Which brand for coupling caps for DR?

[ajeffcote]

Rick,I started my modding with a speaker(Eminence GB12),then tubes,then the output and reverb trannys,then the choke,then the power tranny,then the bias circuit(necessitated by the power tranny)and now tweaking.At each step I have listened to and noticed the improvements.The Mercury Magnetics transformers have made the most difference.They are a little pricey,but they sound good.JMI Music has them at discounted prices and give excellent service.I'm sure there are other brands that are good,but I am sold on MM.

[Rick1114]

After reading these posts I decided to try a few cap changes myself.For C7 I used a 390pf silver mica.I like that one.
R18,an 82K(actally tested at 84.5K),R21 a 10K carbon comp resistor.
Replaced C12 with an Orange Drop same value.
C27 + C28 .047 Orange Drops.Left C10 empty.
I was going to replace the tone stack caps,C8 + C9 but there is not much room there for the OD caps that I have.Also have some Kimber caps that I use for the tone controls in my guitars,but again ,not enough room.
So I guess I need to change C25 according to what I have read so far.Didn't have the right value to put in there.
What is suggested for the tone stack?
I like the changes that I hear so far,although some of the bass did disappear.Is that from the slope resistor change?I am new at this,so this is all experimentation and advice is always welcome.Thanks,Aubrey

I experimented with most of the things you have tried above regarding cap changes. I am pretty new to this as well so it's been a fun learning experience. The bass loss is most likely due to the slope resitor change. You might want to try 90k or go back to stock if you want the "jazzy" bass sound back. If you see Bruce's post below, he recommends .0022 for C25, you won't find better advice thas his. I also changed C8 & C9 to .022 Orange Drop's (I managed to squeezed them in) and I did not like that mod too much - it seemed to add a TS like mid hump that messed with my pedals, so I went back to stock.

WRT the tone stack - I'm still struggling with this amp a bit. It sounds harsh with the stock 100 slope resistor, but swapping with a 90k resistor solves the harshness, but you lose your low bass frequencies...

[Bruce / Mission Amps]

...
WRT the tone stack - I'm still struggling with this amp a bit. It sounds harsh with the stock 100 slope resistor, but swapping with a 90k resistor solves the harshness, but you lose your low bass frequencies...

?? If both of you heard a bass reduction from 100K to 91K.... I'm at a loss as to why.
Using a smaller slope resistor should not reduce the bass, it should increase the bass and low mids.

With respect to the Eminence RWB speaker... I've used a few and I think they are pretty darn good in Fender style amps trying to keep more of the classic or standard Fender ceramic speaker sound.

[Rick1114]

?? If both of you heard a bass reduction from 100K to 91K.... I'm at a loss as to why.
Using a smaller slope resistor should not reduce the bass, it should increase the bass and low mids.

With respect to the Eminence RWB speaker... I've used a few and I think they are pretty darn good in Fender style amps trying to keep more of the classic or standard Fender ceramic speaker sound.

Bruce,

It makes no sense to me either. I used the Tone Stack Calculator to see if could figure it out and it doesn't match up with what I hearing! Even with the bass on 9-10 I can't get those lower bass frequencies back. I'm hearing a noticable bass rolloff with a small value tweak...weird. It's as if the highest & lowest frequencies were both cutoff and it's more focused all together. I do like how the mids and high frequencies sound focused with 90k in there, it has a "modernish" sound, but still Fendery - I just wish I could get the low bass back in there, because there's a lot of mojo in those low bass frequencies!

[Bruce / Mission Amps]

That is odd to me too. Did you do anything else to the cap values or pots in the tone stack?

[ajeffcote]

The only change I made to the tone stack was the treble cap(390pf silver mica),tha slope resistor(82k) and the mids resistor(10k).I replaced C12 with an orange drop,but the same value(.022).Changed the phase inverter coupling caps to orange drops(.047).The loss of bass is not substantial but it is there.Before these changes I would usually set the bass pot between 4 and 5.Now it's at 5 to 6 range.?????????

[ajeffcote]

The bass response now seems to be a little tighter,just not as deep.I kind of like the way it sounds now,but I am going to swap some Mallories in for some of the orange drops and the tone stack caps.At least the bass and mids caps.I'll try that first,leaving the orange drop couplers.

[Rick1114]

After playing the amp some more tonight, I think it's just the added mids "fooling my ear" into thinking there's less bass. When the mids are scooped it gives the impression of more bass. Like ajeffcote, I'm running bass aroung 6-7 with the 90k slope resistor again. I also have a 10k mids resistor, so the combination gives a nice mid boost.

I just ran the reverb to my normal channel so now I have one tonestack stock and one modded. They both sound good!

[ajeffcote]

I would like to make the normal channel on mine into a "tweed channel".Or at least a high er gain,more distortion oriented channel.
Oh,and when I replace C25 with the .0022 cap what change will it make?

[Rick1114]

I would like to make the normal channel on mine into a "tweed channel".Or at least a high er gain,more distortion oriented channel.
Oh,and when I replace C25 with the .0022 cap what change will it make?

It's the phase inverter cap. It just adds a little "phatness" to the tone without throwing anything else off. These DRRI's tend to sound a little thin especially at low volumes and that will help. It is a pretty common mod that is even used on original DR's I think.

I was thinking about doing one "Marshally" channel, but now I'm thinking I'll keep one channel stock and one with the extra mids that I modded (with both channels going to the reverb). The both sound good so why keep screwing with it?

Rick