6505+ Bias check and comparison

[TheWinterSnow]

Wait, are you fucking kidding me? What could possibly be the logic of doing it that way? (rather than *gasp* going sequentially up in number from left to right, arrggghhh) I'm not doubting you dude, I just hate needlessly confusing things! (or maybe there's some profound wisdom to it that my plebeian brain can't grasp )

peavey did some weird shit with their tube locations, because on the back their is a little bay that opens up with the tubes coming out sideways (laying down horizontally) the tube order goes V1 V2 V5 V3 V4 (for some reason they made V5 the tone stack so its placed square in the middle). Becuase the little compartment is ont he other side of the amp they have to place V4 closest to the Power Tubes and that happens to be to the far left, so they go V4 V3 V5 V2 V1. When they go to the II/+ they added another gain stage to the saturation section which would be V6, but its used as a buffer tube so it goes first so the final order at how you see the tubes from the back is V4 V3 V5 V2 V1 V6.

Is Peavey retarded...YES!!!

 

[::XeS::]

Ok but.......apart the tube numbers....is there any difference compared to other amps?
V6 is the first tube but it's like the V1 in other amps. And V4 is the phase inverter so it's like call it V6 in other amps. Or not?
If I wanna replace the V1 (First gain stage) and the PI tube, I have to replace V6 and V4, right?

 

[Wolfeman]

peavey did some weird shit with their tube locations, because on the back their is a little bay that opens up with the tubes coming out sideways (laying down horizontally) the tube order goes V1 V2 V5 V3 V4 (for some reason they made V5 the tone stack so its placed square in the middle). Becuase the little compartment is ont he other side of the amp they have to place V4 closest to the Power Tubes and that happens to be to the far left, so they go V4 V3 V5 V2 V1. When they go to the II/+ they added another gain stage to the saturation section which would be V6, but its used as a buffer tube so it goes first so the final order at how you see the tubes from the back is V4 V3 V5 V2 V1 V6.

Is Peavey retarded...YES!!!

I remember discussing this with some amp guys a while back... the reason the V numbering is all screwed up is Eddies fault. They started out with a pretty normal schem, but Eddie couldn't decide what he wanted for the tone stack. So they drew it up without the tone stack, so they numbered the schem as they usually would. Down the road they decided on the tone stack, and placed it in the schematic. Since you don't change everything on the schematic when something like that happens, they just popped it on the drawing as V5....

If you look at the schem, you can actually see that they were toying around with the idea of an active EQ, but later decided against it.

 

[Wolfeman]

Ok but.......apart the tube numbers....is there any difference compared to other amps?
V6 is the first tube but it's like the V1 in other amps. And V4 is the phase inverter so it's like call it V6 in other amps. Or not?
If I wanna replace the V1 (First gain stage) and the PI tube, I have to replace V6 and V4, right?

Correct. Don't let it confuse you, the V numbering system is schematic specific, and shouldn't always be used as a guide to where the tubes are physically in the amp(well you can in pretty much every amp other than this one).

In most cases the PI will be closest to the power tubes, and the input circuit tube will most certainly be closest to the input jack.

 

[::XeS::]

Don't you think that a hotter bias can make the amp more boomy? For example a 5150, if you change the bias from 14mA to 40mA you can notice more bass and more volume....but is it better?
Sometime it seems that with a cold bias the 5150 is more heavy and aggressive. With an hot bias it's more big and bassy.
What's your impressions?

 

[TheWinterSnow]

Don't you think that a hotter bias can make the amp more boomy? For example a 5150, if you change the bias from 14mA to 40mA you can notice more bass and more volume....but is it better?
Sometime it seems that with a cold bias the 5150 is more heavy and aggressive. With an hot bias it's more big and bassy.
What's your impressions?

A hotter bias adds warmth, its not intense, and does not make it boomy at all, if not make it more aggressive and articulate. It makes the tone more solid, not more bassy.

And something I have wanted to say for awhile but haven't move the power tubes around, you have the lower current on one side and the upper current on the other which means each side of the push-pull is not even wattage wise. Put either the higher current tubes in the middle or outer positions and that way you will have equal wattage on both the push pull, should help the tone until you get new tubes.

I think the reason that the amp sounds muddy when you bias it hotter is that you have the mismatched tubes pair together, because that would cause the speaker to not be moved correctly causing it kind of flop (not really, but one side won't have the power to properly return the speaker to resting position for the other tube to take over) around on one half causing you to loose clarity, when you have the lower bias the difference in power is trivial because they are closer together, but still even with the lower bias, the speakers are not being powered correctly like they should with those tubes (that's why they have a wattage ratting, its a balance between maximum current and working correctly)

 

[::XeS::]

Thank you for the answer.

 

[::XeS::]

In the last 2 days I did some tests micing my amp with different eq (my next work is in Eb so I try different settings) but nothing satisfied me in terms of sound. Uncontrolled bass, bad top ends..also trying different mic position.
Today I tried to lower the bias (the pot was maxed and I turned back an half turn or a little more)....tadaaa....the sound was immediately way better, much more controlled bass (no more boomy bass) and the same for the bad top ends.
I don't know if it's because I have bad power tubes unmatched, or because with the bias maxed I was in the crossover distortion.... but with a lower bias the amp seems way better.
Here 2 samples, sorry for the very sloppy playing

Riff with the bias maxed
http://dl.getdropbox.com/u/1436721/Riff_Eb_hot.mp3

Riff with a colder bias
http://dl.getdropbox.com/u/1436721/Riff_Eb_cold.mp3

 

[TheWinterSnow]

what cabinet are you using? Mic? It may be an issue of the cabinet getting muddy because it can't handle that amount of low end. Most tube amps are not even nearly as close to low end as a solid state/digital. I have my bias at 70%, my bass at 8 and my presence at 10 (yes all the way up) and I haven't had a uncontrolled bass problem, and I am using a ported 212 cab.

From the clips I like the hotter one better (I am using a laptop but the lowend tends to fart out easily if the bass is out of hand. It could be a large factor of things like room acoustics, mic choice, mic placement, eq etc etc. Since I have switched over to tube including the horrible HORRIBLE comb filtering and house resonance that accentuates the lows massively I have never had uncontrolled bass from any sort of proximity effect, a high pass at 60 usually trims up the sound but still, has never been too much.

But again you said it, and so have I, old and mismatched tubes, they can't properly power the speakers, pushing that much uneven current to the speaker is mud city.

 

[::XeS::]

Yes it could be different factors.
I have a custom 2x12 with v30's and this clip is recorded in my bedroom.
The eq was:
Bass: 6
mids: 5
high: 4
reso: 6
pres: 7

The mic was an sm57 on axis in the edge of the dustcap.
About the samples, I think the hotter one is more brutal but to my ears the colder one seems more controlled overally...don't' know how to explain it.
Probably it could be also a volume problem, because here I have to set the post gain below 1. Probably with post gain at 2 or more, the amp would open up better.

 

[TheWinterSnow]

Amps are biased colder so that they sound better at lower volumes, while they may suffer at higher volumes and vice versa with hotter bias. However the resonance control is basically and impedance controller, its basically a lowend dampener that dampens the frequency response of the speaker. If you are having a low end control problem, you bring down the resonance.

 

[::XeS::]

Now I've placed the high current tubes in the external slots (waiting for a matched 4 set of JJ).
The amp definitelly sounds better with the lower bias at bedroom level (post gain under 1) but next week I'll try the amp louder with a marshall 1960 and I'll compare the 2 bias another time.