200- 500 watt Tube Amp project

[Arnulf]

Originally Posted by prairiemystic

The Hammond 1650W is rated 280W at 1900ohms primary, weight is 28 lbs, about $315.

The Plitron PAT-4141 is rated 400W at 1250ohms primary, weight is 23.5 lbs, about $410.

Something doesn't quite add up here. When it comes to cars the saying goes "there's no replacement for displacement". Can one of you native English speakers make a rhyme out of "there's no substitute for iron" ?

[toddbailey]

Originally Posted by richwalters

Toddbailey......what is the lowest frequency operation at full power you are anticipating ? I'm strongly inclined to keep design to commercial tubes that are currently manufactured. 6550,KT88,KT90 and so on.

Example:-An E&I 200W o/p tranny set at 15Hz will weigh 25Lbs. (designing for 40Hz can expect half the iron weight) and the mains probably around 35Lbs or more. With the chassis (reinforced), Can you lift this heap or need a fork truck ?

Parallelling same make o/p trannies is an idea but not a space saver, but I prefer a single lump.


richy

I am looking to replace several transistor amps (5) (home theater) and a McIntosh tube amp (audio only) with higher power designs

some movies like Terminator present problems. After reading the above posts any tube amp much larger than 200 wpc might be impractical. perhaps I could use the mono block design using a single or a pair of 813 tubes per channel

[prairiemystic]

Originally Posted by Arnulf

Something doesn't quite add up here. When it comes to cars the saying goes "there's no replacement for displacement". Can one of you native English speakers make a rhyme out of "there's no substitute for iron" ?

I believe in Einstein's equation E=mc^2 as applied to tube gear:
More power, more mass. More iron. It doesn't rhyme.

I have some Hammond 1650N's rated 60W and find they are conservatively rated, good to 90W.

[richwalters]

Originally Posted by Arnulf

Something doesn't quite add up here.

There is always a weight difference vs performance between E&I and toroids.

Toddbailey: a clue is look at SOWTER AUDIO TRANSFORMERS
tab p-p amps and scroll at p-p UO72 relevant to 400W amp. Note LF cut off 40Hz. The price ? a sloppy pound.

richy

[nigelwright7557]

A hybrid would be much more practical.

A valve front end with SS class ab stage.

[tubelab.com]

Something doesn't quite add up here. When it comes to cars the saying goes "there's no replacement for displacement". Can one of you native English speakers make a rhyme out of "there's no substitute for iron" ?

When all automobile engines were of similar design and all had 2 valves per cylinder, the saying was true. Today it is hard to judge an engines output potential by displacement alone.

When all transformers were of EI construction, mass was a suitable means to judge the power capabilities of a transformer. In this case we are comparing a 2 valve cast iron engine, the EI constructed Hammond, to a 4 valve VVT aluminum headed high RPM screamer, the toroidal Plitron. Since a toroid makes more efficient use of the magnetic flux, it can have less iron (but about the same copper) for a given power output.

I purchased a pair of surplus Plitron OPT's that were intended for a bass guitar amp (discussed in the 8 X 807 thread). The label on the transformer says 400 watts at 20 Hz. I have not tested them at this power level yet, but I have been to 200 watts at 20 Hz. No saturation was seen. You do however need to carefully balance the DC current between the two sides to avoid saturation.

I am building a big P-P amp for two reasons. One is just because I can, and the other is that over the years I have already collected all the expensive parts without spending a fortune. I plan to build this amp for $500 to $1K including the chassis. Much of that has already been spent since I have the tubes and transformers. Yes it will be heavy, but I will deal with it. Do I need 200 to 500 WPC? NO. Will I use 200 to 500 WPC, Not unless I want to set my speakers on fire!

If I wanted to set up a big HT system (no room in my tiny house) I would use a big fat SS amp for the sub. Something like the 950 watt Crown that I recently gave away (half of a CE2000, the other channel is blown), or a class D amp. For the 4 main channels I would use a P-P tube amp of about 50 WPC. 200 watts of tube amp power could be run a lot closer to clipping without sounding bad and be as loud as 1000 watts of SS power set to avoid clipping on loud peaks.

Something like that would be a realistic build and wouldn't heat your whole house.

[dggs]

For OTL, it's possible. 500W MA-3
Only $147,100.00/pair
$?????? if you DIY

[nigelwright7557]

Bibani used to have a valve book with amplifiers upto 1k5 watts.

[tubelab.com]

For OTL, it's possible. 500W MA-3
Only $147,100.00/pair

So that's where all of the 6AS7G's went!

[Michael Koster]

Originally Posted by toddbailey

I am looking to replace several transistor amps (5) (home theater) and a McIntosh tube amp (audio only) with higher power designs

some movies like Terminator present problems. After reading the above posts any tube amp much larger than 200 wpc might be impractical. perhaps I could use the mono block design using a single or a pair of 813 tubes per channel

100 watts per channel can be done with pairs of 6550s or KT88s or any of a bunch of the bigger sweep tubes e.g. EL509, or transmitter tubes as small as the 6146B, all under 800V B+. You could build 2 channel 100 WPC amps with three $100 transformers each. And you could lift them. I think that's a sweet spot for practicality and I would bet will be overkill for everything but the low end. There maybe some monster amp but maybe it doesn't need to be a tube amp.