Hi-Fi Output Transformer: Any good in Guitar Amp application?

[Wharfcreek]

As the subject line suggests, the question is: Is a 'hi-fi' output transformer considered to be any good for use in a Guitar Amp? I'm aware that going the other way has it's limits....specifically in Frequency Response. I guess it's pretty common for a 'musical instrument' output transformer to simply roll off after about 10K. But, with a Hi-Fi output transformer have better response....is this considered to represent any kind of 'dis-advantage' in a guitar amp? Thanks, WC

 

[arts]

Some of the finest sounding musical instrument amps in history used ''hi-fi'' grade output transformers. Hiwatt,Sound City,West and Sunn being some of the ones I'm familiar with.The advantages,in addition to a very crisp,sparkling top end,include a much tighter and clearly defined bottom end.Dynamics are also improved,as core saturation only becomes an issue at extreme power levels,and,due to the higher grade lamination materials used,recovery time from saturation is much quicker.

I don't see any disadvantage in using this grade of iron in a guitar amp,except perhaps as a replacement,where the additional frequency response may require adjusting the feedback loop to maintain stability.

For some people,it may seem like a waste of a higher quality transformer.After all,how high does a twelve inch speaker go? Many guitarists prefer the cheapie transformers,claiming they provide a more ''focused'' sound due to their limited bandwidth.Kinda like shouting through a megaphone....

Personally,I lean towards using the Higher-Fi output transformers in MI amps

 

[Wharfcreek]

Arts, thanks! For me, this will simply be to use up some surplus iron where I don't have a 'match' for the output transformer. I've got a few such 'orphans'.....and rather than just keep leaving them sitting around, if they'll make a good 'guitar' amp...then I may have found a few 'winter projects' to keep me busy when the snow flies and the water freezes. The likelihood of every 'pairing' any of these up is pretty slim.....so I'll pick the one I want to start with first and go from there. By April I may have a few decent guitar amps to play around with....but I still have another 'objective' I have to fulfill yet before I actually start! I need to find out how to build a 'pre-amp' section that has switchable and 'adjustable' gain such that I can go from a 'clean' to a 'dirty' sound and 'adjust' the drive on the dirty side....using 'tubes' of course. I know NOTHING about transistors, and wish to keep it that way!....lol

Thanks again! Tom D. PS, nice T shirt! I miss my '79 Commando!

 

[rothwellaudio]

I need to find out how to build a 'pre-amp' section that has switchable and 'adjustable' gain such that I can go from a 'clean' to a 'dirty' sound and 'adjust' the drive on the dirty side....using 'tubes' of course.

You'll find plenty of circuit diagrams of guitar amps online from Marshall, Mesa/Boogie, Soldano etc. etc. Study them and see how they do it. Basically, there are multiple cascaded gain stages to mangle the signal.
Personally, I prefer the vintage-style amps that don't have high gain preamps and which you have to turn up loud to get distortion. Anyway, that's just my preference. Tone shaping to avoid the "wasp in a jam jar" sound is the key to getting high gain preamps to sound good (in my opinion).

 

[Wharfcreek]

I too want to keep this simple. I'd like to stick with just 2 driver tubes.......and with one of them being used for a phase inverter....... I guess that could leave me with 3 triode sections to work with........ But, I have no real experience in building 'gain' stages for this kind of purpose. So, this will be an 'educational' process as much as the desired success of the project outcome. May take me a few tries to get it right. I'm not looking for that 'Paul Riverra' kind of set-up. I'll try to keep the wasp out of the jar!

 

[arts]

I know exactly how you feel Tom.I also have a large box of orphan output transformers that I don't have a clue what to do with.I have never liked the high-gain preamp ''bee-in -a-bottle'' overdrive sound. I much prefer the sound of a power-amp/output transformer blowing it's guts out,haha! Did I mention that I'm a big Humble Pie fan?

That avatar photo was taken in 1982/3. I'm still playing the same bass,but I've had to buy a rug and much larger t-shirts lately...I stopped counting my collection at thirteen bikes,all old Brits.Norton,Matchless & Triumph.If you like Nortons,here's my daily driver Commando & my P11 (which ain't so pretty anymore after 20 years of scrambling and trail bashing.Makes you wonder what's the point in restoring them if you're gonna use them?)

 

[Wharfcreek]

Wow!! I can't tell you how jealous I am of all the old bikes!! At one point I had a pretty substantial 'collection' myself. But, as a casualty of the US Automotive Market 'crash' back about 10 years ago, I lost my job when my company filed for bankruptcy. My 32 year career came to an abrupt halt....not in a good way!! The revenue from many of the motorcycle sales kept me going at that time.......and in all honesty it's been a bit 'rough' ever since. Funny, I spent all day yesterday as the local Social Security Admin. office.....and it looks like May of '17 can't come too soon for me!! I no long have any of my 'Brit' bikes.....but I retain one of my prior 7 HDs.....as well as about 6 old Yamaha XS650s in various stages. I also recently obtained a 'gift' from a friend in the form of an old Honda CB350/4. Came 'carb-less'......and so far is also sans title. But, he assures me he can come up with the title.....and I found a set of carbs on ebay. So, one day I may get that thing running again. But, I'd like to find another 'Brit' bike, and keep my eyes open all the time. While I LOVED my Nortons (had 3 of them), perhaps my favorite bike was an old '68 TR-6 Triumph that had Bonneville pipes on it and had a 'Mikuni' carb conversion. The Mik carb made the bike run beautifully, and with the low pipes it was hard to tell it from a standard Bonneville unless you looked closely at the 1-carb head. That bike started on the first kick every single time.....and NEVER let me down! But, a bad divorce forced the sale of that thing. I had a few more since, but nothing ever compared to that bike. A little Daytona 500 I had came close......but, ..... nah!! Ever have a Royal Enfield? I did a couple Bullets a few years ago! They were fun....but VERY sketchy in terms of reliability! Also, they were seemingly very under-powered IMHO. I've now settled in with just my old '01 Fatboy that has MASSIVE engine modifications......and then all the XS bikes! Maybe I'll take a ride to Canada and you can put me on one of your Nortons again for a day in the north woods!!

 

[Brice]

I restored a couple of Eico HF60 with one of the finest OT from Acrosound, the TO330.
They were rigged for guitar and obviously have been used (and abused) quite a bit. So I am guessing Yes, it should sound better.
From a logical point of view, Hifi OTs have larger bandwidth than guitar amps. Can't hurt then

 

[Wharfcreek]

Brice...... I may be mistaken about this....but I seem to recall that the original circuit used in the Dynaco Mk III amp....including the output and power transformers, was the basis of some of the Sun and other guitar amps that developed in the late '60s and early '70s. Given a guitar player's propensity to strive for some harmonic overtones and a real 'interaction' between the instrument and the amp...... I'm thinking the use of the better output transformer is a no-brainer. But, I also considered the possibility that using something like this could actually create a 'sterile' affect.... and maybe actually lose some of the harmonics because they just weren't part of the 'signal' the amp was putting through to the OT. In the end, I'm guessing that the proof will be in the pudding.....so to speak!

 

[Lavane]

I have a 6v6 SE stereo amp build in a pdf file that uses some Fender guitar amp OPT's. The punishment ive seen my son put through his tube guitar amp some must be pretty well made.

 

[Brice]

That's possible. I never touched a guitar amp.
My hypothesis was what can do more can do less, so a Hifi amp should do better than a guitar amp in term of quality, not raw power and not in robustness.
Am sure on this board some guitar amp expert can add some light to this.
There is probably something I am missing, else all known bands with large $$ will run many MC275s to get the groove sound

 

[Wharfcreek]

Actually, I think the 'output' section of a guitar amp and that of a 'typical' power amp......both of those may be pretty close. It's the 'pre-amp' section that is where a lot of the mojo comes into play. I know some amps used dual volume controls.....one that controlled the input level.....and one that also controlled the 'output' of the pre-amp section to the power amp....also known as a 'master' volume control. That way they could run all kinds of gain in the first few sections of the pre-amp portion of the amp, but keep the volume under control by reducing this 'hi-gain' signal to the power amp. I think this was the very foundation of 'over-drive'....which eventually became known simply as the 'distortion' or 'dirty' channel. It's fun stuff....hence my desire to build something. That, and the fact that a friend brought over a nice set of transformers and a nice speaker.....and he want's his buddy (me) to build him something! And....... I 'owe' him....so...guess I gotta get it done.

 

[Duce67us]

Mr. Tom,
I have been playing around with some old PA amps lately. I stumbled across http://el34world.com/
a while back and love it as a resource. Good place to poke around has a nice schematics section, and good people in the forums to provide some helpful answers.
Best of all, it is focused on Guitar amp building / repair.

 

[arts]

That's possible. I never touched a guitar amp.
My hypothesis was what can do more can do less, so a Hifi amp should do better than a guitar amp in term of quality, not raw power and not in robustness.
Am sure on this board some guitar amp expert can add some light to this.
There is probably something I am missing, else all known bands with large $$ will run many MC275s to get the groove sound

Been there,done that. My MC275 (in mono) coupled with an Alembic preamp has seen the inside of a few studios. Best bass tone I've ever had.
Honestly,it makes my old Ampeg's sound thin.And believe me,that's saying something!

I tried it at home just for the fun of it,then had one of these moments:

 

[arts]

Tom,I just couldn't resist,although I couldn't roll her out due to the recent snow. '68 Trophy? Ya gotta be kidding!! Here's mine,a TR6C (R-piped,got tired of burning my leg) awaiting her rebuild.And I fully agree with you,this is the most reliable,trouble-free bike I've ever owned.Nothing but general maintenance since I rebuilt her in 1999,and she's still a one-kick-wonder! I still have to machine an intake manifold for the new carb.I'm going with a single 1 1/4'' SU. My buddy has a pile of these as he used to race Mini's,and they work exceptionally well on almost any Brit bike.

 

[Wharfcreek]

Well......there ya go! Explains why those Dynaco MkIIIs become so popular as musical instrument amps back in the day!

Duce, I'll give that web site a look-see! Seems like I may have run across that site some time in the past....but long forgotten it. Good to get back acquainted with it. Thanks for the reference.

 

[Wharfcreek]

Arts.....u'r killin' me!! I don't suppose you'd ever consider 'parting' with that thing would you? I've been known to make a run to 'Canada' from time to time. In fact, I used to go there pretty often! I grew up outside of Detroit......so going 'south' to Canada was a pretty common recreational activity. Funny story: When I graduated from College in '75 I decided to make a 'run' up to Toronto. Myself and a friend hopped on our bikes on a nice sunny April day......and made it as far as London on the first day. Day 2 got us to Toronto, but our 'broke college kids' wallets were pretty thin....so we spent the night at the YMCA and left our bikes on the sidewalk. When we awoke the next am the bikes were under 4' of snow!! We ended up having to dig them out.....'push' them to a gas station where the attendant graciously let us park them in the back of his shop while we hopped a train back to Windsor, walk across the bridge.....and hitch a ride to go get a truck and trailer. Then turn around, drive back to Toronto to fetch the bikes to return home! Not one of my better trips!! That was done on an old 450 Honda 'twin'.

Here's a few pics of my latest XS project: Kind of a true 'restoration' project as it's pretty much bone stock....and in essentially 100% showroom condition. Also tossing in a pic of my 'last' Brit bike!

 

[arts]

Ha,I know how you must have felt. Unpredictable doesn't even begin to describe the weather up here. I got your PM,and you are absolutely right! We should probably just start an old bikes thread in the off-topics forum But at least we're still talking about ''iron''

 

[whoaru99]

AX84 has all sorts of guitar amp plans. Preamp sections, power amp sections, clones, tweaks, you name it, it's probably there.

I built one out of a Grommes S35. Three gain stages, cathode follower driving the bass/mid/treble tone stack, master volume controls, and a few other tweaks. Left the original phase splitter and p-p 7868 output stage pretty much unaltered.

Can go from clean to grunge at anywhere from low to high volume.