Bushmaster HP MOD B4 & after

[StanleyB]

It's getting cold out there and time to think of something to do indoors. That gave me the excuse to upgrade the headphone amplifier section of the Bushmaster. Someone on AoS offered to be the guinea pig and give me an unbiased and personal opinion of the mod that I have done.

Picture of the smaller original caps and the larger Nichicon equivalent. The 100uF and 47uF are shown.

http://www.homehifi.co.uk/aos/CAPS.jpg

The unmodified headphone amplifier section

http://www.homehifi.co.uk/aos/B4MOD-900.jpg

The modified headphone amp

http://www.homehifi.co.uk/aos/AFTERALL-900.jpg

[DSJR]

Stan: Can't you do this at manufacture, since these Nichicons seem good to me as well?

[StanleyB]

Most people never use the headphone section and would balk at having to pay £50 or more extra for the unused pleasure.

[NRG]

Stan, what was the mod you did to mine?

[StanleyB]

Stan, what was the mod you did to mine?:eyebrows:

[StanleyB]

http://www.homehifi.co.uk/aos/nichicon.jpg

I have finished replacing all the electrolytics that I picked up from the Far East and eBay. Not all of them are the original value though. I also increased the power supply filtering circuit by changing the chokes from 2.2mH to 10mH.

Update
After listening to this mod for two days I am so impressed by the improvements that I am going to make up one or two kits with all the required parts. If there are any genuine DIYers with the right tools and with the proper skills to copy this mod who would like to try it out for themselves then let me know. You'll have to provide some pictures and a write up as well to show how you did your upgrade.

[worrasf]

OK so my BM arrived back from Stan and I've had chance to have a listen over the last 3 hours.

Stan had already had it running for many hours on test before sending it back but I also let things warm up for an hour before listening commenced.

I used my Grado HD1000's and for comparison my Graham Slee Solo SRG/PSU1.
Initially I listend to 2 or 3 tracks of each CD and after a while "hot swapped" between the 2 amps when I was convinced I'd got the volume's equally matched.

First up Einaudi's "Nightbook" - the BM sounded detailed and delicate but the piano sounded more like an upright than a Grand Steinway - the Slee had more depth and authority - the cellos's sounded more resonant and tuneful. On the other hand the percussion on the BM was tighter and brighter but overall I preferred the Slee.

Then came Page & Plant "No Quarter" - again the BM showed a delicacy in the midrange with more fine detail with percussion - the emotion in Plant's voice was more obvious but the overall presentation seemed a bit thin and less "interesting"

Next up Nils Molevar's "Khemer" the pathos and emotion was very similar but the trumpet sounded a bit "plasticky" with the BM whereas it had the brass timbre that made it recognisable as a trumpet with the Slee - at this stage I was definitely preferring the Slee - the sound being more to my taste.

Female vocals and acoustic guitar was provided by Thea Gilmore on "Murphy's Heart" - here the BM just started to sing - there was so much more expression in her voice, more air and detail, less "muddle" in the mix - definitely a "nicer" presentation than with the Slee. Similar findings on Mark Knopfler's "Killing to get crimson" - better separation, bass was more controlled and tuneful - more involving.

So I went back to "Nightbook" and "Khemer" and now the depth of the piano was there and the resonance of the brass trumpet as well! But in addition the delicacy and fine detail of percussion was still present.

Going back to "No Quarter" PRaT was better with the BM, I was tapping my foot and "getting into the mood" on the track "Morning dew" so much more than with the Slee.

So - once warmed up a bit more the BM presents music (to my ears and through the Grados) in a more neutral, delicate, detailed involving way than the Slee. Solo vocals have more emotion and expression and the timing seems more accurate giving an overall more enjoyable experience. I think that because of the better clarity (less muddle and confusion in the mix) it will be more relaxing for extended listening.

One thing I mentioned to stan before the mod was that the BM was "noisier" than the Slee when playing loud - background noise was quite evident. Not any more, if anything its less obvious than on the Slee at the same volume

Now Stan setup the BM specifically to match the low impedance of my Grados - the comparison using my Beyer DT990 600 ohm may be different.

So overall and after very limited time the new mod is superb - when you consider the cost and rave reviews of Slee/PSU1 the BM with this mod is an absolute bargain. My only problem is that now I am preferring to use the headphones via the BM I can't use it for my vinyl system. Mind you, it's a bit rich to complain when the Slee Solo SRG/PSU1 is still a fabulous headphone amp.

Steve

[StanleyB]

Bear in mind that the mod Steve is trying out is limited to mods of the headphone caps. I hadn't yet received the parts to let him try out the full recap mod. Those bits arrived a few days too late for me to hang on to his DAC. The full recap is a lot more analogue.

[Fi-Wi]

Thanks for sharing your review Stephen, that sounds very promising.

Does the full recap mod involve the overall (headphone and non-headphone) output?

[StanleyB]

Thanks for sharing your review Stephen, that sounds very promising.

Does the full recap mod involve the overall (headphone and non-headphone) output?
Yes. But the full mod involves more than just changing caps. At this moment in time I do the full mod by myself so that I can make sure that it is done properly and that the outcome is consistent, clearly audible, and passes the big grin test.

[Ammonite Audio]

Since I'm looking at ordering a Bushmaster specifically for use as a headphone amp, what would the cost be of one (with silver grey front) fitted with all your recommended mods?

[StanleyB]

I only intend to do the mod on a Bushmaster that the owner has had time to burn in and confirm that it is working fine.
As for cost: it's a sin on many forums to mention cost outside of the trade section. I accidentally violated that rule on a few forums due to the lenient principles on AoS. So PM or email me when it comes to prices. I also only have a mere handful of kits to do the mods, and so far half of them are already allocated.

[ukemaxxer]

http://www.homehifi.co.uk/aos/nichicon.jpg

I have finished replacing all the electrolytics that I picked up from the Far East and eBay. Not all of them are the original value though. I also increased the power supply filtering circuit by changing the chokes from 2.2mH to 10mH.

Update
After listening to this mod for two days I am so impressed by the improvements that I am going to make up one or two kits with all the required parts. If there are any genuine DIYers with the right tools and with the proper skills to copy this mod who would like to try it out for themselves then let me know. You'll have to provide some pictures and a write up as well to show how you did your upgrade.

Hi Stan,

My Bushmaster is used exclusively on my Senheiser HD650's. I purchased the Bushmaster after I had built a Panda headphone amp. I now wish I had seen your offering before the Panda, as that never gets used now! The headphone stage on the Bushmaster is already better than the Panda, but if it can be improved upon, then I'm in.

I would be very interested in carrying out the mods, I have all the necessary kit required, and have been working in electronics as an engineer both audio and industrial control stuff since 1982.

Pics are of the Panda Headphone amp kit.

http://i1056.photobucket.com/albums/t361/ukemaxxer/IMG_1330.jpg

http://i1056.photobucket.com/albums/t361/ukemaxxer/IMG_1286.jpg

http://i1056.photobucket.com/albums/t361/ukemaxxer/IMG_1339.jpg

[Søren]

Stan, are we going to see a diagram and a parts list on this, anytime soon?

[StanleyB]

I have bought the various required parts in a small quantity. If anyone wants to try out the mod then I suggest that you get in touch with me via PM or email. I figured out that if people have to buy several pieces of a cap when they only need one or more, and then factor in the cost of postage for each part they order, the mod will be too expensive to implement. So I can knock up a parts kit for you. Each component comes in a little bag and the board location of that part is written on the bag. I also include a modded firmware that takes account of the new power supply readings.
The price of the kit works out at £15 posted to the UK or £18 to the continent. There is no profit taking on my part on the sale of the kit. Those Nichicon caps didn't come cheap I am afraid.

Note an update to the price of the headphone mod parts. I had previously posted the cost of the complete Venom mod parts.

[Ammonite Audio]

I'm looking forward to hearing my Bushmaster after Stan has upgraded its headphone circuitry with these mods.

[Søren]

Awaiting parts for the full upgrade. I will post my impressions when it is done.

[Fi-Wi]

Are there any first impressions that are worth sharing with the curious among us?

[sq225917]

Stan, I ahve to applaud you on offering a group buy for this. Always good to see designers standing behind upgrades to their gear, it's a great way of adding further value.

[ukemaxxer]

Gents, I have recently done the full mod supplied by Stan on my Bushmaster.
Quite easy mod to do, as long as you know your way round a circuit board.

My DAC was well burnt in, so I knew the sound well. However, I still picked a few well known tracks from my playlist, and listened to them over and over before fitting the parts.

There is definitely more bass once these parts are installed, also there appears to me more attack to the bass notes. Sorry, can't do all that flowery musicality description! This is not at the expense of the mids or highs though.

I'm using mine with Sennheiser HD650's exclusively, it is not connected to any other amps.

I already loved the Bushmaster, now it's even better.
If you are considering the mod, go for it.

A few pics of the before and after.

The unmolested item!
http://i1056.photobucket.com/albums/t361/ukemaxxer/20121110_153022.jpg

I chose to remove all the components to be replaced at once, if you are unsure, just go one at a time.
http://i1056.photobucket.com/albums/t361/ukemaxxer/20121110_165002.jpg

For the reassembly, I started with the surface mount replacement Wima's
http://i1056.photobucket.com/albums/t361/ukemaxxer/20121110_170652.jpg

Some of the spacing between components is a little tight.
http://i1056.photobucket.com/albums/t361/ukemaxxer/20121110_172725.jpg

http://i1056.photobucket.com/albums/t361/ukemaxxer/20121110_172733.jpg

Job done. Pop the lid on and burn in again.
http://i1056.photobucket.com/albums/t361/ukemaxxer/20121110_172706.jpg

Mine has probably had a few hundred hours on it now, I am well happy with the results.

Cheers

[mkrzych]

It's getting cold out there and time to think of something to do indoors. That gave me the excuse to upgrade the headphone amplifier section of the Bushmaster. Someone on AoS offered to be the guinea pig and give me an unbiased and personal opinion of the mod that I have done.

Picture of the smaller original caps and the larger Nichicon equivalent. The 100uF and 47uF are shown.

http://www.homehifi.co.uk/aos/CAPS.jpg

The unmodified headphone amplifier section

http://www.homehifi.co.uk/aos/B4MOD-900.jpg

The modified headphone amp

http://www.homehifi.co.uk/aos/AFTERALL-900.jpg

Is it something worth to try with Caiman II as well in your opinion Stan?