Hi
Ok, so you have a plate voltage of 228V? or is that the A-K voltage, with the plate at around 330V (or so) with the cathode at around 102V? If this is the case, then you're a lucky person. 😉
Btw - Most of us really do like to help here. It is best to post as much accurate information as possible in Post #1.
Lucky? Not really. I did my homework. A-K to be more precise is 228V. Yep 330V exactly. Yes on the cathode V. Originally I used a PT more inline with the 2A3 tube requirements. I saw a post on another forum where the builder used a PT from a Sony TC500 reel to reel unit. It worked out perfectly with just a change of the rectifier, that's it. As can be seen I did make corrections throughout the thread from post #1. I gave as much info as possible but I find I had to repeat myself a few times while getting faces made at me, not cool.
My conclusion- It's the OT's, beautiful beautiful sounding above 60hz and beyond. Somewhat misleading low end specs. Could also be that the Bolero woofers respond better with SS amps. I'm done with this thread now.
Michael C: yep correct with your deductions..2.2lbs for mine.
I do appreciate the helpful guidance.
Your previous posts gave an impression that you didn't have much experience, but I see that you are able to do design changes and implementation quite alright. That's great. By posting the most accurate information in the first post, you avoid making such an impression - that has been my experience. 🙂
So, tell us about these Altec Bolero's where the LF rolls off. Sure, they may be 8 ohm and 90db sensitivity, but maybe there is more out there, because your RCA LC-1 sound quite alright with this amp. Of course the RCA LC-1 is a fantastic speaker from the age where we didn't have solid state amps with gobs of power. The Altec Bolero 89c (for example) came out of the 1970's where solid state amps with gobs of power were all the rage.
Since you're definitely not getting more than 1W out of this amp, this could be an explanation. Some speakers need a little more power before their bass response 'wakes up'. I would not immediately blame the finmet OPT's.
Edit - I see that there are some postings on other boards regarding 'improving bass response' for Altec Bolero speakers. So this might be something for you to investigate further. They look like nice speakers, but yeah they're bookself units from an age where a 100W SS amplifier was considered 'normal'.
Further Edit - Also, this specs sheet for Altec Bolaro's from the 1970s suggests frequency response as being from 40-20'000 Hz. Altec Lansing 890C Bolero
So, tell us about these Altec Bolero's where the LF rolls off. Sure, they may be 8 ohm and 90db sensitivity, but maybe there is more out there, because your RCA LC-1 sound quite alright with this amp. Of course the RCA LC-1 is a fantastic speaker from the age where we didn't have solid state amps with gobs of power. The Altec Bolero 89c (for example) came out of the 1970's where solid state amps with gobs of power were all the rage.
Since you're definitely not getting more than 1W out of this amp, this could be an explanation. Some speakers need a little more power before their bass response 'wakes up'. I would not immediately blame the finmet OPT's.
Edit - I see that there are some postings on other boards regarding 'improving bass response' for Altec Bolero speakers. So this might be something for you to investigate further. They look like nice speakers, but yeah they're bookself units from an age where a 100W SS amplifier was considered 'normal'.
Further Edit - Also, this specs sheet for Altec Bolaro's from the 1970s suggests frequency response as being from 40-20'000 Hz. Altec Lansing 890C Bolero
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With my SET amp the Bolero's start to roll-off at 100Hz and really not much below 60Hz. With my cheap little T-amp the roll-off starts around 60Hz with not much below 40Hz. A couple of Bolero owners on another forum said they really need much more power to get the low-end going. The higher impedance OT's on my SET aren't helping here. Damping factor issues? I am extremely happy with the OT's overall. Though I haven't seen official specs the Bolero's are closer to 95dB. I'm going to borrow a modern PP tube amp this weekend.
@Cetla416a
I don't have experience with the Altec Boleros but have a pair of Maderas. In the video below, they're driven by my DIY Radiotron SE2A3 amp with FM6WS opts.
IME, the sealed Madera box limits the Altec 406-8Y driver's potential. I've had more success using the 406-8Y in a larger ported box like my repurposed Altec Coronados (~ 2.75 cf) below.
FWIW, I've also been playing around with the Robin and Lipman 6SF5 DC schematic and in spite of the vivid midrange, I find that bass slam/extension isn't its forte. The anachronistic Radiotron even edges it in the bass department. Subjectively, the widest bandwidth sounding SE2A3 amp I've built uses a choke-capacitance coupled circuit.
I don't have experience with the Altec Boleros but have a pair of Maderas. In the video below, they're driven by my DIY Radiotron SE2A3 amp with FM6WS opts.
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Hey Joseph, thanks for your input! I had a fi X years ago that needed some trouble shooting and Don was kind enough to send me the schematic with voltages so I could do the repairs. The X was pretty much the R&L design I believe. He also granted me permission to build one for myself. I built up a mono breadboard like 15 years ago and I finally built my stereo version last summer. Here’s my Bolerosteins.
Attachments
Hi Dan, I think you've left a comment(s?) in my blog.🙂
Nice custom Finemets + your chassis captures the essence of Don's Fi 2A3 stereo amp.👏
I'm not surprised that you've had much better luck driving your RCA LC1s with the Fi/R&L derived amp since those thrive on low damping factor. IME, similar speaker/cabinet designs from the 50s by Altec/Jensen/RCA get choked by amps with lots of NFB.
Unfortunately, Altec stuck a very fine 10" driver with a 414a/z motor/magnet in cabinets designed to compete with the ARs & Dynaco A25/A35 of that era. I get better bass from the Maderas when I drive it with my ST35, Nobsound/JLH 1969 amp or NAD 3020 but lose the SE-DHT midrange magic.
BTW, what driver are you using with the Stein horns?
Agreed!👍
The ST35 was the first tube amp I acquired ca. '81 in what was left of Radio Row in the WTC area of NYC. Through the years I've bought/traded quite a few thinking they'll always be available and affordable. Finally in 2018, I grabbed this one and will keep it for good.
No experience with the paper diaphragm, but cool concept! 🙂
Since I'm also a collector, I'll keep the Maderas in their original condition. I don't use them much since I get better quality sound and wider bandwidth from my 755As and 755Cs (+ 3000Hs) in the smaller Silbatone box shared by Joe Roberts driven my flea power DIY SE-DHT amps.
I've got other stuff lined up, but yes, I'll upload an article hopefully sooner than later.