My first tube project help thread (NYD one bottle)

[buildafriend]

What if I used http://angela.com/angelametalizedpolypropylenecapacitor18uf630vdc-2.aspx as my output coupling capacitor? ( 1.8uF instead of 2.2uF )

The smaller the cap you put in, the higher the lowest frequency AC signal it can pass. Depending on the circuit it may or may not start audibly rolling off the lows, or phase shifting low frequency content. I would stick with at least 2.2uf.

Yeah forget that, I'm hoping this thing sounds good on drums.

 

[dustbro]

I got bored...

TOP COPPER

BOTTOM COPPER

BOM FOR ONBOARD COMPONENTS

 

[buildafriend]

;D I've never used that smiley before.

 

[buildafriend]

I guess ill just grab those big wima caps for coupling. I am sure it will still sound really good.

 

[buildafriend]

what is C1 doing? 47pF

 

[abechap024]

what is C1 doing? 47pF

The 47pf in series with that resistor strapped to the secondary of the input transformer form a zobel network, this tames "ringing" and flattens the frequency response of the input transformer. Depending on what trasformer you choose, you could optimize those values, but might as well stick with whats on the schemo for now, it will sound fine.

 

[Blue Jinn]

Allied has a 250v transformer for something like US$15.00.

 

[buildafriend]

Allied has a 250v transformer for something like US$15.00.

Sold.

 

[buildafriend]

what is C1 doing? 47pF

The 47pf in series with that resistor strapped to the secondary of the input transformer form a zobel network, this tames "ringing" and flattens the frequency response of the input transformer. Depending on what trasformer you choose, you could optimize those values, but might as well stick with whats on the schemo for now, it will sound fine.

When you say ringing do you mean like from a steel snare?

 

[dustbro]

When you say ringing do you mean like from a steel snare?

sort of. the sound would be very similar to putting a Ring Modulator on your audio... any type of sound source would create a HF oscillation

 

[dustbro]

Allied has a 250v transformer for something like US$15.00.

Also keep your eyes open for a transformer that will have taps for B+, Heaters, and phantom power. and maybe even a tap for 12V to run a relay and led's.  ;D

 

[gemini86]

by "ringing" he means a resonant peak in the frequency response, like a bell ringing in sympathy to a bell of the same note stuck next to it.

 

[buildafriend]

by "ringing" he means a resonant peak in the frequency response, like a bell ringing in sympathy to a bell of the same note stuck next to it.

Ah I see. so the input transformer can achieve resonance and that causes modulation that can be referred to as ringing.

If I remember right resonance is when your capacitive and inductive reactances are as close as possible to zero. I cant remember if thats a combined total?

1 over 2 times pi times frequency times farrads, and 1 over 2 times pi times freq times inductance?

It's time to hit up my books again. Am I trying to avoid max resonance?

 

[buildafriend]

I checked the hammond site and found some power transformers for 120 or 240 50/60 Hz transformers with secondaries that put out 240 but they are also giving me options for amperes on the secondaries. I can choose anywhere from 63mA to 6.3 amps. Huge range. This seems like something that I should clearly be paying attention for.

Some of these look like they might work.

http://www.hammondmfg.com/182.htm 

 

[buildafriend]

Allied has a 250v transformer for something like US$15.00.

Also keep your eyes open for a transformer that will have taps for B+, Heaters, and phantom power. and maybe even a tap for 12V to run a relay and led's.  ;D

Would those things not be tapped off of the 240 secondaries and then coming from a regulator/zener?

 

[gemini86]

by "ringing" he means a resonant peak in the frequency response, like a bell ringing in sympathy to a bell of the same note stuck next to it.

Ah I see. so the input transformer can achieve resonance and that causes modulation that can be referred to as ringing.

If I remember right resonance is when your capacitive and inductive reactances are as close as possible to zero. I cant remember if thats a combined total?

1 over 2 times pi times frequency times farrads, and 1 over 2 times pi times freq times inductance?

It's time to hit up my books again. Am I trying to avoid max resonance?

You just might have to use a zobel network to tame peaks in the frequency response...

see this for an example.

http://www.lundahl.se/pdfs/datash/1528.pdf

Where it says "Optimum termination for best square-wave response", that would be a zobel network. 9KΩ in series with 3nF.

Some transformer companies will show you response curves quoted only with the recommended zobel network or load conditions.

 

[buildafriend]

im still held up on what schematic I can use to start making a phantom power PSU..

 

[audiophreak]

Hi ,
    I think I used the 48vdc  circuit from the PSU of the SSL9k project ,  P2P on  perf board.

 

[buildafriend]

At the junction of R12 and and pin one of the gain pot, I have what is in the video below which seems to then get amplified through the circuit. Do these sharp little peaks that stick out of the clean signal ring any kind of a bell with you tube gurus? One channel is fine, the other one gives me this. It looks horrible by the time it reaches the output cap but the buzz is not actually that bad, it's just enough to bug me. I tried moving all the transformers and I shielded the power tranny.

http://smg.photobucket.com/albums/v207/whpnewjersey/?action=view&current=709ab0a5.mp4

 

[buildafriend]

Here are some new front panels that were designed by someone WHO KICKS THOROUGH A**.  8) I wish that I could take credit for these, but they were not designed by me.

The one out of the two channels that I have working thus far sounds really great. I'll post pics of the inside when shes done and working right.

Some info: Metal film resistors, Wima caps, GE 5965 tubes, Sowter 9735 input iron (ampex 350 replica input iron)