Is 400 VDC B+ too low for a 2204 to sound heavy and punchy?

[LPman]

There must be a reason that all of the 50W Marshall models run on a plate voltage in the 430 - 450 VDC range. The only exception is the 2204 and 1987 model made between '72 to '82. Those models have a PT that provides only around 400 and sometimes as low as 350-370 VDC. For downtuned music with heavy riffing and fast palm mutes, can a lower plate voltage 2204 (400 VDC) be adequate like the ones made between '72 and '82? Or is it better to look for a later post-82 one when the Drake PT was changed to the 450 VDC version?

Or can the lower plate voltage be compensated by jumpering one of the 10k dropping resistors to significantly raise preamp voltage? Would that solution make the tone equal to a post-82 2204?

My 2204 has only 400 VDC and I'm wondering if I should replace the amp to a later one or simply change the PT for a new Dagnall that is used in the current Reissue models and provides 450 VDC.

 

[junk notes]

 

[Tatzmann]

I dont think this will be of any concern in that matter if you imagine how much of "metal-type-music" has been played/recorded with 9volt pedals infront of transistoramps, that usually work with voltages under 100volts.

I wouldn't worry. It'll do.

Speakers are more of a concern, i'd say.

 

[Pete Farrington]

For downtuned music with heavy riffing and fast palm mutes, can a lower plate voltage 2204 (400 VDC) be adequate like the ones made between '72 and '82?

It might be more adequate, in that the HT will be stiffer, as for a given OT, less current can be drawn.

 

[LPman]

I dont think this will be of any concern in that matter if you imagine how much of "metal-type-music" has been played/recorded with 9volt pedals infront of transistoramps, that usually work with voltages under 100volts.

I wouldn't worry. It'll do.

Speakers are more of a concern, i'd say.

I play my amps cranked so it's a different situation when the power section of a tube amp starts to saturate. I'm wondering if a higher plate voltage 2204's lows would remain more intact and solid when the amp is pushed hard in comparison with a lower voltage one. Wouldn't the latter tend to become more saggy at cranked volume levels?

 

[Tatzmann]

I do play pretty loud too sometimes and i understand fully what the question was about.

What does cranked mean, everything on 10?

With or without loadbox/ir gadget/attenuator?

If any of those come into play, there are even more variables and it would be even less of concern if you have 380 or 450 volts in there.

If cranked up real good without any volume restricting devices straight into speakercabs, then i would just look for speakers that can take it without mushing out on the bottom.

Hence all the highpowered speakers since the late 70s.

I know, its not a specific answer to your question, but related.

I have all sorts of 800 type amps in which the
supplyvoltages and preampvoltages do vary quite a bit, and under normal "bandconditions"
(surely not everything on 10, more like master 5 and preamp 7, if master 10 i'd have to roll the guitarvolume off or lowering the pre-amp, and that wouldn't be "cranked" anymore) they all do the tight bottom metal without sag/mush, if desired.

(BTW: I have a 1989 2205 to trade if interested, it has 480 or 490 something volts at v3b...and about 60 at v1b. (voltages from memory +-10v) (meant in good fun, but i actually prefer it to my 2203 type amps for the metalbrootz.)

 

[LPman]

I do play pretty loud too sometimes and i understand fully what the question was about.

What does cranked mean, everything on 10?

With or without loadbox/ir gadget/attenuator?

If any of those come into play, there are even more variables and it would be even less of concern if you have 380 or 450 volts in there.

If cranked up real good without any volume restricting devices straight into speakercabs, then i would just look for speakers that can take it without mushing out on the bottom.

Hence all the highpowered speakers since the late 70s.

I know, its not a specific answer to your question, but related.

I have all sorts of 800 type amps in which the
supplyvoltages and preampvoltages do vary quite a bit, and under normal "bandconditions"
(surely not everything on 10, more like master 5 and preamp 7, if master 10 i'd have to roll the guitarvolume off or lowering the pre-amp, and that wouldn't be "cranked" anymore) they all do the tight bottom metal without sag/mush, if desired.

(BTW: I have a 1989 2205 to trade if interested, it has 480 or 490 something volts at v3b...and about 60 at v1b. (voltages from memory +-10v) (meant in good fun, but i actually prefer it to my 2203 type amps for the metalbrootz.)

By cranked I mean the master on 5 or above, but 5 is a sweat spot. No attenuator BS or anything. At 4, I start to hear the power amp saturation and at 5 it fully kicks in and transforms the amp into a beast. After 7, the amp really doesn't get any louder, just saturates even more and more. I like to set the gain to 5 too, if I turn it 3/4 way up, the low-end gets too bassy and mushy. All 70s and 80s 2204 I've had behaved the same. So I keep the gain at 5 or 7 at max.

I'm currently on the hunt for speakers. I have tried quite a few speakers and cabs over the years. Various 4x12s from current times and the 90s and 70s. V30 cab (hated it), G12T-75 cab (hated it even more), old Blackback cab (better), old '74 Creamback cab (even better) and I've been using the 90s 6402 Greenback Pulsonic RI's now for about 6 years with that '74 checkerboard cab (sold the stock Creambacks). These are the best Celestion speakers by far I've come across. The next set I want to try are the G12-65s.

I also improved the cab by replacing the stock buzzy plastic handles to metal ones. It's an insanely good cabinet. The plywood is super hard compared to new cabs and the bracing is tight and solid. I had newer 4x12 Marshalls where the center post would break, really disappointing construction. My '74 is all 15 mm ply including the front baffle minus the back. I compared it recently to an early 70s Laney cab with 18 mm ply including the back panel, stock metal handles, heavy as hell and it didn't sound as tight and punchy as my Marshall so I don't feel an urge to replace the back panel to ply.

Regarding the 2205, I owned one, I don't know which version it was. That amp sucked big time. The strange thing is that one of my friend also had a 2205 at the same time (combo version) and his amp had a fabulous tone, really similar to the 2204. There was a change in construction in these amps somewhere around '84, there were two or three different versions of it to my knowledge.

 

[LPman]

Still, there should be a reason all of the 50 W Marshall amps in history run on 430-450 VDC plate voltage, no? Besides the 72-82 JMPs. If it makes no difference why don't we see more 50 W Marshall amps with 350 VDC?

 

[john l]

It absolutely makes a difference. No one who knows anything about tube amps would argue that. I too prefer the higher B+ amps. That said you'd be surprised what you can coax out of one of the 380v models if you beef up the mains filtering and play with the preamp droppers. I certainly wouldnt let this be the deciding factor in whether or not I bought an amp. 72-82 were fantastic years for Marshall.

 

[LPman]

It absolutely makes a difference. No one who knows anything about tube amps would argue that. I too prefer the higher B+ amps. That said you'd be surprised what you can coax out of one of the 380v models if you beef up the mains filtering and play with the preamp droppers. I certainly wouldnt let this be the deciding factor in whether or not I bought an amp. 72-82 were fantastic years for Marshall.

Well, mine at 400 VDC (which I find to be an optimal plate voltage - close to the 68 Plexi's range) with one of the 10K droppers removed can sound brutal that's for sure. Very heavy and punchy. With the 400 VDC its clean power is right about 40W and at full saturation it produces 60W. I have seen JMPs from the 70s with only 350 VDC, I'm not sure about those though. Seems low.

At this point I'm just wondering what was the incentive from Marshall to put those weaker PTs into the 50W heads in that period.

 

[john l]

I would consider anything below 365v to be in an over biased condition or to have something at least partially shorting somewhere in the amp. Youd be surprised how little it takes to give the B+ a good tug. The amp may even sound fine for the most part in a lot of these scenarios.


The 100s had double the power handling on the mains and screens even though they actually have less filtering than the 50s due to the filters being two 500v caps in series while the 50s did not and topped out at 500v. Less B+ wouldnt be a bad thing if one wanted to avoid warranty claims in this case.

Totally spit balling here. Maybe @neikeel will come along and school us both.

 

[Pete Farrington]

what was the incentive from Marshall to put those weaker PTs into the 50W heads in that period.

Not popping the G12M25 speakers in the combo versions is my guess for the reason for bringing the ‘50W’ model power output down a bit.
The heads probably followed suit for the purposes of consistency, so as not to confuse customers.

 

[john l]

Not popping the G12M25 speakers in the combo versions is my guess for the reason for bringing the ‘50W’ model power output down a bit.
The heads probably followed suit for the purposes of consistency, so as not to confuse customers.

This is very true. Brings the rms wattage down to 30-35w. much better for a cab with 100w power handling

 

[Dr.Twang!]

Well, mine at 400 VDC (which I find to be an optimal plate voltage - close to the 68 Plexi's range) with one of the 10K droppers removed can sound brutal that's for sure. Very heavy and punchy.

Sounds like you’ve answered your own question.
The difference is the Drake 1202-164 vs 1202-118 PT. Production availability of the higher voltage -118 or manufacturing issues could have been a factor, please chime in anyone with some deep factory history. The 164 appears as original installation on 2204/1987s but I’ve seen the 118 over some periods in there as well.
I currently own 70 & 71 1987s each with different PTs and they both sound very similar with the biggest difference being mostly the overall output volume.

 

[shredless]

I added a resistor to the b+ on my 2203x, plate voltage is now 385 and to me it does heavy so much better than at 450. Of course tone is in the hands, right.

 

[neikeel]

Can't claim to be an expert but I think that 400-420v is pretty decent for one of these.
I think Marshall were happy with the lower voltages as that gives the output tubes and easier time (remember there were problems with EL34s going to the US) and it gives a browner sound with lower preamp voltages - most people never really have/had the chance to truly crank these in most applications either recording or gigging (unless you use an ISO box or huge stage).
The one I've just built with Selmer iron will put about 380v (by my calculations) which will be fine for a 30-40w combo. I do have bigger iron knocking around (and similar size RS that would be 500v but decided against it on grounds of manageablity).

 

[LPman]

I added a resistor to the b+ on my 2203x, plate voltage is now 385 and to me it does heavy so much better than at 450. Of course tone is in the hands, right.

That's really interesting. You say that at that much lower plate voltage setting the amp sounds punchier? It seems to be contrary to the general consensus that higher B+ in the same Marshall model equals to more punch and a tighter bottom-end for heavy palm mutes.

 

[Pete Farrington]

I added a resistor to the b+ on my 2203x, plate voltage is now 385

Is that measured at idle, or with the amp putting out audio power?

 

[FourT6and2]

I prefer higher B+. Amp is tighter, stiffer, punchier. But there is a trade off in that it also fights back a bit, is a bit cleaner, etc. Some people like more sag and bounce. You can get the best of both worlds if you know how to tune the circuit and are comfortable modding the amp. Everybody has their own preferences. Some like more squish and bounce, some want tight and punchy. Tweaking the NFB circuit and preamp voltages can go a long way. I try to target at least 160v on V1a plate. Nothing lower, and a power tube plate voltage of at least 450-480v. If amp is too bright/harsh and stiff, you can alter NFB and add a depth control to compensate.

 

[Pete Farrington]

I prefer higher B+. Amp is tighter, stiffer, punchier. But there is a trade off in that it also fights back a bit, is a bit cleaner, etc. Some people like more sag and bounce.

Might you be conflating a lower HT with one that’s more saggy?
I don’t think that’s necessarily the case, (though it might be with the particular PTs here ).
For a given OT load and reservoir and screen grid cap values, as with Marshalls, and for a given HT winding gauge wire, the lower HT should be stiffer.