2204's , bottom end, and output transformers

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3/20/2000 4:09 PM

Bob S (II)

2204's , bottom end, and output transformers Hiya,     Was reading another thread in this forum, and the subject of installing 100 watt Marshall OT's in 50 watt models was touched upon.This got me wondering, have any of you guys done this switch?     I have a 1987 JCM800 model 2204, and this amp is really kind of light on the bottom end. I've already eliminated the bright caps and tried different values of cathode bypass caps on V1a, but the problem isn't excessive brightness, but rather lack of bottom end punch. It gets better with volume, but is still seriously lacking compared to my 73 Super Lead 100 watter (which has that "punch-in-the-chest" bottom even at low volume).     My question is, will swapping in a 100 watt or repro Plexi OT get me any more bottom out of the 2204?     FWIW, at one point, I rewired the preamp to 1987 specs, but it didn't help the bottom much.     Any thoughts or opinions, I'm all ears!     =Bob

 

3/20/2000 4:56 PM

Trace

quote: "Was reading another thread in this forum, and the subject of installing 100 watt Marshall OT's in 50 watt models was touched upon.This got me wondering, have any of you guys done this switch?"     Ok, let me clear this up (ha, ha) I was the one who stated that I switch "50 watt" (not 100 watt) trannies in place of the stock 50 watt trannies in the JCM2204's. I've done this in a couple of 4-input 50 watters from the 70's as well. I believe someone assumed that I used 100 watt trannies but I do not.     This got mentioned because many people prefer the sound of the 100 watters over the 50's in many different models. For example the 2203/2204's are pretty much identical but the OT's sound different therefore causing a tonal difference. It's often times cheaper to replace the OT in a 2204 than to have the person sell it and try to find a 2203 (which are becoming pretty hard to find, in my experience that is).     I'm sure there's a way to put a 100 watt tranny in a 50 watter and make it work but I've never gone that route before.     quote: "I have a 1987 JCM800 model 2204, and this amp is really kind of light on the bottom end. I've already eliminated the bright caps and tried different values of cathode bypass caps on V1a, but the problem isn't excessive brightness, but rather lack of bottom end punch. It gets better with volume, but is still seriously lacking compared to my 73 Super Lead 100 watter (which has that "punch-in-the-chest" bottom even at low volume)."     You could try a new OT. I seriously doubt you'll be disappointed but you have to make sure it's better than the one that's in there. Personally I think Obsolete Electronics is making the best sounding plexi OT I've heard. It's not a plug but just my opinion Speedracer is the guy who owns the company and he posts here pretty regularly.     quote: "My question is, will swapping in repro Plexi OT get me any more bottom out of the 2204?"     In my opinion "yes", in the 2204's that is. Those amps "fold up" or "compress" mighty quickly and never really sound a tight or punchy as the 2203's do. I've always figured the OT's were made differently but I can not say that as a fact. Maybe Speedracer can shed some light on this??? All I know is they sound totally different to my ears.     quote: "FWIW, at one point, I rewired the preamp to 1987 specs, but it didn't help the bottom much."     I'd replace the OT personally speaking.     I hope this helps   Trace

 

3/20/2000 7:10 PM
Liam	I've been told the PT makes a big difference to this as well. The 2204 being a fair bit lower rated than the 2203. Don't know if it's true. As Trace says, they're vastly different sounding amps.

 

3/20/2000 7:43 PM
Southpaw	I just picked up a 50W plexi repro from Speed. I installed it in a JCM900 modded to "older" specs. The OT replacement was well worth it!

 

3/20/2000 10:33 PM

SpeedRacer

I usually try and stay out of these threads, having what the SEC would no doubt deem a "conflict of interest" issue and all.. that said -     I'm not personally a fan of the 800-900 series 50W OT's and IMHO switching to a different unit will open the amp up dynamically and bring back not only the 'punch' but also enhance your ability to go from "clean to kill" with just the volume pot (if you're using the old style circuits - eg 1986/87/59). The 800-900 series units sound to my ears like they compress more and don't have as much tighness in the bass. To be fair, those amps used different circuits (esp pre-amp) and had different tonal goals than did the now classic 'plexi' style 4-prongers.

 

3/21/2000 12:54 AM
Tonefactor	What cabinet are you using? Through a 4-12 loaded with V-30's, my 1987 has a huge low end, in fact I have to turn the bass down to 2 at higher volumes.

 

3/21/2000 2:54 PM

Richie

Does it make a difference..heck yes..   everything from your fingers on through the amp come to the OT.. and have tried different ones in amps..it does change the sound and tone..or breakup of the amp. I know Speedracer has really dug into finding out about OTs. Speakers make all the difference too. Some of the celestions are way toooooo thin sounding,no matter what you would put in front of them. If i remember right(on my first cup of coffee here) the 100watter and 50 watter Marshall OTs are made by different companies. This also come to mind in a post where someone asked about EL34s and KT66.. and a JTM sounding diferent..or was it MArshall like. It used different transformers too, compared to newer amps.so much of the sound was due to this factor also.   Richie{~}==:::

 

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