DIY Audio Projects Forum

Still my advice, start with regular standard devices and if you ar curious, try swapping components that may do a difference. Starting with the tubes - they would have the biggest impact on sound quality.

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Magnus

“If you don't know where you are going, any road will get you there.”
―Lewis Carroll

Thanks for taking the time to reply. I have been on RS and some other websites and I have found it hard to know which caps to buy. From the projects page the caps look like coaxle caps, and the ones on RS look like through hole ones. Can you recommend the actual good quality standard caps to go for that will be easy to find online?

I see that there are different lifetimes for the caps and if possible would go for 10,000 - 12,000 hours . The Nichicon and Panasonic look good but are through holes. Would you mind going to the RS website and copy the links for me for suitable caps and 1w resistors such as Vishay?

The website is here https://uk.rs-online.com/web/

Thanks for your help

Lee

I am not familiar with RS, use local companies in Sweden, but for electrolytics, if possible pick 105 degrees. Also when it comes to mounting, I always use through holes caps. Either use those plastic straps to tie them down or solder on small boards and screw in place.

_________________
Magnus

“If you don't know where you are going, any road will get you there.”
―Lewis Carroll

Here is the list I made while building my 4s + buffer preamp. There is french words here and there, but don’t hesitate if you need more explanations (or translation).

I personally recomend you to pick cheapest caps for power supply avalible as they won't effect the sound much or at all.
The rating of 10-12k hours is at maximum temperature below that most caps last very long

Concerning the transformer for the UK the BOM recommended a Hammond 269EX whereas I have read in another thread that a 240v will be required for the UK and so to use a Hammond 369EX

https://www.mouser.co.uk/ProductDetail/546-369EX

Download the PDF here for the 369EX
https://www.mouser.co.uk/datasheet/2/177/300-951115.pdf

Is the 369EX the correct one to use?

Thanks for all the help so far

Yes.

In the UK you have 240V, 50Hz mains. The Hammond 300 series power transformers have universal primaries so you can connect it appropriately. Here is the 300 series general primary diagram...
And here is how you wire it for 240v mains...
Does this make it more clear?

_________________
Matt
It's all about the Glass!
http://www.CascadeTubes.com
Cascade Tubes Blog

Thanks for confirming that the Hammond 369EX is the correct one for the UK Matt.

As I am in the U.K. I would be looking to use a Hammond 369EX transformer (if that is the correct one to use 240v and the wiring diagram.

AC High Voltage Secondary R.M.S 380V C.T. @ 75ma.
Bias Tap: 50 VAC tap from high voltage secondary C.T
Filament 1 VAC 6.3V C.T. @ 2.5A

Can you please something about the 380v C.T.@ 75ma in relation to what the B+ voltage will be with the components you have specified? What voltage can I expect and also the mention that the 12au7 works really well with 300v.

Also are hammond transformers a good choice and how important is the quality of the transformer in relation to the preamp, is it one of the most crucial things in the circuit and so the main cost of the amp should be invested in it?

I am almost ready to order with Mouser UK.

I am almost ready to make my order from MouserUK and I have kept to good quality components I think, including Nichicon, IDC and Kemet /Rifa Caps and Vishay Dale resistors.
I have ordered slightly more than I need for spares and future projects.

Also Orange drops from Watford Valves
Sprague Orange drop 715p Capacitors / CAP-OD-715-.47/400V
https://www.watfordvalves.com/product_detail.asp?id=1357

Can anyone say how important the tube bases are and which type to go for

'9 pin B9A Belton VT9-ST-2 is a very high quality Micalex valve socket for chassis mounting'
https://www.watfordvalves.com/product_detail.asp?id=1887

or
Russian military grade ceramic chassis mount B9A with vented screening can.Ideal for all ECC83 types and for high grade audio use.
https://www.watfordvalves.com/product_detail.asp?id=427

'These were made for the Russian military and as you can see from the pin pattern they were designed to give a very tight fit so the valve would not come loose. Ideal for all ECC83 types and for high grade audio use. The socket requires a 22mm cut out so will not fit in old vintage amps as they normally have a 19 mm cut out. These are the best qualiceramicaic bases that we have come across and are ideal for small amplifier builders.'


I also have a question about the power supply.

As I am in the UK I will be going for the Hammond 369EX with Mouser

However there is an alternative for half the price for Primary Windings in the UK and it's the

AMP MAKER PWAM03D 190V – 0 – 190V @ 80MA 6.3V @ 2A

http://primarywindings.com/product/amp-maker-pwam03d-190v-0-190v-80ma-6-3v-2a/

This power transformer is designed as a replacement or alternative for those popular amp circuits that specify the Hammond 269EX or 369EX power transformer. It has dual 120V/240V primary windings and two secondary windings. The high voltage winding is 190-0-190V rated at 80mA. In a typical circuit, this will produce a B+ of around 250V after smoothing.
The heater supply secondary is a non-CT 6.3V rated at 2A. That makes it perfect for an amp using two 12AX7s and a single EL84 or 6V6, or a channel-switching preamp using as many as six 12AX7 valves.

This is what they say about their transformers
'The PWHT range of transformers are superb transformers for general purpose use. Using Grain Orientated M6 silicon steel, core losses are reduced.
All our wire is grade 2 enamelled copper wire. This ensures the insulation between turns is extremely high.
All our transformers are resin impregnated with a modern varnish that improves electrical insulation, heat conductance and reduces vibration.
Many cheaper transformers will push the flux density to the limit to reduce the copper used, and increase their margins. Here at Primary Windings we believe that the flux density should be set to allow for mains variations, and the reduction of external magnetic flux, that can cause problems with circuit layout, due to coupling with this stray flux. Lower flux density also allows the reduction of noise from the transfromer. We are proud of our designs, and work to ensure that we produce the best transformers at a reasonable price.'

John who is the owner and designer made me a brilliant transformer and choke for my EAR 834P Phono Clone project.

Answers on a postcard or better still this forum.

Thanks for your help and patience

Sprague orange drops are good signal caps for this project. The 715p or 716p are both acceptable.
These Belton top mount sockets are fine. I wouldn't bother with the shielded versions; I've never needed them at this gain level.
This looks like great option for you. Being in the US I've never used their transformers. However, as it's advertised as a direct replacement for the Hammond, I'd give it a go.

_________________
Matt
It's all about the Glass!
http://www.CascadeTubes.com
Cascade Tubes Blog