Rozenblit 300B SEOTL 1.5W

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Thermionic Idler
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Re: Rozenblit 300B SEOTL 1.5W

Post by Thermionic Idler » Tue Mar 21, 2017 1:09 am

Ray P wrote:
Mon Mar 20, 2017 8:55 pm
Cressy Snr wrote:
Sun Mar 19, 2017 10:10 pm
Had a lovely email from the customer earlier this evening.
He is over the moon with the way these amps sound with his 105dB/W horns. "Unbelievable clarity and detail and so musical" was one of the comments.
A job well done then. :)
Good stuff Steve; another member for our small elite club! :D

Rozenblit isn't everyone's cup of tea but he does produce some very good kits. All three of his SE-OTL kits (original SE-OTL, MiniBeast and 300B SE-OTL) are fantastic amplifiers.

Ray
Is membership open to us plebs with the EL509 push-pull "muscle" OTL's?
Deck: Garrard 301
Audio Origami PU7
Van Den Hul Black Beauty
Phono: Whest PS30RDT
Pre-amp - Scratch built AMB α24/LCDuino
Amp - Transcendent "Son of Beast" 15W OTL
Speakers - FF225WK Metronomes

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Ray P
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Re: Rozenblit 300B SEOTL 1.5W

Post by Ray P » Tue Mar 21, 2017 6:21 am

Well, you have a Transcendent OTL so I suppose we could allow you in :P

Ray

Thomas Turk
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Re: Rozenblit 300B SEOTL 1.5W

Post by Thomas Turk » Thu Sep 06, 2018 6:03 pm

NO it's NOT SE it's a push pull. called the Pinnacle.. also in kit form from him. The original SE 300B OTL Project that seems to have been in his Tubes and Circuits.. has disappeared.. with the Pinnacle 300B PP Project inserted. I just bought his book to build the SE 300B OTL.. and found out. Not Kosher, Bruce.

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Re: Rozenblit 300B SEOTL 1.5W

Post by Thomas Turk » Thu Sep 06, 2018 6:18 pm

Cressy Snr wrote:
Thu Feb 23, 2017 10:10 pm
The curse of the OTL struck when a bad Sophia Electric mesh plate arced over and took out the 36V zener that was part of the mod introduced, that protects the CCS that biases the output stage. God was I cursing! What the hell is it with me and OTLs? :x

A bit of fault finding revealed that the zener had failed short circuit as a result of the arc.

I replaced the CCS chip as well as the zener as a precautionary measure.

There's a whole thread on the Transcendent forum about the perils of using Sophias in this amp.

Anyway I had no trouble with the four new EH gold grid 300Bs that Ant's client sent me the other day, and after fixing the faulty monoblock, I was able to test each one individually using them. Everything worked perfectly.
NOT SE Complete plans for a 300B OTL. Own most glorious 1 watt in all of audio. Pure single-ended, Class A sonic heaven.
Thomas Turk wrote:
Thu Sep 06, 2018 6:03 pm
NO it's NOT SE it's a push pull. called the Pinnacle.. also in kit form from him. The original SE 300B OTL Project that seems to have been in his Tubes and Circuits.. has disappeared.. with the Pinnacle 300B PP Project inserted. I just bought his book to build the SE 300B OTL.. and found out. Not Kosher, Bruce.
From his site.
The Pinnacle OTL

300B Push Pull Tube Amp

6 watts into 8 ohms

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Thermionic Idler
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Re: Rozenblit 300B SEOTL 1.5W

Post by Thermionic Idler » Fri Sep 07, 2018 12:49 pm

So are you saying that the latest edition of Tubes and Circuits has the 6W Pinnacle, instead of the SE circuit?

I have the early version of the book with the SE circuit in, but I am more interested in the Pinnacle circuit, which I thought was only available as a kit. Why don't we just swap copies - PM me if interested.
Deck: Garrard 301
Audio Origami PU7
Van Den Hul Black Beauty
Phono: Whest PS30RDT
Pre-amp - Scratch built AMB α24/LCDuino
Amp - Transcendent "Son of Beast" 15W OTL
Speakers - FF225WK Metronomes

Wolfgang
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Re: Rozenblit 300B SEOTL 1.5W

Post by Wolfgang » Fri Sep 07, 2018 7:34 pm

Why don't you build the much better sounding SE DC version? Not the AC version from the book (hum) and not the TS DC version but the version which Ray and myself have build with the JB output stage. And its 1W into 8ohms unless you decrease NFB if you have the right speakers for this.

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Ray P
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Re: Rozenblit 300B SEOTL 1.5W

Post by Ray P » Fri Sep 07, 2018 10:03 pm

Wolfgang wrote:
Fri Sep 07, 2018 7:34 pm
Why don't you build the much better sounding SE DC version? Not the AC version from the book (hum) and not the TS DC version but the version which Ray and myself have build with the JB output stage. And its 1W into 8ohms unless you decrease NFB if you have the right speakers for this.
Yep, the DC version that Wolfgang and I have is the way to go...

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Re: Rozenblit 300B SEOTL 1.5W

Post by Wolfgang » Sat Sep 08, 2018 3:58 pm

And if you are not attached to the TS input stage with 12AU7 (why would you?) you could use the 6SN7 input stage as shown in the 6C33C OTL project and simply connect it to the better sounding but more complex JB 300B output version (each 300B has its own regulator/output cap and the Ip is individually controlled). No copyright and strings attached and we could post the circuit here.
Gain in the TS is around 54, with the 6SN7 around 48 so it will be a little less for driving the output but with reduced NFB (sounds anyway better with more sensitive speakers) no problem.
The 6SN7 needs ,however, an extra psu. The 12AU7 was hooked up to the same psu as the 300B. I would guess that the amp would sound a little warmer with the 6SN7 and have better lower mids expression and better punch. Definitely no disadvantage to the 12AU7 version.

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Re: Rozenblit 300B SEOTL 1.5W

Post by Clive » Sun Sep 09, 2018 7:14 pm

I've just about convinced myself to build the Pinnacle PP. Does anyone have experience of hearing the SE vs PP? I'm sure the PP dynamics will be better but does it lose out in anyway musically vs the SE. My speakers are 16R OBs 100db. The kits plus valves and tax are not cheap....so I want to double and triple check the likely results if possible.

Thomas, I believe you've somehow got mixed up on this SE vs PP thing around what's published in Bruce's book. The Pinnacle circuit is not out there or so I believe.

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Ray P
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Re: Rozenblit 300B SEOTL 1.5W

Post by Ray P » Sun Sep 09, 2018 8:05 pm

Clive wrote:
Sun Sep 09, 2018 7:14 pm
I've just about convinced myself to build the Pinnacle PP. Does anyone have experience of hearing the SE vs PP?
Wolfgang has heard both the Pinnacle and the 300B SE-OTL and can probably give some insight. As an alternative, with those speakers, you might consider this project;

viewtopic.php?f=11&t=7265&sid=8a4b297d6 ... 811285fdb6

Ray

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Ray P
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Re: Rozenblit 300B SEOTL 1.5W

Post by Ray P » Sun Sep 09, 2018 8:38 pm

Clive wrote:
Sun Sep 09, 2018 7:14 pm
Does anyone have experience of hearing the SE vs PP?
Thinking on this further, I've built the 300B SE-OTL (much modified from the originally published version) and it was highly rated by the guys at the 2017 Owston meeting (about 80% down Simon's blog);

http://simonsnewadventuresinhifi.blogsp ... -2017.html

Could perhaps consider bringing the amps up to Cheshire if that's of interest - I would be interested in seeing and hearing your OBs with them too.

Clive
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Re: Rozenblit 300B SEOTL 1.5W

Post by Clive » Sun Sep 09, 2018 9:16 pm

Ray P wrote:
Sun Sep 09, 2018 8:38 pm
Clive wrote:
Sun Sep 09, 2018 7:14 pm
Does anyone have experience of hearing the SE vs PP?
Thinking on this further, I've built the 300B SE-OTL (much modified from the originally published version) and it was highly rated by the guys at the 2017 Owston meeting (about 80% down Simon's blog);

http://simonsnewadventuresinhifi.blogsp ... -2017.html

Could perhaps consider bringing the amps up to Cheshire if that's of interest - I would be interested in seeing and hearing your OBs with them too.
It's a long way from Somerset to Cheshire - near Altrincham! Let's discuss. I know that Ali was majorly impressed with your version of the 300B SE OTL. On the Rozenblit BB Kelvin from Glasgow clearly likes both SE and PP versions and comes out just prefering the PP. I had originally thought about building Mini Beast but comments about Pinnacle caught my interest. Bruce even suggested Mini Beast was best for my speakers but gave no reasoning for this. Maybe I should try to quiz him by email. Mini Beast is much more attractive price-wise but I might as well go with the best if it's truely better.

I'd prefer to not scratch build so a Rozenblit kit seems like the best route. I'm using his Sub Buddy in conjunction with my Slagle based AVC pre to very good effect.

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Ray P
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Re: Rozenblit 300B SEOTL 1.5W

Post by Ray P » Sun Sep 09, 2018 10:32 pm

Clive wrote:
Sun Sep 09, 2018 9:16 pm
On the Rozenblit BB Kelvin from Glasgow clearly likes both SE and PP versions and comes out just prefering the PP.
IIRC Kelvin has the DC kit version of the 300B SE-OTL; it's not the same as the verson Wolfgang and I have built and I don't believe it is as good (too many Rozenblit compromises).

That said, it's academic if you're not prepared to scratch build as you only have a choice between Pinnacle and Minibeast.

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Re: Rozenblit 300B SEOTL 1.5W

Post by Clive » Mon Sep 10, 2018 5:51 pm

Thanks for your thoughts Ray. Yes I believe Kelvin has the DC 300B PP version. I fully expect your SE with AndrewL's heaters etc will be top notch or better! The heaters on the DC PP will be nothing special for sure; at least being PP they should be quiet (ie self-cancelling in terms of hum).

I will get back to scratch building but for now I want a simple way to scratch my OTL itch. Maybe Mini Beast would be more sensible if it gives 90% of the sound of Pinnacle. If (as I expect) Pinnacle can be bettered then for scratching that OTL itch, Mini Beast may suffice for now and be far more cost effective. Total cost with valves, shipping and tax look to be about £1k for Mini Beast and £2k for Pinnacle.

I've had 2 pieces of advice from Bruce separated by a few months:

"I think think the Mini Beast will give you the best all around performance for your speakers."

"If you want to spend the money, then definitely the Pinnacle is the way to go. It will drive your speakers very easily."

I suspect the nature of Bruce's personality leads him to believe deep down that Pinnacle is more expensive than makes sense. Just a guess.

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Re: Rozenblit 300B SEOTL 1.5W

Post by Ray P » Mon Sep 10, 2018 6:48 pm

I was suggesting that the 300B SE-OTL that Kelvin compared with the Pinnacle would have been the DC heater version of the kit, i.e. not the same 300B SE-OTL as mine and Wolfgang's. He also has the Pinnacle 300B PP-OTL, again built from the kit.

I would still be interested in hearing my 300B SE-OTL with your OBs - I'll PM you to see if we could arrange something.

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