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#2898408 - 12/28/17 06:26 PM Re: Feel free to ask Myles [Re: BadLife]
myles_rose Moderator Offline
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Registered: 11/28/01
Posts: 5046
Loc: Los Angeles CA, UNITED STATES
Do you know if V4 is good? Start with that tube.

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#2898409 - 12/28/17 06:28 PM Re: Feel free to ask Myles [Re: CEB]
myles_rose Moderator Offline
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Registered: 11/28/01
Posts: 5046
Loc: Los Angeles CA, UNITED STATES

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#2898416 - 12/28/17 07:08 PM Re: Feel free to ask Myles [Re: myles_rose]
BadLife Offline
Gold Member

Registered: 02/01/06
Posts: 648
Hum is that the 7025 which is 4th from the right looking at the back of the amp or the 12AT7? The 7025 was bad and I replaced it. Before I replaced it the amp was going crazy when the vibrato was on.

That tube was the original as the one installed during the rebuild was bad. It was all frosty looking and the vibrato channel did not work at all if I remember correctly.

I need to order some new Preamp tubes anyway as I have several tube amps as well as two I built from scratch.

I don't get why it goes away at full intensity.

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#2898585 - 12/29/17 09:15 PM Re: Feel free to ask Myles [Re: BadLife]
myles_rose Moderator Offline
MP Hall of Fame Member

Registered: 11/28/01
Posts: 5046
Loc: Los Angeles CA, UNITED STATES
V1 is farthest from the output tubes. Count from there.

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#2934867 - 06/27/18 06:41 AM Re: Feel free to ask Myles [Re: myles_rose]
Paul K Offline
MP Hall of Fame Member

Registered: 05/16/06
Posts: 3650
Loc: Ithaca, NY
Greetings Myles;

I've a Carvin AG-300 amp that has an intermittent and loud as hell white noise that comes and goes. It's level is controlled by the master volume, not affected by the channel preamp volumes, so I assume it's in the power amp section. Re-boot the amp, and it's gone until it comes back again. Carvin has gone tits-up and doesn't repair this amp anymore.

I'm pretty sure I'm not the only one with this situation, and expect it will be outside of my normal DIY comfort zone...but who knows? I can remove the electronics plate from the cabinet for easy mailing. Got a repair guy/gal in mind or other ideas on how to proceed?

Worst case scenario is that I find the specs for the crossover in the passive version of that cab and swap those bits in. Shame that the crossover is built into the plate--I had hoped it would be as easy as soldering up an input jack.

Best,
Paul K
_________________________
Things are just the way they are, and they're only going to get worse.
www.home.roadrunner.com/~kempkes/fundus.html

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#2934936 - 06/27/18 12:50 PM Re: Feel free to ask Myles [Re: Paul K]
myles_rose Moderator Offline
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Registered: 11/28/01
Posts: 5046
Loc: Los Angeles CA, UNITED STATES
Paul,

Lots of great repair folks in New York. The master is .... https://www.blackiepagano.com/

Have a great day. Blackie

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#2934938 - 06/27/18 01:09 PM Re: Feel free to ask Myles [Re: myles_rose]
Paul K Offline
MP Hall of Fame Member

Registered: 05/16/06
Posts: 3650
Loc: Ithaca, NY
Thanks, baby! Looks like he's a tube guy. I'll find out if he does the class D amp also.


Edited by Paul K (06/27/18 01:12 PM)
_________________________
Things are just the way they are, and they're only going to get worse.
www.home.roadrunner.com/~kempkes/fundus.html

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#2936799 - 07/08/18 10:25 PM Re: Feel free to ask Myles [Re: Paul K]
J. Dan Offline
Bannination Free Since '08
10k Club

Registered: 07/25/08
Posts: 12515
Loc: St. Louis, MO
Wondering from a reliability standpoint how you feel about running keyboards (wide range, possibly hot signal) through an all tube guitar amp. It's been done by keyboard players dating back to Deep Purple using Marshall amps. Not talking about the speaker cabinets - I'm well versed on the physics and design of speakers and enclosures. I have an electrical engineering background as well, but all solid state, almost nothing on Tube amps. This would primarily be for lead synth, but could possibly get into some deeper bass frequencies, and since it will be a pure analog synth, voltages generated could spike fairly high. Just wondering if tube preamp stages are well suited to handle this without shortening life, or if it would be better to possibly limit the frequency range, or at least maybe put a compressor/limiter inline. If it matters, this particular amp uses (2) 12AX7 tubes in the preamp stage, and (2) GE 6AQ5 Beam Power tubes (Class A/B) in the output stage - only 18W but I don't need a lot of power for this application. For what I'm looking at doing, think Derek Sherinian (Dream Theater, Sons of Apollo). Just wondering about longevity.


Edited by J. Dan (07/08/18 10:30 PM)
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Dan

Acoustic/Electric stringed instruments ranging from 4 to 230 strings, hammered, picked, fingered, slapped, and plucked. Analog and Digital Electronic instruments, reeds, and throat/mouth.

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#2936873 - 07/09/18 09:41 AM Re: Feel free to ask Myles [Re: J. Dan]
myles_rose Moderator Offline
MP Hall of Fame Member

Registered: 11/28/01
Posts: 5046
Loc: Los Angeles CA, UNITED STATES
Originally Posted By: J. Dan
Wondering from a reliability standpoint how you feel about running keyboards (wide range, possibly hot signal) through an all tube guitar amp. It's been done by keyboard players dating back to Deep Purple using Marshall amps. Not talking about the speaker cabinets - I'm well versed on the physics and design of speakers and enclosures. I have an electrical engineering background as well, but all solid state, almost nothing on Tube amps. This would primarily be for lead synth, but could possibly get into some deeper bass frequencies, and since it will be a pure analog synth, voltages generated could spike fairly high. Just wondering if tube preamp stages are well suited to handle this without shortening life, or if it would be better to possibly limit the frequency range, or at least maybe put a compressor/limiter inline. If it matters, this particular amp uses (2) 12AX7 tubes in the preamp stage, and (2) GE 6AQ5 Beam Power tubes (Class A/B) in the output stage - only 18W but I don't need a lot of power for this application. For what I'm looking at doing, think Derek Sherinian (Dream Theater, Sons of Apollo). Just wondering about longevity.


Dan,

No reliability issues at all. If the output from the keyboard is too hot the tube in the first gain stage will compress and sound pretty awful (but that may be an effect on it's own smile ) but you can just turn down the keyboard output or pad it prior to the guitar amp input.

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#2938344 - 07/18/18 01:13 AM Re: Feel free to ask Myles [Re: myles_rose]
J. Dan Offline
Bannination Free Since '08
10k Club

Registered: 07/25/08
Posts: 12515
Loc: St. Louis, MO
Thanks, another unrelated question....

We got rained out in an outdoor gig about a month ago. I had my guitar on a stand under a tarp but apparently at some point somebody tripped in the cord and knocked it over and I found it laying face up on the ground completely soaked. I tried it but it was extremely muddy and weak output. I was hoping it would dry out and work again, but it's been about a month and exactly the same. Note: it's an explorer with 2 SD humbuckers.

So time to open it up and trace down the problem. First, same symptoms on both pickups, so either both suffered the same fate or it's something else - the muffled sound would suggest to me tone poor capacitor, but the level is also extremely weak suggesting maybe some sort of partial short - I would think would clear after drying out unless it's corrosion,

So I have a Fluke DMM and a BK Precision LCR meter similar to This. I just want to make sure I'm in the right track with my troubleshooting.

I figure for each pickup I can check DC resistance and coil inductance and compare to the Seymour Duncan specs and look for deviation, as well as maybe just bypass the volume/tone pots and look for a normal output direct from each pickup. If they check out, pots are easy enough to check with a DMM checking resistance. The capacitor in the tone pot can be checked with the LCR and the pickup switch and Jack can be checked with simple continuity. Anything to add?
_________________________
Dan

Acoustic/Electric stringed instruments ranging from 4 to 230 strings, hammered, picked, fingered, slapped, and plucked. Analog and Digital Electronic instruments, reeds, and throat/mouth.

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#2946927 - 09/06/18 05:45 PM Re: Feel free to ask Myles [Re: myles_rose]
Kenji13 Offline
Senior Member

Registered: 04/30/18
Posts: 38
Loc: NY
Hi Myles,

I am looking for a small amp that I can carry around when I teach. I see great review of Roland - CUBE-10GX on the internet. Could you tell me your opinion. The quality of sounds does not really matter, but I am looking for something that last long. If you have any other suggestions with similar size amp, please kindly let me know.

Thank you so much for your help in advance.
_________________________
Kenji

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#2947029 - 09/07/18 09:10 AM Re: Feel free to ask Myles [Re: Kenji13]
myles_rose Moderator Offline
MP Hall of Fame Member

Registered: 11/28/01
Posts: 5046
Loc: Los Angeles CA, UNITED STATES
Originally Posted By: Kenji13
Hi Myles,

I am looking for a small amp that I can carry around when I teach. I see great review of Roland - CUBE-10GX on the internet. Could you tell me your opinion. The quality of sounds does not really matter, but I am looking for something that last long. If you have any other suggestions with similar size amp, please kindly let me know.

Thank you so much for your help in advance.


Kenji13,

When it comes to small amps, Roland has been making them for longer than anybody else. Sure, there were fun toys like the original Pignose amps, but Roland stuff has always been full featured stuff with the emphasis on playing, not novelty.

Their products are well engineered and very reliable. I have owned a Roland Cube 60 since the eighties. It never failed. It is being used in Seattle by a bass player for small gigs on a continual basis .... with the original speaker no less.

There are many amps of these types out there but Roland sort of set the stage for all others. Their Micro Cube stuff have been used on more recordings for high gain stuff than I can being to count.

Happy playing .... for a toss and go amp to teach their lineup is pretty darn cool.

Myles


Edited by myles_rose (09/07/18 09:11 AM)

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#2948250 - 09/14/18 07:17 AM Re: Feel free to ask Myles [Re: myles_rose]
Kenji13 Offline
Senior Member

Registered: 04/30/18
Posts: 38
Loc: NY
Hi Myles,

Sorry for my late reply. Thank you so much for sharing your experience and thoughts! I'm going to buy Roland Cube. Hope it lasts like yours.

Thank you!

Kenji
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Kenji

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#2949755 - 09/24/18 08:35 AM Re: Feel free to ask Myles [Re: myles_rose]
allthekeys59 Offline
Member

Registered: 02/14/18
Posts: 25
I have a peavey kb 300 solid state amp that got left turned on over night , next day turned it off let it cool down a few hours . Turned it back on power light comes on ,but amp is dead , where should I start to look ,thanks Myles any ideas

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#2949758 - 09/24/18 08:52 AM Re: Feel free to ask Myles [Re: allthekeys59]
myles_rose Moderator Offline
MP Hall of Fame Member

Registered: 11/28/01
Posts: 5046
Loc: Los Angeles CA, UNITED STATES
Originally Posted By: allthekeys59
I have a peavey kb 300 solid state amp that got left turned on over night , next day turned it off let it cool down a few hours . Turned it back on power light comes on ,but amp is dead , where should I start to look ,thanks Myles any ideas


It's amp tech time. It could be too many things to check if just "shotgunning". They are a pretty nice keyboard amp as a side note, easy to get around and use for local gigs. Good luck. If you are in New York or can ship it I'd go with Blackie. Link

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