Loudness250
New member
I had the reissue and it was 440v or so so I was curious to what the originals are pumping out voltage wise.
peterc52
Well-known member
duesentrieb
Well-known member
2203: ~480-500V normally
depends where the prim. selector was at - in germany the mains is 230V - while the older transformers have prim for 220 and 240V - and a bit on the "freshness" of the filters . . .
Reissues are lower because todays tubes will run more reliable with plate voltages around 450V (which in the 70s was more the plate voltage for the 50s Marshalls).
@peterc52: thats the max. consumption in Watts, not the voltage on the plates of your powertubes.
depends where the prim. selector was at - in germany the mains is 230V - while the older transformers have prim for 220 and 240V - and a bit on the "freshness" of the filters . . .
Reissues are lower because todays tubes will run more reliable with plate voltages around 450V (which in the 70s was more the plate voltage for the 50s Marshalls).
@peterc52: thats the max. consumption in Watts, not the voltage on the plates of your powertubes.
Vrad
Active member
psychodave":23gcl08e said:
Yeah my '71 is right there in the 520-530 range.
duesentrieb
Well-known member
The newer, the less 
orig. schem. from the first MVs: http://www.drtube.com/schematics/marshall/2203u.gif
PV = 482V.
orig. schem. from the first MVs: http://www.drtube.com/schematics/marshall/2203u.gif
PV = 482V.
MrDan666
Active member
Many of the JMP 2203/1959/1992 heads that i have modded, have varied anywhere between 450vdc-485vdc on the plates. Most of those are amps from the '76 - '82 era. I know that the early 70's Marshalls have much higher plate voltages, in excess of 500vdc.
duesentrieb
Well-known member
Yo, my 1970 SB has 520V or so . . .
MrDan666
Active member
duesentrieb":26hey198 said:
Nice!
I definitely need to pickup an early 70's SB or SL at some point, love those amps!
tonmazz
New member
Whatever it is, I got hit with it the other day while biasing my new tubes. Never felt a whack like that before. Youch! 
Loudness250
New member
Thanks for the feedback. I was also curious since now I have confirmed that the reissue has a lower plate voltage. Does this change the sound or the attack/feel of the amp since the reissue is running 40volts or so lower than the originals?
duesentrieb
Well-known member
Less PV = earlier distortion of the preamp (if the preamp has the same values, normally it has), looser (spelling?) feel.
stratotone
Active member
I'll measure mine tonight (72 100w SL, 74 50w SL). Recently did a recap with F&Ts on my '72, but I used a 32/32 for the preamp filter instead of a 50/50. Gave it a TOUCH more sag... I really dig it. Something to think about when recap time comes around.
My 74 is getting recapped in a few weeks, going to 32/32 it also.
Pete
My 74 is getting recapped in a few weeks, going to 32/32 it also.
Pete
duesentrieb
Well-known member
Few designers today are doing this (of course there are exceptions - Cameron, Bogner, most of those who are trying to get an oldschool Plexi-ish thing), but in the minute they are producing some more units than small boutique manufacturers, tube-reliabililty issues make things bad. MAss producers on the other hand are selling their higher PV amps with very cold bias to get rid of it . . .
Diezel reduced the voltages lately from 480V to 450-460V for this reason. Its just too hard to find sufficent quantities of tubes which are good (robust) enough.
With some tweaks here and there (using the preamp tube data sheets and some calculations) it is possible to achieve almost identical results with those lower voltages though IMO.
IMO the OT can get close to "'late-'70s-JMP-sounds" by tweaking the inter-B+-Rs in the preamp a bit to lower values by reading off the plate volts in the preamp of an older JMP and then adjust his reissue - and he should use well selected =C=.
Diezel reduced the voltages lately from 480V to 450-460V for this reason. Its just too hard to find sufficent quantities of tubes which are good (robust) enough.
With some tweaks here and there (using the preamp tube data sheets and some calculations) it is possible to achieve almost identical results with those lower voltages though IMO.
IMO the OT can get close to "'late-'70s-JMP-sounds" by tweaking the inter-B+-Rs in the preamp a bit to lower values by reading off the plate volts in the preamp of an older JMP and then adjust his reissue - and he should use well selected =C=.
killertone
Well-known member
My '77 JMP 2203 running 6550s is around 475V.
On those amps running over 500V, especially running EL34s. it must be hard to find curent production tubes to use as most are not rated for over 500V.
On those amps running over 500V, especially running EL34s. it must be hard to find curent production tubes to use as most are not rated for over 500V.
duesentrieb
Well-known member
http://www.hifitubes.nl/weblog/wp-conte ... a-el34.pdf
A standard EL34 made after Telefunken specs normally handles a PV of 800V - but just screen volts of 500V - and most power amps are designed after the typical Marshall 100s power amp where PV is almost equal to SV. So its more the SV which limits its use - and while the Svet =C= handles 500V SV max, most other tubes just handle 450V SV max.
Its worse for 6L6GCs . . . often PV is max 450V.
A standard EL34 made after Telefunken specs normally handles a PV of 800V - but just screen volts of 500V - and most power amps are designed after the typical Marshall 100s power amp where PV is almost equal to SV. So its more the SV which limits its use - and while the Svet =C= handles 500V SV max, most other tubes just handle 450V SV max.
Its worse for 6L6GCs . . . often PV is max 450V.
stratotone
Active member
Kevin O'Connor's ultimate tone book had a way of rewiring the socket on a Marshall for more reliability - it was more like the Traynor setup. If I start popping tubes I may do that... never did get a chance last night to measure voltage but will try tonight.
Pete
Pete
Greazygeo
Well-known member
My old Orange OR120 was over 600 pv and no standby.....it went thru tubes fairly often. My plexis are all over 500 with the current line voltage. I use a variac now set at 110v and the voltages are lower. The amps seem much happier.
Digital Jams
New member
Damn, good information going on here.