Hello all, I have started this thread as I am starting a build of Pete's excellent Engineers Amp. This will be my first ever Valve amp project so I expect it to be challenging/fun and knowledgeable along the way.
I have already ordered the PCB from Pete's ebay site and will be waiting for this to arrive (safely hopefully) in the UK.
First thing to do is start sourcing the materials. I live in the UK so a lot of US parts that are easily to come across are more expensive here over the pond.
Has anyone in the UK built his amp. If so please let me know how you got on and what materials you used. Has anyone ordered Encore transformers from the US, if so what cost did you pay on import.
I want to use Edcor transformers as they look cool and are very well recommended as good transformers . Getting this imported from the US is expensive for postage around £220 for the transformers plus postage but then I expect to get stung by import taxes. I have found a European supplier https://www.don-audio.com that are more expensive on the buy of them but cheaper on the postage total will be approx £290 but may not get import tax and will be a quicker order. Not sure what supplier to use yet, this will be my biggest problem so far.
As for Valves the 6CB6 are easy to get over here on ebay but the 6JN6 and 6JM6 are not. Will have to see if I go with the original design valves if I can get hold of them at a good price.
So my first thing when the PCB is here is to start sourcing the valves.
Love to know what others think
I have already ordered the PCB from Pete's ebay site and will be waiting for this to arrive (safely hopefully) in the UK.
First thing to do is start sourcing the materials. I live in the UK so a lot of US parts that are easily to come across are more expensive here over the pond.
Has anyone in the UK built his amp. If so please let me know how you got on and what materials you used. Has anyone ordered Encore transformers from the US, if so what cost did you pay on import.
I want to use Edcor transformers as they look cool and are very well recommended as good transformers . Getting this imported from the US is expensive for postage around £220 for the transformers plus postage but then I expect to get stung by import taxes. I have found a European supplier https://www.don-audio.com that are more expensive on the buy of them but cheaper on the postage total will be approx £290 but may not get import tax and will be a quicker order. Not sure what supplier to use yet, this will be my biggest problem so far.
As for Valves the 6CB6 are easy to get over here on ebay but the 6JN6 and 6JM6 are not. Will have to see if I go with the original design valves if I can get hold of them at a good price.
So my first thing when the PCB is here is to start sourcing the valves.
Love to know what others think
Thanks for the replys and sujestions. I have not had a good look at Sowter as this did come up on any google searches.
i've just had a quick look and the push pull OTs would be around £200. each
If this is the cheapest they do at 8K ohm primary winding then they will be out of my budget for a first project. I think this would be hard to explain the the wife.
i will look at the site more when i have time. i'm suppose to be ordering the dinner at the moment so dont have much time
i've just had a quick look and the push pull OTs would be around £200. each
If this is the cheapest they do at 8K ohm primary winding then they will be out of my budget for a first project. I think this would be hard to explain the the wife.i will look at the site more when i have time. i'm suppose to be ordering the dinner at the moment so dont have much time
Thanks guys. theres some great sites you have suggested. will get round to checking them all soon. First look i am interested in the toroidal transformer here
I need to check the spec first with the original Encor OT but it seems to be ok. also need to research about the noise and quality of these OT.
if all good then they are a good contender, they work out at about £40 a transformer so may be worth getting for a first project and upgrading at a later date.
I need to check the spec first with the original Encor OT but it seems to be ok. also need to research about the noise and quality of these OT.
if all good then they are a good contender, they work out at about £40 a transformer so may be worth getting for a first project and upgrading at a later date.
The noise from the toroidal OPT's are likely lower than the EI-core's, but they may require more care to null out the imbalance between the output tubes, as toroidal OPT's tend to saturate more easily. But given the low cost, why not give them a try?
if i can't get the output balanced properly with the on board pot's what effect will this have on the sound. I expect the output would be distorting at certain levels. but at low levels would the sound still be good.
i will only have a thew valves and i expect these will not be matched well so with these being out of balance would it be a big problem with the toroidal's.
i will only have a thew valves and i expect these will not be matched well so with these being out of balance would it be a big problem with the toroidal's.
Try RES: Vacuum Tubes Radio Tubes - 5,000 different tubes in stock - Over 10 million tubes! - great guys, and they will ship internationally. They should have 6JN6, listed for $5 each. USPS to UK should only be about $10-15.
Pete
You should know that when changing the output transformer, negative feedback amount / compensation calculations mostly go out the window. Do you have a scope to check/adjust them? Surprised nobody mentioned that yet.
Or you can happily disconnect the feedback, there is an option for that on the board
Or you can happily disconnect the feedback, there is an option for that on the board
I have had excellent results with transformers from Valve Push-Pull Output Transformers
They will do specials as well. Otherwise Majestic Transformers of Parkstone, Dorset will wind any transformer. Just give them the spec. and they will quote you.
They will do specials as well. Otherwise Majestic Transformers of Parkstone, Dorset will wind any transformer. Just give them the spec. and they will quote you.
thanks for the reply's. I do have a PC scope but have never balance tube amps before. This is a first project to learn from.
i have looked at Valve Push-Pull Output Transformers this was my first place i went to and was also were i got my original amp design from. I just did not know how good there OT are. I will price up them and see what difference they come to. Obviously these are a UK company so much better for supplies.
i have looked at Valve Push-Pull Output Transformers this was my first place i went to and was also were i got my original amp design from. I just did not know how good there OT are. I will price up them and see what difference they come to. Obviously these are a UK company so much better for supplies.
The original design spec for the engineers amp was for OT with 8K primary winding center tapped and 8 ohm output rated at 25 Watts with 150 mA primary.
Below is the Edcor design
https://www.edcorusa.com/cxpp25-ms-8k-23
and this is the UK design
Valve Transformer VT1545
Do you think this would be a good match.
Below is the Edcor design
https://www.edcorusa.com/cxpp25-ms-8k-23
and this is the UK design
Valve Transformer VT1545
Do you think this would be a good match.
VVT has a wide range of affordable transformer:
'Vvt Ltd' design and make Wound Components including Transformers, Chokes and special Coil Winding.
Cheers
Ian
'Vvt Ltd' design and make Wound Components including Transformers, Chokes and special Coil Winding.
Cheers
Ian
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