5e7 build - where to use carbon comp resistors?

[Gibsonman63]

I just had an original on my bench. The 5E7 originally had a selenium rectifier instead of a silicone diode. The selenium rectifier has a greater breakover voltage, so you may have to adjust your bias resistor. If I was building from scratch, I would just put a bias pot in it and be done.

[ChopSauce]

Leo did it that way, thus, that way is best, and all other ways sucketh.

The fact is that - best or not - it is the way it was done. So if you clone it, you should use CC (mostly) anywherere.

Many people build improved tweed amps, which are better amps than the originals with respect to some criteria, but which do not sound like the originals.

I read the commented post as this, at least.

[M Fowler]

When I build an old circuit like the tweed Fenders I use NOS carbon comp from Steve Slater at Apexjr

Mark

[Colossal]

Alright sorry, I've never built anything with carbon composition resistors. There was just a guy at an old electronics store in Atlanta where I would buy some parts and that is what he said. He built some tweed stuff and swore by them. I stand corrected. I don't want any extra noise myself, and I'm not happy with the white noise in certain amps but sometimes it's just part of the gain. I'll shut up.

I feel like, when I started building about 10 years ago, that there were still a few "vintage cork sniffers" in town, who held similar beliefs, like, "Leo did it that way, thus, that way is best, and all other ways sucketh." Seems like the cork sniffers are a dying breed around here...or at least, around me...and the musicians who remain much prefer tone, low noise, and reliability over snake oil.

Just for that crack, young man, my next build is gonna be all carbon comp.

carboncomp.jpg

[xtian]

Just for that crack, young man, my next build is gonna be all carbon comp

My plan is already working. Bwaaaa ha ha ha!

[Charlie Wilson]

Count me in as a cork sniffer. Not just any carbon comp, use Allen Bradley. New production carbon comp are awful.
CW

[wpaulvogel]

I hope I didn’t tick anyone off with my input about the need for the cc resistors.
I’ve never played a 5E3. Do they really sound that good? I’ve heard a lot of tracks and like what I hear but I make recordings of my stuff and it sounds different than live. I’m thinking about building another amp but with 6K6GT output. I’ve got the right transformers and want just a simple gain stage tone volume gain stage into a long tailed pair into output. Maybe I’ll make 10 watts. Just simple.

[xtian]

No problem. That's what we're here for!

I just sold my third or forth 5e3 build. I like them, but they suit a particular style. Not much clean headroom, lots of brownish distortion available. My builds had combined Volume and Tone controls, and MOSFET B+ reducers, to set plate voltage at ~350. Look up my builds if you're interested: https://ampgarage.com/forum/viewtopic.php?f=6&t=28653

Also look at Supro 6424T--the Jimmy Page amp. About 10 watts, great distortion at full volume: https://ampgarage.com/forum/viewtopic.php?f=6&t=31639

[ginomolinari]

OK, I had to put the 5E7 project on hold for a little because the "music" room also happens to be the guest room. But now it's on again. I did appreciated everyone comment and I read mr Keen article about carbon composition resistors. He mentions that the right use of CC resistors would be for PLATE and PRE PHASE INVERTER. I still don't know for sure what exactly he is referring to. The preamp tubes have 100K plate resistors, but what about the the 6L6? And what constitutes a pre-phase inverter? I would areally appreciate any pointers.
Thank you.

In the mean time I am sending a pic of the stage I am at. The metal film resistors are shorter than the CC ones so I had to connect them to the legs of the 25mF caps. Is that acceptable?

Thanks again.

[martin manning]

He mentions that the right use of CC resistors would be for PLATE and PRE PHASE INVERTER. I still don't know for sure what exactly he is referring to. The preamp tubes have 100K plate resistors, but what about the the 6L6? And what constitutes a pre-phase inverter?

He means before the phase inverter in the signal flow, and not in the power stage.

[ginomolinari]

So, everywhere before the second 0.1mF cap? Looking at the layout and starting from the right.
Sorry I am learning as I go.
Thanks.

[martin manning]

There is one location that fits RG's recommendation, the 100k plate load on the second tube socket (pin 1 to pin 6). The 100k cathode resistor on the board connected to that same tube's pin 8 might be a candidate too, since it will have 140V or so across it.

Are those old electrolytics any good? That is not a component that gets better with age.

[Colossal]

Are those old electrolytics any good? That is not a component that gets better with age.

I was wondering about that myself. Best just to carefully open the old apacitor and repackage it with a new one inside, preserving the outer covering.

[ginomolinari]

Thanks! Yeah those capacitors look suspicious. They are old but never used. The guy who gave them to me said that if current never passes trough their shelf life is longer.

[Roe]

Thanks! Yeah those capacitors look suspicious. They are old but never used. The guy who gave them to me said that if current never passes trough their shelf life is longer.

old filter caps should be reformed. try a 100k resistor between the cap and the power source. wait til the voltage across the 100k drops to ca 5v. for more info see threads on forming caps on the metro board by larry/novosibir (who's also a member here)