding of the theory, but a lot of it is pieced together. Basically, will the following design work? The css would be borrowed from morgan jones, the output valves could be css biased ala baby huey. no feedback shown, but i could work it in. I am new at this, so constructive criticism is very very welcome. my valve choices are what i have in my box.

20th October 2009, 08:11 PM	#2
aardvarkash10 diyAudio Member Join Date: Mar 2007 Location: Auckland, NZ	Go to SY's website and read through his desription of the Heretical pre-amp. Sure, its not at all what you are aiming to build, but it is a grerat insight into a detailed design process. I was just blown away by the new to me yet oh-so-obvious considerations that are set out there. It has completely changed how I think about designing ANYTHING... __________________ Yes, conservatism thrives on low intelligence and poor information. But the liberals in politics... continue to back off, yielding to the supremacy of the stupid. It's turkeys all the way down. - George Monbiot, guardian.co.uk, 6 Feb 2012

21st October 2009, 12:55 PM	#5
SY diyAudio Moderator Join Date: Oct 2002 Location: Austin, TX Blog Entries: 1	It would help if you could number the components so that the design could be discussed. Some stuff on there looks not-quite-right, but I don't have you here to point at the screen. __________________ “Listening to records is like ****ing a picture of Brigitte Bardot.” - Sergiu Celibidache

21st October 2009, 06:32 PM	#9
SY diyAudio Moderator Join Date: Oct 2002 Location: Austin, TX Blog Entries: 1	Brilliant! Let's start with R11. What's it doing in there? You've got a CCS keeping the two sides of the phase splitter balanced- why not return the grid of the bottom side to the upper grid through a large resistor, then bypass that lower grid to ground? This will give you balance limited only by how well you can match R5 and R6. That also allows you to eliminate C2. Do you have any philosophical objections to getting rid of R2/C1 and replacing with a diode or LED? Will the rather high source impedance of the output stage without feedback be a problem with your speakers? I will not be popular for saying this, but an output stage CCS is not generally a good idea, especially if you're going to clip the amp every once in a while (as we all do, at least all of us who don't have 102dB/1W speakers). __________________ “Listening to records is like ****ing a picture of Brigitte Bardot.” - Sergiu Celibidache

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20th October 2009, 08:15 PM	#3
adamus diyAudio Member Join Date: Apr 2008	will do mate, cheers.

21st October 2009, 12:42 PM	#4
adamus diyAudio Member Join Date: Apr 2008	any glaring errors? Any tips for bias points of the input and splitter?

21st October 2009, 02:14 PM	#6
kavermei diyAudio Member Join Date: Jan 2005 Location: Lokeren, Belgium	I don't understand the use of CCS in the cathode of the power valves...?

21st October 2009, 02:56 PM	#7
adamus diyAudio Member Join Date: Apr 2008	sy. thanks forthe advice. I will number the components tonight. the css is just a better auto bias.

21st October 2009, 06:24 PM	#8
adamus diyAudio Member Join Date: Apr 2008	Here is the number schematic

21st October 2009, 06:48 PM	#10
adamus diyAudio Member Join Date: Apr 2008	Sy, how is this looking. Re led bias for the first stage, i like it and will have a play when buiilding. As for the CSS in the output, I have some bias perfboards that i can take from my baby huey and try. I did try the huey without, and it lost something. clipping.... not in my flat with my neighbours unfortunately! Feedback, i will apply some and i have shown how, but just to the first stage. I'll have to keep an eye on oscillations.

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