Is it possible to build a "bad" 45 amp? I recently built a pair of PP45 amps with a 53 transformer coupled driver and an 80 rectifier, adjustable bias, very old-school. The iron is ISO and Lundahl. I've built a lot of amps, but I think these beat them all! About 6 watts before clipping, but they sound much more powerful. Listening on EV Aristocrats right now, but they also sound great on my Cornwalls.
Nice job on the amp... and 6-watts is pretty much right in the middle from the tube data sheet for the 45 in PP AB1 mode... with 7.5 watts being at the upper end. Any other specs available, i.e., S/N, Freq. response, THD?
Jealous, if for no other reason than having those beautiful 45's available. Good call using transformer coupling to that PP output - I am convinced it's the way to go after enough trials and tribulations.
Curious, how are you using the 53? It is a dual triode, and you have a monoblock.
Lundahl under the hood, what is its use?
Curious, how are you using the 53? It is a dual triode, and you have a monoblock.
Lundahl under the hood, what is its use?
Yeah, those are nice tubes. It's difficult due to their age to find a pair that will bias. I really like the simplicity of transformer coupling. More expensive, but it doesn't wear out.
The 53 is paralleled, so it's essentially a single triode. Gain is limited, so you need a preamp. I'm using a customer's Bottlehead BeePre that I had for repair. It's OK, but runs hot. There's an LL1660 in there wired for 1+1:1+1. I apply the negative bias to the secondary winding, so directly to the 45 grids, no other phase splitter. I have two 10K pots to adjust bias and balance (within reason) so you don't need matched tubes. Bias is very stable after the tubes get warm. I listened to the pair all afternoon and thoroughly enjoyed listening.
The 53 is paralleled, so it's essentially a single triode. Gain is limited, so you need a preamp. I'm using a customer's Bottlehead BeePre that I had for repair. It's OK, but runs hot. There's an LL1660 in there wired for 1+1:1+1. I apply the negative bias to the secondary winding, so directly to the 45 grids, no other phase splitter. I have two 10K pots to adjust bias and balance (within reason) so you don't need matched tubes. Bias is very stable after the tubes get warm. I listened to the pair all afternoon and thoroughly enjoyed listening.
anychance you can share the schematics? did you parallel the 53? or is it deployed as a phase splitter?
Very good indeed. My 45SET amps measure 0.35% THD at 1-watt @ 1KHz, and lower (THD) as the frequency goes up. They're within -1dB from 25Hz to 50KHz and S/N referenced to 1-watt is close to 90dB (hand selected 45 triodes).
I've a large stash of 45 triodes... including some of the older balloon glass tubes. While they (balloon glass) do look really nice, they always seem to be very sensitive to any mechanical vibration.
Do you use a specific company do fabricate the alloy chassis parts or do them yourself? I'm getting ready to start some new gear for myself... including a pair of 300b PP transformer driven monoblocks. Chassis work is generally more of a problem/expense.
Please use Roberts Rules . . .
hacknet said: "anychance you can share the schematics?"
I Second the Motion.
Thanks!
Now you have got me interested in pp 45 amplifiers.
I used to have the EV Aristocrat corner horn enclosure. There was an EV T35 tweeter; I tried the Stephens Free Cone 8 Inch, then Stephens Free Cone 12 Inch woofers.
I also had the EV Marquis enclosure. It was far superior for many typical woofers of the day. More volume, and a sloped enclosure wide duct at the bottom of the back.
hacknet said: "anychance you can share the schematics?"
I Second the Motion.
Thanks!
Now you have got me interested in pp 45 amplifiers.
I used to have the EV Aristocrat corner horn enclosure. There was an EV T35 tweeter; I tried the Stephens Free Cone 8 Inch, then Stephens Free Cone 12 Inch woofers.
I also had the EV Marquis enclosure. It was far superior for many typical woofers of the day. More volume, and a sloped enclosure wide duct at the bottom of the back.
I'd rather not share the schematic, but it's not difficult. Yes, the 53 is paralleled and the phase splitting is via the LL1660.
I have a good number of 45s myself, been collecting them for years. I generally reserve my globe 45s for SE use, since it's so difficult to find a pair that will bias together, even with adjustable bias. I've not had an issue with microphonics with them though.
I friend of mine has a small company that makes the chassis for me and I can highly recommend them: LandfallSystems.com. I do the chassis design in AutoCad and send the .dwg file to Dave. He sends me a complete (flat pack) brushed and anodized chassis. They can do other finishes as well such as powder coating. I do the labeling layout on AutoCad as well and I have a local person with a 65 watt laser engraver to do the lettering/artwork for me.