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Post subject: Re: New Amp Build - Trainwreck Express Clone
Posted: Sat Sep 07, 2013 4:49 pm
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Retroverbial wrote:
bluesky636 wrote:
1. The tone controls need more range to them. They are good at levels below about 6, but when the volume is dimed, they lose their effectiveness.


This is often the case, even with Leo's original designs. However, extending the boost range may be detrimental to the S/N ratio.


Yes, that is a concern. Considering that I don't gig and don't play the amp with the gain set to 12, I'm not sure I want to make any changes. There are some differences between the Wrecking Ball tone stack and a 5F6A tone stack (the treble cap and bass pot values are different) that I can easily model to see the effect of any changes.

bluesky636 wrote:
2. The amp has too much gain in the front end.


Retroverbial wrote:
If you haven't already given them a go, you might try 5751's and/or 12AY7's in the V1 and/or V2 sockets.


I tried a 5751 in V1 when I was initially testing out the amp and felt that it dropped the gain too much. Again, that was when I was having problems with oscillations and noise. It might be different now. I'll also run some calculations with different cathode resistors and un-bypassed/fully bypassed cathode resistors.

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Post subject: Re: New Amp Build - Trainwreck Express Clone
Posted: Sat Sep 07, 2013 4:58 pm
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The impromptu "field demo" seems to have proven useful for highlighting a meager few purported deficiencies.

Hopefully, everything will "click together" soon.

Rawk on!

8)

Arjay

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Post subject: Re: New Amp Build - Trainwreck Express Clone
Posted: Sat Sep 07, 2013 6:43 pm
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I'm kind of torn as to how much I want to change things mainly because no one plays these amps with the gain maxed out. By 4 or 5 on the volume control with any decent pickup there is plenty of overdrive. My Strat with SCNs really sounds good at that level. My humbucker equipped guitars can create plenty of drive with the amp gain set at 3 to 4. Turning the guitar volume down at those amp levels results in a really nice clean sound. The amp is pretty compressed by 6 and by 7 or 8 there is really no more volume, just more compression. What's really nice though is that the overdrive and compression has no fizziness at all. It is very thick and full sounding. The more I read about the Hall VVR, the more I am interested in it, though. I could install it in place of the second speaker output jack and not mess up the front of the amp.

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Post subject: Re: New Amp Build - Trainwreck Express Clone
Posted: Sat Sep 07, 2013 11:26 pm
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I installed one of those vvr's in my 18w Marshall clone and rarely use it. At least in my application it tends to cut out the high frequencies. Although I've read that where you install it in the circuit plays a big part on how it will affect the tone. I have it installed in series with the stand by switch on mine.
Hope this helps

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Post subject: Re: New Amp Build - Trainwreck Express Clone
Posted: Sat Sep 07, 2013 11:56 pm
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Bluesky,

Ever try a pair of 6V6GTs in that EL34 amp? You need a tough pair (like NOS 6V6GTA or GTY) & rebias to around 7-10 watts per tube. Be interesting to see what the OD tone would be like.


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Post subject: Re: New Amp Build - Trainwreck Express Clone
Posted: Sun Sep 08, 2013 8:38 am
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socal323 wrote:
I installed one of those vvr's in my 18w Marshall clone and rarely use it. At least in my application it tends to cut out the high frequencies. Although I've read that where you install it in the circuit plays a big part on how it will affect the tone. I have it installed in series with the stand by switch on mine.
Hope this helps


Thanks for the info. I've been looking at some You-Tube demos and as always, they are quite variable. Which version do you have? Is your amp cathode or fixed bias? I have e-mailed Hall Amplification for more information on the VVR and sent them a copy of my schematic to get their advice. $50 is not bad for the device.

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Post subject: Re: New Amp Build - Trainwreck Express Clone
Posted: Sun Sep 08, 2013 8:42 am
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BMW2002Ti wrote:
Bluesky,

Ever try a pair of 6V6GTs in that EL34 amp? You need a tough pair (like NOS 6V6GTA or GTY) & rebias to around 7-10 watts per tube. Be interesting to see what the OD tone would be like.


I considered that when I built the amp and found a few demos on You-Tube with Express type amps using 6V6s. I wasn't really that impressed. The EL34s just had more of everything. I have been considering putting some 6V6s into my BDRI though. Then I would have 6L6, 6V6, and EL34 based amps. Not a fan of EL84 based amps.

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Post subject: Re: New Amp Build - Trainwreck Express Clone
Posted: Sun Sep 08, 2013 9:02 am
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bluesky636 wrote:
...I have been considering putting some 6V6s into my BDRI...


EH :D

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Post subject: Re: New Amp Build - Trainwreck Express Clone
Posted: Sun Sep 08, 2013 9:59 am
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shimmilou wrote:
bluesky636 wrote:
...I have been considering putting some 6V6s into my BDRI...


EH :D



Are you Canadian? I thought you were from Indiana. :lol: :lol: :lol: :lol:

Yes, Electro-Harmonix. The JJs are too 6L6-like. Although I do have a JJ 6V6S in my Champion 600 and it sounds really nice.

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Post subject: Re: New Amp Build - Trainwreck Express Clone
Posted: Sun Sep 08, 2013 4:09 pm
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Bluesky,

The JJ 6V6S sounds good in many cathode-biased, Class "A," single-ended amps. Maybe because of the higher headroom of the tube, which has a more 5881-tone than a true 6V6GT tone. In push-pull setups you lose that creamy midrange and gradual OD of the Class AB, 6V6GT amp.

NOS Tungsol or RCA 6V6GTA have a cleaner top end with better bass, than a typical 6V6GT. Nearly all 6V6GTY have a more potent tone, too. Both keep that nice rich midrange tone.

FWIW...


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Post subject: Re: New Amp Build - Trainwreck Express Clone
Posted: Sun Sep 08, 2013 4:33 pm
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BMW2002Ti wrote:
Bluesky,

The JJ 6V6S sounds good in many cathode-biased, Class "A," single-ended amps. Maybe because of the higher headroom of the tube, which has a more 5881-tone than a true 6V6GT tone. In push-pull setups you lose that creamy midrange and gradual OD of the Class AB, 6V6GT amp.

NOS Tungsol or RCA 6V6GTA have a cleaner top end with better bass, than a typical 6V6GT. Nearly all 6V6GTY have a more potent tone, too. Both keep that nice rich midrange tone.

FWIW...


See my BDRI mod thread:

viewtopic.php?f=13&t=80142

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Post subject: Re: New Amp Build - Trainwreck Express Clone
Posted: Sun Sep 08, 2013 4:52 pm
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bluesky636 wrote:
socal323 wrote:
I installed one of those vvr's in my 18w Marshall clone and rarely use it. At least in my application it tends to cut out the high frequencies. Although I've read that where you install it in the circuit plays a big part on how it will affect the tone. I have it installed in series with the stand by switch on mine.
Hope this helps


Thanks for the info. I've been looking at some You-Tube demos and as always, they are quite variable. Which version do you have? Is your amp cathode or fixed bias? I have e-mailed Hall Amplification for more information on the VVR and sent them a copy of my schematic to get their advice. $50 is not bad for the device.



Bill,
I don't remember the version I have but here is a link to the schematic for my 18w clone build. I installed the vvr's after the stand by switch. The amp is cathode biased.
http://mhuss.com/18watt/schematics/18wattLite2b.gif
Hope this helps.

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Post subject: Re: New Amp Build - Trainwreck Express Clone
Posted: Sun Sep 08, 2013 5:11 pm
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Location: Natural Bridge, Virginia
socal323 wrote:
bluesky636 wrote:
socal323 wrote:
I installed one of those vvr's in my 18w Marshall clone and rarely use it. At least in my application it tends to cut out the high frequencies. Although I've read that where you install it in the circuit plays a big part on how it will affect the tone. I have it installed in series with the stand by switch on mine.
Hope this helps


Thanks for the info. I've been looking at some You-Tube demos and as always, they are quite variable. Which version do you have? Is your amp cathode or fixed bias? I have e-mailed Hall Amplification for more information on the VVR and sent them a copy of my schematic to get their advice. $50 is not bad for the device.



Bill,
I don't remember the version I have but here is a link to the schematic for my 18w clone build. I installed the vvr's after the stand by switch. The amp is cathode biased.
http://mhuss.com/18watt/schematics/18wattLite2b.gif
Hope this helps.


I see. Ok. Thanks. :D

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Post subject: Re: New Amp Build - Trainwreck Express Clone
Posted: Tue Sep 10, 2013 5:02 pm
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Performed a quick, but interesting experiment tonight with trying lower gain tubes in my amp. The results were surprising and not at all what I expected.

All amp controls were kept at my normal settings:

P = 6, B = 4, M = 5, T = 6, V = 6, Bright = Off. The guitar was my Fender MIM Strat with Fender SCN pickups, plugged straight into the amp.

Stock configuration: V1, V2, V3 = Gold pin JJ ECC83S (12AX7)
Very gainy with a nice, smooth overdrive. Cleaned up nicely as the guitar volume was decreased from 10 to 8 to 6. Nice highs, a little bright but not harsh. Moderate amount of amp hiss.

Test 1: V1 = NOS JAN GE 5751; V2, V3 = Gold pin JJ ECC83S (12AX7)
No real difference in overall gain with guitar volume on 10. This amp has a LOT of gain. Did not seem to have as much compression, though and cleaned up much quicker as guitar volume was lowered. Overall hiss was about the same as stock, but the highs were overly bright and very harsh on the bridge pickup. Overall tone seemed kind of ragged. I did not like this tone.

Test 2: V1, V3 = Gold pin JJ ECC83S (12AX7); V2 = NOS JAN GE 5751
Again, no real difference in overall gain and hiss. Highs did not seem as harsh, but not as smooth as stock. About the same level of compression a test 1, maybe a little more. Tone a little better than test one, but I still did not like it as much as stock.

Test 3: V1, V2 = Gold pin JJ ECC83S (12AX7); V3 = JJ ECC81 (12AT7)
Interestingly enough, there was a noticeable drop in max gain with this configuration. There was still a good overdrive with the guitar on 10, but it was less than the three previous tests. Overall tone was better than test 1 or 2, but not quite as good as stock. This was also the quietest configuration. Highs were almost as smooth as stock and the bass definitely had more punch. Might be almost too much bass with humbuckers. This configuration has promise.

Keep in mind that this was a very quick comparison. I will repeat Test 3 tomorrow with humbuckers. I will try a 12AY7 in V1 or 2 when I have some more time. I don't think more than one lower gain tube (particularly 5751s) will sound good in this amp.

Stay tuned.

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Post subject: Re: New Amp Build - Trainwreck Express Clone
Posted: Wed Sep 11, 2013 4:27 pm
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Did a little more experimenting with a JJ 12AT7 in the PI position.

Maybe I was hitting the strings a little harder tonight than last night as the overall gain did not seem to be much lower than with a 12AX7. The bass is definitely stronger and tighter with the 12AT7 than with a 12AX7. Too much so with humbuckers. I would attribute that to the higher current drive capability of the 12AT7 allowing it to loaf a little when driving the power tubes compared to the 12AX7. The 12AT7 is also definitely a little brighter in this amp. I guess you could say the 12AT7 had a bit of a midrange dip.

I noticed an unusual noise, kind of hard to describe. Sort of like a buzz/rattle that died out real quick. It did not occur after switching back to the 12AX7. When I installed the 12AT7, I put the tube shield on but left the back off the head, so I'm not sure if it was the tube or something in the room. This was the only balanced 12AT7 I have so I didn't try another tube.

I decided to order a pair of JJ gold pin 12AT7s since the sound of the gold pin 12AX7s is definitely better in this amp. However, I'm beginning to believe that with the amount of gain this amp has on tap, I would have to install a really low gain tube, a 12AY7 or lower, and I'm not sure I want to do that. I have 12AY7s installed as V1 in both my BDRI and 5F6A/C Bluesman. All three amps sound very different from each other. We'll see what happens when the new JJs arrive.

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