Recent Posts

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Tube Amp Building - Tweaks - Repairs / Re: 6M5 6EM5 Valves in Push Pull

« Last post by TIMBO on September 08, 2025, 04:44:15 am »

Hey guys, This one is gathering some interest, so I was able to get some shed time on the weekend.

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Tube Amp Building - Tweaks - Repairs / one-tube-reverbers

« Last post by Bieworm on September 08, 2025, 04:06:47 am »

A howl out to the on-tube-reverb experts...

My experience with the 1tube reverb is that each time I try  one in a build they are a lot noisier than a blackface type 2 tube reverb. Is there some magic to be performed to make these more quiet?

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Tube Amp Building - Tweaks - Repairs / How to identify a tube in the ecl/pcl range ???

« Last post by kagliostro on September 08, 2025, 03:51:52 am »

Yesterday I've find in my stock about 10 tubes I got 7 years ago

they are surely NOS, selled without a box (if I remember correctly I payed it really on the cheap)

They are surely triode/pentode tubes but on it there isn't a standard Tube Label, only a number

My memory is I got it as ecl8* or pcl8* tubes but I don't remember if they are the 82 or 84 or 86 models, may be pcl86 but not sure at all 


What can I do to identify it correctly ? (I've an emission tube tester to perform measures, the other one that can measure gm need some manutention)

Many Thanks

Franco

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Tube Amp Building - Tweaks - Repairs / Re: Hum and Buzz in Cordovox Build

« Last post by Platefire on September 07, 2025, 10:46:28 pm »

I'm Sorry!   I sketched the Princeton 5F2A Tone Control.  I thought the 5E3 and the 5F2A tone stacks were the same, but they are a little different

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Tube Amp Building - Tweaks - Repairs / Re: Hum and Buzz in Cordovox Build

« Last post by scstill on September 07, 2025, 06:48:29 pm »

I don't know if this is contributing to the noise but it appears to me the 5E3 tone stack is wired wrong on the schematic?? Double check that anyway

Why did you draw the vol pot before the tone pot? Doesn't 5E3 have the tone first?

Anyway I did correct this tone/vol circuit to match the 5E3. It did not make any difference to the hum.
I corrected this in the original post schematic.

Still hopeful for a solution...

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Tube Amp Building - Tweaks - Repairs / Re: Troubleshooting a new build amp

« Last post by Wardy on September 07, 2025, 05:40:18 pm »

Many Thanks for all the suggestions and looking at this with me. I really appreciate it.

I have to say I'm sorry I have been wasting some of your time due to a stupid mistake.
I realised that I have been using the sine generator I have wrong. It has a DC offset button that is default on and I got 12v dc on the signal as well as the ac. Its not the best and I have a better one on order. I have attached new readings with the thing without the DC. It now looks like I'm actually not getting a bad signal from V1a. The amp is still quiet though and not achieving anything near full power.

It would be helpful if someone could review the readings I have and let me know if they are in the right ballpark or if there is a problem in this part of the circuit or not.

I have also attached an updated Voltage chart with all the grids. V3 is an added single tube reverb circuit and the pin 1 reading is not a typo. I did wonder about this although 460v was specified here on fender blackface amps. They used 12AT7 in parallel though. not a single 12ax7. The reverb is working ok though. after I get the main problem with volume output sorted I'll revisit the reverb and add some mods to better accommodate the high voltage.

best

Steve
 

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Tube Amp Building - Tweaks - Repairs / Re: Blackstar Club 40 - Have you ever seem such a failure?

« Last post by Lectroid on September 07, 2025, 01:54:48 pm »

If it were me...I would just buy another amp OR buy another used Club 40.  They are 250-300 all day long on the used market.  BUT he likes THIS one soooo who I am to judge :)

I'm with you.  I don't like the looks of that cap-stuff.  Btw, I think I know that guy. 

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Tube Amp Building - Tweaks - Repairs / Re: Deluxe 5E3 tone stack

« Last post by Lectroid on September 07, 2025, 01:44:08 pm »

If you put it after a pentode, which has extremely high output impedance, what happens is:

The pentode cannot provide enough current to properly drive the potentiometers and capacitors in the network.
The tone stack heavily loads the anode signal gain collapses and the frequency response becomes unstable.
The result is a choked, unmanageable sound.

Franco, thanks for that great summary.  I still have trouble remembering how important impedance is, how many parts of the circuit it affects.  (everything?)   Your explanation made perfect sense.

Fun discussion! I find the tweed fender 5E3 and 5F2A tone stacks very interesting. They are so simple but can be very effective. On the old tweed amps just the raw signal sounds pretty good without anything added but are sometimes too dark, especially for humbuckers. So this tone stack can throw in just the right amount of sparkle into the mix as needed.

BTW--just a few simple changes, you could get your 5E3/5F2A tone stack back  

It's true.  The 5E3 is so simple, it's like the one-celled organism of tone stacks.  But it works well in my Bell&Howell conversion and does add that sparkle you mentioned.

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Other Topics / Re: Meme of the day

« Last post by shooter on September 07, 2025, 08:24:43 am »

...

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Tube Amp Building - Tweaks - Repairs / Re: Blackstar Club 40 - Have you ever seem such a failure?

« Last post by jukelemon on September 07, 2025, 07:04:40 am »

I may just buy another board if they are still available.  I see them for ~200.00

Is that for an empty board? This could get unreasonably costly - you might want to check back with the owner first.

Oh no no.  Completed board i.e. literally a drop in.

It is what a service center would do in other words.  The caps alone would run ~100.00 (I am not buying cheap caps like what came with it) so I think it makes sense IF he wants to fix it.  I only posted a pic of a few caps.  There are 10 that look just like these which makes me very suspect that other things are going on AND why I think a new board is the way to go as opposed to spending the money on caps only to then find out other components have failed-which is very very common on these amps.

If it were me...I would just buy another amp OR buy another used Club 40.  They are 250-300 all day long on the used market.  BUT he likes THIS one soooo who I am to judge :)