Most expensive parts in DIY tube amp

[maggiesnmacs]

I've been thinking about doing a basic single-ended amp design as a first amp build. Something similar to this...

http://www.bonavolta.ch/hobby/en/audio/kt88.htm

But when I looked up output transformers they're 2-300 dollars for each, which would be 4-600 dollars for a stereo amp just in output transformers...My jaw just about dropped to the ground with that...Am I right? For an amp somewhere around 10WPC its gonna cost 500 bucks in output transformers? Or am I missing something... And also what are the other main expensive parts? I've assumed of course the tubes, which I'm guessing would be about $100 total for a stereo amp, the power supply transformer and inductor which I also didn't expect to top $100. And then besides that its mostly the case and miscellaneous resistors and capacitors etc. right?

But those damn output transformers...are they really that expensive?

 

[20to20]

You have a lot of researching to do before you decide on doing this project.

 

[M Gregg]

It all depends,

What are you trying to create?..yes I know its a SE amp however there are SE amps and SE amps..you can build to a budget.

Have you looked at the Edcor site?
There are SE output Tx's and output Tx's..what I'm saying is: If you build with Tango etc expect to pay..there are higher prices you could build with Audio note silver wound transformers which are ridiculous money..its a trade off..
This is just an example:

https://edcorusa.com/gxse15-8-2_5k

Regards
M. Gregg

 

[famousmockingbird]

Everyone wants to build a single ended amp at first because they appear to be a simpler design. BUT besides less components single ended has bad PSRR and not to mention as you have noticed the price of output transformers, the output iron needs an air gap so the core doesn't saturate with the standing DC current, the air gap then causes the inductance to drop so in order to make up for it they use larger cores and more windings. You can use non air gapped smaller transformers if you go parafeed but then you will just end up spending the money in good quality chokes. Push pull transformers are smaller and cheaper, plus you get more audio watts and better PSRR and distortion cancellation.

 

[famousmockingbird]

I don't trust people who make dedicated detailed web pages about their cats.

http://www.bonavolta.ch/hobby/en/various/cats.htm

 

[deafbykhorns]

I spent $1000 on OPT transformers, worth every penny.
My last SET 10 yrs ago had some "off the shelf" iron and performed poorly.
If your going to build and SET, spend every dollar you can on the transformers.

 

[famousmockingbird]

I wonder how much Magz spent on his Monolith output iron for his 833C amp?

I wish I could find the thread where he posted pictures of them completed......they look sooooooo boss!!!

 

[chrisb]

+2 on the Edcor recommendation - and don't overlook the excellent circuits and perhaps still parts offering at George's Tubelab
Tubelab | Dedicated to advancing the state of the art in affordable high end audio.

I built one of his SimplePP a few years back - happened to be able to recycle some vintage Scott P/P outputs, and settled on an Edcor power TX - do not try to save money on thermal rating of the Power TX

but yah, iron costs money, then there's the chassis and miscellaneous mechanical and passive circuitry parts that depending on how boutique you wanna go can easily run into several hundreds of dollars.

 

[M Gregg]

So you see,

We don't know if your trying to make Ongaku on the left.. mortgage money

Or something like this middle EL34 and right 6L6..which was a fun project..😀<<using Edcor..

Sorry just resized the pics..

Regards
M. Gregg

 

[K.A.B]

+3 on Edcor iron.

I have built an EL84 SE with Edcor opt and all who have listened are impressed but I'm looking to try a pair of Lundahl opt to see if it could be worth an update.

Anders

 

[famousmockingbird]

Edcor is great for the money, but I have only used their PP iron. Their XSE line is only rated down to 70Hz.........and their GXSE line goes lower down almost a full octave to 40Hz, something to think about.

What is the frequency response of your current speakers?

 

[M Gregg]

I used Edcor GXSE on the amp shown and XSE on an RH 84.

The RH is lower power sounds nice.. 😀

Regards
M. Gregg

 

[KenTajalli]

Everyone wants to build a single ended amp at first because they appear to be a simpler design. BUT besides less components single ended has bad PSRR and not to mention as you have noticed the price of output transformers, the output iron needs an air gap so the core doesn't saturate with the standing DC current, the air gap then causes the inductance to drop so in order to make up for it they use larger cores and more windings. You can use non air gapped smaller transformers if you go parafeed but then you will just end up spending the money in good quality chokes. Push pull transformers are smaller and cheaper, plus you get more audio watts and better PSRR and distortion cancellation.

+1 +1 +1
on every count!
Good advice here.

 

[multi]

Before making SE amps, consider if your speakers are suitable, most Modern speakers are designed for transistor amps, very poor damping and need lots of power. Speakers for low powered even high power SE need drivers with good damping and sensitive.
Phil

 

[Magz]

I wonder how much Magz spent on his Monolith output iron for his 833C amp?

I wish I could find the thread where he posted pictures of them completed......they look sooooooo boss!!!

Roughly $5k for two OPTs, plus shipping from Belgium to US, customs duties, etc.

Given the current state of the Euro, however, you could get them about 20% cheaper now, though...

Thread: http://www.diyaudio.com/forums/tubes-valves/232484-midlife-crisis-my-833c-amp-build.html


PS: These sound fantastic with the very inefficient acoustic suspension Infinity RSIIb's in the picture. This is a bit of a special case, however.

 

[KenTajalli]

Roughly $5k for two OPTs, plus shipping from Belgium to US, customs duties, etc.

A very strong case to go OTL!
I did, never looked back.

 

[TheGimp]

+4 on Edcor Iron.

Both their OPTs and PTs are great value transformers. GXSE15-8-5K is a terrific transformer for the money, based on my experience.

Downside is waiting time for delivery which typically runs 4-6weeks.

 

[Gorgomat]

You don´t have to spend 300+ for output iron ( many companies let you charge for their names ). There are good manufacturers too which provide a similar or even better performance at a way lower price ( eg. Audioröhrentechnik Ausgangstrafo Übertrager Bandfilter Spulen Röhren Audio Fassungen 516201 516228 516236 516260 516686 NF-Übertrager Drossel Trafo Hifi Highend in Germany ).

A good SE amp requires some precautions though ( good power supply filtering ) and sensitive speakers.

Best regards,

 

[RajkoM]

A good SE amp requires some precautions though ( good power supply filtering ) and sensitive speakers.



...and most importantly, good input/driver stage.

 

[MrCurwen]

In my builds the most expensive part is the PT, and the second most expensive is the OTs, both of them combined.

Once again, depends on what kind of a build you're making and what are your priorities. There are many ways of "designing around" cheaper OTs and still getting premium sound quality.