Tweed Champ Build - In the spirit of Dumble

[ToneMerc]

I finally found a home for those 3 short Sprague Atom 20uF caps that I had lying around.


Magnetic Components PT
Mercury Magnetics OT
RCA 5Y3, 6V6GT
TS RI 12AX7A

121.2 VAC mains

6.84V filament

187.3, 183.5, 1.51

381V/336V, 22.9V

TM

[mhartman]

Looks great (as usual for your builds)!

[dorrisant]

I like it, a lot.

Tony

[ToneMerc]

Thanks guys

TM

[dcribbs1412]

Looks great TM
looks like a deceivingly
sweet little amp.
12" or 10" speaker?

D

[Charlie Wilson]

That looks great Mike. I was wondering if someone was going to do one. Do you like the sound of it? I would like to hear your opinion before I give you my impression of the Dumble one I played through.
CW

[martin manning]

Pardon my ignorance, but what is Dumble about it?

[Colossal]

Looks cool TM. Did you go with the 5k or 8k OT? 12" speaker? how's she sound?

[Charlie Wilson]

Martin, besides the Tweedle D (Dumble modified Tweed Deluxe), Dumble does a much less modified Tweed Champ. He increases the filtering and increases the value of the NFB resistor.
CW

[martin manning]

Ah yes, I remember now there was a bit of discussion on this in the Tweedle Dee 5E3 thread. Thanks. I guess HAD really couldn't find too much to improve on, eh?

[Synchu]

Sweet little amp and great looking build

Mmmm... I have a fried studio monitor distribution box that seems like a good host of a P2P build...

Niki

[rp]

I guess HAD really couldn't find too much to improve on, eh?

To his credit.

[Mark]

Firstly nice build, but that is typical of the caliber of your work. I hope you don't mind me asking a few questions?

Which model Mercury transformers did you use, they make quite a variety.

http://www.mercurymagnetics.com/pages/c ... htm#Champ_

Looking at the Dumble-like version, I wonder if the feedback resistor is doing much or anything, I found the 68K resistor in my amp did very little, I remember liking 33K or 39K.

How come you used carbon comp resistors in the input?

Did you experiment at all with the component values?

What is the plate dissipation of the output tube?

I found my 6V6 output tube was enduring 15 watts of dissipation. I'm not convinced this adds to the tone of the amp. It certainly doesn't effect the clean tone, but when was a Champ about clean tones.

I like using a 6L6 with a 5K transformer (large core too), it's a bit louder and more solid sounding than the 6V6, the trouble is it is brutal upon the power transformer. It runs hotter than the power tube.

I've been a bit obsessed with Champs over the years about getting "that" sound out of them. Here is a link on the madness I endured or created.

http://ampgarage.com/forum/viewtopic.ph ... ight=champ

I think the trick with any Champ build is the transformers used. I'm inclined to not be a big fan of the stock transformers in Champs. I think raising the rail voltage in 59 (PWR TXER secondaries 330-0-330vac) increased mids and bass a little, but the problem was the output transformer, the core is too small.

I think the amp sounded it's best with the rail around 360VDC and the fat stack transformer. I A/Bed the stock transformer and the fat stack transformer to another amp builder, they too preferred the fat stack. They aren't as rattley sounding as the stock transformer.

I pull the amp out to mod every few months. Who was ever entirely happy with an amp?

[ToneMerc]

Firstly nice build, but that is typical of the caliber of your work. I hope you don't mind me asking a few questions?

Which model Mercury transformers did you use, they make quite a variety.

http://www.mercurymagnetics.com/pages/c ... htm#Champ_

Looking at the Dumble-like version, I wonder if the feedback resistor is doing much or anything, I found the 68K resistor in my amp did very little, I remember liking 33K or 39K.

How come you used carbon comp resistors in the input?

Did you experiment at all with the component values?

What is the plate dissipation of the output tube?

I found my 6V6 output tube was enduring 15 watts of dissipation. I'm not convinced this adds to the tone of the amp. It certainly doesn't effect the clean tone, but when was a Champ about clean tones.

I like using a 6L6 with a 5K transformer (large core too), it's a bit louder and more solid sounding than the 6V6, the trouble is it is brutal upon the power transformer. It runs hotter than the power tube.

I've been a bit obsessed with Champs over the years about getting "that" sound out of them. Here is a link on the madness I endured or created.

http://ampgarage.com/forum/viewtopic.ph ... ight=champ

I think the trick with any Champ build is the transformers used. I'm inclined to not be a big fan of the stock transformers in Champs. I think raising the rail voltage in 59 (PWR TXER secondaries 330-0-330vac) increased mids and bass a little, but the problem was the output transformer, the core is too small.

I think the amp sounded it's best with the rail around 360VDC and the fat stack transformer. I A/Bed the stock transformer and the fat stack transformer to another amp builder, they too preferred the fat stack. They aren't as rattley sounding as the stock transformer.

I pull the amp out to mod every few months. Who was ever entirely happy with an amp?

Hi Mark and thanks, honestly I didn't put much effort into this at all. My only goal was to aesthetically mimic HAD's Tweedle Dee Champ with as many parts as possible that I had lying around. For example, the input resistors are A-B 56K(actually 63.3 & 63.4K) verses 68K because I had this value in hand and wasn't going to spend money chasing down two A-B 68K-10% resistors.

The OT is the FTCHO-5.

TM

[Mark]

Good point I missed the 56K resistors, I dare say I was too busy looking at the Charlie Wilson picture.

What are your thoughts on the amp and how does it differ from a typical 5F1 Champ?

I haven't got any recent pictures of my amp, though I have a grid stopper on the output tube a 470 ohm screen grid resistor and a 1 ohm resistor off the cathode to measure current.

Others will disagree but I don't think there is a great tonal difference between correctly biased and the typical over biased Champ. I'm happy to be proven wrong, but I've got two 1K resistors in my amp and there isn't a lot of change switching between 500 ohms and 1K ohms.

What speaker will you use with this amp?

I'm using a 10" Ceramic Weber Silver Bell, it fits into the amp and it has good bass response. I do want to try other speakers with the amp, I did have an original 10" ceramic Weber Signature speaker in the amp, but it was too bright, and that was with a output transformer with a larger core.

Thanks for the post, If you can post audio that would be great if not that's cool too.