H&K Edition tube 25 mods

psyx

Ok So... I want to mod my amp and I'm looking for some ideas...

Things I like about my amp:
Magical clean tones
Nice hair on the clean channel when cranked
Good compatibility with fuzz pedals
Excellent lower frequencies
Awesome spring reverb from the Accutronics long spring reverb tank

Things I dislike:
The overdrive channel because:
-Its fizzy
-I can't really get alot of usable sounds from it
The fact that the combo speaker works in unison with the external speaker when plugged into a cab
It doesn't have a stand by switch, which causes some strange occurrences when left idle with the volume knob turned down

Soooo...
What I want to do:
Install a switch which can cut out the combo speaker when plugged into a cab
Install a new speaker, it currently has a G12T-100
-Maybe a Celestion Vintage 30?
Install new tubes, currently has NOS Russian EL-84's and some 12AX7's
-Maybe some other NOS tubes which would give a tone with less fizz and some real usable gain?

Any recommendations or comments?
Also, any guys in the Alberton or greater Joburg area you would recommend for the job?

Thanks! ?

Gearhead

I can't find a '25 schematic so quickly, but from the looks of the '20 it has a cathodyne phase splitter with opamp buffer - not exactly the ideal recipe for cool power amp distortion. It will need a bucket of work for this to change. My vote is to replace it instead of modding. You will want to buy a 18 Watt Plexi.

Replacing the speaker is a good idea, but mind the Vintage 30s are a little on the bright side. Fine if you want in-your-face Marshall tone but you will not get sparkly cleans anymore. Rather look at a G12H-30 for a more sixties tone.

Don't worry about getting a standby switch, just turn off your amp when not using it.

psyx

Gearhead wrote: I can't find a '25 schematic so quickly, but from the looks of the '20 it has a cathodyne phase splitter with opamp buffer - not exactly the ideal recipe for cool power amp distortion. It will need a bucket of work for this to change. My vote is to replace it instead of modding. You will want to buy a 18 Watt Plexi.

Replacing the speaker is a good idea, but mind the Vintage 30s are a little on the bright side. Fine if you want in-your-face Marshall tone but you will not get sparkly cleans anymore. Rather look at a G12H-30 for a more sixties tone.

Don't worry about getting a standby switch, just turn off your amp when not using it.

I was worried that it may turn out like that!

Thanx for the info!

Attila

yaa this could be an interesting project and EXPENSIVE.

As GH sez without a schematic on hand it will be pretty much guess work added that you in all likelihood have a PCB construction, which makes it difficult to mod

Speakers will most certainly give you the most dramatic changes, second to changing preamp valves to temper or charge the circuit more.

as an example: Usually placing a lower Mu preamp valve before the PI circuit yields good results but that is dependent on a bunch of stuff.

It would be fun though if time and money was not the deciding factors.

Want the sound of a JM45 - BUY one

psyx

Well I decided to take the modding route, so I took my amp to JP le Roux. He told me that he had worked on amps like mine before and some new JJ tubes and a new speaker yielded some good results.
The other ampbwas fitted with a Celestion G12H, which apparently worked very well... But he said I should also consider the Jensen Blackbird 100Watt Alnico. After alot of reading and Youtube vids, I'm leaning more towards the Blackbird...

Attila

the blackbird is a great speaker I was lucky enough to pick one up in SA for under a "G" which was bargain shmargain for me

psyx

Attila Barath wrote: the blackbird is a great speaker I was lucky enough to pick one up in SA for under a "G" which was bargain shmargain for me

Yikes, thats a bargain! The speaker sure has alot of mojo... Looks pretty impressive with that giant Alnico magnet! With what amp do you use it..? Pros and cons?

Attila

I have it on my dumble style SE at the moment the amp is only an 8 watter max, but was thinking of moving it to my AC30 where it will work harder for sure

I have not really put it though its paces yet, so cons I don't have any at this stage.... but I like it

Infact if you listen to the demo sounds on the Jensen website, the one of the speaker that sounded good/better (to me ) than the rest was the BB.

BTW - your tube and speaker upgrade is going to push your spend close to the R4k mark ....... and you will not necessary find that tone you are chasing ... just saying boss... just saying

psyx

Attila Barath wrote: I have it on my dumble style SE at the moment the amp is only an 8 watter max, but was thinking of moving it to my AC30 where it will work harder for sure

I have not really put it though its paces yet, so cons I don't have any at this stage.... but I like it

Infact if you listen to the demo sounds on the Jensen website, the one of the speaker that sounded good/better (to me ) than the rest was the BB.

BTW - you tube and speaker upgrade is going to push your spend close to the R4k mark ....... and you will not necessary find that tone you are chasing ... just saying boss... just saying

I realise that... However, if I dont like it then I can just pull the speaker and reinstall the old one. Then I can start shopping for a replacement or w/e... However, I'm optimistic that it will deliver some good results. Lets hope I'm right! ?