Guitar amp question

[nhuwar]

That will be remedied Also I'll be using a choke input filter instead of a cap input. The transformer is a little high which is why I decided on the choke input.


Nick

 

[nhuwar]

What type of caps were used as coupling caps in most of those old tube guitar amps?


How will mica caps work for this, I know they aren't good for hifi but how about a guitar amp?

Nick

 

[DaveMcLain]

For a guitar amp anything goes for a coupling cap if it makes a sound that you like..

 

[nhuwar]

Thats what I thought, Just wanted to check around.
Thanks
Nick

 

[llwhtt]

Nick

The transformer dimensions are;

Length=4 1/2"
Height=3 3/4"
Stack=2 7/16"

This transformer is mounted like a Fender output, long side horizontal. The output transformer is about the same for what it's worth.

The voltages measured at 118VAC input which is what this Orange called for. When I biased this amp I first biased it at 118 and figured out the idle Watts per tube then adjusted for the same Wattage at 120VAC input. The DC volts are off a tad (high) because of this.

PT HV winding= 190VAC no load (no output tubes)
#1 HT= 494VDC
#2 HT=492VDC
#3 HT=453VDC
#4 HT=435VDC
#5 HT=405VDC
All DC volts WITH output tubes installed.

Craig

 

[llwhtt]

Just saw you had emailed Mercury Magnetics, they were busy with NAMM last week so maybe the reason for no reply. You need to talk with Paul in sales. Had dinner with him and a bunch of others last night at the Hollywood Gun Club (aka Vitello's, where Robert Blake used to eat).

Craig

 

[nhuwar]

Thanks Craig you have been a big help.

Cool another fellow gun owner on here a, good to know.
I just ordered a output transformer from antique electric supply, it's one for a marshall jcm800. And with the info you gave me I am pretty certain that I have a power transformer on hand that will do the job also.

Nick

 

[llwhtt]

It wasn't a dinner for gun owners, just a gathering of guitar players, amp guys, guitar guys,etc. George Lynch, Howard Leese (Heart), KingsX, Joe Bonamassa, Keith from Buckcherry, Carl Verheyen from Supertramp, and a few more I can't remember. We do this a couple times a year. The Hollywood Gun Club refers to the Robert Blake fiasco. Good food, good drink and good fun.

Craig

 

[DaveMcLain]

I've never spent the money for a Mercury Magnetics or other premium output transformer for a guitar amp but it does make me wonder if it would be worth a try sometime in one of my amps as an experiment.

 

[llwhtt]

All depends on what you are doing. If you are building from scratch with no particular sound in mind I guess any transformer will do and you can can tweak it until it's what you want. However if you have a bad transformer in your $15000 or more Marshall JTM 45 you just can't throw in anything. Even just repairing a normal amp Fender, Vox, Hiwatt you must have the correct transformer, both physically and electrically if you want to keep the same tone. Mercury is just one a few that actually make new "old" transformers. Most of the big companies have gone to China for manufacturing and the transformers have suffered because of the cheap steel. A customer brought in his new Marshall Super Lead because it didn't sound like an old Super Lead. We removed all the extra parts and made it exactly like an old Super Lead, very little change. It wasn't until we installed a Mercury Magnetics old style OPT did it sound like an original Super Lead. Another example, swapped out the OPT in a Peavey Delta Blues (2xEL84) with one of Mercury's Vox AC15 OPTs, made all of the difference in the world. There were 3 or 4 of us there, couldn't believe the difference. I use Mercury because they'll work with you and they are local, shipping large amounts of iron ain't cheap these days. All depends on what you want.

Craig

 

[DaveMcLain]

I have two 1974 Marshall 50 watt tops, a pair with consecutive serial numbers. I've had them since the early '90's and they have been very reliable. I've maintained them carefully, new filter caps etc. I'm using KT66 output tubes in them as well. Both amps sound virtually identical. In back to back tests it's impossible to tell them apart by listening and or playing guitar. What's interesting is that one amp has both of it's original transformers, mains and output yet the other head has had both of them changed over the years. The output had been changed before I owned the amp and the mains about 8 years ago by me. I used a Marshall replacement that I got from New Sensor, not their Taiwan version but the other one. That amp now has a bit more voltage B+ than the other by about 15% yet they still sound the same. The replacement output transformer is one from Chicago Transformer or some outfit like that and it looks a little different.

So from my experience the differences in say the Mercury transformer and a new stock transformer(current production stuff) must be very much different. Is it then that the Mercury ones are made better or deliberately compromised so that they SOUND better in a guitar amp?

Great thread..

 

[llwhtt]

I would say the biggest difference would be between the off shore stuff and the American stuff. Maybe you just got lucky with the higher voltage and that specific OPT. Also I think you'll hear more difference on the 100 Watt because of the differences between four output tubes. There are many people out there changing their reissue xfmrs to aftermarket xfmrs, be it Mercury, Heyboer or OEI, if they're still around. It's a combination of the steel and windings.

Craig

 

[JandG]

All I know is Mercury Magnetics is in my Soldano & it is sweet, of course I have know idea how much the MM iron has to do with it, unless I did a swap. I do think Mike only uses MM , Young & O'Netics..? Heyboer does great copy iron & does go by the original samples & I use them alot. Then again the thumble sized OT's in alot of the old 6v6 SE amps sound superb in saturation mode. Guitar amps are such a fasinating subject, they all sound so very, very differant. = Night & Day type stuff
J & G