Need some treble

solution would be either an equalizer box or preamp with tone controls. 

If there is a tape loop, put a Schiit Loki there

Second the recommendation for a Schiit EQ -- they have three options. The Loki Mini is only $150 and offers four bands. The Lokius is $300 with six bands (and offers balanced XLR in/out as well as RCA) and the top-of-the-line unit is the Loki Max for $1,500 which is six bands but with all the stops pulled out (relay potentiometers, full inductor coils, remote control, etc.)

If you are streaming and using Roon software, Roon DSP is the ultimate tone control.  No special hardware required.

Did you verify that the tweeters in your speakers are working?

Can you adjust your seating position so your ears are at the same level and directed towards your tweeters or tweeter array? I have the same problem and even small adjustments can make an audible difference. Listening near-field will help too if you can.

I'm not streaming. Strictly records and CDs.  Tweeters are working.

My 80 year audiophile friend thought his ears do have problems hearing treble, after bringing the B&W for cleaning . He realize it was his B&W 802 monitor is the problem.

Get a McIntosh integrated. It has very good tone controls.

@sureshmirchand -- just a thought, but one other question for you. How does live unamplified music sound to you?  The reason I ask is that the brain is pretty good about making adjustments as our hearing ages.  I'm in my 70s and hear nothing above roughly 12KHz but live music sounds just as good to me these days as it ever has.  So, if live music still sounds good but your system doesn't, it might be that you need to look at something other than just tweaking treble up.

Add silver interconnect cables.  Preferably Amadi Cables. Maddie signature silver cable.  Great price and quality  . You will get extended clean highs,  perfect mid-range,  very dynamic and extended bass reproduction.  I hope this helps.  

Ear cups

What are your speakers? 

I'll second Philip's post for Amadi.  Have had several pairs of Amadi Maddie Signature ICs and they show very well in the highs because of the silver wire used. They are also excellent at all frequencies so you would be lacking nothing.  They are also a low to mid cost IC.  

Bob

Get hearing aids and put it on a setting called HIFI

What I like beyond the inevitable is it how it makes me back up a few years. Decades even. Just enjoy...

Better audio cables or loudspeakers.

I use a Schiit Loki Max and can't recommend it enough...tweak recordings from your listening chair with its remote, and it works with any system as it's analog adding no detectable noise of its own. 

The B135 has pre-out and main-in jacks. Buy an equalizer. The Schiit ones are good, but a vintage 10 or 12 band in good working order is better. Audio Control, ADC, Soundcraftsman, Pioneer, etc.  Check your local repair shop. Or contact Vince at audioproz.com. His used gear selection is excellent and all tested. 

Schiit Loki +1

Pure diffusers at first reflection points could do wonder for treble clarity.

The Schiit units are returnable if you want to try one.You'll be able to tell immediately if it does what you need. I had the mid priced Lokius for a few weeks but ultimately felt my older less than stellar recordings needed a bit more fine tuning. I ended up with a unit by API that I purchased from Reverb.com.They have many used and new parametric equalizers to research further if you that's something that interests you.

The Schiit Loki Max importantly allows settings control from your listening position with the supplied metal remote. As the remote has a bypass button you can confirm  the quality of circuitry and its lack of degradation on the musical signal.  A heck of a deal at the asking price. 

Hearing aids! Why isn't that the 1st thing to check out?

Hearing aids! Why isn't that the 1st thing to check out?

Are you wearing hearing aids.  If not, it might be time to get your ears checked and perhaps demo a pair to see if that helps.  As we age, we lose our higher frequencies,

I just did a 2-week demo of Phonax Lumity hearing aids, and was surprised how well they worked when I listening to music. They come with an app that lets you control the parameters, including EQ. And you can store personal settings and recall easily.

My hearing was tested and found to be progressively lower after 2KHz, dropping down quite substantially up to 8KHz. Outboard EQ can certainly help, but the aids generally have more amplification than an EQ device, and are custom-designed to counter the measured hearing loss.

That said, they are far more expensive than an outboard EQ. But, at least, you can listen to music alongside another person who doesn’t suffer the loss that you do, and both enjoy the system.

Best, JAMES.

Depending on your speakers and placement, you might be able to get a bit more perceived treble from just toeing them in more towards your listening position.  It's an easy and free adjustment.

What speakers?  I have a suggestion but you must be comfortable getting inside the cabinet and get access to the crossover.  If the tweeter circuit is designed with a choke(resistor), reduce the ohm value a bit.  Maybe 0.5 ohms.  Had to the same myself. 

@sureshmirchand ....an equalizer can 'fix' that high-end 'roll-off' to the degree of another listener noting that everything is beginning to sound 'shrill' to them but ok to you....🙁
If you haven't already, go have your ears checked, generally can be done for free.

The most common 'flaw' in our experience of audio is the age of the listener and the degradation of 'our equipment' in a world of noise.
If you find yourself saying "What?" more of late to people, there's a clue... ;)

Here's a 'quickie cure', meanwhile... 

I've a pair of the earlier 8024's, whereas the 2496 has it on steroids.

Available used....I've some other Behr items, their 'loudspeaker mgmt.' digital x-over is sweet...👍

...does depend upon how one feels about mixing 'phile with pro gear...

I agree to look into modern programmable hearing aids.  They often have music programs that expand the frequency range of the aid and remove filters. The Oticon aids I have do a great job in both normal life situations and listening to music. 

McIntosh has a new 8 band EQ @ 3K...awesome

Suresh

Some great suggestions here, and I have no experience with hearing aids or equalizers. I however can recommend silver cables for increasing treble; either high purity silver, or silver plated. For me personally (since my hearing is not yet fading), they can be a bit much in the detail department....but I could definitely see them as beneficial for needing more emphasis with treble.

Some cables I've tried (some of which I still own): LavriCables, DHLabs, and Zavfino. Those brands seem to offer a very cost effective entry point

This Chase RLC-1 is perfect for a unit with no features. It gives you REMOTE Control of Volume, Balance, Treble, Bass, and has 4 selectable inputs.

Chase RLC-1, MUST have the remote!

No controls on the unit, only buy one with the remote.

No one can ever tell if it is in or out of my systems, I use them differently in 3 systems.

1. Main System: all sources to vintage feature-full tube preamp; preamp out to chase, chase to 1st input of my integrated amp. Select source manually on Preamp, use Chase for Remote Power/Volume/Balance. Preset Integrated Volume and Chase Default volume for my 'normal' volume, use chase for up/dn.

2. Office System: using chase for remote power only so I don't need to walk around my desk, sources direct to integrated, it's push button power button will stay in/on.

3. Shop/Garage system. all sources to Yamaha receiver. chase used for remote power, and optional use of it's features via tape loop (actually my Yamaha has a separate processor loop also). While working, remote volume and remote mute. Here again, you cannot tell if it is in or out of play.

And, last but not least, the Chase unit has automatic and progressive implementation of Fletcher Munson Eq for low volume listening, which boosts both low bass and high treble progressively as volume reduces. This is good for anyone, perfect hearing, due to our hearing's characteristics.

Thank you all for your suggestions - except maybe the one about the earcups.  I've decided to try out one of the Schitt equalizers and see if that solves my problem.  My question is, since I'm only interested in increasing the treble frequencies and not messing with anything else, should I go for the basic Loki Mini*, or is there any reason to get the more expensive Lokius?

For only $299 I would suggest the Lokius with a 6 kHz adjustment for treble and 16khz to add some “air” to the sound. Schiit gear is built incredibly well for the modest asking price. You,after experimenting, may find the other bands on the Lokius to enhance your overall musical experience. All the best!

Agree with @hifiman5 -- the Lokius gives you a bit more flexibility in the upper range. The Loki Mini does 2K and 8K in the treble while the Lokius does 2K, 6K and 16K. Keep in mind that the highest note on a piano is 4,186 Hz. Everything above that is harmonics. Only percussion instruments like snares and cymbals have any fundamental output over that. 

Seems to me that, if you're not hearing high frequencies, boosting them via tone controls may do nothing.

Much like having a null in your listening room. 

My question would be. Do those cymbals reappear when you crank it up a few notches?

Go to Costco (etc) get hearing aids

My high frequencies are attenuated, not non-existent, so boosting them makes sense to me.  Getting ready to order my Lokius.

Sounds like the equalizer is your best bet. It is hard to imagine that putting hearing aides in the loop would result in better sound across the spectrum. 
 

Tell us how this works out for you.

Good advice in above but be careful with EQs and boosting treble. It can burn out tweeters.

Maybe try some super tweeter ad ons. Your pets may not like it, but they can just 

leave the room.