Attenuator recommendation

cbakay

Hey guys,

Could anyone suggest a good attenuator that works well with a DRRI65 for my home set up. Open in terms of budget, though hopefully not the price of a new smaller amp.

I want it to get a fuller clean tone, as in I'm not trying to get an overdrive at a low volume. I'm happy with the drive from pedals.

A recent more efficient speaker upgrade means what I got from 2,5 I now get from 2.

Hopefully won't suck the tone but really wanna get the full bodied clean you'd get from say 3,5/4 at the dB level of 2.

thank you! 

ICBM

Does it have the bright cap on the volume control removed? If not that's why it sounds thinner when the volume is lower. It's a simple mod if you can use basic tools.

If that's not what you want to do, a basic L-Pad attenuator will be fine, or one of the cheap Harley Benton ones. If you're not overdriving the amp it's much less critical to find the 'right' one.

erky32

...after a bit of research I'm awaiting delivery of an L-pad from PartsExpress in US, it's for my 18/30 Bassbreaker which is too loud on the clean 30watt side to get power drive. (the 18w drive side is a tad compressed for me)  I ordered a 100watt 16ohm L-pad to give a good safety margin. I'll let you know how it goes when I fit it. My friend lent me a Palmer unit to try. I jumped it between the "main out" (cut int. spkr) and made a speaker lead with two spade conns to jump back into int. spkr. (as discussed with @ICBM )  The Palmer worked really well, but I really prefer a built-in unit. I'm only really taking the top 20% off so the attenuator runs really cool.

normula1

Wilmslow audio do 8 ohm versions.
http://www.wilmslow-audio.co.uk/l-pad-attenuator-at-62sk---19mm-thread-1840-p.asp

the_jaffa

I've recently bought a 2nd hand Jet City Jettenuator to do the same job with my 68 Custom Vibrolux and it works a treat. Sounds great, good amount of control of the volume and means that my pedals work much better with the amp. The Harley Benton ones seem to be the same so look for either.

Babones

The Swart Night Light works as a good home attenuator. I found it better than the Dr Z, which in ime is more suited to shaving off a bit of volume in a gig situation.

zepp76

It's expensive but the Rivera Rock Crusher is a fantastic attenuator, I can bring any of my amps down to reasonable levels while really driving them without any tone sucking whatsoever. 

ThorpyFX

Im selling a 16ohm THD Hot plate if its of any use?

Dodge

Jettenuator / Harley Benton equivalent. I've got a spare one too if you're interested.

rze99

I use THD Hotplates with all my amps and have done for many years. It's great even at low volumes wiht the frequency compensation switches) but not cheap and they are fixed Ohm (which makes them bad value) but they aare very well made and you can sometimes pick them up used (as I have done)

ICBM

rze99 said:

I use THD Hotplates with all my amps and have done for many years. It's great even at low volumes wiht the frequency compensation switches) but not cheap and they are fixed Ohm (which makes them bad value) but they aare very well made and you can sometimes pick them up used (as I have done)

Their only problem is that their impedance curve is wrong, with the deep and especially bright switches on - this makes the impedance significantly below that of a real speaker at high frequencies, which with some amps can put a lot of stress on the power valves. (I've noticed it with Marshalls in particular.)

The solution is to run the amp at one impedance setting below that of the Hotplate, eg 8 ohms for a 16-ohm Hotplate.

ThorpyFX said:

Im selling a 16ohm THD Hot plate if its of any use?

In fact, for a Deluxe Reverb a 16-ohm Hotplate would be ideal rather than 8, because a DR has a mismatched OT ratio and its real output impedance is closer to 16 than 8 ohms - and Fender amps don't mind a low mismatch anyway.

erky32

This impedance matching technology can get very complicated and sticking a variable output resistor like an L-pad into a dynamic output impedance is bound to have compromises. Although I've ordered a 100w 16ohm L-pad for a 30watt 16ohm out put, I feel I've given a high safety margin. Also considering its for live use so I will only be dumping say, 25% max as heat. But after reading various threads on the subject, I just have a slight sense of doubt that a simple L-pad inserted could put some risk on the output txfmr, but maybe only if used at high attenuation levels? I think what I'm planning to do is no different from the lower priced attenuators like HBs or JCA, (unless they have a more refined power dump not entirely relying on the Lpad? - I dont know!) certainly not as sophisticated as the Weber with its dynamic impedance, but I'm open to comments on the safety/risk aspect if anyone has any offerings. 

ICBM

erky32 said:

This impedance matching technology can get very complicated and sticking a variable output resistor like an L-pad into a dynamic output impedance is bound to have compromises. Although I've ordered a 100w 16ohm L-pad for a 30watt 16ohm out put, I feel I've given a high safety margin. Also considering its for live use so I will only be dumping say, 25% max as heat. But after reading various threads on the subject, I just have a slight sense of doubt that a simple L-pad inserted could put some risk on the output txfmr, but maybe only if used at high attenuation levels? I think what I'm planning to do is no different from the lower priced attenuators like HBs or JCA, (unless they have a more refined power dump not entirely relying on the Lpad? - I dont know!) certainly not as sophisticated as the Weber with its dynamic impedance, but I'm open to comments on the safety/risk aspect if anyone has any offerings.

Unfortunately none of those things are true.

The '100W' L-Pads that are normally available are not capable of dissipating 100W of electrical power - they're rated for the system power in a 'music' application (clean signal with peaks several times higher than the average), and as far as I understand they were originally intended as treble or midrange attenuators, so they're only expected to handle a fraction of that power. Having looked at the physical size of them I would guess the electrical power rating is well under 50W, and maybe as low as 25W. What I should really do is test one to destruction and find out where it fails…

A 30W amp could be putting out a lot more than 30W of electrical power too - fully overdriven, up to about 50W is possible. You also aren't only turning 25% into heat - at only 3dB attenuation, which is about the minimum useful even for live use, 50% of the amp's power is going into the attenuator… at 6dB it's 75%. So you have little to no safety margin at all, and quite possibly the other way round.

But L-Pads actually do give quite a safe loading on the OT, in fact - being purely resistive there are no problems with changing impedance with frequency, or voltage/current phase shifts - as long as you don't burn it out.

Don't be fooled by the marketing hype about the Webers either - they're mostly resistive, the speaker coil only acts as a small part of the load and isn't very important. I haven't been very impressed by the build quality of the ones I've seen either, although the bigger models are better.

Exorcist

Another vote for the 'jettenuator' works great with my Fuchs, my old VHT and my Engator.

erky32

ICBM said:

erky32 said:

This impedance matching technology can get very complicated and sticking a variable output resistor like an L-pad into a dynamic output impedance is bound to have compromises. Although I've ordered a 100w 16ohm L-pad for a 30watt 16ohm out put, I feel I've given a high safety margin. Also considering its for live use so I will only be dumping say, 25% max as heat. But after reading various threads on the subject, I just have a slight sense of doubt that a simple L-pad inserted could put some risk on the output txfmr, but maybe only if used at high attenuation levels? I think what I'm planning to do is no different from the lower priced attenuators like HBs or JCA, (unless they have a more refined power dump not entirely relying on the Lpad? - I dont know!) certainly not as sophisticated as the Weber with its dynamic impedance, but I'm open to comments on the safety/risk aspect if anyone has any offerings.

Unfortunately none of those things are true.

The '100W' L-Pads that are normally available are not capable of dissipating 100W of electrical power - they're rated for the system power in a 'music' application (clean signal with peaks several times higher than the average), and as far as I understand they were originally intended as treble or midrange attenuators, so they're only expected to handle a fraction of that power. Having looked at the physical size of them I would guess the electrical power rating is well under 50W, and maybe as low as 25W. What I should really do is test one to destruction and find out where it fails…

A 30W amp could be putting out a lot more than 30W of electrical power too - fully overdriven, up to about 50W is possible. You also aren't only turning 25% into heat - at only 3dB attenuation, which is about the minimum useful even for live use, 50% of the amp's power is going into the attenuator… at 6dB it's 75%. So you have little to no safety margin at all, and quite possibly the other way round.

But L-Pads actually do give quite a safe loading on the OT, in fact - being purely resistive there are no problems with changing impedance with frequency, or voltage/current phase shifts - as long as you don't burn it out.

Don't be fooled by the marketing hype about the Webers either - they're mostly resistive, the speaker coil only acts as a small part of the load and isn't very important. I haven't been very impressed by the build quality of the ones I've seen either, although the bigger models are better.

Thanks @ICBM , another good insight to potential pitfalls!! ....I normally run the BB around 12 o'clock on the volume, so hopefully not totally peaking. Do you think good heatsinking on the L-pad should dissipate, or help. As I'd said previously, borrowing my mates Palmer PDI 06 barely got even warm (even down at 60%). I've already got the L-pad en-route from US so I'd like to try using it, ...do you think there would be any way to help it by adding power resistors/network around it ?

ICBM

Give it a try and see how hot it gets - if you're not pushing the amp really hard that will make a fair difference. The standard L-Pads are difficult to heatsink because they're mounted only by the bushing, you just have to make sure they're well-ventilated.

erky32

Cheers mon, ...I think I owe you a pint or two if ever our paths cross!! ....much appreciated! ...I'll let you know how it goes.

erky32

UPDATE: A friend of mine gave me a P&P 100w attenuator. It was really made for domestic/bedroom use I think, - the ranges started at -12dB and stepped down to -30dB, so the ranges were not really of any use for a loud 30watt amp for gigging. I decided to modify it for my use & integrated my recently purchased 100w L-pad. With good recognition of @ICBM thoughts I lightened its workload by building a potential divider around of 40ohms & 4.7ohms, which gave me a -3dB cut, then put the L-pad across the 47ohm. The result was damn near exactly what I wanted, altho' the -3dB cut was hardly perceivable, the L-pad pulled the driven volume into a small gig venue level. So I'm getting some sweet sounds from the BB 18/30 clean channel now running around 12 o'clock, without blowing the windows out!!  I only use the L-pad in its first 30% so heating doesnt seem to be an issue.
Further info: I'd already tried a Palmer att'r which worked well, also peeked inside to see some neat well built gubbins inside- a stark contrast to the garage quality build of the P&P which looked like an experimental lash up! - best thing I did for it was to recycle it ! (they're not cheap either!)
I'm undecided now whether to build my homebrewed attenuator into the BB, or just carry on using drive pedals at the front of this very solid/simple valve amp, the driven sound is different but both are acceptable drive sounds, - the biggest difference I guess is the simplicity of power-valve drive, it's fun just to plug a guitar straight into the amp and use the guitar dynamics/volume to bring in the drive. But if you need pedals for wah/tuners/delay/chorus etc then a couple of extra pedals for overdrive are ok for gigging!
It's been an interesting experiment!

FarleyUK

For anyone else looking for an attenuator, I cannot recommend the PAN PB1 enough; got it from the US, and it's amazing. No tone loss, and works incredibly well, and is multi-ohm:

https://www.amazon.com/KLD-AMPS-PB-1-ATTENUATOR-CRANKED/dp/B009DUH4E8

PonchoGreg

Have been using a big L-pad with my 68 DRRI for a couple of years now. Same application (taking the edge off so I can push it to maybe 3-4 at home instead of 2 for a fuller sound and a bit of compression). Works a treat, robs a bit of highs but easy to compensate.

I fitted the pad in a computer PSU enclosure so I could use a fan if needed to cool it. Never felt the need for it.

For maybe £20 in parts and 5mins of drilling/soldering, can't complain. 

Dominic

Dr Z brakelite worked well for me and very affordable