Upgrading output transformers in tube amps?

[diamondsouled]

Just wondered what is involved in upgrading output transformers in a tube amp.

Is it fairly easy to do? If you have the room of course.

Cheers

Lar

 

[ferninando]

just a matter of unsoldering wires from old OPTs and removing from chassis and installing/ soldering in new OPTs. No magic. May have to drill holes for new mounting and use machine screws, nuts and washers to remount.

 

[diamondsouled]

just a matter of unsoldering wires from old OPTs and removing from chassis and installing/ soldering in new OPTs. No magic. May have to drill holes for new mounting and use machine screws, nuts and washers to remount.

You would need to match input impedance at least, wouldn't you?

Cheers

Lar

 

[ke4mcl]

of course. most transformer manufacturers will have charts showing what tranny they reccomend for what tubes.

 

[Hi-FiGuy]

It also helps to know what kind of circuit the tubes are being used in Fixed BIAS, Self BIAS. For instance I have seen a pair of 6L6GB tubes used in circuits from 30 to 60 watt range. I do have a question about output transformers if you are replacing a non ultra linear transformer, with an ultra linear transformer and wanted to use the UL taps, how much would the feedback loop have to be changed?

 

[goldear]

Why do you want to upgrade your OPTs? In most cases that negates the entire reason for modifying an amp if you throw-out the classic iron.

 

[Steve O]

From AA:

If the original OPT is inside a feedback loop, you're probably going to have to tweak components that determine feedback and stability parameters too. If this is the case, test equipment will be required.

 

[bowtie427ss]

Why do you want to upgrade your OPTs? In most cases that negates the entire reason for modifying an amp if you throw-out the classic iron.

I would partially disagree, OPT's are the performance "brick wall" in many of the amplifiers(console pulls, ST-70, etc.) discussed here.

In terms of "hifi" and especially regarding extended frequency response, there are MANY tube amplifiers that can benefit from better OPT's. I realize there are also many amps where the inverse is true, they have fabulous iron from the factory but cannot exploit it's full potential without upgrades to the power supply and basic amplifier circuit.

Just my .02 y'all understand....................

 

[ferninando]

I would partially disagree, OPT's are the performance "brick wall" in many of the amplifiers(console pulls, ST-70, etc.) discussed here.

In terms of "hifi" and especially regarding extended frequency response, there are MANY tube amplifiers that can benefit from better OPT's. I realize there are also many amps where the inverse is true, they have fabulous iron from the factory but cannot exploit it's full potential without upgrades to the power supply and basic amplifier circuit.

Just my .02 y'all understand....................

me too. my 8802 has anemic opts and the low freq sinewaves suffer for it. All distorted and bent 40hz and below. the lo freq rolloff aint good but it do sound nice even tho. at 120/pair I can do without awhile. of course Z matching and output config needs knowing to get the rite opt.

 

[Redboy]

Based on what I've seen of Lar's collection, most of his amps will do just fine with the stock iron - they're not cheap console pulls, most of them.

 

[diamondsouled]

Why do you want to upgrade your OPTs? In most cases that negates the entire reason for modifying an amp if you throw-out the classic iron.

Good question.

Well Nate I just picked up a pair of Electrohome 6V6 console pulls

The OTs that they come with look to be a bit undersized. Also they are mismatched. They are the ones at the top of the inside of the chassis. I will have to hear how they perform of course. I do have some nice Hammond output iron around though so if it can be used I'm thinking: "why not?".

Looks to be enough room on the chassis for a slightly bigger OT.:yes:

Will have to track down a schematic first.

Cheers

Lar

 

[Redboy]

What model, Lar? I might be able to help you with the schematic. Drop me a PM w/ your email addy, okay?

 

[diamondsouled]

By the way these fine amps came out of a Chipendale 3 and Original Chipendale console.

Cheers

Lar

 

[mhardy6647]

I would partially disagree, OPT's are the performance "brick wall" in many of the amplifiers(console pulls, ST-70, etc.) discussed here...

Just my .02 y'all understand....................

Umm, not in the ST-70 (assuming you mean the Dynaco ST-70?). The output transformers are legendary; there's really not much else about the ST-70 that's worth the space it takes up (that's why mods for everything else in an ST-70 became, and still are, a cottage industry).

Actually, the EICO ST-70 has pretty fine output iron, too.

 

[hotroady]

Umm, not in the ST-70 (assuming you mean the Dynaco ST-70?). The output transformers are legendary; there's really not much else about the ST-70 that's worth the space it takes up (that's why mods for everything else in an ST-70 became, and still are, a cottage industry).

Actually, the EICO ST-70 has pretty fine output iron, too.

Yeah, the output transformer of the Dynaco ST-70 is what made it worth owning /modding. It's power supply tranny is nothing to write home about.

 

[mhardy6647]

...nor is anything else about it (even the nickel plating on the chassis, used instead of chrome to keep the cost down)

David Hafler put the money in the best possible place, the output iron.

 

[bowtie427ss]

Umm, not in the ST-70 (assuming you mean the Dynaco ST-70?). The output transformers are legendary; there's really not much else about the ST-70 that's worth the space it takes up (that's why mods for everything else in an ST-70 became, and still are, a cottage industry).

Actually, the EICO ST-70 has pretty fine output iron, too.

I used to agree with this 100%, not so much anymore.

I've heard a Lundahl OPT equipped Dyna ST70 next to my cloth lead A-470 equipped ST70. Both amps were restored by the same fellow with minimal differences outside of output iron, the difference between these amps on his Cornwalls was huge, almost embarrassing. I really had no complaints before, but i never loved my ST70 the same after that afternoon and sold it soon after.

 

[goldear]

Umm, not in the ST-70 (assuming you mean the Dynaco ST-70?). The output transformers are legendary; there's really not much else about the ST-70 that's worth the space it takes up (that's why mods for everything else in an ST-70 became, and still are, a cottage industry).

I guess that this has been my experience too. To me, any amp that requires new iron is probably not worthy of my efforts to modify. I mean, if you have to put new Iron on an amp, then why even bother? You will have nothing but the chassis itself left when you are done!

I've been consistently amazed at how good Dynaco Iron can sound when the circuit was replaced with a really good design. But Dynaco made some very good, yet relatively inexpensive transformers. However, there are some classics which contain iron which will absolutely put the old Dynaco Iron to shame (such as the Citation II, and the Heath W-5M, and the Eico HF-87, among others).

 

[mhardy6647]

these are yet more audio examples of the old folk tale known as "Nail Broth" or "Stone Soup".