Tightening lows

[iknowjohnny]

In a high gain pre that is. This is like a 2204 but with a second stage thats not cold biased. On V1 i have 2.2k/.68uf on A and 1.5k/1uf on B. I have the first coupling cap as a .0047uf. The second coupler is .022, but using a .0047 there didn't help much. I have two 470k/cap filters, one with a .0047uf and the other a 500pf. Filtering in the preamp is 20uf at the PI and V2 node, but i have 60uf on V1, and previously tried the 60uf on the PI....neither seems to matter much, and i don't want to go any higher because i tried 80uf in my other amp and it killed the tone and didn't tighten things up in any real way. So the lows should be awful tight i would think. They aren't. I still want to tighten up the lows so that they aren't as fuzzy and more clear/articulate. seems i've done everything but i thought someone here mmight have other ideas. The PA sports 100/100uf for plates and screens, so it's not that or the bias. Tried many NFB scenarios. (different taps, resistors, resonance cap,etc) It's definately in the pre stages, not the PA.

It's not real loose or fuzzy to a degree i'd call abnormal at all, but enough that i want tighter cleaner lows. Any tricks to get closer?

[Andy Le Blanc]

voicing can be tuff, whats the speaker? box?, look at the whole system.

with cap values, start with a value that is smaller than you think and then
parallel small values up to your critical point, I used to have a small board
with several values and a couple three clips to use as jumpers.

cap type can matter, and you can set up simple rc to get a stepped response.

you can try paralleling your power filter caps and cathode bias with film poly too

[Jana]

Tightening lows--

Bigger PT so there is more current in reserve.
Bigger OT so it is cleaner in the low end.
More PS filtering to give more reserve current on transients.
Bigger output tubes.
Less distortion on the low end.
Even bigger tubes, lots of them.
Big iron.
Bigger iron.
Really big iron and lots of really big tubes.

Closed back cabinets with lots of speakers driven by big iron with lots of really big tubes.

[iknowjohnny]

cap type can matter

Are mallories typically fuzzy in the lows? Because thats what i use, tho i have tried orange drops for a few things but not sure if i noticed anything. Maybe i'll try a orange drop in place of that .0047uf coupler since i have a ton of oranges in that value.

The one thing that does seem to help that Jan mentioned is tubes. I was able to use 6550's in my last one and that certainly helped. But i didn't care much for the harder less smooth tone. I suppose i could try them in this new amp and maybe i'd like them better now with 50v higher plate voltage. i wonder if i can tho because the last amp's PT was 250Ma while this one is only 150. Both have 5 amp heaters tho so that should be no problem i believe.

[Darkbluemurder]

What is your gain pot value? Do you go directly from the coupling cap off the first gain stage to the gain pot? If so, a 0.0047uf cap may still be too high - check whether a 0.0022uf or a 0.001uf solves the problem.

Alternative - insert a 470k II 470pf before the gain pot (if it is 500kA) or 1 Meg II 220pf (if it is a 1MA).

[iknowjohnny]

I have a 220k/.0047uf in front of the 1m gain pot now, but i have had it with nothing there and also with 470k/.0047uf, 470k/500pf, 470k/1000pf. It gets too bright with the others. I have another one at the V2a grid with 470k/500pf and i have also swapped the two around (that one & the one in front of gain pot) and tried using nothing there and one at the gain pot, visa versa, and even AFTER the gain pot. In fact, thats been the main thing i've been experimenting with since the amp was first fired up a couple weeks ago. I've been trying every imaginable value combo of whatever they're called (R/C filters??) in different places. right now i have 470k/500pf at the V2A grid and a 220k/.0047uf in front of the gain pot for mids. this has been the best setup so far, but i did it for overall tone shaping, not to lose the low fuzzies because none of the scenarios did that. I think there is something else at work in the preamp here but i'm not sure. If i go any lower one the couplers it starts getting too skinny. But i may try that again with a value closer to the .0047 there now. But i have nothing like a .0022uf now so i'd have to order more.

[Structo]

In my experience if I want tighter low end the first place to look is the first B+ filter value.
For a 100w amp I would use at a minimum of 100uF.

Size of screen resistors can also affect it. Bigger = mushier

Higher preamp plate and cathode resistors will produce tighter bass.

On bypass and coupling I tend to go against the grain and use a smaller value at the end of the stage. So large going in, smaller coming out.

[iknowjohnny]

In my experience if I want tighter low end the first place to look is the first B+ filter value.
For a 100w amp I would use at a minimum of 100uF.

it's only a 50 watter, but i have 100/100uf anyways.

Size of screen resistors can also affect it. Bigger = mushier

True, and i use 1k. But i'm quite sure for several reasons it's the pre stages where this is happening otherwise it would always happen. But the lows are only like this when the preamp is overdriven a lot. Clean and slightly distorted tones are fine.

Higher preamp plate and cathode resistors will produce tighter bass.

I agree and have them pretty high. I can get them higher but the PI and CF don't seem to sound good with voltages higer than i have now. i was actually thinking of using parallel nodes ala matchless chieftain so i could get V1 much higher w/o going too high on v2 and PI.

On bypass and coupling I tend to go against the grain and use a smaller value at the end of the stage. So large going in, smaller coming out.

never thought to do that for obvious reasons, but if it works for you i'll give it a shot.

Thanks all

[tubeswell]

What Jana said.

[M Fowler]

I also agree with Jana, but I didn't hear anyone talk about cap materials such as film verses poly caps.

I think the film caps are a bit better in the bias cap spot and I have not really experimented with them in the the tone stack. I tried three different caps OD, 150 & film for the .68uf bias cap and ended up keeping the film cap there.

Just a thought.

[iknowjohnny]

I don't know what caps are film. Are mallories film? Last nite i tried orange drops in place of the mallories for the V1 coupling caps and it did sound different. More clear and defined it seemed, which is what i'm going for. On the V1 cathode bypass caps i have a .68uf on A which is a type that looks like a mallory, then a 1uf electro on B. I have a 1uf non electro i can use there but it's big so i used an electro instead because i've never noticed much difference even tho people always say non electros are better.

How about sozo? i think what i'm really after isn't as much fuzzy bass as just overall clarity in all ranges, and the orange drops seemed to do that a bit better, and i always hear that sozos are clearer sounding.

[iknowjohnny]

Turns out i have several of those 1uf poly caps or whatever they are. they're blue and look like an orange drop tho more squared. Put them in place of the two bypass caps on V1B and V2a and they really cleared up the tone nicely. I also have orange drops for the first two couplers as i said before, but i may put the 150's back there and see how it sounds just with the bypass caps. they seemed to make the most difference. really makes me wanna try sozos.

[Jana]

Sozo vintage is the way to go. But, know that they take a while to break in. Sticking them in and expecting immediate results probably won't happen.

[iknowjohnny]

I found sozo at several places, but i never noticed a choice of different kinds. Are "sozo vintage" the only ones they make of that type, or do i actually have to look for someone who sells them with the word vintage in the name? The places that have them only seem to have one type so i assume thats the one even tho there is no "vintage" in the name.

[Jana]

I haven't seen any place other than Sozo that sells the Vintage version.