Output Transformer on my AB763lite build and Biasing my power tubes

[Toxophilite]

Hello
On my AB763lite build in the early stages I very rashly hooked up the power without having a bias on the power tubes..For a short time. However I did hear a little tiny pop out of the speaker.

After I got it all going I was experiencing some distortion when the amp was turned up around 4 and past, and not normal tube distortion but kind of a crapping out/buzz, particularly on low notes. With my older gretsch it becomes much more apparent when I flip the funny tone switch and get the muted sound, then it's really obvious.
I tried several speakers, different tubes etc.
I'm not entirely sure what the output impedance is on the OT
But I measure 17 ohms off the original speakers in what i believe was their original configuration but they're funky coaxs with a pair of tweeters inside the speaker. I'm pretty sure I have them right
(note to self...always measure the impedance of donor units prior to disassembly!)
My test speakers are all 8ohms

Looked into a lot of stuff and no dice, still distortion, not tonnes but distorting buzzing kind of slightly after the note/chord

I have another 6V6 pushpull OT from a 5U4GB rectified lowrey organ. I believe it was designed for a 16 ohm output load

I disconnected the original OT from the 6V6 plates and wired up the Lowrey OT to the AB763lite using alligator clips
 Hooked up to the same speaker and NO distortion
Also the amp was much much louder. As one would expect running into a smaller load

IS this evidence of a Cooked OT ??

It'd be kind of sad as the original OT looked like a heftier unit but the Lowrey one sounds good regardless

My apologies for the long explanations
I just like to present all the facts
Thanks

[Toxophilite]

Oh I did some measuring of resistance on both transformers

The original suspect OT (still in situ but with the primaries to the plates disconnected)
measures about 2 ohms between the secondaries (speaker hookup)
Between the primary B+ wire(better name?) and the primary plate leads I get around 330K and 290K
Between the 2 primary plate leads I get around 600K
Between the primaries and the secondaries ,On one secondary I get open, then it quickly changes to many megs then starts to diminish rapidly, On the other the opposite happens ??..I'm wondering if this is because it's still in situ

The amp is off, unplugged and the caps are drained

the Lowrey OT,  which works fine, (outside the amp, not hooked up)measures 2.8 ohms between the secondaries
All the other readings are proportionately higher but between the secondaries and the primaries I get open circuit

[jojokeo]

Lots of fragmented and unknown and unconfirmed info here trying to make sense of things. Either way high resistance on primary is not normal, it's completely disconnected when u made measurements right?

[HotBluePlates]

Between the primary B+ wire(better name?) and the primary plate leads I get around 330K and 290K
Between the 2 primary plate leads I get around 600K ...

Triple-check your meter range setting and/or the range indication on the readout. Are you sure those aren't 330Ω, 290Ω and 600Ω? If they are, those would be normal resistance readings.

... Between the primaries and the secondaries ,On one secondary I get open, then it quickly changes to many megs then starts to diminish rapidly, On the other the opposite happens ??..I'm wondering if this is because it's still in situ
...
the Lowrey OT ... between the secondaries and the primaries I get open circuit

This is probably because the transformer is in-circuit.

This is the 5F11 amp conversion, right? (You really oughta keep all posts on the same amp together so people know quickly what they're dealing with).

If so, the 5F11 has a feedback connection from speaker hot to a 56kΩ resistor, then a 1.5kΩ resistor to ground. At the OT pimary, the center-tap is connected to a filter cap whose other end is grounded. I think the drop from open-circuit to some number is the filter cap being charged up by the voltage output when the meter tries to read resistance.

The fastest way to eliminate this possible error is to temporarily unsolder the wire from the speaker jack hot terminal back to the feedback resistor. That breaks the circuit and takes the cap out of the equation.

[Toxophilite]

Gosh
I'm doing the best with the limited facilities I have both mental and physical..haha
Believe or not I did actually imagine I was being very thorough, rather than fragmented, unknown and unconfirmed.

My apologies for starting another thread, I did put the name of the build in the first line

Hello
On my AB763lite build in the early stages I very rashly hooked up the power without having a bias on the power tubes..For a short time. However I did hear a little tiny pop out of the speaker.

l

As stated it's a AB763 lite build, not a 5F11. The other thread started off with the idea of building another 5F11 but I got some interesting suggestions so I switched it to a AB763lite
I started another thread about the specific topic, as I wasn't getting a response on the other one , likely I'm just being impatient but I get excited about the build and the trouble shooting inherent and there's much excellent information provided here
I have been trying forum searches and looking on line as well

Yes I meant ohms not kilo-ohms on the primaries, my mistake.

Thanks for the tip on the meter chargong that filter cap
I'll de-solder the B+ line before I test again
I know they can test good on resistances but still have internal shorts

Any other ideas/comments

[HotBluePlates]

As stated it's a AB763 lite build, not a 5F11. ...

My bad.. I overlooked that you'd said the amp model.

That said, the AB763 circuit has a feedback loop exactly like the 5F11, but with different resistor values. Same trick applies for breaking the circuit with the filter cap.

Any other ideas/comments

Since your resistance measurements look correct, I'm gonna guess that you'll find there is not short between primary and secondary. Therefore, "Hoffman's Law" is likely in effect:

• Hoffman's Law: If the amp was wired properly, it would be working now.

That sounds like a jerk thing to say, but it's unfortunately true. In any new build, when the amp doesn't work properly, you have either wiring error, a parts-value error (like a 470k resistor instead of 470Ω), a bad connection (poor/loose contact, bad ground) or poor solder joint (good solder joint assumes perfect mechanical connection with no solder present; solder only keeps the connection from moving, and does not form the electrical connection).

I would triple-check the build against a schematic and/or layout, and use a highlighter with a printout to allow you to check off parts and wires one by one, as you re-verify everything is in the right place.

[eleventeen]

"I would triple-check the build against a schematic and/or layout, and use a highlighter with a printout to allow you to check off parts and wires one by one, as you re-verify everything is in the right place."

This is exactly how it is done, except I recommend using a colored pencil which can be erased. A highlighter can't. Many, many times you will imagine or project that a connection is completed when it is not. So you highlight the connection and oooops, it was never made. Now what do you do?

I also buzz out connections using the "beep" function of my DVM. I also measure resistances between nodes that are separated by pairs of resistors. Sometimes our eyes play tricks on us.

Another wrinkle is, when you are building an amp with several dual triodes (12AX7, 12AT7, etc;) it is very easy to get the two (identical) halves confused. You can freely "exchange" one for the other as long as you are consistent.

I'll give an example of how you must keep clear in your mind which triode half is which triode half. Following is a piece of a 5E3 Deluxe schematic.



The plate of one triode connects to B+ via a 100K resistor.
Let's call that triode "A", but calling it "triode A" does NOT mean that it necessarily uses pins 1-2-3! (We could fool ourselves into thinking that it does, though) It may actually be much more convenient to use pins 6-7-8 for that triode. Depends upon layout and how you have the tube socket mechanically rotated. You MAY not want to number the pins before you build, or, you MAY wish to swap halves depending upon how your layout comes out. You are free to do so. Maybe the grid wires will be shorter if you call pins 6-7-8 triode "A". Most of the time, I can not decide until I go to wire the thing. But you gotta be consistent! Once I decide, THEN I write in the pins on the schematic.

I rarely use fully-developed layout dwgs, but that doesn't mean you shouldn't if you find them easier.

However: If I WAS building on a pre-spaced parts board like a Hoffman board and I DID have a specific wiring pictorial for that specific board, no doubt I would work to follow the visual of that pictorial as close as possible.

The other (triode "B") triode's plate connects to B+ via a 56K resistor. Should be able to measure that.
Indeed, I should be able to measure 156K from one plate to the other plate, right?
If I can't....then one or both tube's B+ connection is missing.

Measuring from the cathode of the triode "A" (whose plate connects to B+ via the 100K) should read 1500 ohms.
The other triode, his cathode should read 57.5K to ground.
Triode B grid should read 1 Meg plus a little to ground. (1.056 Meg)

Most Fender amp triode tubes, the cathodes are common, eg; pin 3 is jumpered to pin 8. These are not.

These kinds of double checks, visual against buzzer, ohmmeter against what resistors should measure, are things I like to do along the way...because once they are done and test the way they should, I can flush them out of mind and focus elsewhere.

Hope this helps.

[Toxophilite]

You're not being a jerk
That's a sound idea and I will check it over again
I have been over it several times but once more certainly can't hurt

However it does seem to operate perfectly well with a different OT wired in and then to test it further I switched back to the original OT and got the bit of distortion again.

I only went to that step after checking things over a few times
I should also say that there have been NO nasty smells, smoke or signs of excessive heat..(like wax leaking out) at any point

I am getting a nice sound, except for the little buzzy distortion at the tail end of louder notes/chords,,almost like a mechanical rattle but obviously not
i wondered if it was my speaker but my little Vibrolux doesn't do it
Also the amp was tested on other speakers with the same buzzy response

I like the highlighter idea...I wonder if my teacher girlfriend has one..I'm a pencil man myself!

[HotBluePlates]

However it does seem to operate perfectly well with a different OT wired in and then to test it further I switched back to the original OT and got the bit of distortion again.

Hmm... The original transformer is the 10kΩ Hammond, right? What is the impedance of the other transformer you used?

[sluckey]

No Hammonds in this amp which is a conversion from a hifi receiver. See this thread...

http://www.el34world.com/Forum/index.php?topic=16510.0

[HotBluePlates]

Once again I can't keep the threads straight...   

[Toxophilite]

I'll shoulder the blame for the thread confision
I have two amp builds I 'm discussing
One is a 5F11 build/conversion with vintage hammond transformers

This one is an AB763lite build with stock transformers
I'm going to go try your negative feedback removal trick for testing impedances
THough I've heard an impedance test doesn't cover internal shorts...which sounds kind of like underwear if you ask me.

[Toxophilite]

i tried diconnecting the negative feedback from the speaker but got the same results, so I disconnected the B+ and got and open circuit between the primaries and secondaries just like the spare Lowrey 6V6 transformer I tried in it.
I'm going to hook it back up and try a 4ohm speaker just for kicks. my test equipment is limited to a DMM so my methods are a little medieval. They had DMM in the dark ages didn't they?

[Toxophilite]

Testing some continuities again around the power tubes..I seem to have heater continuity to ground
Is this normal?, I do have a filiment center tap
Seems wrong to me
Is it?

Tried the transformer swapping test again got the same results.

[sluckey]

I seem to have heater continuity to ground. Is this normal?, I do have a filiment center tap

Perfectly normal.

However it does seem to operate perfectly well with a different OT wired in and then to test it further I switched back to the original OT and got the bit of distortion again.

Sooo, install that OT.

[HotBluePlates]

Testing some continuities again around the power tubes..I seem to have heater continuity to ground
Is this normal?, I do have a filiment center tap
Seems wrong to me
Is it?

My Fluke will beep if the meter is on the 400Ω range and measures a resistance below 40Ω.

Your filament winding measures ~2-8Ω (and maybe lower) if you have none of the wires connected to anything. Now connect the center-tap to ground, and measure either filament strand resistance to ground. It'll be below the 40Ω my meter beeps at, so...

The filament winding is just that: a winding of wire.

[Toxophilite]

Thanks
I have an idea
and please excuse my vast ignorance in asking this question
If I'm wrong about the output impedance of my OT say it's 16 or 4ohms
Will it make the amplifier itself unhappy if it's not an 8 ohm output impedance Transformer?

[thermion]

Probably not, it'll just reflect a different load back to the output tube plates. Tube amps can typically handle this mismatch with slightly reduced power .

[Toxophilite]

THanks
I went over my circuit again, bit by bit
All seems to be in order
Did a lot of continuity checking, some checking of connections for cold solder joints
Swapped in a new standby switch as my cheap one well..cheap.
Even swapped out the one vintage cap I put in there (it was a .1 mfd Goodall in the negative feedback circuit of the PI) I had to put in a .1 green cornell dublier as I ran out of new caps.
No change in the slight distortion.


I did install the other transformer but had a hell of a time with squealing once it was actually in the chassis, despite it being bolted in securely and ground connections made.
Strangely it doesn't do it outside the chassis hooked up with alligator clips???

[jojokeo]

I did install the other transformer but had a hell of a time with squealing once it was actually in the chassis, despite it being bolted in securely and ground connections made.
Strangely it doesn't do it outside the chassis hooked up with alligator clips???

You switched the primary plate wires w/out knowing it causing the positive feedback to occur. Reverse them and you'll be fine.

[Toxophilite]

AHA!
That's interesting I just assumed they would be hooked the same way,
The original transformer which has a orangy cream wire and a dark bluish wire

The 'new' one has a orangy creamy wire and a blue wire so I hooked it up the same way

When I reversed the hook up as per your suggestion and it doesn't squeal like crazed weasels anymore.

Thanks
I had thought that there was some standardization in the taps colour scheme
It it commmon for transformers to be set up different like that?

[Toxophilite]

I measured the resistance from the red B+ line to each plate lead on each transformer and one plate lead is 30 ohms lower ( I had noticed this before),
however on opposite coloured leads (I had not noticed that!)

[Toxophilite]

I got the new(old lowrey organ) OT in with the plate lead colours reversed and everything hooked up, Sounds great, Just finished rehearsing some of my Jazz/caberet stuff I play with my band The Colorifics for about an hour and a half..Nice!, no problems
Somewhat sad to remove the old OT which was about 1.25 the size and weight, but it sounds good now which is what's important.
Thanks all
Now to hook up the pilot light, and maybe wire up the tremelo circuit.

[jojokeo]

I had thought that there was some standardization in the taps colour scheme
It it commmon for transformers to be set up different like that?

Colors on transformers between manufacturers are not the same so don't assume this.

I measured the resistance from the red B+ line to each plate lead on each transformer and one plate lead is 30 ohms lower ( I had noticed this before),
however on opposite coloured leads (I had not noticed that!)

There is a beginning and ending of the wire's turns similar to a pickup. This is why one end's resistance between CT will be different as related to whichever color is used. Pickups also are wired using different colors and amount of turns on windings will be different as also the size of wire used too. So that's why there are differences in trannies just like differences with pickups.

[PRR]

> B+ line to each plate lead on each transformer and one plate lead is 30 ohms lower

Simple OTs are wound half primary, CT, half primary. The average length of turn on the outer primary is larger, so the resistance is larger.

Does it matter? The winding passes 50mA, 100mA, maybe 200mA. Times 30 Ohms is 1.5V, 3V, 6V. Compared to 300V-450V of the total circuit, 6V is "nothing".

There's other ways to wind. Bell System line coils were wound to 0.1% unbalance. This means splitting the winding up into many sections, usually with a divider. Costs a lot more. Matters in huge telephone systems. Not in a gitar amp.

> however on opposite coloured leads

Interesting but not conclusive. For signal polarity, it does not matter which winding is "outer", you need to know the winding direction primary and secondary.

However a "cream" wire is odd. Was this supposed to be an "exact replacement"? Then they should have copied the winding direction/polarity also.

[Toxophilite]

Interesting stuff!

and no, the 'new' OT is not an exact replacement

The unit the build is based on is a Electrohome Hifi amp

The replacement OT I put in is from a similiar vintage Lowrey organ that had a 2 6V6 power amp

Upon taking the original OT out there was sign of past or present overheating(oops), Some drippy hard brown laquer residue(doesn't seem like wax) on the bottom, not tonnes , but there.

Out of curiousity, can under, or overpowering an OT with plate voltage cause it produce some flabby distortion (particularly when the guitar is hit hard and loud) ?

As you can see my understanding, while growing a little, is still very limited

[Toxophilite]

here's a picture of the OTs in question
1st picture 'new' OT installed
2nd picture a comparision of the two size wise
3rd picture the bottom of the original

[sluckey]

Both of those OTs use a standard color code... Brown (plate), Red (B+), Blue (plate)

That stuff on the bottom of the OT did not ooze out of it. That's varnish. It was common to dip transformers in varnish back in the old days.

[Toxophilite]

Well that's good to know about the varnish
Could it be seeing the wrong voltage, too much too little
Would that make it have the distortion I was mentioning earlier?

Also a different transformer question

I have an OT on a hammond L-100 amp.it's a dual 6BQ5 transformer, could it be used for 6V6s?


It's funny about the standard colour code

The new one hooked up to the plates in the same way the old one did worked fine when it was out of the chassis with no negative feedback hooked up (though of course loud and tweedy)

As soon as I grounded it to the chassis and hooked up the negative feedback it squealed like crazy!

When I reverse the plate leads it worked great

[sluckey]

As soon as I grounded it to the chassis and hooked up the negative feedback it squealed like crazy!

When I reverse the plate leads it worked great

The colors were standard. It's still a 50/50 bet about the squeal.

BTW, did you ever reverse the plate leads on the original transformer?

[Toxophilite]

No didn't actually
Is it something I should've tried?. Wouldn't it just squeal like a banshee?
I still could  , I just do a bit of desoldering and use a half dozen alligator clips

By the way, thanks again for the schematic, It makes a cool sounding, relatively simple to build amp

I'm going to attempt the tremelo soon
I was curious about on thing
The 6G11 schematic calls for 364 volts coming from  (A) just after the choke for the tremelo circuit

On my AB763lite build I have about 407-412 just after the choke (A)
I know I have 363 or around there at the phase inverter stage
Should I take my voltage from there?

[HotBluePlates]

No didn't actually
Is it something I should've tried?. Wouldn't it just squeal like a banshee?

If the primary wires are installed the wrong-way, the negative feedback loop becomes a positive feedback loop, as you found out first-hand.

Most of the time, that creates a full-power howl. Sometimes it doesn't, but rather oscillates at a very high frequency above what the speaker will reproduce (or us hear). However, that high pitch beats against/modulates the normal guitar signal, and can sound like a raspy edge to the treble.

Without a signal generator and o'scope, it's hard for you to diagnose something like that and what's causing it. A simple trick Sluckey & others have used here before is to disconnect the feedback wire running from the speaker jack back to the circuit. If the howl/rasp/etc stops, it is being caused by the feedback loop, and the first next step is to swap output tube plate wires (because the "negative" feedback is probably positive feedback).

But at this point I'm thinking the OT that's been giving you problems just has an issue itself. You've already proven repeatedly that the new OT cues the noise issue, so I'd be inclined to stick with that OT and view the old one as suspect.

[sluckey]

No didn't actually
Is it something I should've tried?. Wouldn't it just squeal like a banshee?
I still could  , I just do a bit of desoldering and use a half dozen alligator clips

Any time you build an amp that has a negative feedback loop from the OT secondary you should do some test to insure the feedback is properly phased. The symptoms are not always a squeal/howl. Sometimes they just sound bad. And if there is a presence control the symptoms may be frequency dependent.

In your case, I'd connect that original OT one more time just as it was before. Then I'd swap the plate leads. If the problem clears up, then the OT is good. Keep it for your next project or put it back in the amp. If the problem does not clear up, the OT is definitely bad. If that's the case, cut the wires on the bad OT close to the body and throw it away. You don't want to have a bad or questionable OT laying around because some day you'll forget all this and try to use the bad OT in another project.

[Toxophilite]

That's good to know and I think I'll give that a try with the old OT, if only for peace of mind.
It's been bugging me

Because I was using an existing amp I left many things hooked up as is (heaters, OT , PT )
Which might be something to consider for future builds especially if I'm building a whole new amp on an old platform
Thanks

[Toxophilite]

Well
Now I'm pretty baffled!

I hooked up the original OT as per Sluckeys suggestion (all original except plate leads reversed)and tried engaging the negative feedback. SQUEAL!!!
So the original phase was right

HOWEVER!!

I did notice something strange and maybe revealing?

In either configuration of plate leads, with the negative feedback DISENGAGED
I didn't have any of the weird distortion/buzz/crap out that's been bugging me with this OT

So I hooked the transformer up as original and engaged the negative feedback..quieter of course but distortion is back, disengage, way louder (of course) but no distortion

Can someone explain this ?

A side note and possibly helpful is the original transformer (that I'm referring to)tested out to have an approx 23:1 turn ratio
The replacement has a 30:1 ratio

[Toxophilite]

I have another tidbit of info
I hooked up a bias control pot
And out of curiosity I ran the bias at around -30 rather than -35ish...My distortion went away
I turned the bias back up(down) to -35 and it came back
turned it down again..no distortion
 

[Toxophilite]

Can anyone explain what's happening
I get none of the buzzy distortion (when I hit it hard, worse on the low end, amp about halfway up) if I
A: unhook the negative feedback...way louder but no distortion noise
B Bias the amp 'colder' (I think) at around -29 to -30

Any ideas..it kind of baffles me with my extremely limited knowledge

And is it unsafe to run the amp at that low bias?

[sluckey]

Are you certain it is wired correctly?

There's more going on with the bias than just adjusting for a particular voltage. Read this page to get a better understanding of the bias circuit and how to correctly check bias...
http://aga.rru.com/TechTips/disp.cgi?file=LV/BiasAdj.tt

Also, it's time to start visiting some of the technical sites such as Hoffman's Library of Information, Valve Wizard, and Randall Aiken (use google for the links). And there are some good books available that deal with tube theory as applied to guitar amplifiers. The Ultimate Tone (TUT) by Kevin O'Connor.

[Ed_Chambley]

Can anyone explain what's happening
I get none of the buzzy distortion (when I hit it hard, worse on the low end, amp about halfway up) if I
A: unhook the negative feedback...way louder but no distortion noise
B Bias the amp 'colder' (I think) at around -29 to -30

Any ideas..it kind of baffles me with my extremely limited knowledge

And is it unsafe to run the amp at that low bias?

Change you bypass cap in V1.  Make it a 4.7uf if you have one.  See if your "distortion" goes away.  If it does, a little tweaking may be necessary.  Sounds similar to passing to many low frequencies.  I say this because of your comment about it showing up on the low end.

[Toxophilite]

I haven't tried the bypass cap thing but I read the article on biasing and I've been trying it out
I'm using some old 6V6gts

To keep my 6V6s within their specified range I need to send about -40- -48 volts to pin 5 of the 6V6s
-45 gives me about 425 volts on the plate( pin 3)! and .022ma on the cathode
about 9 watts if I do the math
Then when I use the tremelo, which works great by the way except I get the 6V6s flashing blue up around the heaters(looks promising!........kidding)

At my previous bias amount of -35 volts
I have 198 at the plates and .040 ma at the cathode

16 watts!! Aiiieee   gobble gobble the tubes!

At -42 volts I get about 412 at the plates and aboout .0268 ma
11 watts
Pretty close to the deluxe reverb but still with flashing tube tremelo.

One thing I want to ask about is static dissipation vs max dissipation

I've read that you want to bias your amps static dissipation to 70% of the max dissipation
for 6V6GTs that would be(70% of 12) = 8.4 watts

The article in the link (which I enjoyed, thanks)seems to suggest I can set it a fair bit higher as long as I don't exceed the max.?
is it a balance between what you like to hear, the tubes capabilities and tube life?

And should I be biasing it colder for use with this sort of tremelo?

Am I making more sense now???  (please oh please!)

I'm going to read the article for a third time

[sluckey]

Then when I use the tremelo, which works great by the way except I get the 6V6s flashing blue up around the heaters

That's normal. The tremolo signal modulates (varies) the grid bias voltage just as if you were turning the bias pot up and down at about 5 times per second.

At my previous bias amount of -35 volts
I have 198 at the plates and .040 ma at the cathode

16 watts!! Aiiieee   gobble gobble the tubes!

That plate voltage doesn't seem right. And 198 x .04 = 7.92W, not 16.

Pretty close to the deluxe reverb

Your numbers are close to my Deluxe Reverb. I have 423V_plate and .024mA current with bias set to -36V. That's 10.2 watts.

I've read that you want to bias your amps static dissipation to 70% of the max dissipation
for 6V6GTs that would be(70% of 12) = 8.4 watts

You misinterpreted the 12 WATT MAX figure that LV listed at the end of his bias article. That list is the maximum you should adjust for, not the maximum plate dissipation for the tube. A 6V6 is good for 14 Watts max. Go to this website and look up a 6V6. The number you're interested in is under the heading "PaMax". That means Power Anode(plate) Max and is 14W. 70% of 14 is 9.8 which is LV's target, but don't exceed 12. Here's the tube data link...

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

is it a balance between what you like to hear, the tubes capabilities and tube life?

And should I be biasing it colder for use with this sort of tremelo?

Yes, you have to juggle between what your meter and calculator tell you and what you hear (but don't exceed 12 watts). It's the same with the bias vary tremolo. You have to juggle between good strong tremolo and good sounding bias.

Am I making more sense now??? 

Absolutely. And you're having more fun too, right?

[Toxophilite]

Thanks you very much
I made a typo
It should've read 398 and not 198
and yes I am having more fun, thanks for that as well
Now, More reading!

[sluckey]

The Valve Wizard has a lot of easy reading material on his website. May even inspire you to buy his books.

Another good book that's easy to read is "Electric Guitar Amplifier Handbook" by Jack Darr. Go to this website and download all 8 chapters. Do it now because it may disappear since that book is now available in reprint.

http://www.diyguitarist.com/Misc/J_Darr.htm

[Willabe]

Another good book that's easy to read is "Electric Guitar Amplifier Handbook" by Jack Darr.

Yeah I have that book and would recommend it too.


              Brad