how to make tube amp sound layback and mellow?

[jj2]

how can I change my preamp and amp to sound more layback and mellow ? tube , ps or caps ?
preamp 12b4 linstage.
amp sun audio 2A3.
Thanks for any help.
John

[spock]

tube rolling would seem to be the first preference; providing you have a supply of difffernt tubes to try.

[ashok]

Maybe a gentle HF roll off starting quite early?

[mach1]

Vitamin Q or Russian K40Y paper in oil coupling caps (ebay).

[hagtech]

Forget the rolloff. Rebias the preamp tube. Run it at much lower current! Then you will get the warmth and mellowness all at once. You have to run the tube where it distorts the most.

jh

[ashok]

I've no idea how the distorted sound by re-biasing would be to the ear.

However the suggestion of changing coupling caps might be a very good idea. Some caps can soften up the sound .

Maybe you should try all suggestions because its your ear that wants a particular type of sound. Easiest will be to try the re-bias suggestion as it only needs resistor juggling. Caps might require an expensive purchase!
Cheers.

[Elso Kwak]

Increase feedback!

[arnoldc]

Originally posted by Elso Kwak
Increase feedback!

huh?!

Rebias the preamp tube. Run it at much lower current! Then you will get the warmth and mellowness all at once. You have to run the tube where it distorts the most.

Based on experience, I would tend to agree with Jim here. I've been playing with a Western Electric tube, biased it to what should be the linear region. It sounded good but some people complained about being analytical. I dropped down the voltage and a little bit current and they liked it more.

My 12B4 preamp is also biased lower when compared to the rest of the gang (see 12B4 linestage thread). Mine is at 17mA and 180V only.

If you're using Sovtek 2A3, you may also want to look for RCA which will improve the mids.

Another thing is that the SV-2A3 is using a 750R cathode resistor. I find that it sounds a bit shouty at that current. I use 880R resistors which are good for my taste.

[cogsncogs]

Here too.
Lowering the current through the tube will give you a more 'toob' sound, if my head is screwed on right more 2nd harmonics. Don't know about till distortion is max tho...
Running with low B+ will work also (along with lower bias) but lower max output. You will need to find the 'sweet spot' to your ears.
Tube rolling? nah. If that route try a different tube circuit altogether. May be a little off topic btw but one experiment I've tried to get a 1950's sound (used w/ a NAD SS pwr amp) was a 6BQ7 both sections in //, 80V B+, 47k or 33k (dunno) plate load, 470 or 390 cathode resistor, 500k volume control, ?k grid stop, 12AU7 and/or 6BQ7 cathode follower w/22k load resistor. It gave a very old 1950's rolled off sounding pre. Most likely due to the 500k volume control and low (80V) B+.
I've found that using a B+ of 80V and below with tubes such as 12xx and 6DJ8, 6Bxx gives a very pleasing to the ear sound, tho maybe less lively.

Oh hi Arnold! I think Elso Kwak is talking about the increasing the value of the cathode resistor, less current. I would increase the value of the anode resistor also for a 'warmer' sound.

Cheers
Wayne

[ashok]

This topic continues to interest me. If you listen to many amps you will probably find that some patches of difficult vocals can appear to be " shouty " . How much the effect is depends on the amp and keeping everything else unchanged I have found the difference between amps quite remarkable . However in the rest of the music the differences between amps seem to be very hard to find.

So would vocals with sections that tend to " shout" in some systems be a method of determining how good the amp / system is ........all else being similar ?
The difference can be quite subtle sometimes but certainly audible. This problem is probably level dependent also.

Any thoughts?