Tweed Champs what do you like?

[rp]

RP, what part were you specifically looking for the specifications for?

I was hoping for the final word on Tweed Champ OTs or at least on the 5F1. I spent a lot of time on this, the word on the web seems to be 5K on the tweeds and 7-8K on BFs. My 5C1 has 5K cause at the time I thought that was right. I've decided 8K sounds authentic to me, but it'd be nice to find someone who could say for sure. You'd think Hammond would have done their research, but you never know with these things, I'm sure guitar OTs are a very tiny part of their income.

[Mark]

I'm still plodding along with my Champ. I have been A/B the stock transformer and the transformer with a larger core size. I decided to use the 4 ohm tap on the transformer with the larger core. The idea being I didn't want to be swayed by the increased output of a 5K primary, so the primary was now effectively 10K.

This still didn't change the response too much, the output from the transformer has more bass and mids. The thing to bear in mind is the amp doesn't sound so ragged as it would with the stock transformer. The amp sounds so much smoother and more like a larger amp than a economy model. I should also mention the negative feedback resistor does pull this raggedness in and I think the 68K used by Gerard Weber in this position is excessive, I'm using 27K at the moment and I suspect something in the order of 33K or 39K would be fine. The amp does break up early without the negative feedback resistor so this is also a factor in choosing a suitable value.

Regarding circuit variations, I found this interesting.

http://www.soundclick.com/bands/page_so ... ID=5100928

http://www.paleoelectronics.com/2008/11 ... gs-second/

[Mark]

This sounds terrible, but I did purposely keep it simple for evaluation.

The recording is of my Strat (everyone has/had a Strat.) I play three chord in one position with the stock transformer and three chords with the Martin Kell transformer. I then move to the next position on the pickup switch and repeat. This is done till all pickup positions have been played.

What are your thoughts on the transformers?

http://www.soundclick.com/bands/page_so ... D=12151927

BTW you might have to download the track, I had a bit of trouble playing it.

[Mark]

I was working on a Valvetrain 205 and I wanted more bass from the amp. In this case the transformers are good but the amp uses a 1uF cap on the first cathode to limit bass response. To my ears the amp came alive with a 4.7uF cap across the first pre-amp cathode resistor and approached lifelessness with a 22uF. I also tried a 10uF but it was much the same as using a 22uF.

I also tried to put a larger cap (100uF) across the eisting 25uF cap. I couldn't get over how this made the amp sound quite lifeless. I dare say bigger isn't always better.

Decreasing the negative feedback helped the amp too, I replaced the 22K NFB resistor, this made the amp sound a bit more lively without it sounding wooly (an Eminence Legend 12' speaker was used in the amp.) The tone control worked better with these mods too.

I'm inclined to believe with the right output transformer and cab a 8" speaker isn't necessarily a bad thing. I suspect a lot of people have taken the non technical option with these amps and simply used a larger speaker where a better O/P transformer was the better option.

[M Fowler]

Not a tweed but I like my cage amp.

http://ampgarage.com/forum/viewtopic.ph ... hamp+aa763

[Mark]

Mark, I reckon they are a great little amp to mod as they are simple and you get a good idea of what does what, there are other challenges such as implementing Gibson Skylark values and seeing if they work for you.

I recently fixed and modded a Valvetrain 205 (Tallboy with 12" Eminence Legend). The first cathode cap and negative feedback resistor changes really opened the amp up.

[img768]http://i149.photobucket.com/albums/s69/ ... 435627.jpg[/img]
[img768]http://i149.photobucket.com/albums/s69/ ... a5c914.jpg[/img]
[img:768:1024]http://i149.photobucket.com/albums/s69/ ... 73d39a.jpg[/img]
[img:768:1024]http://i149.photobucket.com/albums/s69/ ... 1a9bda.jpg[/img]

[Mark]

Getting back to Tweed Champs again as I must.

I've found for the resistor value of 470 ohm to work (or at least work in the 6V6 tubes I have) the rail voltage shouldn't exceed 360VDC.

I am currently turning an old recorder player into a guitar amp. The turntable is gone, but the transformers are still there.

As the output transformer is quite tiny and Gibson amps I'd seen have small output transformers I thought I'd use Skylark values, I'm really surprised how good this little amp sounds.

Just wondering if there is any love for the GA-5 values in a Champ?

[rp]

Just wondering if there is any love for the GA-5 values in a Champ?

Never built one, haven't played one in decades (it's no longer years passing by it's decades) but I remember a cleaner tamer less loud Champ. If you want a tamer Champ it's fun. They sound very nice for recording clean, they are sweet sounding, don't know full tilt, I don't crank old amps with old speakers that aren't mine.

Maybe someone skilled in tube theory can explain how much the 2.2K/220K Kr/Pr really differs from 1.5K/100K. Should take you 20 minutes to find out. Report back.

5F1s own the little SE world, want sweet clean just turn them down to just at break-up and then use your fingers/pick to push and hold back. Their forte is that they have more dynamic life than the others, AC4, GA5 etc.

[Mark]

http://www.ampbooks.com/mobile/amplifie ... capacitor/

There is about two dB difference, or a gain of 15. I'll have to A/B the two values at some stage.