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If you think this amp is too bright sounding try this mod .Open er up find C6 cap and cut .Pull it back slightly. Now fire it up and listen to the difference.If that is not enough Cut C5 [.This was enough for me ].Again not enough C10 [.have not gone here yet .] The brightness is gone the EQ way more tweak-able .I am Jumping between Tung-sol 5881's and a THD yellow jacket with el84's that's right 84's with these this amp cooks .Also Weber speaker diffusers and for God sake put it on an amp stand .This is a jaw dropping experience .This is how this amp is supposed to sound

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I definitly agree with you about the amp stand. Got mine sitting on top of a couple milk crates. Makes quite a difference.

 

I haven't found it to be too bright though but I'm sure it could use some tweeks and better components.

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Going to do more mods today. This is for an EL34 tube swap.Should be correct.First Ground tube pins #1 Then replace Resistors R45 &R46 With 1K /5Watt .Then R42 & R43 With 5.6 - 1/2 watt I should now be able to switch between EL34's and 6L6's .I have been wanting to try this for awhile any comments??

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Anybody knows where i can find a schematic on these amp?I want to see if i could do a good harp amp out of it.

You say it's too bright to you guitarists and then its probably awful to harp.:-({|= But thats a real challenge](*,)

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http://www.ppwatt.com/files/ppwatt/EPIPHONE_BLUES_CUSTOM_30_SCHEMATIC_VER01_DPPT.pdf This is where I found mine .I play some harp through this amp it's so/so. You would be betteroff playing through a Mic'ed 5 watt amp.I'll try it with the EL84's and let you know

 

I was wondering about mods a while back and was looking for schematics. Couldn't find any at the time. Gibson/Epiphone actually has schematics on their site but not for all of their amps. Go figure. Are these accurate?

 

And does anyone know if there are different versions of this amp? Some reviews I've seen online seem to say BC30's bought more recently have a slightly different sound and come with different stock tubes. Anyone?

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Yes the schematic is accurate.So are the mods.Although tubes will make some difference it's the other mods that do the trick .I'm just waiting for the 1K resistors to come in then onto the El34 mod

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I was wondering about mods a while back and was looking for schematics. Couldn't find any at the time. Gibson/Epiphone actually has schematics on their site but not for all of their amps. Go figure. Are these accurate?

 

And does anyone know if there are different versions of this amp? Some reviews I've seen online seem to say BC30's bought more recently have a slightly different sound and come with different stock tubes. Anyone?

 

The later ones come with Sovtek 6L6's rather than 5881's. I haven't heard one of the earlier ones but there certainly wasn't the 'ice pickiness' in the tone that people remarked on when I got mine so poss the vale change made a difference.

 

Dumping the Sovteks and the Chinese Rectifier for some vintage valves certainly sorted the tone out with mine. I'm on the hunt for some vintage ECC83's at a sensible price now to complete the package.

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The real difference between 6l6 and 5881's is that the 5881's will break up a little earlier[ imop.] from the testing I have done .But these amps are made on the bright side according to Gibson r&d depart. That's why i clipped some caps To lesson the brightness these amps are made to do .With the next mod I'm working on I will be able to add EL34's for some British flavor .I also tested with EL84's Very articulate Breaks up much sooner for that deep tube drive. But more defined drive. Bass all the way up ,Trem at 12:00 and Mids from 1 to 3:00 depending on the song I would say more of a Vox AC30. Roll back the volume and you definitely get a Marshall tone .I fired up a Fender Bass man for a side by side using a Tele and if you closed your eyes you would be hard pressed to tell the difference

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Well you guys got me curious so I brought my bc30 home from where my band reherses and did the c6 mod. I removed one leg from the circuit board instead of clipping it. Thought it would be easier that way in case I ever want to put it back in. Did a smoke test after that but I won't really be able to take it for a test drive until Tuesday.

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Ok here's a post from another site about EL34 tube swap idea I've been toying with .What do you think ??? An chanOK Tremo, here's the amp specs, straight from Pyotr Belov:

 

Straight out of the Box BC30 with stock Sovtek 5881 - Line Voltage 120

 

Sovtek 5881 Plate 23W dissipation + Screen 3W dissipation.

 

B+ Voltage - 406VDC - Measured from Pin 3 to ground

 

Plate Voltage - 375VDC Measured from Plate to Cathode

 

Screen Voltage - 374 VDC Measured Pin 4 to Cathode

 

Cathode Voltage - 31VDC - Measured from Cathode to ground

 

Cathode Bias Resistor - 250 Ohm Rated 25W

 

Cathode Current - 62mA per tube

 

These specs were at idle.

 

I spoke with Pyotr on the phone tonight. He seemed to favor the 6L6GC for a replacement output tube, but he said that any 5881/6L6GC should be alright in this amp. While we were on the phone, Pyotr popped in a pair of EL34's and got these numbers: B+ 396v, Plate 367V,

28.5v Cathode voltage, 57mA per tube, Line Voltage 116v.

 

I'm going to run these numbers by Lord Valve to get his opinion....minus the 6550 recomendation that is...ce of op trans failure?or do you think it will handle it?

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I think this is what your looking for.http://www.ppwatt.com/files/ppwatt/E...VER01_DPPT.pdf

 

That'll get it.

 

Let's do this conservatively. Remove ONE cap, then play and see if it's better (to your ears) or still needs less brightness. If it needs less, remove one more and then re-play. Etc.

 

First - remove C6.

 

Second - C5

 

Third - C10.

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to answer my own question, it does not appear to be wired to take EL 34. If anyone wants to try that, first off you need to make the following mods:

 

1. - Hard wire pins 1 and 8 together on the output tube sockets, or better yet, hard wire pins 1 straight to ground.

 

2. - Change R45, & 46 to 1k/5W.

 

3. - Change R42, & 43 to 5.6k/1/2 W

 

 

With these mods, you can go back and forth between EL34 and 6L6 by just swapping the tubes.

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Ok this is where i'm at I did the cap mods .Im thinking about the EL34 mod .My Question is can the Output trany handle it?

 

That is indeed a good question. The OT still isn't designed for the 3.2k impedance EL34's like. Probably closer to 4k. The optimal bias for EL34 might require resistor R44 swapped for 120R, 25W, which would potentially draw 50ma more current through the OT. That extra 50ma could overheat the OT and eventually kill it.

 

Another big question is how long would the PT last supplying an extra 1A of heater current? A day? A week? Forever? Can't say till somebody does it and reports back. If the amp had started with EL34's, it'd be easy to go down the pecking order of tubes as it were. But by going uphill from 5881/6L6 to EL34, you may be forcing yourself into a corner that's gonna require buying all new iron for that thing. Is it worth it?

 

Gil...

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That's what has me going . I think I'm going to let this one go. I have a Carvin T 100 with 34's and an ADA MP-1 pre that I would like to piggyback to the Bc .I'm also going to isolate the speakers so I can use either amp with a splitter. I am also looking into an effects loop and maybe a vibrato I think this amp should have had one . Have you looked at the schematic of this amp? And if so Where would you add the loop?[ Someone said maybe Kt77's ] I had to give it one more shot.:- Thanks Gil

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The KT88, 6550, KT77, KT66, EL34 all fall under the "more" category. I'm afraid you're pretty much stuck with 6L6, 5881, and 6V6 on the low end.

 

http://tdsl.duncanamps.com/tubesearch.php

 

As far as adding an FX loop goes, there really isn't a good place to throw in a passive loop like we did on the VJr, and there isn't a typical cathode follower stage for properly driving a loop unless you want to make your own. If you want to add the tube (or 3SB board) and circuitry for a driver and recovery stage, I'd recommend inserting it before the reverb send.

 

A Vibrato circuit is gonna be yet another tube. Honestly, if you want an AB763, ya might as well just gut it and start fresh. Or keep it for what it is and get to butchering a fresh chassis.

 

Gil...

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