4-4-0 [2 NEW BUILDS WITH PICS; THE 2 WATT WRECK]

[mss1]

Thanks for responding Brian.

I figured R13 was there as a good safety idea, but it sure made me wonder if we still need the 10ohm/5w on the first jack, when using the Firezog output without a speaker.

Is it that the R13 resistance value is too high for the expected impedance match, to just eliminate the 10ohm/5w?

MSS

[GainMaster]

Thanks for responding Brian.

I figured R13 was there as a good safety idea, but it sure made me wonder if we still need the 10ohm/5w on the first jack, when using the Firezog output without a speaker.

Is it that the R13 resistance value is too high for the expected impedance match, to just eliminate the 10ohm/5w?

MSS

The 10R is switched in only if no jack is plugged in. It keeps a proper load on the tube in the event you don't want to use a speaker but want to use the line out. Yes, R13s resistance value is too high to maintain the impedance match without a speaker plugged in. If you plan to always use a speaker when using the line out then no, the 10R is not needed.

Brian

[mss1]

Depending on the situation, we may not have a choice but to go without a speaker, using the Firezog output.

I think it is good practice to just keep the 10ohm there, and actually, I am surprised it is not a safety standard on all tube amps.


MSS

[GainMaster]

Depending on the situation, we may not have a choice but to go without a speaker, using the Firezog output.

I think it is good practice to just keep the 10ohm there, and actually, I am surprised it is not a safety standard on all tube amps.


MSS

The 10R is not totally safe. If you had a jack plugged in with nothing plugged into the other end of the jack you could still blow the amp. The 220R on the other hand makes it totally safe because it is allways in the circuit. Use both. You won't regret it.

Brian

[arjepsen]

Oh, btw Brian, you mentioned using a .68uF cap by the presence pot.
Just to make sure: you meant .68 and not .068?

[GainMaster]

Oh, btw Brian, you mentioned using a .68uF cap by the presence pot.
Just to make sure: you meant .68 and not .068?

Yes .68u. While a bunch of changes were being made, they forgot to recalculate the presence cap. Works much better with the .68u. Also, I put a NFB pot on mine and prefer it set from 1/4 to 1/2. You could try raisng the NFB resistor to 10k or so.

Brian

[arjepsen]

ok, thx. Had hoped it was .068, since I don't have a .68 around
I'll have to order one, and maybe start out with a .1 untill I get it.

I put the NFB pot on my october studio, but I really don't have the space for it, in this build....

Another thing.. I also realized, that I don't have any 180k/1w around.
So I'm wondering what the effect would be, of using a higher/lower value?

[GainMaster]

ok, thx. Had hoped it was .068, since I don't have a .68 around
I'll have to order one, and maybe start out with a .1 untill I get it.

I put the NFB pot on my october studio, but I really don't have the space for it, in this build....

Another thing.. I also realized, that I don't have any 180k/1w around.
So I'm wondering what the effect would be, of using a higher/lower value?

Try the original NFB resistor. Just realize it is like having the NFB pot on 0. I like mine higher than that. The highs sound a bit clearer and the bottom end a bit less muffled. Not that they are not clear or muffled in the first place. Just descriptive terms. Then change to 10k or 20k and take a listen to see what you think.

If you are talking about R8, raising or lowering it will change your bias voltage. A tad more bias voltage would not be a bad thing to have so without doing math, I would say that you might get away with as little as 150k there without problems. Hope that helps.

Brian

[GainMaster]

Double Post

[arjepsen]

Well.. it's both R6 and R8 I don't have.
I do have a 150k/1W that I will try instead of R8, but how about R6...?
I think I also have a 220k... that I could use instaed of R6, unless that would throw anything out of whack....?

[GainMaster]

Well.. it's both R6 and R8 I don't have.
I do have a 150k/1W that I will try instead of R8, but how about R6...?
I think I also have a 220k... that I could use instaed of R6, unless that would throw anything out of whack....?

220k should be fine for R6. All that portion of the curcuit is doing is lifting the heater voltages off the 0v floor. You just won't be quite as far off the 0v floor.

Brian

[mmmoser]

Hi- I have pretty much finished the build of one of these little devils- I also built a Liverpool TW awhile ago which is 36 watts of screaming fury, so I wanted more of a practice amp from this one.
Now that I am listening to it on the bench I am wanting to adjust the tone. To my ears the amp has a lack of lower end and midrange and has a rather fizzy distortion sound. Having not used these type of tubes for power tubes before, I bought a half dozen to see if there was an appreciable difference from one to the next. They are all US made RCA tubes. I do not hear a huge difference with the sound from one tube to the next.
I have the two sides of the tube biased at about 6ma. Bias does not make a huge difference in the amps tone except at the extremes. So I am wondering what changes I can make to tailor the sound to reinforce the bottom end and bring out a midrange creaminess to the amp. I also realize I may actually be limited by the tube type- that they naturally have this sound. So I might consider rewiring for a 6V6 tube for a little more power but only if I can get the amp sounding how I want it that way. the 2-3 watts is actually plenty of volume for the practice space.
Anybody have any mods that might help out??

[GainMaster]

Hi- I have pretty much finished the build of one of these little devils- I also built a Liverpool TW awhile ago which is 36 watts of screaming fury, so I wanted more of a practice amp from this one.
Now that I am listening to it on the bench I am wanting to adjust the tone. To my ears the amp has a lack of lower end and midrange and has a rather fizzy distortion sound. Having not used these type of tubes for power tubes before, I bought a half dozen to see if there was an appreciable difference from one to the next. They are all US made RCA tubes. I do not hear a huge difference with the sound from one tube to the next.
I have the two sides of the tube biased at about 6ma. Bias does not make a huge difference in the amps tone except at the extremes. So I am wondering what changes I can make to tailor the sound to reinforce the bottom end and bring out a midrange creaminess to the amp. I also realize I may actually be limited by the tube type- that they naturally have this sound. So I might consider rewiring for a 6V6 tube for a little more power but only if I can get the amp sounding how I want it that way. the 2-3 watts is actually plenty of volume for the practice space.
Anybody have any mods that might help out??

Increase the coupling caps between the second and third stage from .002u to .003 or higher. You should also bias the output tube for 2.5 watts per side. About 9.4mv with a B+ of 340 or so. Also, R20 and R21 were changed from 250k to 330k to combat the bit of fizzyness. Play with R31. I like it at 100k but earlier schematics have this at 150k. Swap V3 for a 12av7. You get a much wider sweet spot. The NOS Tung Sol 6sn7s sound best in this amp. Much more chimey than the RCA.

Brian

[JoeyE]

Hi- I have pretty much finished the build of one of these little devils- I also built a Liverpool TW awhile ago which is 36 watts of screaming fury, so I wanted more of a practice amp from this one.
Now that I am listening to it on the bench I am wanting to adjust the tone. To my ears the amp has a lack of lower end and midrange and has a rather fizzy distortion sound. Having not used these type of tubes for power tubes before, I bought a half dozen to see if there was an appreciable difference from one to the next. They are all US made RCA tubes. I do not hear a huge difference with the sound from one tube to the next.
I have the two sides of the tube biased at about 6ma. Bias does not make a huge difference in the amps tone except at the extremes. So I am wondering what changes I can make to tailor the sound to reinforce the bottom end and bring out a midrange creaminess to the amp. I also realize I may actually be limited by the tube type- that they naturally have this sound. So I might consider rewiring for a 6V6 tube for a little more power but only if I can get the amp sounding how I want it that way. the 2-3 watts is actually plenty of volume for the practice space.
Anybody have any mods that might help out??

Like the TW, the amp is on the trebly side which even sounds piercy with the best alnico's. I'm using greenbacks with it and it balances just right for me. Creamy midrange without the fizzy highs. Since greenbacks were the staple speakers of the 80's and big hair music i guess this is what the TW was tested with (just an opinion but i may be wrong). Maybe more bass needed but im using an openback cab.

[GainMaster]

Hi- I have pretty much finished the build of one of these little devils- I also built a Liverpool TW awhile ago which is 36 watts of screaming fury, so I wanted more of a practice amp from this one.
Now that I am listening to it on the bench I am wanting to adjust the tone. To my ears the amp has a lack of lower end and midrange and has a rather fizzy distortion sound. Having not used these type of tubes for power tubes before, I bought a half dozen to see if there was an appreciable difference from one to the next. They are all US made RCA tubes. I do not hear a huge difference with the sound from one tube to the next.
I have the two sides of the tube biased at about 6ma. Bias does not make a huge difference in the amps tone except at the extremes. So I am wondering what changes I can make to tailor the sound to reinforce the bottom end and bring out a midrange creaminess to the amp. I also realize I may actually be limited by the tube type- that they naturally have this sound. So I might consider rewiring for a 6V6 tube for a little more power but only if I can get the amp sounding how I want it that way. the 2-3 watts is actually plenty of volume for the practice space.
Anybody have any mods that might help out??

Like the TW, the amp is on the trebly side which even sounds piercy with the best alnico's. I'm using greenbacks with it and it balances just right for me. Creamy midrange without the fizzy highs. Since greenbacks were the staple speakers of the 80's and big hair music i guess this is what the TW was tested with (just an opinion but i may be wrong). Maybe more bass needed but im using an openback cab.

Small changes in the coupling caps between the second and third stages yeild huge changes in bass response.

Brian