7591 twin amp for acoustic guitar,,,,, any good ? recommended acoustic amps

[Tom_Hull]

hi ,,,,,,,I am still here

I have been asked to build a acoustic guitar amp. for a gig
what amp would you build ???
I was thinking about a ampeg super echo twin ET-2B

I have a pt and 2 ot that match ,,,,,for 4 ,,7591
and I have two transformers for 6v6 s and the output transformers ,...

thanks
tom

[quayhog]

I can't tell you what to build.  But do look at some Hi-fi schematics, remove the RIAA circuits for used for playing records.  The AUX channel would probably work.   Input impedance needs to be larger than the approx 1Meg of a guitar amp.  Ampeg originally used something along 4Megs with their B-15.  you could go up as high as abut 10M.   You'll need to experiment some for taste.

Hi-fi quality OP transformer, and quiet lower gain tubes such as 12AU7 for the pre amps.   
I've built a similar amp for piezo string bass use.   Came out OK.

[eleventeen]

I'm not aware of any great advantage of 7591's over plain old 6L6 tubes...and they are lots more expensive.

[Tom_Hull]

Hi

quayhog

thanks for reminding me about the acoustic bass,my daughter has an electric bass and a acoustic bass.
I did try playing through my tube stereo,  but with a electric guitar .yes its way cleaner sounding. I'll check it out .
and learn more ..once it's built it s fun to experiment

I just built a b15n changed a bit though,, very nice sounding bass amp. I put a 1mil pot in place for the ultra bass switch for a more controlled ultra bass . works great...

eleventeen

hi
i do have the 7591 tubes that sound strong ,,,,and the 6l6  types but are are about 60% . just test tubes .so i need to buy the 6l6s
and the output transformers are  for 7591 tubes . but i do have 2 other op transformers for 6l6 gc
i read that 7591 sound very clean for a hi fi amp

right now with a load  .the pt.. the voltage is about 420 v with tunnel diodes

thanks for replying

tom

[stratele52]

An amplifier for acoustic guitar should not be conceived as a guitar electric amp .

An amplifier for electric guitar color is more or less the sound of the guitar. Using an acoustic guitar on the same amplifier, it is far from certain that you will like the sound.

Try your guitar to an Twin Amp before  build one.

[Tom_Hull]

hi

well now

drgonzonm
thanks for the link
but the second link does not wotk for me ,, no mater ,,,,I was planning on SS version
I cannot be sure what type of pickup he has . I believe its in the hole . he also keeps the martin  in a case with humidity and he bought an expensive pickup for a Martin  .nicer sounding  now.

thanks ,,,stratele52
'52 suggestion of trying the amp before building is an excellent idea.

well I built an  Ampeg's Reverberocket .with.5y3 and 6v6 s but it s running at 18 watts  . and it was 15 watts for a while .That means I should ask him to play through it when they practice this week.
I thought the SS version would sound different because of the tubes .. my amp is a m12 but brakes up earlier  then the rocket for some reason

when he first asked me for an amp ...I told him   acoustic amps,,,  they are  sold  in music stores and asked him to buy the one he likes but he is back now . so not sure what to do

ill ask him which amp he liked better ..

thanks  tom
 

[HotBluePlates]

I have been asked to build a acoustic guitar amp. for a gig
what amp would you build ???

I wouldn't. In fact, I didn't.

What I mean is I had this exact same situation several months ago, and told my friend to go out and buy a small acoustic amp or a small portable PA system.

The reason was good reproduction of acoustic guitar begs a wider range speaker than is typical of guitar amps, and also begs a bit different EQ with some capability for feedback reduction (variable notch filter).

And after a survey of available equipment, one of the Fender Passport compact PA systems and an acoustic-centric EQ pedal (a la Baggs Para DI) were cheaper, even new, than any feasible tube amp I could build him from scratch. In the end, he bought the new stuff better-geared to his application.

[Tom_Hull]

hi
HotBluePlates
ok thanks

so to scare him into reality,, ill quote him a price $4000. for an acoustic amp. i know he does not want to spend that amount of money

I hope it does not backfire on me and he says yes. 
That  happen with a commissioned painting .
I did not what to paint the scene the customer  wanted so I quoted him $6ooo, he said yes and I charged him $7000 .
and had fun spending his money

thanks everyone
tom

[eleventeen]

"And after a survey of available equipment, one of the Fender Passport compact PA systems and an acoustic-centric EQ pedal (a la Baggs Para DI) were cheaper, even new, than any feasible tube amp I could build him from scratch."

An inescapable reality. You/we cannot build a Deluxe Reverb for the parts cost of a superb-condition used one until you/we are ordering in significant bulk. And if a solid state amp can work for a "cabaret-sized" PA (and it can, and it is lighter and arguably more reliable and rugged) that type of thing (Fender Passport) cannot be duplicated for what a nice used one or even a best-discount-price can be bought for. Can't be done.

[HotBluePlates]

An inescapable reality. You/we cannot build a Deluxe Reverb for the parts cost of a superb-condition used one until you/we are ordering in significant bulk. ...

My friend's question came up after he heard my Standel-style amp and played through it with my Gretsch. But he's an acoustic player more than electric, and also didn't have a concept of how much it cost me to build the amp (without paying myself labor).

I explained to him that the cost-performance for his situation would be better if he bought something solid-state new or used; if he had to have a "tube amp" it would be better suited to electric where a little (or a lot) of distortion wouldn't be a problem, and that the cheapest route there is for me to modify a used amp he owned/purchased.

When we looked hard at the options together, we couldn't come up with a plan better than buying off-the-shelf (he wanted very clean reproduciton of his guitar and possibly a mic channel, and that really pointed to a PA).

[sluckey]

When I bought my Taylor 614CE several years ago I thought I'd be happy with the sound through my TR. But I wasn't. I went through three real ss acoustic amps, all which sounded better than the tube TR, until I finally settled on the Fender Acoustasonic SFX. It had everything I was looking for and more. Plus it had the most refined sound of any of the acoustic amps I tried. They can be had for $350 on eBay, which is where I got mine. I don't know if Fender still makes these or not.

Take a look. It's a lot more amp than I could build for that kind of money.

http://www.ebay.com/itm/VINTAGE-FENDER-ACOUSTASONIC-PR-370-ACOUSTIC-GUITAR-AMPLIFIER-AMP-/290950242212?pt=LH_DefaultDomain_0&hash=item43bdfc5fa4

[eleventeen]

"When we looked hard at the options together, we couldn't come up with a plan better than buying off-the-shelf (he wanted very clean reproduciton of his guitar and possibly a mic channel, and that really pointed to a PA)."

Then I would say you reached a decision better and simpler for both of you. Kudos.

[jjasilli]

Ditto to the PA solution.  I'm using an acoustic guitar with '70's Lawrence soundhole PU > Behringer Eurorack mixer > Vintage tube Bogen PA amp > house speakers.  This set-up sounds amazing.  Far superior to the venue's SS Peavey PA amp.  No need for sound enhancement, digital imaging preamps, etc.

[Tom_Hull]

 

Just out of curiousity, how did he like the Reverbrocket sound?  

hi well phone up my son in law . about the rocket ..
I forgot to ask.
the conversion ended up about how he is using my daughters amp b15n without a speaker and jacking it into a mixer .and he was told not to touch her amp as she does not use his amp  .i quoted him $200 if he cooks the ot,    Mr Hoffman nice output transformer the  one with  2 ohm  4omh and 8 ohm connection

thank you      good  phone call because of you.... thanks

thanks for asking

[smackoj]

I purchased a Marshall AS50R in 'not working' condition and all it took was a re-solder on the volume pot. I think this amp is a very good sound quality SS amp.
Mine was made in the UK and they also made/make a 100 watt version which would be very nice to have the extra ponies. I know they changed the build to use all
digital and those amps have a 'D' on the end on the mod. num. instead of an 'R'. The few reviews I have seen recommend the R version for a warmer, smoother sound.

adios,   

[SILVERGUN]

I finally settled on the Fender Acoustasonic SFX.

+10
I owned the original Acoutisonic 30,,,,gigged with it for 2 nights a week, for about a year.....solid performance
I really like the sound of the guitar through this amp........has a nice, touch sensitive response
If it's just him and a mic, the second input (XLR) comes in very handy

I used to just take it, my guitar, and a mic out to small bars with a female singer and never needed more

Actually played 4-5 different Chi-Chi's restaurant locations every tues. for a while.........ah, the things we do for money   

[SoundmasterG]

I'm not aware of any great advantage of 7591's over plain old 6L6 tubes...and they are lots more expensive.

The 7591 (and 7868) will give you less power than a 6L6GC. They are somewhat in the middle between a 6L6 and a 6V6 with a pair able to produce 44 watts with 450V plate and 400V screen, according to the RCA tube manual, but actual power out is probably a little less. As far as power tubes go, they have a fair bit of gain, not quite as much as an EL84, but more than a 6L6 or 6V6, so you don't need much of a preamp in front of them to drive them. As a result they can give you lots of sweet tones if you design things right. Back in the day they were used in a lot of hi-fi things, and the 7868's were used a lot in jukeboxes. The 7355 is also similar along with a couple other types. The 7591 back in the day was way cheaper than a 6L6, but nowadays they are more expensive. They were used in a lot of Ampegs, but in those they were used very conservatively, so they have this rep as being a cleaner tube, but it couldn't be farther from the truth. They are a great power tube with tons of potential, if you can get over the price.

Greg