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Dynacord Twen/Cathode Bias im Allgemeinen - Mods re. mehr Headroom?

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Racing:
Word of advice for a stocker.

First up the Twens MIGHT carry a groundloop stock.Take a look at if the groundbus running the length of the amp grounds at both the inputjack and the other side of the amp where it´s to run for the centertap/fuse of the stocker.

Second up,whoever designed the positioning of the cathode resistor e-lyte was a friggin idiot. In stock form that electrolyte is a mere few millimeters away from that stinking hot cathode resistor,and to make matters worse that electrolyte is specified to 85degC stock. If you´re to run the amp as cathode bias move that electrolyte as far away from the cathode resistor for the powertubes as you can get it.

As much as i understand that stock is on the agenda here...i´m not all about that.
Someone mentioned Fiat vs Ferrari.
Well.



A generic "Vox" board makes life a little easier when setting the thing up differently. Presentation becomes way more neat too.
Now. Dynacord in their wisdom supplied us with a hole ment for yet another noval already in stock form. It resides just inwards/below the input jacks.
So. Apart from resetting the entire amp as far as topology and making it run fixed bias i also opted to install an EF-86 that can be switched in/out of the circuit to hearts desire. In turn i opted to setup a James network for tonecontrol and lastly..a Celestion Vintage 30 speaker.

https://www.youtube.com/watch?v=KEhLr131ajo&feature=youtu.be

Result is right there. Guitar used is a P90 equipped lespaul copy. Pickups are generic,"vintage", Toneriders. Amp hands you just about 26 watts before clipping.

Recky:
Hi Racing,

thanks for your contribution to this thread. In fact, I have been following your musings on all things Dynacord elsewhere religiously and felt encouraged to check out this first Twen of mine. I wanted to restore it to stock because I wanted to find out what this simple circuit is capable of - I like simple things...  ;)

My Twen actually did suffer from the ground loop you mention, and I duly removed it. The amp was also desperate for a cap job, during which the cathode bias electrolytic cap was upgraded and moved a bit further away from the resistor.

I'm all about a classic/vintage clean and crunchy tone and have since modded the amp for more headroom and a 'creamier' tone. This is the first time I've read up on concertina PIs, and of course I stumbled across Merlin Blencowe's extensive writings on the subject as well as your suggestions with respect to the Twen, I believe, and managed to turn this amp into a truly world-class vintage-tone amp. Obviously, the feeble original speaker had to go and was replaced with a WGS G12C, which I wholly recommend as a vintage Jensen C12N replacement.

I like this amp so much that I'm seriously thinking about building my own from scratch, with a slightly larger cabinet and a better chassis layout.

Cheers,
Recky

Racing:
Thanx!

Ontopic,and mind you...just an opinion...there actually IS one really good German made speaker in my opinion if one´s after the "old school" sound and that is the Isophon P30/37.
A bass speaker from the onset...but as distorted guitar came into the picture,before the 30/37 was conceived, things changed.
Only drawback is that their dB number ain´t all that high...but hey,we´re talking a mid -60´s AlNiCo speaker here. One thing´s for DAMN sure and that is that a P30/37 will hand a Vox blue a run for the money any day of the week. IMO one of the industries well kept secrets.

I´ve modified quite a few Twens by now,to differing stats,and the speaker upgrade is an absolute must. The stock speakers of an old Dynacord (Elbau´s or whatever) simply won´t cut it of modern music in any form is on the agenda.

Ditto for the actual cab,and this holds true for many of Dynacords spawns across time. The Twen in specific IMO has shown its best results when the rear plate is deleted completely.
The amp in the clip above runs a Celestion V-30 (which is a speaker i normally don´t fancy at all) and runs sans the rear plate. Cut a small piece of plywood to act as protection for the tubes and in turn...to hold the speaker out jack.

For the Rex and what not,that runs dual speakers,the cab is to shallow to work with modern day n era speakers and thus...comes to life as you install a divider wall between the two onboard speakers.
Then...we can enter rocknroll territory.

But by all means..yep. Has come to be a Dyna or two that i´ve modded by now. Fantastic value for money as platforms in my opinion.

That said,don´t sell the Twen cheap. They´re great little amps that surely can be turned into "the little engine that could".

Racing:
Btw.
No offense,but feel free to wright in German if you wish. I understand it perfectly well,it´s just way faster to me to wright in English as i was brought up with it.
Hope none of you guys mind that.

Recky:

--- Zitat von: Racing am  2.09.2015 00:27 ---Ontopic,and mind you...just an opinion...there actually IS one really good German made speaker in my opinion if one´s after the "old school" sound and that is the Isophon P30/37.
A bass speaker from the onset...but as distorted guitar came into the picture,before the 30/37 was conceived, things changed.
Only drawback is that their dB number ain´t all that high...but hey,we´re talking a mid -60´s AlNiCo speaker here. One thing´s for DAMN sure and that is that a P30/37 will hand a Vox blue a run for the money any day of the week. IMO one of the industries well kept secrets.

--- Ende Zitat ---

I own two of those P30/37s (Hifi Echolette brand) from an Echolette ET-100 cab and am really quite impressed! As a single speaker, they do not seem to be a very good match for a small combo amp, as they are not very loud, as you say, and their impedance is around 4.5 Oms. My pair, however, is currently living under an Echolette BS40 and waiting for a 2x6V6 or EL84 head i intend to build.


--- Zitat von: Racing am  2.09.2015 00:27 ---Ditto for the actual cab,and this holds true for many of Dynacords spawns across time. The Twen in specific IMO has shown its best results when the rear plate is deleted completely.
The amp in the clip above runs a Celestion V-30 (which is a speaker i normally don´t fancy at all) and runs sans the rear plate. Cut a small piece of plywood to act as protection for the tubes and in turn...to hold the speaker out jack.

--- Ende Zitat ---

I found this out entirely by accident, during my cap 'taste tests', where I forgot to reinstall the back panel and thought 'hey, this sounds really open now'. But it wasn't the cap I had changed... The mini-back panel is a good idea!

Cheers,
Recky

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