I recently built my first tube amplifier a 6EM7 which is a television tube and I thoroughly enjoyed the sound. I started considering building a better tube amplifier and thought maybe a 300B amp but the prices for these tubes are outrageous on my budget. I proudly admit that I am a cheap Diy'er. After searching the web I came upon Vinylsavor's web page and did some reading. I like the fact that the 6CB5A's are not expensive and Thomas states the amps he design can and do sound better than many 300B amps. I decided to build one of his cheaper designs, this one.
VinylSavor: Single Ended Amplifier Concept, Part 4
The closest transformer I could find with the specs he specifies was a toroid from Antek.
AS-4T320 - 400VA 320V Transformer - AnTek Products Corp
This transformer has dual voltage sources so I decided to build separate PS so in effect I would have mono amplifiers using a single transformer. A 10Hy choke gets pricey and as I have stated I am a cheap Diy'er so I chose to use a 6Hy Triademagnetics C-14X you can purchase for $15 and for 2 PS the cost is $30. I used one in my 6EM7 build and it was very satisfactory. I used Edcor for my OPT's specifically the GSXE15-8-3.5K. Later I noticed Thomas recommends using a 5K OPT but I found this out after ordering. It sounds great with the 3.5K though. I used my first PIO Russian coupling capacitors and other than these changes I built it as per schematic. I just finished it yesterday so I cannot give a review yet but first impressions are very positive. It has great authoritative bass much as a SS amp and a great holographic sound stage. The tubes have no hours on them and the sound is amazing from the first listening and one of the first things I noticed is how quick it is, good transient response. I am going to do some more listening and will give more of a review later. Many thanks Thomas Mayer for making this amplifier available for DIY'ers.
VinylSavor: Single Ended Amplifier Concept, Part 4
The closest transformer I could find with the specs he specifies was a toroid from Antek.
AS-4T320 - 400VA 320V Transformer - AnTek Products Corp
This transformer has dual voltage sources so I decided to build separate PS so in effect I would have mono amplifiers using a single transformer. A 10Hy choke gets pricey and as I have stated I am a cheap Diy'er so I chose to use a 6Hy Triademagnetics C-14X you can purchase for $15 and for 2 PS the cost is $30. I used one in my 6EM7 build and it was very satisfactory. I used Edcor for my OPT's specifically the GSXE15-8-3.5K. Later I noticed Thomas recommends using a 5K OPT but I found this out after ordering. It sounds great with the 3.5K though. I used my first PIO Russian coupling capacitors and other than these changes I built it as per schematic. I just finished it yesterday so I cannot give a review yet but first impressions are very positive. It has great authoritative bass much as a SS amp and a great holographic sound stage. The tubes have no hours on them and the sound is amazing from the first listening and one of the first things I noticed is how quick it is, good transient response. I am going to do some more listening and will give more of a review later. Many thanks Thomas Mayer for making this amplifier available for DIY'ers.
Hi
The 126C from Hammond (1:1, 15mA, about 100H) could work as well in this design - is "made in Canada" ok? Still, Edcor will surely make you something nice as well, but asking for 1:1.125 will surely be a custom job which costs some $$ extra. So, to stay cheaper, just ask them if they have a 1:1 project ready: the 12% difference in ratios is barely audible (if my math is right it is about 0.98dB.
erik
Hi!
I am glad that you like the sound of this concept. The interstage transformer coupled version will improve the sound considerably, depending on the quality of the IT of course. However make sure to use good quality capacitors. The last cap in the power supply becomes much more audible in transformer coupled designs.
best regards
Thomas
I am glad that you like the sound of this concept. The interstage transformer coupled version will improve the sound considerably, depending on the quality of the IT of course. However make sure to use good quality capacitors. The last cap in the power supply becomes much more audible in transformer coupled designs.
best regards
Thomas
Hi,
as you are in the US, Lundahls can be bought from K&K audio (price for a single LL1660 is 125 USD)
K&K Audio | Prices
Indeed, the LL1660/10mA does have a bit more H than the Hammond (datasheets state 130H vs 106H), so the Lundahl would do better in the bass. OTOH, the Hammonds 106H is at 15mA DC - the H will go up a bit if you run only 6 to 7mA.
If budget is not a problem I would go for the Lundahl. Member Andy compared both and liked the Lundahl better, besides the Lundahl is way more flexible for a possible future project (can be used for line out, OPT for high impedance - >300R - headphones, even as PP to PP interstage).
Cheers, Erik
as you are in the US, Lundahls can be bought from K&K audio (price for a single LL1660 is 125 USD)
K&K Audio | Prices
Indeed, the LL1660/10mA does have a bit more H than the Hammond (datasheets state 130H vs 106H), so the Lundahl would do better in the bass. OTOH, the Hammonds 106H is at 15mA DC - the H will go up a bit if you run only 6 to 7mA.
If budget is not a problem I would go for the Lundahl. Member Andy compared both and liked the Lundahl better, besides the Lundahl is way more flexible for a possible future project (can be used for line out, OPT for high impedance - >300R - headphones, even as PP to PP interstage).
Cheers, Erik
Thanks everyone for explaining what is needed. I must admit that I had a sticker shock when I found out what was needed. I am a relatively new tube builder and interstage transformers are something I knew nothing about. What could I expect in improvement of sound using transformers vs capacitors. I have heard that it would be an improvement but not much on what exactly would be improved. Mine sounds better than any amp I have ever used with my horns just using a capacitor.
Hi!
If you are thinking about merely sticking a interstage transformer in the existing circuit, I would not recommend it. Better to adapt the IT coupled circuit which I posted. The IT-coupling is just one part of the game. The difference in sound will depend on the quality of parts, power supply and especially ITs.
Best regards
Thomas
If you are thinking about merely sticking a interstage transformer in the existing circuit, I would not recommend it. Better to adapt the IT coupled circuit which I posted. The IT-coupling is just one part of the game. The difference in sound will depend on the quality of parts, power supply and especially ITs.
Best regards
Thomas
I thought as much and if I decide to try an interstage transformer amp it will be a totally new build using the other schematic. It would be virtually impossible to put those big transformers in my present build. This amp sounds so great as I have built it that I would love to hear a better version though. The interstage amp build is definitely going on my bucket list.
Thanks again Thomas for publishing these builds.
I recommend trying a cheaper and better solution, buy some of Pete's A2 driver boards using current source loaded Source Followers and you won't go back. The board is $15 and parts are probably another $15.
DIY PCB MOSFET Source Follower Buffer for Class A2 Drive | eBay
DIY PCB MOSFET Source Follower Buffer for Class A2 Drive | eBay
I finished this amp a couple of weeks ago. It has about 6W. it is connected to small B&W 805 Signature speakers with REL woofer. Sounds quite well despite the fact that the speakers are insensitive (89dB producer claimed).
Yesterday I decided to hook it up to my B&W 802D out of curiosity. This is a 93dB (producer claimed) but very difficult to drive as it has a bumpy impedance curve. What I'd say? This amp is a real fighter!
Of course, it sounds as if it needs more power but there was music, and it was good And it was quite loud.
Yesterday I decided to hook it up to my B&W 802D out of curiosity. This is a 93dB (producer claimed) but very difficult to drive as it has a bumpy impedance curve. What I'd say? This amp is a real fighter!
Of course, it sounds as if it needs more power but there was music, and it was good
And it was quite loud.