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 Post subject: hot rod deluxe mod suggestion
PostPosted: Tue Nov 23, 2010 1:37 am 
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just like to share a simple mod i did on my hot rod deluxe(not the new generation).
the amp just sings now.sounds way way better now then any other amp in this price point.



so the MOD:
1.replace stock speaker with celestion vintage 30
2.add a 0.0155uf cap parallel to C23 to remove the violent bass cut on the overdrive channel.
3.replace C11 to 270pf to add more highs to the drive
4.put TUNG-SOL 12ax7 Russian reissue in V2 (only tung sol, believe me i tested many others they didn't sound better than the stock sovtek which is surprisingly GOOD!!...)
5. bias the power tubes to 74mV combined

WARNING: DIGGING INSIDE TUBE AMPS WITHOUT KNOWING WHAT YOU ARE DOING CAN KILL YOU!!!!
DRAIN THE CAPS FIRST!


you can skip stages 2 & 3 if you don't want to VOID your warranty. but who cares :lol:

thoughts and opinions are welcome.


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PostPosted: Tue Nov 23, 2010 8:20 am 
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Hi babatube,

Cool stuff! I have played my 98 HRDlx stock for many years, trouble free, before doing any modifications. Very recently I did the popular "Twin Tone" mod (jumper on mid pot), new orange drop tone caps, changed Plate resistors to carbon comp, changed input jacks to Switchcraft metal jacks. While doing some of the mods, I repaired a broken circuit trace, and had to replace the PS caps because a couple were leaking, also added another 47 uF cap to first stage of the PS. I think my tubes are biased around 68-70 mV. Still using the original output tubes and speaker, and the amp still sounds pretty sweet, and great sound with my POD in front of it. I also got an audio taper pot for the master, haven't installed it yet, I don't use the drive channel much. To me the amp sounds best when used on the clean channel with a pedal or POD in front for distortion or drive. Glad to here you're happy with yours too. :D

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PostPosted: Tue Nov 23, 2010 9:31 am 
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I've considered doign something like #2 to my BDRI as it has the same bass cut when using the drive channel. I was just going to just bypass it completely though since it is bypassed when using the clean channel. Any thoughts on the difference between either approach and which might sound better?

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 Post subject:
PostPosted: Tue Nov 23, 2010 11:22 am 
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bluesky636,

I would think that you want some value of cap there instead of bypassing, it is a necessary coupling cap to keep DC out of the signal path. Yes, C23 is bypassed in the clean channel, but then C18 is the coupling cap for the clean channel, so there is always a coupling cap whichever channel is selected. With the parallel cap that the OP installed, the value of both together adds, so now the capacitance is actually higher, not lower. :)

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PostPosted: Tue Nov 23, 2010 12:43 pm 
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shimmilou wrote:
bluesky636,

I would think that you want some value of cap there instead of bypassing, it is a necessary coupling cap to keep DC out of the signal path. Yes, C23 is bypassed in the clean channel, but then C18 is the coupling cap for the clean channel, so there is always a coupling cap whichever channel is selected. With the parallel cap that the OP installed, the value of both together adds, so now the capacitance is actually higher, not lower. :)


Are you looking at a HRD schematic? I am looking at the BDRI schematic I have. The two are different. Here is the link to the BDRI service manual with schematic (page 11):

http://www.blueguitar.org/new/schem/fen ... eissue.pdf

C18 is the DC coupling cap. C23 is the Bright cap. I think C53 is what rolls off the lows in the drive mode. I'm not sure what the Bright cap does in the Drive mode. It supposedly is not active in the Drive mode, but it appears that it can be in the circuit in Drive mode with C53. I have never heard a difference in sound when switching the Bright cap in and out while in Drive mode.

I normally use the clean channel with my SCN equipped Strat. I would like to use the Drive mode with my humbucker equipped guitar so I can balance the volumes of the two guitars without changing anything else on the amp. I have an ECC81 in V2, so there really is not much "drive" effect at the volume levels I play.

OP: Sorry for hijacking your thread. :oops:

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PostPosted: Tue Nov 23, 2010 12:51 pm 
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Sorry bluesky636, I was looking at the HRDlx schematic. :oops: Even more lame of me, you already gave me the correct schematic for the BDRI and I forgot. Carry on.... :lol:

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PostPosted: Tue Nov 23, 2010 12:53 pm 
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shimmilou wrote:
Sorry bluesky636, I was looking at the HRDlx schematic. :oops: Even more lame of me, you already gave me the correct schematic for the BDRI and I forgot. Carry on.... :lol:


So from my post above, does my thinking appear correct?

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PostPosted: Tue Nov 23, 2010 1:23 pm 
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Looks like C53 is bypassed in the clean channel (shorted), so it would only affect the drive channel. The bright cap (C23) should have an affect on both channels, but maybe less so on the drive channel since C53 is active in the drive channel. If you bypass C53, it would sound closer to the clean channel. Changing the value of C53 would only affect the tone of the drive channel, so that sounds right to me. That is the only cap that I see that would affect the tone of the drive channel and not the clean. I think that you want a lower value in C53 for more bass, right?. Maybe half of the value of the original? (I'm guessing) :idea:

Edit:
You know, it would be easy enough to temporarily jumper that cap with some clip leads to test your thinking and see how it would sound, no harm in that. :idea:

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PostPosted: Tue Nov 23, 2010 4:39 pm 
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If you change C53 to a higher value, say 1000pf, it will give you more bass in the drive channel. Going too large here will tend to muddy the tone. I would use a silver mica cap.


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PostPosted: Tue Nov 23, 2010 4:53 pm 
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shimmilou wrote:
Looks like C53 is bypassed in the clean channel (shorted), so it would only affect the drive channel. The bright cap (C23) should have an affect on both channels, but maybe less so on the drive channel since C53 is active in the drive channel. If you bypass C53, it would sound closer to the clean channel. Changing the value of C53 would only affect the tone of the drive channel, so that sounds right to me. That is the only cap that I see that would affect the tone of the drive channel and not the clean. I think that you want a lower value in C53 for more bass, right?. Maybe half of the value of the original? (I'm guessing) :idea:

Edit:
You know, it would be easy enough to temporarily jumper that cap with some clip leads to test your thinking and see how it would sound, no harm in that. :idea:


Well, I have been playing for the last few hours and I don't hear any difference in the Drive channel with the bright switch on or off.

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PostPosted: Tue Nov 23, 2010 4:59 pm 
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rjake wrote:
If you change C53 to a higher value, say 1000pf, it will give you more bass in the drive channel. Going too large here will tend to muddy the tone. I would use a silver mica cap.


That seems reasonable. Also, bear in mind that the BDRI does not have as much gain in the drive channel that an HRD does, so muddy bass is not that much of a problem. I have a ECC81 (12AT7) in V2 so the drive channel has even less overall gain than a stock BDRI. The BDRI drive channel simply disconnects the volume control from V1 so V1 gets overdriven and adds a volume control (and a master later in the chain) that contols the level into 1/2 of V2 (which is primarily used for tone stack gain recovery). The HRD really does have more of a casaded gain path.

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PostPosted: Tue Nov 23, 2010 5:06 pm 
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Quote:
That seems reasonable. Also, bear in mind that the BDRI does not have as much gain in the drive channel that an HRD does, so muddy bass is not that much of a problem. I have a ECC81 (12AT7) in V2 so the drive channel has even less overall gain than a stock BDRI. The BDRI drive channel simply disconnects the volume control from V1 so V1 gets overdriven and adds a volume control (and a master later in the chain) that contols the level into 1/2 of V2 (which is primarily used for tone stack gain recovery). The HRD really does have more of a casaded gain path.


I agree. I've worked on both. A 12AY7 in V1 or V2 and a 12AT7 in the P/I might tickle your fancy also.


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PostPosted: Tue Nov 23, 2010 5:19 pm 
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rjake wrote:
Quote:
That seems reasonable. Also, bear in mind that the BDRI does not have as much gain in the drive channel that an HRD does, so muddy bass is not that much of a problem. I have a ECC81 (12AT7) in V2 so the drive channel has even less overall gain than a stock BDRI. The BDRI drive channel simply disconnects the volume control from V1 so V1 gets overdriven and adds a volume control (and a master later in the chain) that contols the level into 1/2 of V2 (which is primarily used for tone stack gain recovery). The HRD really does have more of a casaded gain path.


I agree. I've worked on both. A 12AY7 in V1 or V2 and a 12AT7 in the P/I might tickle your fancy also.


I tired the 12AT7 in V1 (AXY in both V2 and V3). I did not like it. Lots of clean headroom and quieter, but too sterile. I've thought about puttng an AX7 back in V2 and an AT7 in V3 but am quite happy with the configuration I have now. All tubes are from Eurotubes (Js)J. The bias on the power tubes is kicked up above the factory settings and that makes a big difference.

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PostPosted: Tue Nov 23, 2010 5:35 pm 
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I usually use the 12AT7 in a phase inverter role (V3 in the BD) because of the better current capability, although an old RCA 12AT7 did sound quite good in V2 of my slightly modded '95 Blues Deluxe.


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PostPosted: Tue Nov 23, 2010 5:50 pm 
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rjake wrote:
If you change C53 to a higher value, say 1000pf, it will give you more bass in the drive channel...


Thanks rjake, I had that backwards. Higher capacitance = lower cutoff freq = more low end passed. :wink:

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