Music Electronics Forum http://music-electronics-forum.com/ This is a discussion forum about building , modifying and maintaing musical electronic devices such as guitar amps and effects. en Sat, 21 Nov 2009 03:36:53 GMT vBulletin 60 http://music-electronics-forum.com/images/misc/black/rss.jpg Music Electronics Forum http://music-electronics-forum.com/ speaker driven reverb http://music-electronics-forum.com/t16230/ Sat, 21 Nov 2009 02:50:12 GMT Hello all

I'm building a speaker driven reverb. Thanks to all who responded to my last thread about this project. This is a refinement of the input for the tank. I've never designed with a panel meter or such a low voltage limiter before. I'm hoping for some critique or suggestions if any is in order.

The unit has to work with amps of different wattages so it must have an adjustable input. The unusual input adjustment keeps the impedance fairly even so the input capacitor frequency knee stays the same. The resistor marked ? is to adjust the needle position on the meter. having never designed with a meter before I'm not sure which meter to get. For this app I'm guessing a mV or uA meter would work. I know that if I choose a DC meter that I'll need to use a diode or possibly a diode rectifier for the meter input. But that's as much as I know about it. The meter is there so the user can set the input level. The diodes are circuit protection for the meter and tank transducers in case the user fails to adjust the input correctly.

The 10r resistor at the tank input adjusts the voltage so the clip level of the diodes is in relation to the voltage needed at the tank.

Hooked to an amp it will change an 8 ohm load to a 7.65 ohm load at 1000hz. But I don't think this is a big problem.

So far it all works on paper as far as I can tell. Any advice?

Thanks

Chuck
Attached Images
File Type: jpg input.jpg (12.9 KB)
]]> Chuck H http://music-electronics-forum.com/t16230/ Peavey Transtube EFX 212 Lost Balls, static distortion http://music-electronics-forum.com/t16229/ Fri, 20 Nov 2009 22:54:31 GMT Hello, I have a Peavey Transtube EFX 212. The amp is in very good condition with very limited playing time. I used this amp a few times during... Hello, I have a Peavey Transtube EFX 212. The amp is in very good condition with very limited playing time. I used this amp a few times during practice and such, then it basically sat in the room for a week or 2. Now the amp has a really ugly distortion, almost like static, and it seems as if the volume knobs and everything else really has no control anymore. Everything works on the amp, even the effects knobs when i switch works. Just the amp has totally lost its output power or something. I do know this amp has at least 2 Fuses inside, but being that it is a TRANSTUBE it doesnt actually run off of a tube, trust me i would have tried to replace it. I'm not sure what the problem could be, but if anyone has any advice it would be greatly appreciated!

- I was planning to sell this due to the fact that I just bought a Marshall AVT150H for 125 bucks that needed repaired, brought it home, bought a 13$ tube and wham! a 500$ amp for 138$ =) Anyways I'm looking to get this transtube back to shape so I can sell it for 300-OBO comes with the footswitch pedal for clean distortion and Effects and amp is in very very good condition and real clean! ]]> soulbind4 http://music-electronics-forum.com/t16229/ Can someone help mod a Peavey Gatekeeper? http://music-electronics-forum.com/t16228/ Fri, 20 Nov 2009 20:58:22 GMT I have a Peavey Gatekeeper which is perfect for our needs, except the gates close too abruptly. It has two controls for each channel - sensitivity... I have a Peavey Gatekeeper which is perfect for our needs, except the gates close too abruptly. It has two controls for each channel - sensitivity and release. The release control, though, acts more like a "hold" control, and when the gate closes it's way too fast.

I would like the release control to be more like a "fade out" control that allows us to choose how long it takes for the gate to close (say, up to three seconds after it opens) and when it closes it is a steady reduction in volume instead of a hard close like it is now. I can do the mod itself, but I don't know what would need to be changed and/or added. Gates are greek to me.

Can someone help with this? I have the schematic from Peavey.

Thanks in advance! ]]> Music Electronics swipesy http://music-electronics-forum.com/t16228/ Need someone more knowledgeable http://music-electronics-forum.com/t16227/ Fri, 20 Nov 2009 19:03:40 GMT Looking for someone with a little more experience to advise me regarding a current build. It's a basic 5F1 - repl. Fender trannies, tube recto, etc. Changes I've made are 1) beefed up supply caps: 40mfd/500v, 20mfd/500v, 20mfd/500v, 2) lower supply resistors for a little higher voltages 1K/1W, 10K/1W, 3) addition of 1N4007 diodes to recto inputs/outputs (ss bridge backup for 5Y3), 4) ability to switch in simple tone stack (5E2 tone control), 5) switchable RC cathode circuit at 1st gain stage (25mfd/1.5K, .68mfd/2.7K) 6) switchable NFB level which all should work with no problems I'm aware of other than 40mfd 1st supply cap is maximum a 5Y3 can handle. Regarding this I've 2 relatively simple questions. I know I can experiment & find this out on my own but... soooo... my questions...

1) since I'm using all new top quality components I no 2.7K resistors in my box & don't wanna wait 3 or 4 days on the UPS driver... Would it change things much if I substituted a 3.3K resistor or if it's thought better a 1K & 1.5K in series?

2) The stock NFB resistor value is 22K & I know omitting it increases gain but not always desireable so I was thinking of adding a switch that instead of eliminating entirely would drop a lower value. 2 ways I've considered doing this are switching in a 2nd 22K resistor essentially cutting the resistance value by half if I remember my training from electronics school so many moons ago or just switch the stock 22K out of the circuit switching in a lesser value... thinking 1/4 or 5.6K value. Can anybody suggest which would be the way to go??? Keeping in my I'm looking for a modest but noticeable increase in gain. Also is would there be any benefit to also adding a cap to ground HPF in the NFB loop? If so any suggestions as to what value might work well .01mfd, .1mfd, larger?

Any help would be much appreciated... pix of this build to follow shortly. ]]> http://music-electronics-forum.com/t16227/ Ruby Reverb Tanks for Blues JR http://music-electronics-forum.com/t16226/ Fri, 20 Nov 2009 18:50:47 GMT I have a few extra New RRVS3eb2c1b Ruby tanks for the Blues Jr in stock. This is the easiest and single best upgrade you can do for the tone of... I have a few extra New RRVS3eb2c1b Ruby tanks for the Blues Jr in stock.
This is the easiest and single best upgrade you can do for the tone of your Blues Jr. At a cost of 31.85 plus shipping. They fit right into a stocking also, you just can't fit as much candy in with it. whole tone music ]]> Flea Market WholeToneMusic http://music-electronics-forum.com/t16226/ Wiring Diagram http://music-electronics-forum.com/t16225/ Fri, 20 Nov 2009 18:32:03 GMT I am putting together a wiring diagram reference book and just completed my first diagram. I am looking for comments. Would you rather see it... I am putting together a wiring diagram reference book and just completed my first diagram. I am looking for comments. Would you rather see it differently in terms of component design? It will have to stay in black and white due to printing costs, but i am open to other ideas.





]]> Pickup Makers automan http://music-electronics-forum.com/t16225/ Mesa GEQ - Changing the freqency. http://music-electronics-forum.com/t16224/ Fri, 20 Nov 2009 17:55:27 GMT I have a Mesa DC3 and the GEQ jumps from 2.2k all the way to 6.6k in terms of frequency control. I find 6.6k to be too high to be useful for guitar;... I have a Mesa DC3 and the GEQ jumps from 2.2k all the way to 6.6k in terms of frequency control. I find 6.6k to be too high to be useful for guitar; most guitar speakers roll off severely after 5k. I'd be happier with that control in the 4.5 to 5k range I think.

Mesa uses a .033uf cap in series with a .033H inductor to get the 6k value; what should I use to get 5K ish? Can someone hip me to the correct formula to calculate the frequency I want?

Also, any suggestion on a source for the inductors?

Thanks! ]]> wizard333 http://music-electronics-forum.com/t16224/ <![CDATA[Ampeg SVT Classic - How Much Background hum is "normal"?]]> http://music-electronics-forum.com/t16223/ Fri, 20 Nov 2009 17:51:14 GMT Just got done with a SVT classic that had bad solder joints in the pre-amp, dead screen grid resistors, and a bad switch. Also retubed it. Now... Just got done with a SVT classic that had bad solder joints in the pre-amp, dead screen grid resistors, and a bad switch. Also retubed it.

Now that its back together and working, it has a fair amount of 60/120 cycle hum. A lot of it I dialed out while biasing, but its still there and audible, just below conversation level. Thats with the pre-amp turned all the way down at gain and master, and as quiet as I could get with biasing.

Is this normal for these amps? I've never owned one so I cant tell. If it was a 100W Plexi I'd say it was normal and call it a day, but I'm not sure what is "normal" level on an SVT.

Thanks! ]]> wizard333 http://music-electronics-forum.com/t16223/ Shin-ei Companion Pickups http://music-electronics-forum.com/t16222/ Fri, 20 Nov 2009 17:19:26 GMT Hi there, been directed here as hopefully some of you may recognise these pickups. I don't know a hell of a lot about pickups but had this set about 10 years and haven't a clue what they are - nothing came up in searches.

They are made by a company called "Shin-ei Companion" in Japan. I guess they are made in the 70's but may be wrong. I'll show you some pictures before I go on . . .







Ring any bells? The size and shape suggest to me that they were intended to go in a rockabilly guitar. They have a very fat, plummy sound that is kind of "low end of a piano" like. has strong detailed bass and low mids but not much in the high frequencies. can feel a bit squashy, almost like tube rectifier sag or something.

Here are some blurry pictures of one of them with it's cover off.







The DC resistance of the pair is 6.49k and 6.66k. Despite the seemingly low output, they seem very loud.

To help explain the blurry pictures, there is a single wide coil. The wire used is green.

-- through the centre of the coil is a kind a blade pole piece thing.

-- on one side there are some adjustable pole pieces although aspersions have been cast by an educated source as to how adustable they are or whether they are just for show. They don't seem to be touching anything mechanical aside from maybe the magnet next to them or the base.

-- the magnets themselves are two long, slim bar magnets.

having never built my own pickups or even understand how they are made, i have very little knowledge on pickups. only other experience of non stock pickups was one made by a certain large scale manufacturer which cost a ridiculous amount for the shoddy quality and could never hold a candle to these 2 tacky looking jobs.

however, having had them for 10 years and being so different to anything else ive tried (both tonally and in looks), i am really curious as to what they are, what they are for, what made them sound like that etc.

if you can help at all i would appreciate it.

cheers ]]> Pickup Makers clear and blue http://music-electronics-forum.com/t16222/ Kit Build Preflight http://music-electronics-forum.com/t16221/ Fri, 20 Nov 2009 16:11:29 GMT My 5e3 kit will probably be arriving in the next week or so. I read a few posts where people have received bad parts and or manufacturing defects... My 5e3 kit will probably be arriving in the next week or so.

I read a few posts where people have received bad parts and or manufacturing defects with some kits and waste time troubleshooting after the kit was built to find the problem.

I am a believer in doing some prep checking upfront to to try to minimize problems on the back end.

Aside from taking an inventory of the parts and comparing to the schematic and bill of materials... what else should I check before starting to assemble?

I read an article about doing some checks of the transformer before the wires are soldered.

Any advice on this topic or pointers to articles that describe a build "preflight" would be much appreciated. ]]> Tweed Builders BluesDude http://music-electronics-forum.com/t16221/ Grub/Set Screws as pole pieces - which is the most magnetic? http://music-electronics-forum.com/t16220/ Fri, 20 Nov 2009 14:32:59 GMT I need to order some grub screws for my Sustainer coils ....they're available in two finishes that suits my needs....

Zinc coated steel
Stainless steel.

Now I'm pretty sure I have some zinc coated steel screws in my screw drawer that aren't magnetic in the slightest (there again I could be wrong - they might not be steel inside, but they are bright/shiny!), so can aynone say that if steel is given a zinc coating that it loses some/all magnetism?

Of the two types above, which would be the most magnetic? ]]> Pickup Makers peskywinnets http://music-electronics-forum.com/t16220/ Mesa Heartbreaker Head http://music-electronics-forum.com/t16219/ Fri, 20 Nov 2009 14:05:33 GMT I have a Mesa Boogie Heartbreaker head with a reverb issue. Both reverb pots are acting like volume controls. I have checked all components in the... I have a Mesa Boogie Heartbreaker head with a reverb issue. Both reverb pots are acting like volume controls. I have checked all components in the reverb circuit, subbed another tank and cables, subbed tubes, replaced both pots. Problem persists even with reverb tank removed, so I assume a recovery circuit problem. Any help at all greatly appreciated. ]]> jvm http://music-electronics-forum.com/t16219/ no sound from an AB763 clone http://music-electronics-forum.com/t16218/ Fri, 20 Nov 2009 09:10:50 GMT hi am completely new here so please excuse my ignorance I have built a single input ab763 clone without the trem circuit , hasmmond transformers... hi
am completely new here so please excuse my ignorance
I have built a single input ab763 clone without the trem circuit , hasmmond transformers JJ valvesand a hammond reverb tray
I have about 5.9 volts dc to ground to heaters, 330v ac to pins 4 and 6 of rectifier tube (GZ34)
all voltages from here seem a little high (but i have a cheap meter)
as follows

first preamp tube (nearest to input) 2.3 v to cathode, (sschematic says 1.3) 187 tio plate1 (schematic says 170 ) similar to pin 6 , 1.3 v to pin 8
reverb tube is 450v to pin1 (schematic 410)and only 4.2 v to pin 8(schematic says 8.7)

the BIG DIFFERENCE in second preaamp trube - reading 316 to pin 1 (schematic 170), 5.2 v to pin 3 (schematic dsays 1.3)and 330 to pin 6 - schematic says 180 v

last 12ax7 readings before 6v6 are 190 to pin 1 and 6 and 80v to pin 3 and8 so are ok I think
450 v dc to pins 3 of each 6v6 (schematic suggests 415)
200v to pin one of last 12AT7 (schematic says 170)
I AM GETTING NOTHING BUT A SLIGHT BUZZ from speaker and when guitar goes thro its just a faint distorted noise BUT I CAN HEAR REVERB TRAY VIBRATING A TREAT WITH VOL UP, nothing to tray with vol down

please help It is driving me to drink
Chris (sheffield uk)

no
about 190 to pin 6 of same tube and
82 volts dc to pin 3 (schematic says 77v)


I have po ]]> chris shaw http://music-electronics-forum.com/t16218/ Saying Hi, asking about some basics http://music-electronics-forum.com/t16217/ Fri, 20 Nov 2009 08:57:38 GMT This forum is stupid addicting.

So, I'm one of those "obsessed" people. I'm probably obsessed more with cars that music gear, but that's only because I've got a much firmer grasp on how it all works. I'm a designer through and through. I'm not happy with knowing HOW to make something, but WHY to make something a particular way. I like to really know the details and remove the mysteries that seem to plague the ignorant.

So that being said, I hope to eventually make some pickups for myself, and I've got ideas for building guitars down the road, which would probably benefit from custom pickups since my ideas are so odd anyways.

I've read as many links as I could find on pickup making and I'm still left with a LOT of questions. If anyone has any answers, or links to where I might find the answers I'd greatly appreciate it.

1. What is the exact tonal difference from one gauge wire to the next, if the mass of the wire is the same? Obviously 7000 winds of 42 gauge will sound different than 7000 winds of 40 gauges, but the mass is not even comparable.

2. Why are the common depths of a pickup common? What happens when you make a pickup "deeper", or "taller"? Does a stronger magnet allow a shallower pickup design? Vice versa? I've found very little information on why certain pickup heights are used.

3. Why don't we cover the pickups with a non-magnetic metal like aluminum? It seems to me that if you covered a pickup in aluminum and grounded the cover then that would help shield the pickup from some (not all obviously) noise. Plus it looks b^@$#in'.

4. Why do I have a hard time finding info on other magnetic materials used and how the actually sounded? I'm particularly interested in experiments with rare earth magnets. Seems to me that they might have their benefits.



Well, that's a start I guess. I'm sure I'll come up with more, but that's what's been nagging me lately. ]]> Pickup Makers Gollum http://music-electronics-forum.com/t16217/ Ampeg SVT4 Pro repair http://music-electronics-forum.com/t16216/ Fri, 20 Nov 2009 08:03:18 GMT I guys, I'm hoping you guys can point me in the right direction here. I have an Ampeg SVT4Pro bass head which has seen much better days. Unfortunately I had a house fire recently and lost nearly everything. Sad story aside, the amp itself was not IN the fire but did have a TON of water dump through it from the firefighters (I have NOTHING but respect for these heros!)

The amp was not plugged in at the time. I removed the lid (it's the rack mount version) to aid in it air drying and allowed it to dry completely and then some.

I cleaned it as best I could but when I plugged it in and turned it on - nothing. It didn't even blow a fuse. Just no signs of life

Everything on the inside looks all and all pretty good - no rust or contamination though clearly something is not good here.

I have an ok understanding of electrical repair and am comfortable with a soldering iron (i.e. I've replaced power connectors on a laptop motherboard, replaced cap's on a pinball machine, modded my xbox, rebuilt the electronics in a number of guitars etc). However, I have very little experience with amplifiers. I feel very comfortable replacing parts but don't know where to begin testing.

I know I should probably have it repaired by a professional but as I said, unfortunately the house burnt down - no insurance money and I have lots of things that need to be replaced before this and not the money to do it. The way I see it at the moment is the amp is blown and I will not have the money for a LONG time to have it professionally fixed. I feel comfortable enough in the skills that I would not make things any worse and really need a working amp.

Thank you so much for any help you can give!

Chy ]]> chymmylt http://music-electronics-forum.com/t16216/