[colinharding]

I did replace the volume pots (and the knobs). Figured with all the work going in it would be silly not to put in some high quality pots.

Think I had a post a while back where I pictured the specific pots but they are TKD (not stepped as that would defeat the purpose of two knobs where you want fine balance between the channels).

 

[colinharding]

I've printed out an earlier post detailing a few steps to minimising noise in this amp and handed it, with amp, to a local technician. I'll have to ask them to wrap the transformers also.

Did you replace the volume pots or just the exterior knobs?

Interested to see what your technician has done to the amp once he's done.

Took a look at the caps you wanted to use in an earlier post - not sure how you'll get those to work as the highest value is only 22uF. What did you end up going with for the full list of mods for your technician?

 

[adeadcrab]

Interested to see what your technician has done to the amp once he's done.

Took a look at the caps you wanted to use in an earlier post - not sure how you'll get those to work as the highest value is only 22uF. What did you end up going with for the full list of mods for your technician?

Did I post those Jantzen here? Yeah I know they're not suitable, I'm not recommending any cap upgrades for the technician as I'm not really looking to alter the actual sound of the amp, it's already much clearer and detailed to my ears than the original. I just want the background noise cleaned up.

I've asked them to do steps 1,2,3 of the aforementioned post - rewiring, DC heater and HV Supply Filtering.
Once that's done I'll ask to continue the job with copper wrapped transformers and DC heater for the power tubes if possible. The volume knobs I'll probably leave as is unless I get a good reason from someone else as to how a replacement is better.

 

[colinharding]

Steps 1, 2, 3 will definitely improve the amp - think you'll be really happy there. To totally get rid of the noise the flux band wrap for the transformer is a must. I'd tell your technician to prioritize that over the elevated heater as I'm positive that had the greatest effect on the noise reduction. I'd also make sure that your tech re-does the wiring topology. Currently it's all routed around the the chassis and you want it to go directly under the 820uF filter caps for a 'Y' topology. This also reduced my noise quite a bit.

All the electrolytics you're going to leave as is then? I found that changing them didn't necessarily alter the sound - it unleashed what the amp was really capable of and just gave you more of what you already like in the amp. Moving the 820uF filtering caps to 1000uF helped the dynamics and reduced background noise to a degree - didn't alter the sound though. Probably worth doing for what you're after. Changing the last 220uF cap and the associated resistors probably had the greatest effect on altering the sound. Here you can choose based on what you want, thicker, more detailed, airier, etc to ensure you 'guide' the sound of the amp further in the direction you're after. It's only going to move you 5% - MAYBE 10% in a different direction. Again you're mostly just letting the amp perform better, not really altering the sound.

Volume pots are up to you, with all the work going and the money spent it just seemed logical to replace them with high quality ones to ensure they aren't a bottleneck in any way. Think the ones in there are MEC and only cost a few bucks a piece. Also didn't like how hard they were to turn, though once the amp warms up it seems to warm the grease up in those pots and they become much easier to adjust.

 

[adeadcrab]

Steps 1, 2, 3 will definitely improve the amp - think you'll be really happy there. To totally get rid of the noise the flux band wrap for the transformer is a must. I'd tell your technician to prioritize that over the elevated heater as I'm positive that had the greatest effect on the noise reduction. I'd also make sure that your tech re-does the wiring topology. Currently it's all routed around the the chassis and you want it to go directly under the 820uF filter caps for a 'Y' topology. This also reduced my noise quite a bit.

All the electrolytics you're going to leave as is then? I found that changing them didn't necessarily alter the sound - it unleashed what the amp was really capable of and just gave you more of what you already like in the amp. Moving the 820uF filtering caps to 1000uF helped the dynamics and reduced background noise to a degree - didn't alter the sound though. Probably worth doing for what you're after. Changing the last 220uF cap and the associated resistors probably had the greatest effect on altering the sound. Here you can choose based on what you want, thicker, more detailed, airier, etc to ensure you 'guide' the sound of the amp further in the direction you're after. It's only going to move you 5% - MAYBE 10% in a different direction. Again you're mostly just letting the amp perform better, not really altering the sound.

Volume pots are up to you, with all the work going and the money spent it just seemed logical to replace them with high quality ones to ensure they aren't a bottleneck in any way. Think the ones in there are MEC and only cost a few bucks a piece. Also didn't like how hard they were to turn, though once the amp warms up it seems to warm the grease up in those pots and they become much easier to adjust.

Thanks for the info on caps; if I can improve the detail retrieval and transparency I'll ask the tech and see what we can do. Volume pots too, why not? May as well get everything changed now rather than some now, some later.

 

[colinharding]

Yeah may as well. To do everything you want you kinda have to take most of the amp apart anyway. May as well just do it while you're in there as it will be easy at that point. Will cost a lot more to have the tech go back in and reroute wires etc after he/she has already put it back together.

I'd suggest changing the coupling caps as well - I haven't actually done this yet so cannot comment on performance increases. But moving from ~160uF to 220uF should give you better bass extension. Can't decide between the mundorf or the clarity caps. @L0rdGwyn used clarity caps in his gorgeous Airmid OTL as the coupling caps - I'm sure he picked those for good reason. He also used 6J5 for the input tubes - something I'm also looking to do if I can figure out the pinout and associated rewire.

 

[colinharding]

Went with the TC Claritycap line for the coupling caps. Fitting these should be a challenge to say the least.

Interested to see if this makes a perceptible improvement in sound quality - though it should as at a bare minimum the capacitance is moving from ~160uF to 230 (220 only came in 800VDC - way too large).

Post this the only other 'improvement' I'll seek to make is changing the input tubes from 6SJ7 to 6J5. Will report back when I've received the new caps and put them in place.

@adeadcrab - can't wait to see your amp (and hear your impressions) when you get it back from the tech!

 

[colinharding]

Zip ties for effect I’ll find a more secure method of attaching these beasts, just wanted to test them out first before a full commitment.

 

[Galapac]

Zip ties for effect I’ll find a more secure method of attaching these beasts, just wanted to test them out first before a full commitment.

Wow I don’t recognize that amp anymore. I guess you can’t use the old housing anymore.
How does it sound with the Clarity Caps? L0rdGwyn swears by them.

 

[colinharding]

Lol I think the tube sockets are the only pieces on this machine that are left untouched at this point.

I had tried the mundorf first and they were pretty dull sounding, really neutral and the highs came through a bit bright (220uf non oil impregnated version). Moved to these and it really opened up, much more dynamic and 3D sounding. With either cap - the amount of extra impact you get moving to 220uf is noticeable and totally worth it.

This will all be tested however as I’ve the chance to listen to my amp vs a stock 339i tonight. Guess we’ll see how much is in my head as opposed to quantifiably better.

 

[Galapac]

They say Mundorfs take a bit of time to break in and settle but not sure if that is true or you get used to them.

 

[colinharding]

Yeah I’d heard the same, though this would be the second project I’ve tried them in with similar result. The mundorfs I used have about 150 hours in them so they should be broken in by now. First time with the clarity caps and have been impressed right out the gate with them.

 

[hp4fun]

Zip ties for effect I’ll find a more secure method of attaching these beasts, just wanted to test them out first before a full commitment.

Did I see a Melos at the back?

 

[colinharding]

Did I see a Melos at the back?

You certainly do

Melos MA-333. Primarily used as a preamp for my mono system, though I also use it as a headphone amp (not its intended design). RCAs output so much current it can easily drive headphones.

 

[colinharding]

Contrary to popular belief you can run this amp with 6J5 if you have an adapter. No modifications are necessary to the circuit. Believe telecaster took the 30ohm to 33ohm and the 200ohm down to 100ohm. I already have the 33ohm resistor installed (mine had come with that value originally anyway) and the 200ohm - have no issues running a 6J5. Friend of mine built the adapter - it was a quick and dirty job bit works well!!

For the test of my 339 vs an original one. As expected mine was just much more of the same. Sound signature was a bit warmer with my component choices but it heavily accentuated all aspects of the original 339 we love. Sound was deeper, more impactful, wider, etc. Worth the effort it took in my opinion.