True, they are guitar amp transformers. If they're not good enough for hifi, I'll have an excuse to build two more guitar amps
@Fuling : did you finally bought and tested these TT-OTG5V3 transformers ?
T
Thanks ! I'm gently planning to buy one for testing with a stereo SE 1WRMS project using a VT25/10Y triode, the output connected in 4R to see a reflected 10K primary impedance.
Of course, a pair of Hashimoto H-20-14U would certainly be a premium choice... at 20X the cost of a pair of TT-OTG5V3 !
T
Of course, a pair of Hashimoto H-20-14U would certainly be a premium choice... at 20X the cost of a pair of TT-OTG5V3 !
T
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I'll report as soon as I have tested them, no idea how long that will take though.
I have a few too many projects going on at the same time right now but building a simple output stage to test these transformers shouldn't take long.
Tube Town also sells a small, nice looking 15k PP transformer that I've been looking at for some miniature, just-for-fun project sometime.
I have a few too many projects going on at the same time right now but building a simple output stage to test these transformers shouldn't take long.
Tube Town also sells a small, nice looking 15k PP transformer that I've been looking at for some miniature, just-for-fun project sometime.
Fine @Fuling !
Guess what ? I ordered one as a test part yesterday... It will be here in a few days.
I think that it should be very interesting to share/match our results about this transformer, right ?
T
That's right : 160mA announced here. Yes, the 10Y only needs 18-20mA, so the primary inductance will be much increased, thanks to the laminations that are rather large :
The air gap is probably not modifiable, thanks to a coating / anti-vibration treatment, I guess... I can't tell since unlike you, I don't have them in hands. If the I of the EI laminations is easily removable, then yes, a modification could be possible, but IMHO, a removable I would then mean a poor impregnation of the transformer, synonym of noises and vibrations...
Another point that I must check is if the transformer is capable to provide the 10K load for the VT25/10Y by using it on the 4R tap.
Of course, the premium alternative choice would be this :
It's just not the same budget... A detail !
T
Yes, I see - you mean this one :
https://www.lundahltransformers.com/wp-content/uploads/datasheets/2735B.pdf
Yes, they are much more affordable than the Hashimoto transformers - prices in Euros from the French distributor :
But unfortunately, there's no casing version available for these transformers, and they have an odd mounting shape and scheme...
... That is not very compatible with a compact amplifier design like those I build :
T
tubelectron: The Lundahls are not a pretty sight, I agree completely with you about that May I suggest that you take a look at this transformer as a budget alternative for your 10Ys: https://shop.piemme-elektra.it/Categories/93/Products/8104
I have a pair of these for an upcoming 807 SE class A2 project (I got this idea that I wanted to try 807 in triode mode at a quite high voltage and with a "flat" loadline, hence the 8k transformer).
I've already made a prototype output stage using one of those transformers and it seemed to work quite well for such a cheap (and good looking) OPT.
As a side note, the trioded 807 seemed to like the high Z load, producing 1,7W in class A1 and almost 3,5W in class A2 with a 6E5P cathode follower driver stage. That was at 360V 50mA, I'm hoping to squeeze a few more volts out of the power supply in the final version.
May I suggest that you take a look at this transformer as a budget alternative for your 10Ys: https://shop.piemme-elektra.it/Categories/93/Products/8104I have a pair of these for an upcoming 807 SE class A2 project (I got this idea that I wanted to try 807 in triode mode at a quite high voltage and with a "flat" loadline, hence the 8k transformer).
I've already made a prototype output stage using one of those transformers and it seemed to work quite well for such a cheap (and good looking) OPT.
As a side note, the trioded 807 seemed to like the high Z load, producing 1,7W in class A1 and almost 3,5W in class A2 with a 6E5P cathode follower driver stage. That was at 360V 50mA, I'm hoping to squeeze a few more volts out of the power supply in the final version.
Aha, yes ! Good information here @Fuling - Thanks !
Looking at the website, I found this one too : https://shop.piemme-elektra.it/Categories/93/Products/8377
Of course, there are large models offered, similar to the Hammond 1638SE, but they would not enter my chassis...
I'll wait for the TT transformer to come and test it - then I'll investigate those Piemme models !
Thanks again
T
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I'm sorry I forgot to mention Piemme earlier, I simply had forgotten about them until a few hours ago when I moved the breadboard to make room for a test rig with the TT transformer and an 808.
Piemme has some nice stuff, including a series of nice transformer covers that I'm using to cover the Lundahls in my PP 6S4S amp. Good prices and fast shipping too.
The transformer in your link probably suits 10Y better than the one I linked to, I seem to remember that I picked the 70mA version because of the lower primary DCR.
Piemme has some nice stuff, including a series of nice transformer covers that I'm using to cover the Lundahls in my PP 6S4S amp. Good prices and fast shipping too.
The transformer in your link probably suits 10Y better than the one I linked to, I seem to remember that I picked the 70mA version because of the lower primary DCR.
I see @Fuling - I did not knew the brand Piemme until that you have just brought it to my attention - thanks again !
I'm now tempted to buy a little SE 5W 8K 50mA Piemme SE-EI68024CV-N for a comparison... no rush though : let's wait for the TT first to check !
After all, the TT-OTG5V3 is a larger unit, with larger laminations, which will be lightly loaded by the small plate current of the 10Y (circa 20mA) and then able to give a high primary inductance, suitable for bass reproduction. If the windings have been made correctly (enough regularity, interleaving and impregnation), then the treble bandwidth and low distortion shoud be met, considering that the 10Y will not give much more than 1WRMS...
Moreover, you mention 808 - I guess it's for the TANGO-Hirata U-808 : did you tested them ? Are they worth their reputation and price ?
T
I saw the name Piemme mentioned somewhere on this forum earlier this year and decided to check it out, shortly after that I ordered some transformer covers for my Lundahls and a couple of bobbins for some other projects. Later, I ordered all the iron for my 807 SE monoblocks from them, and the initial test resuls has not been disappointing. I seem to understand that they make their own transformers, perhaps you could ask for a pair with a smaller airgap for the 10Ys?
By 808, I mean the big nasty RF tube made by RCA and GE: http://www.r-type.org/exhib/aaq0179.htm
Quite similar to the more common 811A but much better looking After collecting them for over fifteen years I finally have three pairs in good condition, which I consider a large enough number to build an SE amp with.
By 808, I mean the big nasty RF tube made by RCA and GE: http://www.r-type.org/exhib/aaq0179.htm
Quite similar to the more common 811A but much better looking
After collecting them for over fifteen years I finally have three pairs in good condition, which I consider a large enough number to build an SE amp with.
I just ran a quick test of the 808 - TT OPT combo and the results are not very encouraging: With my non-optimal setup and primitive measuring equipment in mind, a low-power test with the OPT connected as 5k/8R shows a 23Hz-15kHz -3dB bandwith.
There might very well be something off with my setup and the 808 is a problematic tube due to its high Rp so let's not give up quite yet.
There might very well be something off with my setup and the 808 is a problematic tube due to its high Rp so let's not give up quite yet.
Seems like there is something wrong with my wiring, my driver stage or my tone generator after all. Unless I'm completely wrong, I have pretty much the same HF rolloff at the grid of the input tube as there is at the output of the transformer. Please let me investigate this further before we draw any conclusions about the quality of the transformer. I'm too tired to work with 400V test circuits right now so I'll come back tomorrow.