• TalkBass has been independent since 1998. Add your voice.
    Create a free account to reply to discussions, view embedded media, and browse with fewer display ads.
    Join free Log in
    Want zero display ads or expanded classifieds tools? Compare plans.

[Ampeg B15R] Following Jess Oliver's advice...

#21
Ok, just as an addendum & to clarify... been thinking about what I'm trying to accomplish. And this about sums it up: sometimes I feel like my amp has almost TOO much low end.

When this happens, I feel like I have trouble hearing the fundamental. Again, I am using this B15R strictly as a recording amp. A typical chain would be Sennheiser 421 (few inches off the grill) into a Trident or Neve channel into SSL converters. Occasionally I use an RE20. I'll mix the mic'ed bass with the DI (watching for phase) most of the time, but not always. Then compress a bit with my favorite plug-ins in the box. Amp is always set on 60 watts, and I've got the stock Groove Tube 6l6 tubes (with the back switch set to 6l6).

Amp is always on a custom-built acoustically decoupled riser (although I've tried it on the floor, on carpet, etc.) My main basses are an early '70s Tele ('50s Precision-style modded with an extra Jazz pickup) and a sweet early '70s Epi Hollow body. But this amp has seen tons of basses and bass players... you name it, it's gone through this amp.

Anyway - my B15r already sounds really good. This is all about going that last extra mile and getting the fundamental to sing a bit more (and eliminate some of the unneeded sub-bass). I'd like the bass to sit in the pocket with absolute ease on recordings, which is what these amps are known for.

Hope that helps the conversation (it's helped me to crystalize things as well)... so is the tube swap for EL34's the holy grail I'm after? I'm thinking it's worth a try first.
 
#22
Problem is that the fundamental has much less energy that the first harmonic. Add to that the fact that the cabinet will be cutting off the lower frequencies.

As for the 6L6GC I have to admit it's not one of my favourites. In the UK I growed up with the EL34 and the KT66/88. in my own designs I do use the 6L6GC but it's an option similar to your amp.

If you look at your output stage you'll see pin one of the output sockets is grounded or should be for EL34 pentode. A better option is to return all the pin one connections to the raw neg bias rail. This will run the suppressor grid at a negative potential and promote stability in the stage. As the 6L6GC has no pin one connection this change will not impact operation with those tubes.
 
#23
I emailed Bruce at Fliptops about making a replacement baffle for the R, to make it like an N. Here's his response:

Yes we can make a converter to make it like a Double baffle cabinet.Price for a baffle with just port slots is 75.00, price to complete conversion to double baffle is 125.00 (has both slotted port baffle and front grill/baffle air diverter.* Would need dimensions from you on the original baffle and front grill width, and height.
Click to expand...
 
#25
I've been waiting for this info for months (as evidenced by that prev thread on the baffle). Thanks all for getting some extra details! I actually went to Mark @ VB instead of Fliptops and he seemed to know little of the R compared to vintage models, but Bruce seems totally gung ho on it. Maybe, they'll offer it as a stock option in their catalog if enough of us jump on it.

As for the tubes, been wanting to convert to EL34s too but have not gotten around to it (the B15R sounds pretty damn good stock). Would love to hear some more feedback from anyone who gives it a go. I might just do it in the next few weeks.
 
#26
Triboost said:
Holy moly... that's awesome. Who's going to be the first guinea pig to try this?!

I must admit, I'm tempted... but will try new tubes first (leaning towards the JJ's right now).
Click to expand...

Well, it probably won't be me. If I get confirmation that my 6CA7s will work as subs for EL34s, I'm going to try that, first.

Plus, I'm getting myself together to move across the country at the end of the month. So, money for a baffle and a new speaker, plus time to do the surgery will be scarce for a while.

Speaking of which, I've always heard that a driver that is intended for a sealed enclosure would not be the same as a driver intended for a ported enclosure. At least, that's what I've read many times on the Crutchfield site, regarding drivers for subwoofers. So, my thought is that, if I put in the ported baffle, I would really want to also get a new driver at the same time, rather than re-using the OEM one. Am I correct on this?
 
#27
StuartV said:
Well, it probably won't be me. If I get confirmation that my 6CA7s will work as subs for EL34s, I'm going to try that, first.
Click to expand...

While the EL34 and the 6CA7 are regarded as equivalents they are not the same tube. The 6CA7 is a beam tetrode while the EL34 is a pentode. They do tend to be pretty much interchangeable but you should check/reset the bias appropriately.
 
#28
Thanks, Paul. So, you would expect them to be biased differently?

The extent of my ability to bias a B-15R is to flip the switch on the back from the 6L6 setting to the EL34 setting. If that's not good enough, to use 6CA7s, then maybe I just won't use them. :-)
 
#29
Triboost,
I used the JJ E34L tubes as Bob at Eurotubes told me the E34L is better meant more for bass and is the same variant as the standard EL34. It sounded spectacular, and the sound had more bloom to it, as I felt the 6L6's sounded a bit too stiff and sterile.
 
#31
Caca de Kick said:
Triboost,
I used the JJ E34L tubes as Bob at Eurotubes told me the E34L is better meant more for bass and is the same variant as the standard EL34. It sounded spectacular, and the sound had more bloom to it, as I felt the 6L6's sounded a bit too stiff and sterile.
Click to expand...
Caca - Ah, so two variants of EL34's from JJ. Decisions, decisions.

BluDog - Interested in the hearing about your experiences with the standard EL34's when you get 'em.
 
#32
I don't think that anyone has pointed this out - but the B15R has an 8 ohm tap and a four ohm tap. The amp sounds the same at either setting (to me). IIRC Jess's advice was intended for the vintage model without the ohm selector switch.

Aside from the cosmetic similarities - the two amps are very different and as much as I love my vintage B15's - without hesitation I know the R is my favorite.

I too have felt the need to tinker with porting after comparing the stock cab to other cabs in my arsenal - and although I am not done experimenting, I think I am going to go back to stock.

If I did not gig regularly with my B15R (and just used it in the studio), I never would have considered modding the baffle.
 
#33
Triboost said:
I seem to remember Jess Oliver recommending a 4 ohm hi-wattage as a suitable replacement.
Click to expand...

One thing to keep in mind is that the B-15N was designed to run with an 8 ohm speaker. When owners came to him asking if there was a way to get a little more out of the amp, Jess recommended going to a 4 ohm speaker. In gaining a little bit of output power, there is a price to pay in terms of power tube life, stress on the output transformer, and a slight change in the way the amp performs (sounds).

It isn't that he was recommending that it would be better to run the amp with a 4 ohm speaker. When he was involved with the Heritage B15 design, they kept the 8 ohm speaker on an 8 ohm transformer tap. That's what works the best for the design.
 
#34
Yes, this whole conversation has convinced me to stick with an 8 ohm speaker... perhaps the stock one for now. Especially since I don't need to volume boost in the studio.

Going to try out those EL34's next. And wait for a field report on the Fliptop custom baffle - someone's got to be first on that!
 
#35
Bass 45 said:
If I did not gig regularly with my B15R (and just used it in the studio), I never would have considered modding the baffle.
Click to expand...

Why does gigging engender a need or desire for porting?

I thought the reason people want to mod the baffle is to change the tone to more closely match the B-15N. In which case, I would think using it in the studio would be more the case that would prompt doing the double baffle mod. It doesn't seem very likely that people hearing it on a live gig would ever notice the difference in tone between the ported versus non-ported enclosure.
 
#36
Triboost said:
And wait for a field report on the Fliptop custom baffle - someone's got to be first on that!
Click to expand...

And on that, I called Fliptops and talked to Bruce yesterday. I was unclear, from his earlier response, on why I would need to spend the extra $50 for him to make a replacement front grill to go with the replacement baffle. What he said is that the 15R front grill is just a typical frame with grill cloth over it. But, the 15N front grill is a solid piece of wood, with a hole cut out in the middle. The 15N baffle had wooden spacers attached to the front of it so that there is an air gap between the baffle and the grill. This causes the sound that is coming out of the ports to be pushed to the middle to come out of the grill opening.

So, if you want to make the 15R REALLY sound like a 15N, you probably need the ported baffle AND the replacement grill as well.
 
#37
StuartV said:
Why does gigging engender a need or desire for porting?

I thought the reason people want to mod the baffle is to change the tone to more closely match the B-15N. In which case, I would think using it in the studio would be more the case that would prompt doing the double baffle mod. It doesn't seem very likely that people hearing it on a live gig would ever notice the difference in tone between the ported versus non-ported enclosure.
Click to expand...

Generally speaking, I want more volume (db) and efficiency when using an amp in a large room full of people then I think is generally necessary in a recording or practice studio.

I own another cab that is the same size as the B15R's cab and it puts out more volume and low end because it is ported.

The '60's B15N cab is neither louder nor capable of going deeper then the stock B15R cab - so making the cab put out less sound was not the intention in my situation.
 
#39
JimmyM said:
That shouldn't be a reason for not doing something that might prove to be beneficial to the player.
Click to expand...

Agreed. But, if it's for the player, it seems it would be of equal or greater benefit in the studio. And since he said he never would have considered it if he was only using it in the studio, I didn't understand where he was coming from.
 

Latest posts

Top Bottom
Back